k. pallav kolli, ms4 gillian lieberman, md magnetic resonance … › learninglab › gastro ›...

Magnetic Resonance Magnetic Resonance Imaging in Imaging in

Characterizing Patterns Characterizing Patterns of Iron Depositionof Iron Deposition

K. K. PallavPallav

KolliKolli, MS4, NUFSOM, MS4, NUFSOMBeth Israel Deaconess Medical CenterBeth Israel Deaconess Medical Center

K. Pallav Kolli, MS4Gillian Lieberman, MD


The interesting case…The interesting case…

GRE T1W out-

of-phase image

GRE T1W in-

phase image

Images from PACS, BIDMC

Normal

Requisition: 47 yearRequisition: 47 year--old woman with elevated old woman with elevated LFTsLFTsOur Patient



GRE T1W out-

of-phase image

GRE T1W in-

phase image


NormalRequisition: 47 yearRequisition: 47 year--old woman with elevated old woman with elevated LFTsLFTs

Our Patient↓

signal intensity of liver compared to skeletal muscle

↓


↑


↑




GRE T1W out-

of-phase image

GRE T1W in-

phase image


NormalRequisition: 47 yearRequisition: 47 year--old woman with elevated old woman with elevated LFTsLFTs

Our Patient

↓

signal intensity on bottom image compared to top image

↔ signal intensity on bottom image compared to top image


Based on the findings, the radiologists noted iron Based on the findings, the radiologists noted iron deposition in the liver, spleen, bone marrow, and deposition in the liver, spleen, bone marrow, and pancreas.pancreas.

They further characterized the likely etiology of this iron They further characterized the likely etiology of this iron deposition and its clinical implications.deposition and its clinical implications.

How?How?

The MotivationThe Motivation



ObjectivesObjectives

1.1. Principles of magnetic resonance Principles of magnetic resonance imaging for medical studentsimaging for medical students

2.2. Patterns of iron deposition seen on Patterns of iron deposition seen on MR imagingMR imaging


Principles of MRIPrinciples of MRI““Hydrogen imaging” Hydrogen imaging” →→ H proton as a magnetH proton as a magnet

An electric current flowing in a loop will produce a magnetic field perpendicular to the loop

Similarly, a spinning hydrogen atom proton acts like a tiny magnet

Images from Pooley

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Why Hydrogen?Why Hydrogen?

Any atom with an odd number of protons or Any atom with an odd number of protons or neutrons has a net magnetic moment and neutrons has a net magnetic moment and behaves like a bar magnet. behaves like a bar magnet.

Hydrogen:Hydrogen:1. Is abundant in biologic tissue1. Is abundant in biologic tissue2. Has high sensitivity for its MR signal due to its 2. Has high sensitivity for its MR signal due to its

high resonance frequencyhigh resonance frequency


Tissue Magnetization, MTissue Magnetization, M

A small excess of protons go into the spinA small excess of protons go into the spin--up up alignment, so that the tissue placed under Balignment, so that the tissue placed under Boo has has a small net magnetic field (M) aligned with Ba small net magnetic field (M) aligned with Boo

M

Adapted from Pooley

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PrecessionPrecessionPrecessionPrecession

Frequency of precession (Frequency of precession (LarmorLarmor frequencyfrequency):):

Like a spinning top under a gravitational field, a spinning hydrogen proton under a magnetic field will also wobble, or precess, about its axis

The frequency of that precession is related to an intrinsic property ofthe proton, the gyromagnetic

ratio, and the strength of the applied magnetic field, Bo.

Images from Pooley

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Radiofrequency PulseRadiofrequency Pulse

Magnetic resonanceMagnetic resonanceMagnetic resonance is defined as the Magnetic resonance is defined as the enhanced absorption enhanced absorption of energyof energy that occurs when that occurs when radiofrequency (RF) energy is radiofrequency (RF) energy is applied at the applied at the LarmorLarmor frequencyfrequency to nuclei of atoms within to nuclei of atoms within an external magnetic field an external magnetic field

Absorption of RF energy causes the net magnetization of Absorption of RF energy causes the net magnetization of tissue, M, to rotate away from alignment with Btissue, M, to rotate away from alignment with Boo towards the towards the transverse plane:transverse plane: RF Pulse

M

Adapted from Pooley

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MR SignalMR Signal

MR SignalMR SignalM has been rotated into the transverse plane with the M has been rotated into the transverse plane with the application of RF energy, but it continues to application of RF energy, but it continues to precessprecess at its at its LarmorLarmor frequencyfrequency

After the RF pulse perturbs M, the tissue relaxes back to After the RF pulse perturbs M, the tissue relaxes back to equilibrium. As it does so, it equilibrium. As it does so, it retransmits the energy it retransmits the energy it gained from the RF pulse in the form of the MR signalgained from the RF pulse in the form of the MR signal. . This signal decreases as the tissue relaxes to its equilibrium. This signal decreases as the tissue relaxes to its equilibrium.


