ch 8 mammography 2015 - ucsd radiology...
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MammographyT.R. Nelson, Ph.D.
x41433tnelson@ucsd.edu
Radiology Physics Lectures: Mammography - 2015
• 2005 (in US) Women Men
• Invasive Breast Cancer Diagnosed 211,240 1,690• Noninvasive Breast Cancer Diagnosed 58,940 • Deaths from Breast Cancer 40,410 460
Radiology Physics Lectures: Mammography
Background and Perspective
• Breast Cancer is the most common form of cancer among women other than skin cancer
• Breast Cancer is the second leading cause of cancer death in women after lung cancer
• A woman's chance of developing breast cancer increases significantly with age.
• A woman's chance of developing breast cancer sometime in her lifetime is approximately 1 in 7
• The chance that breast cancer will be responsible for a woman's death is about 1 in 33
• If detected in the earliest stages, the five-year survival rate for breast cancer is 98%.
Radiology Physics Lectures: Mammography
Background and Perspective
Radiology Physics Lectures: Mammography
Mammography Evolution• Introduced in the early 1950’s– little medical benefit – poor image quality• Xerography introduced in 70’s and 80’s– high dose– good resolution and edge enhancement– poor contrast sensitivity• ACR mammography accreditation program– started mid 80’s– improved quality control– improved dosimetry• Mammography Quality Standards Act (MQSA)– passed in 1992
Radiology Physics Lectures: Mammography
Mammography Evolution
• Ultrasound• Cyst / solid differentiation• Biopsy guidance• Operator dependent
• MRI• High contrast sensitivity• Visualize silicone implants• Breast cancer staging• Generally requires contrast
• Thermography• Infrared imaging
Radiology Physics Lectures: Mammography
Complementary Imaging Technology
Radiology Physics Lectures: Mammography
State-of-the-Art - Full Field Digital Mammography• X-ray mammography is current “gold
standard”
• Cancer identification– High contrast between normal and cancer
tissues– Detects calcifications
Radiology Physics Lectures: Mammography
Radiology Physics Lectures: Mammography
Soft Tissue Contrast - Breast
Contrast =(Gland -Cancer)
Glandx100
Radiology Physics Lectures: Mammography
Mammography Equipment
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
ABDC
Radiology Physics Lectures: Mammography
Mammography Equipment - X-ray Tube Design• Anode
– Molybdenum– Rhodium– Tungsten
• Characteristic radiation– Molybdenum - 17.5, 19.6 keV– Rhodium - 20.2, 22.7 keV
• Anode– Angle determines field-of-view– Cathode over chest wall– Anode over nipple– Grounded to reduce space charge
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - X-ray Tube Design
Radiology Physics Lectures: Mammography
Mammography Equipment - Anode - Cathode Axis
Radiology Physics Lectures: Mammography
Mammography Equipment - Focal Spots
• Small focal spots– Reduce blurring– High magnification
• Size depends on use– 0.3 - 0.4 mm for contact imaging– 0.1 - 0.15 mm for magnification imaging
• Size depends on SID– 0.4 mm for SID > 66 cm– 0.3 mm for SID < 65 cm
• Size varies with position in field
Radiology Physics Lectures: Mammography
Mammography Equipment - Focal Spot Size Variation
Radiology Physics Lectures: Mammography
Mammography Equipment - Focal Spot Size Variation
Focal spot size estimated with slit camera or pinhole camera.Effective resolution measured with bar pattern (up to 20 lp/mm).
Measurement incorporates contribution of all components (i.e. image receptor, focal spot, tube motion, etc.)
