365 days of medical physics_ may 2012

8/10/2019 365 Days of Medical Physics_ May 2012

1/16

Nuggets of knowledge about medical physics.

365 Days of Medical Physics

24 May 2012

IMAT/VMAT basics

One of the newest and most interesting external beam delivery techniques today goes by many

names: intensity modulated arc therapy (IMAT), volumetric modulated arc therapy (VMAT), etc.

To make things more confusing, vendors have each given this technique their own proprietary

names: RapidArc (Varian), SmartArc (Philips), and VMATTM[didn't I already say VMAT?]

(Elekta). Maybe the most general and correct name for IMAT would be conebeam dynamic angle

fluence modulated xray therapy(CBDAFMXT), but you might confuse that acronym with a

chemotherapy drug name... In this post I'll discuss some of the ba sics of this arcbased form of

IMRT (and just call it IMAT to keep things simple).

At its most basic IMAT is essentially conventional IMRT, but with the gantry moving in one or

more rotating arcs, rather than delivering from a small number of fixed angles. This means that

most of the concepts and advantages and disadvantages of IMRT apply to IMAT (detailed below).

IMAT was developed (and marketed!) as a conventional linacbased alternative to helical

tomotherapy and as a more conformal / lower critical structure dose andfaster version of static

angle IMRT.

In the figure showing the IMRT hierarchy, IMAT is on the branch of conebeam, dynamic gantry

IMRT. In order to deliver IMAT, a linac must have some of the following capabilities: gantry

motion with beam on, dynamic MLC (i.e. leaf motion with beam on and gantry rotating), and

variable dose rate.

Planning of IMAT is very similar to conventional IMRT. The plan is determined by inverse

planning methods. The degrees of freedom are increased by considering gantry rotation speed,

dose rate, number of field shapes, number of arcs, etc. For planning, arcs are usually

approximated with a f inite number of angles (e.g. 36). Constraints can be more tightly matchedwith multiple arcs at the expense of delivery time. Another important aspect in IMAT

optimization is that MLC leaf speed limits the beam shape "distance" from one angle to the next,

i.e. the MLC leaf positions cannot vary greatly from one angle to the next and thus beam shape

"interconnectedness" must be taken in to account.

Advantages of IMAT include:

Highly conformal target volume dose with lower dose to critical structures than IMRT

or 3DCRT, as dose is spread over more angles.

Faster delivery times and lower MU's (especially single arc IMAT) when compared with

IMRT.

Noncoplanar arcs possible.

Comparable plans to helical tomotherapy, but performed with a conventional linac.

The hierarchy of IMRT techniques.

Roy

View my complete profile

About Me

19

365 Days of Medical Physics blogging

About this blog:

Dosevolume histogram basics

IMAT/VMAT basics

Comparing dose distributions: Thegamma test

Multileaf collimators: modern beamshaping

The many faces of bolus

Popular Posts

Will Work For Science

Go here!

Twitter @MedPhys365

Subscribe To

Posts

All Comments

bolus (2) cDVH (2)DTA (2) DVH (2)

imrt (2) intro (5)MLC

(2) overview (2) QA(2) statistics (3)

Labels

2013 (1)

2012 (15)

May(10)

IMAT/VMAT basics

The many faces of bolus: Part 2


Compensatorbased IMRT

Blog Archive

19 Ms Siguiente blog Crear un blog Acced
http://medphys365.blogspot.com/2012/05/many-faces-of-bolus.htmlhttp://medphys365.blogspot.com/2012/04/multileaf-collimators.htmlhttp://medphys365.blogspot.com/2012/05/comparing-dose-distributions-gamma-test.htmlhttp://medphys365.blogspot.com/2012/05/comparing-dose-distributions-gamma-test.htmlhttp://medphys365.blogspot.com/2012/05/comparing-dose-distributions-gamma-test.htmlhttp://medphys365.blogspot.com/2012/05/imatvmat-basics.htmlhttp://medphys365.blogspot.com/2012/04/365-days-of-medical-physics-blogging.htmlhttp://medphys365.blogspot.com/2012/05/imatvmat-basics.htmlhttp://www.blogger.com/profile/14293477186383292023http://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/search/label/dDVHhttp://medphys365.blogspot.com/2012/05/imatvmat-basics.htmlhttp://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/2012/04/365-days-of-medical-physics-blogging.htmlhttp://medphys365.blogspot.com/search/label/notationhttp://medphys365.blogspot.com/search/label/bloghttp://medphys365.blogspot.com/search/label/compensatorhttp://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/search/label/overviewhttp://medphys365.blogspot.com/search/label/introhttp://medphys365.blogspot.com/search/label/ABRhttp://medphys365.blogspot.com/search/label/cDVHhttp://medphys365.blogspot.com/http://medphys365.blogspot.com/2012/05/comparing-dose-distributions-gamma-test.htmlhttp://medphys365.blogspot.com/search/label/statisticshttp://medphys365.blogspot.com/2012/05/imatvmat-basics.htmlhttp://medphys365.blogspot.com/search/label/imrthttp://medphys365.blogspot.com/search?updated-min=2013-01-01T00:00:00-07:00&updated-max=2014-01-01T00:00:00-07:00&max-results=1http://medphys365.blogspot.com/2012/05/imatvmat-basics.htmlhttp://medphys365.blogspot.com/2012/05/many-faces-of-bolus.htmlhttp://medphys365.blogspot.com/search/label/bolushttp://medphys365.blogspot.com/search/label/medical%20physicshttp://medphys365.blogspot.com/2012/05/dose-volume-histogram-basics.htmlhttp://medphys365.blogspot.com/search?updated-min=2012-01-01T00:00:00-07:00&updated-max=2013-01-01T00:00:00-07:00&max-results=15http://medphys365.blogspot.com/search/label/gammahttp://medphys365.blogspot.com/2012/04/basics-of-imrt-overview.htmlhttp://void%280%29/http://void%280%29/http://medphys365.blogspot.com/search/label/VMAThttp://medphys365.blogspot.com/search/label/journalshttp://2.bp.blogspot.com/-6789y4h130E/T78fsXcxgJI/AAAAAAAAAIw/SeKBsF3UJlY/s1600/IMRT-hierarchy1.pnghttp://medphys365.blogspot.com/2012/05/compensator-based-imrt.htmlhttp://medphys365.blogspot.com/search/label/MLChttp://medphys365.blogspot.com/search/label/open%20accesshttp://medphys365.blogspot.com/2012/05/dose-volume-histogram-basics.htmlhttp://medphys365.blogspot.com/search/label/IAEAhttp://medphys365.blogspot.com/2012/04/multileaf-collimators.htmlhttp://medphys365.blogspot.com/2012_05_01_archive.htmlhttp://medphys365.blogspot.com/search/label/measurementhttp://medphys365.blogspot.com/search/label/QAhttp://medphys365.blogspot.com/search/label/worldhttp://medphys365.blogspot.com/search/label/IMAThttp://willworkforscience.blogspot.com/http://medphys365.blogspot.com/search/label/DVHhttp://medphys365.blogspot.com/2012/05/many-faces-of-bolus-part-2.htmlhttp://medphys365.blogspot.com/search/label/imageshttp://medphys365.blogspot.com/search/label/workforcehttp://void%280%29/http://medphys365.blogspot.com/search/label/DTA