The ‘Skinny on MRI’The ‘Skinny on MRI’

The bar magnetThe bar magnet--like features of the proton can be like features of the proton can be exploitedexploited

The external magnetic field (1.5T, 3.0T, etc) sets up a The external magnetic field (1.5T, 3.0T, etc) sets up a condition favorable for energy exchangecondition favorable for energy exchange

We can apply energy with a radiofrequency (RF) pulse We can apply energy with a radiofrequency (RF) pulse and record the energy given off from relaxation as a and record the energy given off from relaxation as a signal intensitysignal intensity

Image Contrast → Differences in Tissue RelaxationImage Contrast → Differences in Tissue Relaxation


Relaxation from a Perturbed StateRelaxation from a Perturbed StateTissue magnetization (M) relaxes to equilibrium (the Tissue magnetization (M) relaxes to equilibrium (the state imposed by the external magnetic field)state imposed by the external magnetic field)

This relaxation occurs as two simultaneous This relaxation occurs as two simultaneous mechanisms:mechanisms:

TT11 relaxationrelaxation (spin(spin--lattice relaxation) lattice relaxation) TT22 relaxationrelaxation (spin(spin--spin relaxation)spin relaxation)

How quickly a given tissue relaxes by each mechanism How quickly a given tissue relaxes by each mechanism is an intrinsic property, i.e. fat relaxes differently than is an intrinsic property, i.e. fat relaxes differently than water…water…


T1 RelaxationT1 RelaxationAfter a 90º RF pulse, M is completely in the transverse After a 90º RF pulse, M is completely in the transverse plane and the longitudinal magnetization is zeroplane and the longitudinal magnetization is zero

The longitudinal magnetization then grows back, The longitudinal magnetization then grows back, known as the known as the TT11 relaxationrelaxation

Image from Pooley

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T1 RelaxationT1 RelaxationThe time it takes for a tissue to regain 63% of its final The time it takes for a tissue to regain 63% of its final value is T1.value is T1.

Each tissue undergoes T1 relaxation at its own rateEach tissue undergoes T1 relaxation at its own rate

Images from Pooley

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T1 Relaxation and Image SequencesT1 Relaxation and Image Sequences

Time to Repetition (TR)Time to Repetition (TR)In imaging sequences, RF pulses are repeated, and the time In imaging sequences, RF pulses are repeated, and the time between RF pulses is designated the between RF pulses is designated the time to repetition (TR)time to repetition (TR)

TR, T1, and EquilibriumTR, T1, and EquilibriumEventually, an equilibrium longitudinal magnetization is reachedEventually, an equilibrium longitudinal magnetization is reachedbetween TR and T1 relaxation. between TR and T1 relaxation. At short At short TRsTRs, tissues with short , tissues with short T1s have increased equilibrium longitudinal magnetization T1s have increased equilibrium longitudinal magnetization compared to tissues with long T1scompared to tissues with long T1s


T1 Weighted ImagesT1 Weighted ImagesDifferences between tissues are accentuated at Differences between tissues are accentuated at short TR times. short TR times.

Therefore, imaging sequences with relatively short Therefore, imaging sequences with relatively short TRsTRs will emphasize T1 contrast. will emphasize T1 contrast. Hence, these are Hence, these are termed T1termed T1--weighted images.weighted images.