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - Beam Quality
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - Filtration
X-ray Beam Filtration:Inherent: ~1 mm Be
Added: Mo, Rh eliminates low (and high) energy x-rays
Radiology Physics Lectures: Mammography
Mammography Equipment - Filtration
Radiology Physics Lectures: Mammography
Mammography Equipment - Filtration
Radiology Physics Lectures: Mammography
Mammography Equipment - Filtration
Radiology Physics Lectures: Mammography
Tungsten (W) characteristic x-rays from L shell
Mammography Equipment - Filtration
Radiology Physics Lectures: Mammography
Mammography Equipment - Filtration
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - HVL
• Half-value Layer (HVL)– Reflects beam “hardness”– How much soft radiation is present in beam• Small HVL - too much soft radiation
– Dose without information• Large HVL - more penetrating beam
– Aged or pitted anode– Too much filtration
– Depends on• Inherent filtration• Added filtration• Compression paddle composition
Radiology Physics Lectures: Mammography
Mammography Equipment - HVL
Radiology Physics Lectures: Mammography
Mammography Equipment - HVL
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - Tube Output
Must have at least 7.0 mGy/sec at 28 kVp in Mo/Mo mode
to meet MQSA
Radiology Physics Lectures: Mammography
Mammography Equipment - Collimation
Light - x-ray field congruence to <1% for any edge and <
2% overall
Must extend to chest wall
Radiology Physics Lectures: Mammography
Mammography Equipment - Collimation
Radiology Physics Lectures: Mammography
Mammography Equipment - Exposure Control
• Automatic Exposure Control– Uses sensor to monitor exposure– Shuts off at pre-determined amount of radiation– Compensates for breast thickness and density• May use short (< 100 ms) pre-exposure to set technique
– Designed to produce optimum and consistent density
– Adjustments to increase/decrease density– Includes a backup timer
Radiology Physics Lectures: Mammography
Mammography Equipment - Exposure Control
Radiology Physics Lectures: Mammography
Mammography Equipment - Technique Chart
Radiology Physics Lectures: Mammography
Mammography Equipment - Compression
Improves image quality, reduces motion, decreases thickness, decreases blurring, lowers radiation dose
Radiology Physics Lectures: Mammography
Mammography Equipment - Compression
Radiology Physics Lectures: Mammography
Mammography Equipment - Compression
Spreads tissue over localized area
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - Scatter - Primary Ratio
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - Anti-scatter Grids
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
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Radiology Physics Lectures: Mammography - Magnification
• MTF of the focal spot decreases with increasing magnification• MTF of the detector increases with magnification• Optimum magnification depends on both focal spot MTF and
detector MTF• Geometric magnification derives no resolution improvement
from large focal spot - focal spot blur dominates• Geometric magnification shows resolution improvement when
detector has large detector pixels sizes - smaller effective pixel size
The focal spot MTF degraded with magnification while the detector MTF improved with magnification. Representa- tive results shown in Fig. 1 demonstrate that the improvement of the
MTF depended on the tradeoff between focal spot size and pixel size. A large focal spot (0.6 mm) resulted in little or no resolution improvement with the use of geometric magnification. Since the
focal spot blur dominated the system sharpness, reducing the effective pixel size did not compensate for the loss of resolution. A focal spot of 0.3 mm and pixel sizes of 50, 100, and 150
um showed an improvement in resolution for lower frequencies but not for higher frequencies suggesting a task dependent tradeoff for this combination (i.e., depending on the characteristics of the features that need to be imaged, different parameters may be optimal). A 0.3 mm focal
spot with a 200 um pixel size showed an improved MTF for all magnification values although there was an optimum magnification. Magnification with a 0.1 mm focal spot resulted in improved MTF out to very high frequencies regardless of pixel size; specifically for large pixel sizes as the resolution
of systems with large pixel sizes and small focal spots were dominated by the pixel size. Magnification in such systems resulted in a smaller effective pixel size thus increasing the overall
system resolution.
Geometric magnification increased the cut-off frequency of the system. The MTF was seen to improve with magnification for lower frequencies but a crossover point occurred for most
geometries, where the focal spot blurring became more dominant. The improvement in the MTF was particularly noteworthy for systems with larger pixel sizes and smaller focal spot widths since the effective pixel size in the object plane was reduced by magnification, thus reducing the overall
resolution of the system.