2/16

Posted by Roy at 11:52 PM 3 comments:

Labels: IMAT, intro, VMAT

Disadvantages of IMAT include:

Higher cost of hardware and software licensing relative to IMRT.

Increased complexity of plans makes QA a poor diagnostic tool (i.e. hard to

determine source of QA failures).

IMAT delivery techniques are the obvious(?) next step following IMRT. In fact, it's hard to come

up with a list of concrete disadvantages of IMAT over IMRT. (Please comment if you feel

otherwise.) In our clinic it's one of the few new techniques that everyone seems to have adopted

with open arms.

Further reading:

Cedric X Yu and Grace Tang, Intensitymodulated arc therapy: principles, technologies

and clinical implementation, 2011 Phys. Med. Biol. 56 R31 doi:10.1088/0031

9155/56/5/R01(open access).

David Shepard, Clinical Implementation of Intensity Modulated Arc Therapy,

presentation, 2009,

http://www.medicaldosimetry.org/meetings/2009handouts/Shepard_VMAT.pdf

Recommend this on Google

20 May 2012

The many faces of bolus: Part 2

PreviouslyI discussed the role of bolus material in radiation therapy and some of the forms it

takes. This post shows a couple of other examples.

Super Stuff bolus, also known generically as pink bolus, is a moldable bolus material with the

consistency of gelatin. The material is described by the manufacturer as a "hydophilic organic

polymer" and is sold in individual powder packets. Pink bolus is supposed to have a density of

1.02 g/cm3. To use the bolus, you add the necessary amount of water, allow the material to set,

i.e. coming to its gelatinlike consistency, and then knead it into the shape you want. Over time

pink bolus will lose its shape and must be reshaped. Eventually it will lose some consistency due

to moisture loss and a new batch must be made. Care must also be taken to remove as many air

bubbles as possible.

Pink bolus molded into shape.

A packet of pink bolus powder.

Medical physics journals


Comparing dose distributions: DTA anddosediffere...

Radiation therapy availability aroundthe world

New medical physicists in the US:Crunching the nu...


April (5)
http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3098984032248099468&target=twitterhttp://medphys365.blogspot.com/2012/05/imatvmat-basics.htmlhttp://medphys365.blogspot.com/search/label/IMAThttp://medphys365.blogspot.com/2012_04_01_archive.htmlhttp://medphys365.blogspot.com/2012/05/imatvmat-basics.html#comment-formhttp://www.medicaldosimetry.org/meetings/2009handouts/Shepard_VMAT.pdfhttp://void%280%29/http://medphys365.blogspot.com/2012/05/many-faces-of-bolus-part-2.htmlhttp://4.bp.blogspot.com/-2LiQ5Bgh5OU/T7lPCsQ6RtI/AAAAAAAAAII/sgDPZ7GxCRw/s1600/Pink_bolus_finished.jpghttp://dx.doi.org/10.1088/0031-9155/56/5/R01http://medphys365.blogspot.com/2012/05/many-faces-of-bolus.htmlhttp://2.bp.blogspot.com/-oyUB8fNcMIc/T7lQUsusoFI/AAAAAAAAAIQ/FxYO9SipOqI/s1600/Pink_bolus_powder.jpghttp://medphys365.blogspot.com/2012/05/medical-physics-journals.htmlhttp://medphys365.blogspot.com/2012/05/many-faces-of-bolus.htmlhttp://medphys365.blogspot.com/search/label/introhttp://medphys365.blogspot.com/search/label/VMAThttp://medphys365.blogspot.com/2012/05/new-medical-physicists-in-us-crunching.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3098984032248099468&target=pinteresthttp://www.blogger.com/profile/14293477186383292023http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3098984032248099468&target=facebookhttp://medphys365.blogspot.com/2012/05/comparing-dose-distributions-gamma-test.htmlhttp://medphys365.blogspot.com/2012/05/comparing-dose-distributions-dta-and.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3098984032248099468&target=emailhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3098984032248099468&target=bloghttp://medphys365.blogspot.com/2012/05/radiation-therapy-availability-around.html


3/16

Posted by Roy at 2:45 PM No comments:

Labels: bolus

Recently in our clinic we treated a patient with classic (i.e. nonHIV related) Kaposi sarcoma of

the leg with photons. For this we decided to use rice grains as the bolus material. As with all

bolus, the idea of using rice is to simulate tissue and modify the dose distribution as desired. In

this case, increase of skin dose is desired.

For this patient we built a polystyrene foam box and filled it with loose rice grains. It

took approximately 10 kg of dry parboiled rice to fill the box with the patient's leg. The patient

plus rice box was then scanned with the CT and planned as normal.

The open access article linked below from Ahn et al. shows some dosimetric comparisons

between the use of rice as a bolus and a water bolus for irradiating extremities. I will warn you

that both methods create a mess at best :)

Further reading:

Ahn SK, Kim YB, Lee IJ, Song TS, Son DM, Jang YJ, Cho JH, Kim JH, Kim DW, Cho JH,

Suh CO. Evaluation of a Waterbased Bolus Device for Radiotherapy to the

Extremities in Kaposi's Sarcoma Patients. J Korean Soc Ther Radiol Oncol. 2008

Sep;26(3):189194. http://dx.doi.org/10.3857/jkstro.2008.26.3.189 (Open access.

In Korean with abstract and figure captions in English.)

Rice bolus box for treating a patient's leg/foot.