TR

Adapted fromPooley

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T1 Relaxation and MR SignalT1 Relaxation and MR SignalMR signal increases with increased longitudinal MR signal increases with increased longitudinal magnetizationmagnetization

Short T1 (fat) Short T1 (fat) ↑ Long. Magnetization ↑ Signal↑ Long. Magnetization ↑ Signal

Long T1 (spleen) ↓ Long. Magnetization ↓ Signal Long T1 (spleen) ↓ Long. Magnetization ↓ Signal


T2 RelaxationT2 Relaxation

During the application of a 90During the application of a 90ºº RF pulse, all the RF pulse, all the protons protons precessprecess synchronously (“in phase”)synchronously (“in phase”)

Immediately following the RF pulse, the protons begin Immediately following the RF pulse, the protons begin to desynchronize, or “to desynchronize, or “dephasedephase””

The main cause of The main cause of dephasingdephasing is spinis spin--spin interactions: spin interactions: the precession frequency of a single proton is related to the precession frequency of a single proton is related to the magnetic field it sees. When two protons come the magnetic field it sees. When two protons come close to each other, they each are affected by Bclose to each other, they each are affected by B00 AND AND the other proton’s magnetic fieldthe other proton’s magnetic field


T2 RelaxationT2 RelaxationDuring the time the two protons are close to each During the time the two protons are close to each other, other, one proton one proton precessesprecesses at a higher frequency at a higher frequency and the other at a slower frequencyand the other at a slower frequency

When the protons move apart, they only see BWhen the protons move apart, they only see Boo and and resume precession at the resume precession at the LarmorLarmor frequencyfrequency

But, because they spent some time spinning at But, because they spent some time spinning at different frequencies, they’re no longer different frequencies, they’re no longer synchronized, or in phasesynchronized, or in phase


T2 RelaxationT2 RelaxationAs time passes, these interactions cause more and more As time passes, these interactions cause more and more protons to be out of phase with each otherprotons to be out of phase with each other

After T2 relaxation, the tissue transverse magnetic field After T2 relaxation, the tissue transverse magnetic field decays as fewer and fewer of the tiny magnets are lined decays as fewer and fewer of the tiny magnets are lined up togetherup together

Image from Pooley

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T2 Relaxation T2 Relaxation ––

A decay processA decay processA tissue’s T2 is the time it takes a tissue to decrease its A tissue’s T2 is the time it takes a tissue to decrease its transverse magnetization to 37% of initial value transverse magnetization to 37% of initial value due to spindue to spin--spin interactionspin interaction

Each tissue undergoes T2 relaxation at its own rateEach tissue undergoes T2 relaxation at its own rate

Images from Pooley

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T2T2--weighted Imagesweighted ImagesTime to EchoTime to Echo

The time between the middle of the RF pulse and when the The time between the middle of the RF pulse and when the MR signal is recorded is designated the MR signal is recorded is designated the time to echo (TE)time to echo (TE)

Greatest difference in tissues’ T2 values:Greatest difference in tissues’ T2 values:

Therefore, Therefore, imaging sequences that have a relatively imaging sequences that have a relatively long TE are T2long TE are T2--weighted imagesweighted images

Image adapted from Pooley

RA1


T2 Relaxation and MR SignalT2 Relaxation and MR SignalMR signal is maximized when transverse MR signal is maximized when transverse magnetization is completely in phasemagnetization is completely in phase

Long T2 (CSF) Long T2 (CSF) ↑ Trans. Magnetization ↑ Signal↑ Trans. Magnetization ↑ Signal

Short T1 (Liver) ↓ Trans. Magnetization ↓ SignalShort T1 (Liver) ↓ Trans. Magnetization ↓ Signal


T2* RelaxationT2* RelaxationDephasingDephasing occurs due to individual protons “seeing” occurs due to individual protons “seeing” different magnetic fieldsdifferent magnetic fields

There are other reasons for individual protons to There are other reasons for individual protons to “see” different magnetic fields from each other:“see” different magnetic fields from each other:

1.1.

External magnetic field (BExternal magnetic field (Boo

) ) inhomogeneitiesinhomogeneities2.2.

Magnetic susceptibility (to be discussed)Magnetic susceptibility (to be discussed)3.3.

Chemical shift effects (for another day’s discussion)Chemical shift effects (for another day’s discussion)

T2*T2* is the time it takes for a tissue’s transverse is the time it takes for a tissue’s transverse magnetization to decrease to 37% of its starting value magnetization to decrease to 37% of its starting value due due to all effects = T2 + additional to all effects = T2 + additional dephasingdephasing

effectseffects


Correcting for T2Correcting for T2**

with Spinwith Spin--EchoEchoSpinSpin--spin spin dephasingdephasing is a random process having to do with protonis a random process having to do with proton--proton interactionsproton interactions

The other causes of T2* The other causes of T2* dephasingdephasing are due to differences in local are due to differences in local magnetic fields that magnetic fields that remain constant over timeremain constant over time

When a 180 RF pulse is applied halfway between the initial RF puWhen a 180 RF pulse is applied halfway between the initial RF pulse lse and the TE, the and the TE, the dephasingdephasing due to fixed due to fixed inhomogeneitiesinhomogeneities becomes becomes rephasingrephasing!!