Boyce et.al. Imaging properties of digital magnification radiography, Medical Physics, 2006
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M = 1; 0.3 mm Focal Spot; 200 um Pixel SizeM = 2; 0.3 mm Focal Spot; 200 um Pixel SizeM = 3; 0.3 mm Focal Spot; 200 um Pixel Size
M = 1; 0.1 mm Focal Spot; 200 um Pixel SizeM = 2; 0.1 mm Focal Spot; 200 um Pixel SizeM = 3; 0.1 mm Focal Spot; 200 um Pixel Size
Object Plane Resolution
Source - Object
Distance
Object - Image
Detector Distance
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Limiting resolution approximately 20 lp/mm
Requires approximately 12-15 mR exposure for optimal ODRegular film requires approximately 2 mR
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Processing quality control is essential to mammography success
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Peak location shows where greatest contrast
occurs. Provides sensitive means to
monitor processor QC over time
Radiology Physics Lectures: Mammography
Mammography Equipment - Screen-Film Systems
Extended processing used to improve performance in standard film processors
• Optimal viewing requires:– High view box / monitor luminance (cd/m2)
• Mammography view box 3000 cd/m2
• Standard view box 1500 cd/m2
– Masking of non-image areas on view box– Low ambient light levels (< 50 lux or lumens/m2)
• Moon ~ 1 lux• Normal room lighting ~ 100 - 1000 lux
– Bright light should be available
Radiology Physics Lectures: Mammography
Mammography Equipment - Viewing Conditions
Radiology Physics Lectures: Mammography
Mammography Equipment - FFDMDigital Imaging Detector• Large dynamic range• Reasonable spatial resolution (300 µm)• Digital image -> input to CAD system• Expensive ~ $300k
Radiology Physics Lectures: Mammography
Mammography Equipment - FFDM
Digital Detector Film-Screen
Radiology Physics Lectures: Mammography
Mammography Equipment - Stereotatic Biopsy
Small field of view: 25 x 25 mm1k x 1k CCD detector - 25 µm
Radiology Physics Lectures: Mammography
Mammography Equipment - Stereotatic Biopsy
Radiology Physics Lectures: Mammography
Mammography Equipment - Stereotatic Biopsy
Radiology Physics Lectures: Mammography
Mammography Equipment - Tomosynthesis
Tomosynthesis comparable dose to Projetion
Radiology Physics Lectures: Mammography
Mammography Equipment - Tomosynthesis
Radiology Physics Lectures: Mammography
Mammography Equipment - Tomosynthesis
Cranial-caudal conventional mammography view (A) of a middle-aged woman presenting with a palpable mass indicated by a metallic BB marker.
Tomosynthesis 1 mm thick image (B) depicts a circumscribed mass (arrow)Mark A. Helvie, , Digital Mammography Imaging: Breast Tomosynthesis and Advanced Applications, Radiol Clin North Am. Sep 2010; 48(5): 917–929
Radiology Physics Lectures: Mammography
Mammography Equipment - Tomosynthesis
Vertical SectionProjection Tomo
Radiology Physics Lectures: Mammography
Mammography Equipment - Dose
• Factors affecting dose– Speed (efficiency) of imaging system– Preferred image density– Breast thickness– Breast composition
• Fat less dense than gland– kVp selected
• High kVp better penetration• High kVp lower contrast• High kVp lower dose
• Filtration used• Mo or Rh
– Presence and type of grid• Typical Bucky factor ~2x
Radiology Physics Lectures: Mammography
Mammography Equipment - Dose
Radiology Physics Lectures: Mammography
Mammography Equipment - Dose
Radiology Physics Lectures: Mammography