Some leftover rice (not) used as bolus material.


17 May 2012


A dosevolume histogram (DVH) is a mathematical tool to assess the appropriateness of a given

radiation therapy plan. It can be used to assess whether a plan meets desired constraints for a

voulme of interest, within certain limitations. DVHs are widely used and understanding how
http://medphys365.blogspot.com/search/label/bolushttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2591772746618121281&target=facebookhttp://medphys365.blogspot.com/2012/05/many-faces-of-bolus-part-2.html#comment-formhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2591772746618121281&target=emailhttp://4.bp.blogspot.com/-ZZZt6EsZtO4/T7lVtqvHNYI/AAAAAAAAAIk/6fQXFsePj-o/s1600/rice1.jpghttp://medphys365.blogspot.com/2012/05/many-faces-of-bolus-part-2.htmlhttp://www.blogger.com/profile/14293477186383292023http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2591772746618121281&target=bloghttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2591772746618121281&target=twitterhttp://dx.doi.org/10.3857/jkstro.2008.26.3.189http://medphys365.blogspot.com/2012/05/dose-volume-histogram-basics.htmlhttp://3.bp.blogspot.com/-uEP8KqA6siA/T7lSkeSU-xI/AAAAAAAAAIY/0RlVwZio5aw/s1600/rice_bolus_box.jpghttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2591772746618121281&target=pinterest


4/16


Labels: cDVH, dDVH, DVH

they work is a basic skill for treatment plan assessment. In this post Ill discuss some DVH basics.

A DVH is nothing more than a histogram, but it is important to understand where the data comes

from and how the DVH is representing the data. Modern treatment plans are created based on 3D

image sets created using CT, MRI, etc. These data sets consist of voxels (the 3D equivalent of

pixels). A volume of interest, e.g. a PTV, consists of a subset of these voxels. The basic data in a

DVH is generated by binning the dose values from each voxel in the volume. (Interpolation may

be necessary if the bound of the volume intersects a voxel.) This binned dose frequency data

comprises a differential dosevolume histogram, or dDVH, which I will discuss in more detail in a

future post. The dDVH looks like a common histogram and gives you an idea of how many voxels

receive a certain dose, e.g. the dDVH might show that 85% of the PTV voxels received 98%

102% of the prescribed dose and 46% received exactly 100% of the prescribed dose.

The more familiar form of DVH is the cumulative dosevolume histogram, or cDVH. This DVH is

calculated by summing the dDVH starting at the dose of interest, D, up to the max dose, Dmax

(Eq. 1).

The cDVH displays the percent/number of voxels in a volume which receive at least a dose D,

i.e. the cDVH of a volume irradiated perfectly uniformly to 100 cGy will show that 100% of the

voxels received at least 30 cGy, 50 cGy, 80 cGy, etc, but 0% received 105 cGy. Thus for an ideal

treatment plan, the cDVHs of the target volumes will have a rectangular, stepdown function

appearance and the cDVHs of critical volumes will drop immediately to zero.

In the real world treatment plans are not ideal (I know, its sad). Instead acceptable dose

constraints are set for targets and critical structures. DVHs can be used to determine if these

constraints are mets. One caveat is that standard DVHs do not directly provide spatial

information about the dose distribution. One less than ideal method is to create subvolumes,

but creating useful/meaningful subvolumes is a nontrivial exercise.

Top image from Vorwerk et al. Radiation Oncology 2008 3:31, doi:10.1186/1748717X331, used under CC Licenseterms.

A typical cumulative dosevolume histogram (cDVH).

Eq. 1


13 May 2012

Compensatorbased IMRT

Intensity modulated radiation therapy (IMRT) is almost always performed with the use of a

multileaf collimator (MLC). This is, however, not the only way to deliver static angle IMRT.

Another method is with the use of compensator blocks. In this post I will talk a little bit about

this less common IMRT technique.
http://medphys365.blogspot.com/search/label/cDVHhttp://creativecommons.org/licenses/by/2.0http://medphys365.blogspot.com/2012/05/compensator-based-imrt.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4052496099203236182&target=pinteresthttp://medphys365.blogspot.com/search/label/DVHhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4052496099203236182&target=twitterhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4052496099203236182&target=facebookhttp://www.blogger.com/profile/14293477186383292023http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4052496099203236182&target=bloghttp://medphys365.blogspot.com/2012/05/dose-volume-histogram-basics.html#comment-formhttp://www.ro-journal.com/content/3/1/31/http://2.bp.blogspot.com/-QH1LXw2hb40/T7XfTBBs0EI/AAAAAAAAAHw/PZjmkLrHZJ0/s1600/Vorwerk-cDVH1.jpghttp://medphys365.blogspot.com/2012/05/dose-volume-histogram-basics.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4052496099203236182&target=emailhttp://medphys365.blogspot.com/search/label/dDVHhttp://3.bp.blogspot.com/-insnvXwHvks/T7Xywgz16nI/AAAAAAAAAH8/hXh_Vk9sBHs/s1600/cDVH-eq1.png


5/16


Labels: compensator, imrt, MLC

As discussed in a previous post, IMRT requires fluence modulation not possible with conventional

poured / handcut blocks. This fluence modulation is necessary to achieve the desired target

matching and critical structure sparing via inverse planning optimization. This fluence

modulation is typically achieved using an MLC, which has many advantage as well as

disadvantages. An alternative method, in use since at least the mid 1990's, is fluence modulation

via solid compensator blocks designed for each individual field. The above image shows a sample

compensator made of milled brass.

Compensatorbased IMRT is purported to have several advantages over MLCbased IMRT,

including:

Being static, each field is delivered more quickly (also lower MU's).

Fluence patterns can be closer to the ideal, i.e. not limited by leaf size, speed, or

leakage.

Potentially cheaper.

Avoids field splitting. (Did I ever mention I hate split fields?!?)

Along with these advantages come possible drawbacks, including:

Long fabrication times, versus automated MLC patterens.

Therapists must change compensator for each field.

Potential for beam hardening.

Large size / weight to achieve low dose regions.

Compensators can be fabricated from a range of materials, including brass, Wood's metal

(Cerrobend), PMMA (Plexiglas), and tungsten powder composite. Milling. molding, or stacking

and bolting are possible fabrication techniques. A handful of companies sell custom fabricated

IMRT compensators on demand, delivering within one or two days of order.

Do you have any experience with this technique?