Images from Pooley

RA1


T2* T2* DephasingDephasing

A pulse sequence = strategy used to create an MR A pulse sequence = strategy used to create an MR imageimage

There are other types of pulse sequences, the discussion There are other types of pulse sequences, the discussion of which is beyond the scope of this presentationof which is beyond the scope of this presentation

It should be noted, though, that It should be noted, though, that GradientGradient--Recalled Recalled Echo (GRE) pulse sequences, often used to Echo (GRE) pulse sequences, often used to decrease imaging time, do not use a refocusing RF decrease imaging time, do not use a refocusing RF pulse and therefore bring out T2*pulse and therefore bring out T2*--weighted weighted featuresfeatures


Putting T1, T2, TR, and TE TogetherPutting T1, T2, TR, and TE Together

T1 and T2 relaxation occur simultaneouslyT1 and T2 relaxation occur simultaneouslyT1 and T2 relaxation properties are specific to tissue T1 and T2 relaxation properties are specific to tissue typetype

T1W images: short TR, short TE (short T1 = bright)T1W images: short TR, short TE (short T1 = bright)

T2W images: long TR, long TE (long T2 = bright)T2W images: long TR, long TE (long T2 = bright)

Mz

TR

T1

Mxy

TE

T2 Relax Fast

Relax Slow


Magnetic SusceptibilityMagnetic Susceptibility

Magnetic susceptibility is the tendency of a substance to Magnetic susceptibility is the tendency of a substance to attract or repel magnetic lines of forceattract or repel magnetic lines of force

Diamagnetic Diamagnetic substances weakly repel magnetic lines of forcesubstances weakly repel magnetic lines of force

Paramagnetic Paramagnetic substances attract magnetic lines of forcesubstances attract magnetic lines of force

SuperparamagneticSuperparamagnetic substances strongly attract magnetic substances strongly attract magnetic lines of forcelines of force

Ferromagnetic Ferromagnetic substances remain permanently magnetized substances remain permanently magnetized after being removed from a magnetic fieldafter being removed from a magnetic field


Variations in magnetic susceptibility create magnetic Variations in magnetic susceptibility create magnetic field field inhomogeneitiesinhomogeneities, which in turn produce , which in turn produce dephasingdephasing and MR signal lossand MR signal loss

This signal loss is most pronounced on images with This signal loss is most pronounced on images with T2*T2*--weighting weighting

GradientGradient--recalled echo images are more sensitive to recalled echo images are more sensitive to magnetic susceptibility than spinmagnetic susceptibility than spin--echo imagesecho images

Magnetic Susceptibility and IronMagnetic Susceptibility and Iron


Iron in tissue Iron in tissue creates strong local magnetic field creates strong local magnetic field inhomogeneitiesinhomogeneities that that ↓↓ MR signalMR signal

In each of the ensuing cases, we will look at the In each of the ensuing cases, we will look at the difference in difference in signal intensitysignal intensity in ironin iron--laden tissues between two images laden tissues between two images created with gradientcreated with gradient--recalled echo (GRE) technique: recalled echo (GRE) technique: T1T1--W W ININ--PHASE (IP) and OUTPHASE (IP) and OUT--OFOF--PHASE (OP) imagesPHASE (OP) images

The IPThe IP--OP sequence has 2 echo times OP sequence has 2 echo times –– the longer the TE, the the longer the TE, the greater time allowed for greater time allowed for dephasingdephasing, hence signal loss., hence signal loss.

Deposition of iron => loss of signal in tissue on IP (longer Deposition of iron => loss of signal in tissue on IP (longer echo) images compared to OP imagesecho) images compared to OP images



The characteristic findings of tissue iron The characteristic findings of tissue iron depositondepositon described in the literature:described in the literature:

1.1.

Decreased signal intensity on T2WI and Decreased signal intensity on T2WI and T2*WI’sT2*WI’s

2.2.