Glandular Dose (in mrad) for 1 Roentgen Entrance Exposure 4.2-cm Breast Thickness
Assumptions: 50% Adipose/50% Glandular Breast Tissue using a Mo/Rh Target-Filter
25 26 27 28 29 30 31 32 33 34 350.28 149 151 1540.29 154 156 158 1590.30 158 160 162 162 1630.31 163 164 166 166 167 1670.32 167 169 171 171 171 172 1720.33 171 173 175 176 176 176 176 1770.34 176 178 179 179 180 180 180 181 1810.35 180 181 183 183 184 185 185 186 1870.36 185 186 187 187 188 188 189 190 191 1910.37 189 190 191 191 192 193 193 194 195 1950.38 193 194 196 196 197 197 197 198 199 199 2000.40 202 203 204 204 205 205 206 207 208 208 2080.41 206 207 208 208 209 209 210 211 212 212 2120.42 211 211 212 212 213 213 214 215 216 216 2170.43 215 216 217 217 218 218 219 219 220 220 2210.44 220 220 221 221 222 222 223 223 224 224 2250.45 224 224 225 225 226 226 227 227 228 228 2290.46 228 229 229 230 231 231 232 233 233 2340.47 233 233 234 235 235 236 237 237 2380.48 238 238 239 240 240 241 241 242 2420.49 242 243 243 244 244 245 245 2460.50 247 247 248 248 249 250 2510.51 251 252 253 254 254 2550.52 257 257 258 258 2590.53 261 261 262 263 2640.54 265 266 267 2680.55 269 270 271 2720.56 275 276 2760.57 279 280 2810.58 284 2850.59 288 2890.60 293
kVp
HVL
Glandular Dose (in mrad) for 1 Roentgen Entrance Exposure 4.2-cm Breast Thickness
Assumptions: 50% Adipose/50% Glandular Breast Tissue using a Mo/Mo Target-Filter
22 23 24 25 26 27 28 29 30 31 32 330.23 119 1160.24 124 121 1240.25 128 126 129 1310.26 133 130 133 135 1380.27 138 135 138 140 142 1430.28 142 140 142 144 146 147 1490.29 147 144 146 148 150 151 153 1540.30 152 149 151 153 155 156 157 158 1590.31 156 154 156 157 159 160 161 162 163 1640.32 161 158 160 162 163 164 166 167 168 168 170 1710.33 166 163 165 166 168 169 170 171 173 173 174 1750.34 168 170 171 172 173 174 175 176 177 178 1790.35 174 175 176 177 178 179 180 181 182 183
HVL 0.36 179 181 182 183 184 185 185 186 1870.37 185 186 187 188 189 190 191 1910.38 190 191 192 193 194 195 1950.39 196 197 198 198 199 2000.40 201 202 203 204 2040.41 206 207 208 2080.42 211 212 2120.43 215 2160.44 2200.45
kVp
7.64 7.28
1.34 1.27
0.953
4.73 4.70
1.07 1.06
0.992
Entrance Dose (mGy - Console)Entrance Dose (mGy - Measured)Glandular Dose (mGy - Console)
Glandular Dose (mGy)mGy (meter/ESE)
Mammography Equipment - Dose
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Review Question
Radiology Physics Lectures: Mammography
Mammography Equipment - MQSA QA
• Mammography facilities must be:• Accredited by ACR (or agreement states)
– Meet standards• Initial qualifications of team
– Physicians, physicists, technologists• Continuing education of team• Continuing experience of team• Equipment• Quality control program• Image quality
• Certified by FDA– Granted when facility is accredited
Radiology Physics Lectures: Mammography
Mammography Equipment - MQSA QA
Radiology Physics Lectures: Mammography
Mammography Equipment - MQSA QA
Radiology Physics Lectures: Mammography
Mammography Equipment - MQSA QA
Radiology Physics Lectures: Mammography
Mammography Equipment - MQSA QA
Radiology Physics Lectures: Mammography
Mammography Equipment - MQSA QA
Radiology Physics Lectures: Mammography
Mammography Equipment - MQSA QA
Radiology Physics Lectures: Mammography
Mammography Equipment - MQSA QA
ACR Phantom ACR insert(no scatter)
MammographyT.R. Nelson, Ph.D.
x41433tnelson@ucsd.edu
Radiology Physics Lectures: Mammography
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