Further reading:

Chang, S., Cullip, T., Deschesne, K., Miller, E., & Rosenman, J. Compensators: An

alternative IMRT delivery technique. Journal Of Applied Clinical Medical Physics, 5(3),

2004. doi:10.1120/jacmp.v5i3.1965 (open access)P.C. Williams, IMRT: delivery techniques and quality assurance, British Journal of

Radiology (2003) 76, 766776, doi: 10.1259/bjr/12907222(open access?)

Brass IMRT field compensator from .decimal, Inc.


11 May 2012

Medical physics journals

If you want to keep up to date on the latest developments in medical physics, journals are one of

the best resources. In this post I'm going to compile a list of medical physics journals and
http://bjr.birjournals.org/content/76/911/766.fullhttp://medphys365.blogspot.com/2012/05/compensator-based-imrt.htmlhttp://medphys365.blogspot.com/2012/04/basics-of-imrt-overview.htmlhttp://medphys365.blogspot.com/search/label/compensatorhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=8314635032260864515&target=bloghttp://medphys365.blogspot.com/2012/05/compensator-based-imrt.html#comment-formhttp://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/2012/04/multileaf-collimators.htmlhttp://medphys365.blogspot.com/2012/05/medical-physics-journals.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=8314635032260864515&target=twitterhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=8314635032260864515&target=facebookhttp://medphys365.blogspot.com/search/label/imrthttp://medphys365.blogspot.com/search/label/MLChttp://4.bp.blogspot.com/-Gs6Gb6tq6nc/T7CTEAHgzgI/AAAAAAAAAHY/g4ifqrIXOls/s1600/Decimal_compensator_nima.JPGhttp://www.jacmp.org/index.php/jacmp/article/view/1965http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=8314635032260864515&target=pinteresthttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=8314635032260864515&target=email


6/16

Posted by Roy at 12:36 AM 4 comments:

Labels: journals, open access

journals with medical physics related content. I will also mention the degree of open access for

each journal (that I'm aware of) and the hindexas computed by Google Scholar.

Medical physics specific journals:

Medical Physics, published by AAPM. Some article types made open access. h5index:

45.

Physics in Medicine and Biology, published by Institute of Physics. Open access option

for authors with publishing fee. h5index: not available.

Journal of Applied Clinical Medical Physics, published by AAPM. Fully open access. h5

index: 15.

Journal of Medical Physics, published by the Association of Medical Physicists of India.

Fully open access. h5index: 7.

arXiv.org medical physics category. Fully open access. Overall for arXiv.org, h5index:

256.

Magnetic Resonance in Medicine, published by the International Society for Magnetic

Resonance in Medicine. Paid access only. h5index: 50.

Other journals with medical physics content:

The Red Journal(International Journal of Radiation Oncology * Biology * Physics),

published by ASTRO. Paid access only. h5index: 68.

The Green Journal(Radiotherapy and Oncology), published by ESTRO. Paid access

only. h5index: 48.

Radiation Oncology, published by BioMed Central. Fully open access. h5index: 23.

Practical Radiation Onoclogy, published by ASTRO. Paid access only. h5index: N/A.

Medical Dosimetry, published by the American Association of Medical Dosimetrists.

Paid access only. h5index: 15.

More info can be found on the state of open access and medical physics publications in my post

about open access on Will Work for Science.

Any other additions to add?

+1 Recommend this on Google

10 May 2012

Comparing dose distributions: The gamma test

In my last post I discussed dose distribution comparison with dose difference and distanceto

agreement (DTA) tests. Another widely used and closely related method for comparing dose

distributions is the gamma test.

The gamma test was first introduced by Low et al. in 1998 as a single metric that combined

features of both dose difference and DTA, while performing robustly in the regions where those

are prone to failure. Conceptually, gamma is very similar to dose difference and DTA, but

combines them into an abstract metric resembling a distance (Eq. 1). In this way both dose

difference and DTA are taken into account for every point compared (rather than eitheror as

previously discussed).

In the above equations I have used somewhat different notation than Low et al. in an attempt to

make things slightly clearer.

If we wish to compare two dose distributions, e.g. a measured versus a calculated distribution,

we will have a dose, Da(ra), in the first distribution at point ra, and a dose, Db(rb), at the

Eq. 1

Eq. 2
http://www.practicalradonc.org/http://www.jacmp.org/http://medphys365.blogspot.com/2012/05/comparing-dose-distributions-gamma-test.htmlhttp://www.sciencedirect.com/science/journal/09583947http://www.ro-journal.com/http://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/2012/05/comparing-dose-distributions-dta-and.htmlhttp://medphys365.blogspot.com/2012/05/medical-physics-journals.html#comment-formhttp://4.bp.blogspot.com/-pjT5xSJPTDY/T7CD00gG95I/AAAAAAAAAG4/uhIV3uHm_Ps/s1600/gamma-eq1.pnghttp://iopscience.org/pmbhttp://www.medphys.org/http://willworkforscience.blogspot.com/2011/01/open-access-medical-physics-and.htmlhttp://medphys365.blogspot.com/2012/05/medical-physics-journals.htmlhttp://en.wikipedia.org/wiki/H-indexhttp://www.aapm.org/http://www.jmp.org.in/http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1522-2594http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4014840933681586672&target=twitterhttp://scholar.google.com/intl/en/scholar/metrics.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4014840933681586672&target=facebookhttp://medphys365.blogspot.com/search/label/open%20accesshttp://medphys365.blogspot.com/search/label/journalshttp://arxiv.org/list/physics.med-ph/recenthttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4014840933681586672&target=pinteresthttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4014840933681586672&target=bloghttp://2.bp.blogspot.com/-xERYTfAD83I/T7CD1LNvJSI/AAAAAAAAAG8/3GzsPXEy3kw/s1600/gamma-eq2.pnghttp://journals.elsevierhealth.com/periodicals/radohttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4014840933681586672&target=emailhttp://www.sciencedirect.com/science/journal/03603016


7/16


Labels: DTA, gamma, QA

corresponding point rbin the second distribution. The DTA condition is fulfilled when Da(ra) =

Db(rb+r), where ris an arbitrary point a distance |r| away from rb. This condition defines an

isodose contour in distribution baround point rb. Away from this contour the DTA, dDTA, is

undefined. DTA is used with a threshold passing value, DTA, e.g. 3mm. A DTA smaller than the

threshold is considered passing for a simple DTA test. For gamma, DTAis used to normalize the

DTA value, such that a normal passing value would then be unity.