For normal liver, signal intensity should be > For normal liver, signal intensity should be > skeletal muscle on ALL sequencesskeletal muscle on ALL sequences

3.3.

If iron deposition is great enough, decreased If iron deposition is great enough, decreased signal intensity on T1WI’s signal intensity on T1WI’s



ReticuloendothelialReticuloendothelialTransfusion or Transfusion or extravascularextravascular hemolysishemolysis

ParenchymalParenchymalPrimary and secondary Primary and secondary hemochromatosishemochromatosisIntravascular Intravascular hemolysishemolysis

Cirrhosis Cirrhosis SideroticSiderotic nodulesnodules

Patterns of Iron DepositionPatterns of Iron Deposition


Iron MetabolismIron Metabolism

Image from Andrews NC3


ReticuloendothelialReticuloendothelial macrophages in spleen and bone marrow and macrophages in spleen and bone marrow and KupfferKupffer cells of liver scavenge iron from senescent cells of liver scavenge iron from senescent RBCsRBCs

The body has no effective mechanism for losing excess ironThe body has no effective mechanism for losing excess iron

With repeated transfusions or With repeated transfusions or rhabdomyolysisrhabdomyolysis, iron deposits in , iron deposits in the spleen, liver, and bone marrowthe spleen, liver, and bone marrow

Iron deposition limited to the RE system has little clinical Iron deposition limited to the RE system has little clinical significancesignificance

ReticuloendothelialReticuloendothelial

Iron DepositionIron Deposition




28 28 yoyo

M with Hodgkin’s M with Hodgkin’s DzDz

s/ps/p

multiple chemotherapy regimens and BM transplantsmultiple chemotherapy regimens and BM transplants

GRE T1W out-

of-phase images

GRE T1W in-

phase images





28 28 yoyo

M with Hodgkin’s M with Hodgkin’s DzDz

s/ps/p

multiple chemotherapy regimens and BM transplantsmultiple chemotherapy regimens and BM transplants

GRE T1W out-

of-phase images

GRE T1W in-

phase images


↓

signal intensity in liver, spleen, and bone marrow on IP images compared to OP images


When the storage capacity of the RE system is reached, When the storage capacity of the RE system is reached, redistribution of iron to organ parenchyma (cardiac, redistribution of iron to organ parenchyma (cardiac, hepatic, endocrine tissues) is seenhepatic, endocrine tissues) is seen

RE capacity estimated at 10 g iron (~40 units of RE capacity estimated at 10 g iron (~40 units of PRBCsPRBCs))

Organ dysfunction and fibrosis as seen with Organ dysfunction and fibrosis as seen with hemochromatosishemochromatosis can then be seen (to be discussed)can then be seen (to be discussed)

Treatment is phlebotomy (often not clinically tolerated Treatment is phlebotomy (often not clinically tolerated in these patients) or in these patients) or chelationchelation therapytherapy

RE Iron Deposition RE Iron Deposition w/Parenchymalw/Parenchymal RedistributionRedistribution



GRE T1W out-

of-phase images

GRE T1W in-

phase images

47 yo

F with h/o

aplastic

anemia s/p

transfusion > 75 units PRBCs

in 3 yearsImages from PACS, BIDMC



GRE T1W out-

of-phase images

GRE T1W in-

phase images

47 yo

F with h/o

aplastic

anemia s/p

transfusion > 75 units PRBCs

in 3 yearsImages from PACS, BIDMC

↓

signal intensity in liver, spleen, bone marrow, and pancreas on IP images compared to OP images


HemochromatosisHemochromatosis

Intravascular Intravascular hemolysishemolysis

ParenchymalParenchymal



AutosomalAutosomal recessive disease wherein 2recessive disease wherein 2--3x normal amount of 3x normal amount of iron is absorbed from GI tractiron is absorbed from GI tract

Iron deposition in liver first, then heart and endocrine organs:Iron deposition in liver first, then heart and endocrine organs:Cirrhosis and Cirrhosis and hepatocellularhepatocellular carcinomacarcinomaCardiomyopathyCardiomyopathyDM, DM, hypopituitarismhypopituitarism, , hypogonadismhypogonadism, , hypoparathyroidismhypoparathyroidismCan also see destructive arthritisCan also see destructive arthritis

Most patients asymptomatic until adulthoodMost patients asymptomatic until adulthood