Dose difference is simply the difference of the two doses at the corresponding points: |D a(ra) =

Db(rb)|. As with DTA, a pass/fail threshold, DD, is used in the simple dose difference test, but

is used to normalize the result in the gamma equation, such that the normal "passing" value

would be unity.

We now have two components: normalized DTA and normalized dose difference. By squaring

these values, adding, and taking the square root, we have a distancelike metric, , shown in

Eq. 1. Because DTA is only defined for values of r, such that Da(ra) = Db(rb+r), is only defined

when that condition is met (geometrically located along the DTA isodose contour).

Finally, the actual gamma index, , is determined by finding the minimum value of by varying

r. This essentially means traveling along the isodose contour and finding the point at which DTA

is smallest.

The convention is for passing to be 1 and failing to be > 1. You will notice that a point

yielding normalized DTA = 1 and normalized dose difference = 1 would now fail, since the

corresponding would be 2.

What provides is a single value to evaluate, versus using separate tests and then consideringboth. As with DTA, presents challenges in efficient implementation (clearly Eq.'s 1 and 2 are

not hand solvable).

Your comments (especially corrections) are appreciated.

Roy

Further reading:

D. A. Low, W. B. Harms, S. Mutic, and J. A. Purdy, A technique for the quantitative

evaluation of dose distributions, Med. Phys. 25, 656 (1998);

http://dx.doi.org/10.1118/1.598248


06 May 2012

Comparing dose distributions: DTA and dosedifference

Radiation therapy plan quality assurance often hinges on comparing calculated dose distributions

with measured dose distributions. One of the most common techniques to compare dose

distributions is the combined use of distancetoagreement (DTA) and dose difference. In this

post I will give an overview of these concepts.

Dose difference is a very straight forward comparison of dose at corresponding points in two

distributions. Given a point apin the planned distribution and the corresponding point amin the

measured distribution, the dose difference is simply D(am) D(ap). A passing criterion is used,

e.g. 3% of planned dose, such that if the measured dose difference is


8/16


Labels: DTA, QA

Distancetoagreement (DTA) is also very straight forward conceptually. Given a point apin the

planned distribution and the corresponding point amin the measured distribution, the distance

toagreement is the nearest point in the measured distribution from am, such that D(am+ r) =

D(ap). As with dose difference, a passing criterion is chosen, e.g. 3 mm. If the matching dose

level is found within a radius of


9/16

Posted by Roy at 1:00 AM No comments:

Labels: IAEA, statistics, world

The above map color codes each country as a function of radiation therapy machines (linacs,

teletherapy, or HDR) per capita as of 2010. A more uptodate, interactive version is found here.

The DIRAC site also provides the raw data and even information on individual clinics in each

country.

While there are certainly nonnegligible error bars on their data, the numbers are revealing,

though largely what you'd expect. The highest GDP per capita (or likely highest health spending

per capita) countries show up in green on the above map (5 or more machines per million) and

the poorest countries show up in dark orange or red ( < 1 machine per million). Togo is red

because it has zero machines.

I think the main implications on the medical physics end is with regards to education

and dissemination of current knowledge to countries with few physicists. The US, population

approximately 3.1x10^8, is listed as having 1728 therapy physicists (probably a low estimate)

versus India, population approximately 1.2x10^9, listed as having 144 therapy physicists. Clearly

the manyears of experience are highly concentrated in the green countries. I'll claim that it's

our duty in the green countries to help educate our colleagues in the countries with less local

access to their professional and academic peers.

IAEA statistics on radiation therapy machines per capital in 2010.


03 May 2012

New medical physicists in the US: Crunching the numbers

If you are entering the field of medical physics or have been around for a while, you might be

wondering "how many new medical physicists are joining the ranks each year?" In the US this is

an especially important question in light of the 2014 ABR residency mandate and possible effects

of an aging population on cancer incidence.

As a recent graduate, one of the topics fresh on my mind is the number of jobs available to

graduating students. This is of course a supply and demand game (or possibly a supply and supply

game when you consider number of residency spots). Since potential medical physicists in the US

can come from many different "sources" (i.e. accredited medical physics grad programs, non

accredited medical physics grad programs, nonmedical physics grad programs), it would be

somewhat difficult to directly count the number of new grads. I think it is therefore instructiveto look at the raw stats of the number of people taking the ABR medical physics board exams,

which are (recently?) available on the ABR website.
http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=6652680838481765659&target=facebookhttp://medphys365.blogspot.com/search/label/statisticshttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=6652680838481765659&target=emailhttp://2.bp.blogspot.com/-hoy8U00dBQk/T6NxD9cJpeI/AAAAAAAAAFs/7QMmVUA2_zg/s1600/IAEA-Worldwide_therapy_access-2010.pnghttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=6652680838481765659&target=pinteresthttp://medphys365.blogspot.com/2012/05/radiation-therapy-availability-around.htmlhttp://medphys365.blogspot.com/search/label/IAEAhttp://www.blogger.com/profile/14293477186383292023http://www-naweb.iaea.org/nahu/dirac/map.asphttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=6652680838481765659&target=twitterhttp://medphys365.blogspot.com/search/label/worldhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=6652680838481765659&target=bloghttp://medphys365.blogspot.com/2012/05/new-medical-physicists-in-us-crunching.htmlhttp://www.theabr.org/ic-rp-scorehttp://medphys365.blogspot.com/2012/05/radiation-therapy-availability-around.html#comment-form


10/16

Posted by Roy at 12:04 AM No comments:

Labels: ABR, statistics, workforce

What we see in the data is a marked increase in the number of people taking all three parts of

the ABR certification exam over the period of 2006 2010, with a slight downtick in 2008. The

increase in the number taking Part 3 (Oral) in all specialties is +45% (220 in 2006 to 319 in

2010). The increase in the number taking Part 1 over the same time period is approximately

+35%.

This presents the obvious question of what will happen to this trend when the ABR residency

requirement takes full effect in 2014.

For more info on this topic:

Mills MD, Thornewill J, Esterhay RJ. Future trends in the supply and demand for

radiation oncology physicists. J Appl Clin Med Phy. 2010 Apr;11(2) (open access!)