Primary Primary HemochromatosisHemochromatosis


Primary Primary HemochromatosisHemochromatosisDiagnosisDiagnosis

Biochemical evidence of iron overload (serum, liver Biochemical evidence of iron overload (serum, liver bxbx))Genetic testingGenetic testing

QuantificationQuantificationLiver biopsy remains gold standardLiver biopsy remains gold standard

TreatmentTreatmentPhlebotomy or Phlebotomy or chelatechelate txtx once serum once serum ferritinferritin levels reach a levels reach a designated thresholddesignated thresholdIf treated before organ damage, life expectancy is normal. If treated before organ damage, life expectancy is normal. Endocrine abnormalities and cirrhosis DO NOT resolve.Endocrine abnormalities and cirrhosis DO NOT resolve.



Iron DepositionIron Deposition Primary Primary HemochromatosisHemochromatosis

GRE T1W out-

of-phase image

GRE T1W in-

phase image

41 yo

F with incidentally noted elevated serum ferritin

and transferrin

saturation. Sub-sequent genetic testing provedpositive for C282Y homo-zygosity.




Iron DepositionIron Deposition Primary Primary HemochromatosisHemochromatosis

GRE T1W out-

of-phase image

GRE T1W in-

phase image

41 yo

F with incidentally noted elevated serum ferritin

and transferrin

saturation. Sub-sequent genetic testing provedpositive for C282Y homo-zygosity.


↓

signal intensity in liver on IP images compared to OP images

↔ or ↑ signal intensity in bone marrow, pancreas, and spleen on IP images compared to OP images



This patient’s disease has been caught early: This patient’s disease has been caught early: there is only evidence of iron deposition in the there is only evidence of iron deposition in the liver.liver.

This has prognostic significance!This has prognostic significance!


PrecirrhoticPrecirrhotic vs. Cirrhotic Primary vs. Cirrhotic Primary HemochromatosisHemochromatosis((SiegelmanSiegelman et al.)et al.)88

Almost ALL pts with PH and cirrhosis had decreased Almost ALL pts with PH and cirrhosis had decreased signal intensity in the pancreas (10/11)signal intensity in the pancreas (10/11)

ALL pts with PH and without cirrhosis had normal signal ALL pts with PH and without cirrhosis had normal signal intensity in the pancreas (4/4)intensity in the pancreas (4/4)

In ALL pts with cirrhosis not secondary to PH, signal In ALL pts with cirrhosis not secondary to PH, signal intensity in the pancreas was normal (4/4)intensity in the pancreas was normal (4/4)



Secondary Secondary HemochromatosisHemochromatosis

Seen in diseases with ineffective Seen in diseases with ineffective erythropoiesiserythropoiesisThalassemiaThalassemia major, major, sideroblasticsideroblastic anemia, anemia, megaloblasticmegaloblastic anemiaanemia

Spleen and/or bone marrowSpleen and/or bone marrow may or may not may or may not be involved in secondary be involved in secondary hemochromatosishemochromatosis

(muddies the (muddies the

waters of characterizing waters of characterizing parenchymalparenchymal

vs. vs. reticuloendothelialreticuloendothelial iron deposition)iron deposition)


Free hemoglobin binds to Free hemoglobin binds to haptoglobinhaptoglobin and is taken up and is taken up by by hepatocyteshepatocytes

When When haptoglobinhaptoglobin is saturated, free hemoglobin is is saturated, free hemoglobin is filtered by filtered by glomerulusglomerulus and reabsorbed into proximal and reabsorbed into proximal convoluted tubule cellsconvoluted tubule cells

MR: iron deposition in MR: iron deposition in liver +/liver +/-- kidneyskidneys

No known clinical significance of depositionNo known clinical significance of deposition

Intravascular Intravascular HemolysisHemolysis


Common chronic endCommon chronic end--stage liver disease for stage liver disease for variety of hepatic insultsvariety of hepatic insults

Diffuse architectural disorganization with Diffuse architectural disorganization with fibrosis and formation of regenerative nodulesfibrosis and formation of regenerative nodules

MR: preferential atrophy of R lobe with hypertrophy of caudate aMR: preferential atrophy of R lobe with hypertrophy of caudate and nd lateral segments of L lobe, nodular texture, low signallateral segments of L lobe, nodular texture, low signal--intensity nodule, intensity nodule, sequelaesequelae of portal HTNof portal HTN