Jean Moore, Medical Physics Workforce Study: Overview, AAPM presentation, 2010

Final report AAPM Workforce Study Report (AAPM login required)


02 May 2012


Bolus is a simple, yet important technology used in radiation therapy. The most basic function of

bolus material is to shape the dose distribution in a desired way. This generally falls into two

categories: compensating for "missing" tissue and enhancing the buildup effect of MeV energy

photon beams.

The bolus itself can be made of a huge variety of materials depending on the application. Below

are some materials used as bolus, all of which are applied directly to the skin surface.
http://www.aapm.org/AAPMUtilities/download.asp?file=surveys/workforce/Synthesis.pdfhttp://medphys365.blogspot.com/2012/05/new-medical-physicists-in-us-crunching.html#comment-formhttp://medphys365.blogspot.com/search/label/statisticshttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=7243474880050880667&target=pinteresthttp://www.jacmp.org/index.php/jacmp/article/viewArticle/3005/1881http://www.aapm.org/meetings/amos2/pdf/49-14390-20662-212.pdfhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=7243474880050880667&target=twitterhttp://1.bp.blogspot.com/-CsXnH0iz7uU/T6IflhHek2I/AAAAAAAAAFg/aKWXGbuZT8k/s1600/ABR-stats1.pnghttp://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/search/label/workforcehttp://medphys365.blogspot.com/search/label/ABRhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=7243474880050880667&target=facebookhttp://medphys365.blogspot.com/2012/05/new-medical-physicists-in-us-crunching.htmlhttp://medphys365.blogspot.com/2012/05/many-faces-of-bolus.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=7243474880050880667&target=emailhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=7243474880050880667&target=blog


11/16

"Superflab" vinyl plastic bolus in 5mm and 3mm thicknesses.

Edge view of Superflab sheets.

Wet towels can provide bolus with tissue like properties.
http://2.bp.blogspot.com/-PswfhKbRW04/T6DU3TY1jVI/AAAAAAAAAFA/h2spwnEqucw/s1600/towel.jpghttp://3.bp.blogspot.com/-GjfNvYrC5GY/T6DU4JfhyBI/AAAAAAAAAFI/oXJ9qBu9jRo/s1600/vaseline_gauze.jpghttp://2.bp.blogspot.com/-WCgf2FCzj5c/T6DU1vrT5II/AAAAAAAAAEw/erUUhVDrMBo/s1600/superflab_bolus1.jpghttp://4.bp.blogspot.com/-3Y9W0Jy4Wic/T6DU2aG0tJI/AAAAAAAAAE4/yy-n5lUyyVQ/s1600/superflab_bolus2.jpg


12/16

- Pgina 2 -

Nuggets of knowledge about medical physics.

365 Days of Medical Physics

30 April 2012

Multileaf collimators: modern beam shaping

One of the most important aspects of therapeutic radiation delivery is beam shaping. The most

common technology currently used to shape xray beams is the multileaf collimator or MLC.

Roy

View my complete profile

About Me


About this blog:


IMAT/VMAT basics


Popular Posts
http://www.blogger.com/profile/14293477186383292023http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4469041279844463857&target=bloghttp://medphys365.blogspot.com/http://medphys365.blogspot.com/feeds/posts/defaulthttp://medphys365.blogspot.com/2012/05/comparing-dose-distributions-gamma-test.htmlhttp://medphys365.blogspot.com/2012/04/multileaf-collimators.htmlhttp://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/search?updated-max=2012-05-02T00:50:00-06:00&max-results=7http://www.blogger.com/http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4469041279844463857&target=facebookhttp://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/search?updated-max=2012-05-02T00:50:00-06:00&max-results=7http://medphys365.blogspot.com/2012/04/365-days-of-medical-physics-blogging.htmlhttp://medphys365.blogspot.com/http://medphys365.blogspot.com/2012/05/many-faces-of-bolus.htmlhttp://medphys365.blogspot.com/2012/05/many-faces-of-bolus.html#comment-formhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4469041279844463857&target=pinteresthttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4469041279844463857&target=twitterhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=4469041279844463857&target=emailhttps://en.wikipedia.org/wiki/Petroleum_jellyhttp://medphys365.blogspot.com/http://medphys365.blogspot.com/2012/05/dose-volume-histogram-basics.htmlhttp://medphys365.blogspot.com/search/label/introhttp://1.bp.blogspot.com/-MIhzScisQdI/T6DU01vpfqI/AAAAAAAAAEo/x6r7zhSNyIA/s1600/Brass_chainmail_bolus.jpghttp://medphys365.blogspot.com/search/label/imageshttp://medphys365.blogspot.com/search/label/bolushttp://medphys365.blogspot.com/2012/05/imatvmat-basics.html


13/16

Posted by Roy at 11:59 PM 1 comment:

Labels: intro, MLC, overview

MLC's consist of dozens of independently moving slats, or leaves, which can collimate the beam

into nearly arbitrary shapes. MLC's were first introduced in the 1960's in Japan as a means of

replacing conventional blocks in 3D conformal radiation therapy (3DCRT). Today they are

standard on most therapy linacs and enable modern techniques based on intensity modulation.

Key advantages of MLC's include:

Dynamic movement of leaves during delivery allows for intensity modulated fluencepatterns not achievable with conventional blocks.

Finite set of possible aperture shapes results in a reasonable solution space for inverse

planning optimization for IMRT, VMAT, etc.

Significantly more convenient than cutting custom blocks for every field.

Drawbacks of MLC's include:

Large number of leaves increases possibility of mechanical failure (i.e. reliabili ty

issues).

Nonzero interleaf leakage.

Smoothness of shaping dependent on size of leaves and speed of leaf motors.

Almost everyone can agree that MLC's have been a huge advance in radiation therapy, with the

advantages far outweighing the disadvantages. I plan to discuss MLC alternatives in a future

post.

Image courtesy of Varian Medical Systems, Inc. All rights reserved. (source)

120 leaf multileaf collimator.

29 April 2012

The basics of IMRT: an overview

Intensity modulated radiation therapy(IMRT) is one of the workhorse delivery methods in

current radiation therapy. In many ways, it is a significant step up over the previous standard

technique of 3D conformal radiation therapy (3DCRT). I'm going to start talking about IMRT with

a very basic overview of how it works.

IMRT is a technique to plan and deliver MeV range xray therapy. The main advance with IMRT

over 3DCRT is the algorithmic optimization of dose from all delivery angles at the same time to

meet a predefined set of objectives, socalled inverse planning. This is accomplished by using

multileaf collimators, which can create arbitrary aperture shapes (within reason), thus

modulating the dose to the targets. In turn, this gives the dose optimization algorithm a large

number of parameters to work with to achieve the desired dose shape.



Will Work For Science

Go here!

Twitter @MedPhys365

Subscribe To

Posts

All Comments

bolus (2) cDVH (2)DTA (2) DVH (2)

imrt (2) intro (5)MLC

(2) overview (2) QA

(2) statistics (3)

Labels

2013 (1)

2012 (15)

May(10)

April (5)


The basics of IMRT: an overview

Measurement theory in the clinic

What is medical physics?


Blog Archive
http://medphys365.blogspot.com/2012/04/multileaf-collimators.html#comment-formhttp://medphys365.blogspot.com/search/label/QAhttp://void%280%29/http://medphys365.blogspot.com/search/label/worldhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3487667754892183428&target=twitterhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3487667754892183428&target=facebookhttp://medphys365.blogspot.com/2012/04/multileaf-collimators.htmlhttp://medphys365.blogspot.com/search/label/statisticshttp://medphys365.blogspot.com/search/label/bolushttp://medphys365.blogspot.com/search/label/IMAThttp://medphys365.blogspot.com/search?updated-min=2013-01-01T00:00:00-07:00&updated-max=2014-01-01T00:00:00-07:00&max-results=1http://medphys365.blogspot.com/search/label/medical%20physicshttp://medphys365.blogspot.com/search/label/compensatorhttp://medphys365.blogspot.com/search/label/imageshttp://medphys365.blogspot.com/search/label/bloghttp://medphys365.blogspot.com/search/label/notationhttp://medphys365.blogspot.com/search/label/DVHhttp://void%280%29/http://medphys365.blogspot.com/2012/04/365-days-of-medical-physics-blogging.htmlhttp://varian.mediaroom.com/index.php?s=31899&mode=gallery&cat=2473http://medphys365.blogspot.com/2012/04/multileaf-collimators.htmlhttp://medphys365.blogspot.com/2012/04/measurement-theory-in-clinic.htmlhttp://medphys365.blogspot.com/2012/04/what-is-medical-physics.htmlhttp://medphys365.blogspot.com/search/label/imrthttp://medphys365.blogspot.com/search/label/open%20accesshttp://medphys365.blogspot.com/search/label/MLChttp://medphys365.blogspot.com/2012/04/basics-of-imrt-overview.htmlhttp://medphys365.blogspot.com/search/label/gammahttp://medphys365.blogspot.com/search/label/MLChttp://medphys365.blogspot.com/search/label/VMAThttp://medphys365.blogspot.com/2012/04/basics-of-imrt-overview.htmlhttp://void%280%29/http://medphys365.blogspot.com/search/label/DTAhttp://medphys365.blogspot.com/search/label/measurementhttp://medphys365.blogspot.com/2012/05/many-faces-of-bolus.htmlhttp://medphys365.blogspot.com/search/label/ABRhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3487667754892183428&target=emailhttp://medphys365.blogspot.com/2012_04_01_archive.htmlhttp://medphys365.blogspot.com/2012_05_01_archive.htmlhttp://medphys365.blogspot.com/search/label/introhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3487667754892183428&target=pinteresthttp://medphys365.blogspot.com/search/label/overviewhttp://medphys365.blogspot.com/search?updated-min=2012-01-01T00:00:00-07:00&updated-max=2013-01-01T00:00:00-07:00&max-results=15http://medphys365.blogspot.com/search/label/workforcehttp://medphys365.blogspot.com/search/label/dDVHhttp://medphys365.blogspot.com/2012/04/multileaf-collimators.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3487667754892183428&target=bloghttp://medphys365.blogspot.com/search/label/overviewhttp://medphys365.blogspot.com/search/label/IAEAhttp://medphys365.blogspot.com/search/label/journalshttp://void%280%29/http://medphys365.blogspot.com/search/label/cDVHhttp://1.bp.blogspot.com/-Cmwc3YnXvpk/T59zwC9ZgDI/AAAAAAAAAD0/OFK9sv6cGn8/s1600/MLC+-+gold.jpghttp://medphys365.blogspot.com/search/label/introhttp://www.blogger.com/profile/14293477186383292023http://willworkforscience.blogspot.com/


14/16

Posted by Roy at 11:28 PM 1 comment:

Labels: imrt, intro, overview

Key steps in IMRT planning and delivery:

Acquisition of patient geometry (via CT, MRI, etc).

Delineation of targets and avoidance volumes.

Beam angle and energy selection.

Optimization of fluences to desired prescription

and avoidance objectives.

Assessment of DVH's.

QA via secondary calculations and field measurements.

Further reading:

Bortfeld, IMRT: a review and preview, Phys. Med. Biol. 51 R363,

2006 doi:10.1088/00319155/51/13/R21

KY Cheung, Intensity modulated radiotherapy: advantages, limitations and future

developments, Biomed Imaging Interv J 2006;2(1):e19 (open access)

Top image by TaheriKadkhoda et al. Radiation Oncology 2008 3:4 doi:10.1186/1748717X34 licensed under CC licensing.

Bottom image by ZEEs and licensed under CC licensing.

Diagram of a multileaf collimator.

Measurement theory in the clinicCollecting data is one of the main daytoday activities of the clinical physicist. Examples from

the radiation therapy clinic include PDD's, mechanical alignment parameters, ambient

temperature and pressure, source autoradiographs, IMRT planar dose distributions, setup SSD's,

and CT number data. Patient outcomes, safety, and a host of other issues often rely on the

quality and interpretation of that data.

One thing that sets medical physicists apart from most everyone else in the clinical environment

and is crucial to performing our jobs well is having a strong grasp on the theory of measurement.