CirrhosisCirrhosis


Diffuse Diffuse hepatocytehepatocyte iron deposition may be seeniron deposition may be seenMild elevation, seen in up to 50% of cirrhotic livers Mild elevation, seen in up to 50% of cirrhotic livers

SideroticSiderotic regenerating nodulesregenerating nodules~25% of regenerative nodules accumulate iron > ~25% of regenerative nodules accumulate iron >

surrounding parenchymasurrounding parenchymaSomewhat specific for cirrhosisSomewhat specific for cirrhosis

GammaGamma--Gandy bodies (Gandy bodies (sideroticsiderotic nodules) in spleennodules) in spleenPresent in up to 12% of Present in up to 12% of cirrhoticscirrhoticsProvides indirect evidence of portal HTNProvides indirect evidence of portal HTN

Cirrhotic Iron DepositionCirrhotic Iron Deposition



GRE T1W out-

of-phase image

GRE T1W in-

phase image

51 yo

M with h/o

alcoholic cirrhosis




GRE T1W out-

of-phase image

GRE T1W in-

phase image

51 yo

M with h/o

alcoholic cirrhosis


↓

signal intensity in liver on IP images compared to OP images

↓

signal intensity in regenerative nodules compared to surrounding parenchyma

Gamma-Gandy body in spleen


Future Utility for MRI in Iron Future Utility for MRI in Iron Deposition Deposition

MRI may be useful for more than just MRI may be useful for more than just characterizing the pattern of iron depositioncharacterizing the pattern of iron deposition

Much research currently focuses on using MRI Much research currently focuses on using MRI to quantify the degree of iron depositionto quantify the degree of iron deposition


Serum Serum ferritinferritin stores have poor specificity for stores have poor specificity for body iron storesbody iron stores

Liver biopsy is often used to establish and Liver biopsy is often used to establish and quantify biochemical evidence of iron overloadquantify biochemical evidence of iron overload

MR Quantification of Hepatic Iron MR Quantification of Hepatic Iron Stores? Stores? ((GandonGandon

Y et al)Y et al)99


Algorithm based on ratio of signal intensities of liver to Algorithm based on ratio of signal intensities of liver to skeletal muscle on GRE sequences obtained with 1.5T skeletal muscle on GRE sequences obtained with 1.5T magnetmagnet

89% sensitive in detecting clinically relevant hepatic 89% sensitive in detecting clinically relevant hepatic iron (> 60 µmol/g, normal is < 36 µmol/g) with good iron (> 60 µmol/g, normal is < 36 µmol/g) with good correlation with tissue quantification from liver correlation with tissue quantification from liver bxbx

AdvantagesAdvantagesNoninvasive, eliminates risk of Noninvasive, eliminates risk of bxbx w/inadequate tissue, may w/inadequate tissue, may provide better estimate than biopsy of cirrhotic, provide better estimate than biopsy of cirrhotic, heterogeneous liver, less expensive than heterogeneous liver, less expensive than bxbx

MR Quantification of Hepatic Iron MR Quantification of Hepatic Iron Stores? Stores? ((GandonGandon

Y et al)Y et al)99


Principles of MRIPrinciples of MRIHydrogen imagingHydrogen imagingT1 RelaxationT1 RelaxationT2 and T2T2 and T2** RelaxationRelaxation

MR Characterization of Patterns of Iron DepositionMR Characterization of Patterns of Iron DepositionReticuloendothelialReticuloendothelialParenchymalParenchymalCirrhoticCirrhotic

MR Quantification of Iron DepositionMR Quantification of Iron Deposition

ConclusionsConclusions


Dr. Neil M. Dr. Neil M. RofskyRofsky and Dr. Karen Leeand Dr. Karen LeeDrs. Darren Brennan, Mike Schuster, Marty Drs. Darren Brennan, Mike Schuster, Marty Smith, and Eric SteinSmith, and Eric SteinDr. Gillian Lieberman and Pamela Dr. Gillian Lieberman and Pamela LepkowskiLepkowskiPaul Paul GiganteGigante, Carolynn , Carolynn DeBenedictisDeBenedictis, , SejalSejalPatel, and Patel, and ArghavanArghavan SallesSalles

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k. pallav kolli, ms4 gillian lieberman, md magnetic resonance … › learninglab › gastro ›...

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