Key concepts include: the statistical nature of data, the role of calibration, instrument

resolution, and uncertainty and error propagation.
http://medphys365.blogspot.com/search/label/overviewhttp://medphys365.blogspot.com/2012/04/basics-of-imrt-overview.htmlhttp://www.blogger.com/profile/14293477186383292023http://2.bp.blogspot.com/-xNMyksc2fic/T54mmkbbPuI/AAAAAAAAADo/eqoLJiv25s8/s1600/500px-MLCShape.svg.pnghttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3668171343083972570&target=bloghttp://3.bp.blogspot.com/-pPI5PEkbnqc/T54g3FRMHUI/AAAAAAAAADU/u4N1pw1BBGA/s1600/IMRT-1.jpghttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3668171343083972570&target=twitterhttp://creativecommons.org/licenses/by/2.0/deed.enhttps://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Normal_Distribution_PDF.svg/500px-Normal_Distribution_PDF.svg.pnghttp://medphys365.blogspot.com/search/label/imrthttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3668171343083972570&target=facebookhttp://medphys365.blogspot.com/2012/04/basics-of-imrt-overview.html#comment-formhttp://www.biij.org/2006/1/e19/http://dx.doi.org/10.1088/0031-9155/51/13/R21http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3668171343083972570&target=pinteresthttp://medphys365.blogspot.com/2012/04/measurement-theory-in-clinic.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3668171343083972570&target=emailhttps://creativecommons.org/licenses/by-sa/3.0/deed.enhttp://medphys365.blogspot.com/search/label/intro


15/16


Labels: measurement, statistics

While we may not determine strict error levels for every measurement we make, it's important

to have a grasp of these concepts while collecting and interpreting data.

Why does my IMRT data taken with a planar detector array pass, even though it

"looks" totally different than the TPS generated data? Probably because the detector

array has relatively low resolution and the dose shape you see is the result of

interpolation by software.

Is my data skewed due to systematic or random errors?

Is my new outlier subject to regression to the meanor the start of a new trend?

Are my data groupings producing a Simpson's paradox?

What are your thoughts?

27 April 2012


Labels: medical physics

What is medical physics?

...or this blog has to start somewhere.

If you are reading this blog, you are likely familiar with medical physics, but for my first officialpost I'm going to talk about what medical physics is.

Medical physics is a field of applied science and engineering, in which physicsbased techniques

form the basis of diagnostic and therapeutic medical technologies. The most well known of these

technologies are xray imaging, CT, MRI, ultrasound, and radiation therapy. Many medical

physics technologies utilize ionizing radiation. The potential hazard of ionizing radiation is

arguably the reason why medical physicists exist as clinical personnel, versus solely as

researchers and developers, as is the case with biomedical engineers.

While most broadly medical physics is the application of physics techniques across all of

medicine, the term "medical physics" is generally used to refer to three primary areas: diagnostic

imaging, nuclear medicine (radionuclide based imaging and therapies), and radiation therapy.

The majority of clinical medical physicists work in radiation therapy.

Historically medical physics arose from the application of physics discoveries and technologies to

medicine, most importantly the xray for imaging starting in 1896. As these technologies were

more broadly adopted by hospitals, more physicists and knowledgeable personnel were needed in

clinical settings. Eventually, medical physics specific training emerged and technologies, such as

medical electron linear accelerators, were developed from the ground up with medicine in mind.

Today medical physicists work as clinicians, academic researchers, industry experts, and

educators, or spend their time as any combination of those.

Further reading:

Wikipedia entry on Medical Physics

What do Medical Physicists Do?(AAPM)


Welcome to my new blog!I'm intending to make short posts (nearly) every day for the next year

covering a broad range of medical physics topics.

The idea behind this blog is largely to help motivate me to consistently push my medical physics

knowledge, but also to foster discussion online relevant to others learning medical physics.

I am a medical physicist involved in radiation therapy, so this blog will center on issues related
http://en.wikipedia.org/wiki/Medical_physicshttp://medphys365.blogspot.com/2012/04/what-is-medical-physics.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2496027886433369484&target=bloghttp://en.wikipedia.org/wiki/Simpsons_paradoxhttp://medphys365.blogspot.com/2012/04/measurement-theory-in-clinic.html#comment-formhttp://medphys365.blogspot.com/2012/04/what-is-medical-physics.htmlhttp://medphys365.blogspot.com/search/label/statisticshttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2496027886433369484&target=pinteresthttp://medphys365.blogspot.com/search/label/medical%20physicshttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2496027886433369484&target=facebookhttp://en.wikipedia.org/wiki/Regression_toward_the_meanhttp://www.aapm.org/medical_physicist/default.asphttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2496027886433369484&target=twitterhttp://www.blogger.com/profile/14293477186383292023http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=5521944953745025141&target=pinteresthttp://medphys365.blogspot.com/search/label/measurementhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=5521944953745025141&target=bloghttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=5521944953745025141&target=twitterhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=2496027886433369484&target=emailhttp://medphys365.blogspot.com/2012/04/what-is-medical-physics.html#comment-formhttp://www.blogger.com/profile/14293477186383292023http://medphys365.blogspot.com/2012/04/measurement-theory-in-clinic.htmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=5521944953745025141&target=facebookhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=5521944953745025141&target=emailhttp://medphys365.blogspot.com/2012/04/365-days-of-medical-physics-blogging.html


16/16

Newer Posts Home

Subscribe to: Posts (Atom)


Labels: blog, intro

to clinical radiation therapy physics, but I will also venture into some diagnostic and research

territory. For topics more closely related to my research on particle therapy and computational

medical physics, I will probably post on Will Work for Science, the blog I coauthor will Herr Dr.

Niels Bassler.

I hope you enjoy the posts. Please comment, tell me how awesome this is, correct me, and/or

make topic suggestions!

Travel template. Powered by Blogger.
http://medphys365.blogspot.com/2012/04/365-days-of-medical-physics-blogging.html#comment-formhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3015512373681819482&target=facebookhttp://medphys365.blogspot.com/search/label/introhttp://www.blogger.com/profile/14293477186383292023http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3015512373681819482&target=twitterhttp://medphys365.blogspot.com/2012/04/365-days-of-medical-physics-blogging.htmlhttp://www.blogger.com/http://medphys365.blogspot.com/search/label/bloghttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3015512373681819482&target=pinteresthttp://medphys365.blogspot.com/feeds/posts/defaulthttp://users-phys.au.dk/bassler/index.shtmlhttp://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3015512373681819482&target=emailhttp://willworkforscience.blogspot.com/http://medphys365.blogspot.com/http://www.blogger.com/share-post.g?blogID=5277658315766141584&postID=3015512373681819482&target=bloghttp://medphys365.blogspot.com/search?updated-max=2012-05-17T23:54:00-06:00&max-results=7&reverse-paginate=true

365 days of medical physics_ may 2012

Documents