- 2015 Background and Perspective 2005 (in US) Women Men Mammography Invasive Breast Cancer Diagnosed 211,240 1,690 Noninvasive Breast Cancer Diagnosed 58,940 Deaths from Breast Cancer 40,410 460 T.R. Nelson, Ph.D. x41433 tnelson@ucsd.edu 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%. 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
Mammography Evolution Complementary Imaging Technology Ultrasound Cyst / solid differentiation Biopsy guidance Operator dependent MRI High contrast sensitivity Visualize silicone implants Breast cancer staging Generally requires contrast Thermography Infrared imaging 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
Soft Tissue Contrast - Breast Mammography Equipment Contrast = (Gland - Cancer) x100 Gland C D B A
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 Mammography Equipment - X-ray Tube Design
Mammography Equipment - Anode - Cathode Axis 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 Mammography Equipment - Focal Spot Size Variation 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.)
Mammography Equipment - Beam Quality
Mammography Equipment - Filtration X-ray Beam Filtration: Inherent: ~1 mm Be Added: Mo, Rh eliminates low (and high) energy x-rays Mammography Equipment - Filtration Mammography Equipment - Filtration
Mammography Equipment - Filtration Mammography Equipment - Filtration Tungsten (W) characteristic x-rays from L shell Mammography Equipment - Filtration
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 Mammography Equipment - HVL Mammography Equipment - HVL
Mammography Equipment - Tube Output Mammography Equipment - Collimation Must have at least 7.0 mgy/sec at 28 kvp in Mo/Mo mode to meet MQSA Light - x-ray field congruence to <1% for any edge and < 2% overall Must extend to chest wall
Mammography Equipment - Collimation 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 Mammography Equipment - Exposure Control Mammography Equipment - Technique Chart
Mammography Equipment - Compression Mammography Equipment - Compression Improves image quality, reduces motion, decreases thickness, decreases blurring, lowers radiation dose Mammography Equipment - Compression Spreads tissue over localized area
Mammography Equipment - Scatter - Primary Ratio
Mammography Equipment - Anti-scatter Grids - Magnification Source - Object Distance $"!#,"!#+" M = 1; 0.3 mm Focal Spot; 200 um Pixel Size M = 2; 0.3 mm Focal Spot; 200 um Pixel Size M = 3; 0.3 mm Focal Spot; 200 um Pixel Size M = 1; 0.1 mm Focal Spot; 200 um Pixel Size M = 2; 0.1 mm Focal Spot; 200 um Pixel Size M = 3; 0.1 mm Focal Spot; 200 um Pixel Size!#*" Object - Image Detector Distance MTF of the focal spot decreases with increasing magnification MTF of the detector increases with magnification Optimum magnification depends on both focal spot MTF and detector MTF Geometric magnification derives no resolution improvement from large focal spot - focal spot blur dominates Geometric magnification shows resolution improvement when detector has large detector pixels sizes - smaller effective pixel size!"#$!#)"!#("!#'"!#&"!#%"!#$" 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, Object where the Plane focal spot blurring Resolution became more dominant. The improvement in the MTF!"!" (" $" $!" %" resolution of $(" the &" system. %!" '" %(" &!" )" %&'(')$#*+,-+./0$1)&2334$ 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 Boyce et.al. Imaging properties of digital magnification radiography, Medical Physics, 2006
Mammography Equipment - Screen-Film Systems Mammography Equipment - Screen-Film Systems Mammography Equipment - Screen-Film Systems Mammography Equipment - Screen-Film Systems Limiting resolution approximately 20 lp/mm Requires approximately 12-15 mr exposure for optimal OD Regular film requires approximately 2 mr
Mammography Equipment - Screen-Film Systems Mammography Equipment - Screen-Film Systems Processing quality control is essential to mammography success
Mammography Equipment - Screen-Film Systems Mammography Equipment - Screen-Film Systems Peak location shows where greatest contrast occurs. Provides sensitive means to monitor processor QC over time Mammography Equipment - Screen-Film Systems Extended processing used to improve performance in standard film processors Mammography Equipment - Viewing Conditions Optimal viewing requires: High view box / monitor luminance (cd/m 2 ) Mammography view box 3000 cd/m 2 Standard view box 1500 cd/m 2 Masking of non-image areas on view box Low ambient light levels (< 50 lux or lumens/m 2 ) Moon ~ 1 lux Normal room lighting ~ 100-1000 lux Bright light should be available
Mammography Equipment - FFDM Mammography Equipment - FFDM Digital Imaging Detector Large dynamic range Reasonable spatial resolution (300 µm) Digital image -> input to CAD system Expensive ~ $300k Digital Detector Film-Screen Mammography Equipment - Stereotatic Biopsy Mammography Equipment - Stereotatic Biopsy Small field of view: 25 x 25 mm 1k x 1k CCD detector - 25 µm
Mammography Equipment - Stereotatic Biopsy Mammography Equipment - Tomosynthesis Tomosynthesis comparable dose to Projetion Mammography Equipment - Tomosynthesis 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
Mammography Equipment - Tomosynthesis Vertical Section Projection Tomo 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 Mammography Equipment - Dose Mammography Equipment - Dose
Mammography Equipment - Dose Glandular Dose (in mrad) for 1 Roentgen Entrance Exposure 4.2-cm Breast Thickness 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 Assumptions: 50% Adipose/50% Glandular Breast Tissue using a Mo/Rh Target-Filter kvp 22 23 24 25 26 27 28 29 30 31 32 33 119 116 0.23 0.24 124 121 124 0.25 128 126 129 131 0.26 133 130 133 135 138 0.27 138 135 138 140 142 143 0.28 142 140 142 144 146 147 149 0.29 147 144 146 148 150 151 153 154 0.30 152 149 151 153 155 156 157 158 159 0.31 156 154 156 157 159 160 161 162 163 164 0.32 161 158 160 162 163 164 166 167 168 168 170 171 0.33 166 163 165 166 168 169 170 171 173 173 174 175 0.34 168 170 171 172 173 174 175 176 177 178 179 0.35 174 175 176 177 178 179 180 181 182 183 0.36 179 181 182 183 184 185 185 186 187 HVL 0.37 185 186 187 188 189 190 191 191 0.38 190 191 192 193 194 195 195 0.39 196 197 198 198 199 200 0.40 201 202 203 204 204 0.41 206 207 208 208 0.42 211 212 212 0.43 215 216 0.44 220 0.45 Entrance Dose (mgy - Console) Entrance Dose (mgy - Measured) Glandular Dose (mgy - Console) Glandular Dose (mgy) mgy (meter/ese) 7.64 7.28 1.34 1.27 0.953 4.73 4.70 1.07 1.06 0.992 HVL kvp 25 26 27 28 29 30 31 32 33 34 35 0.28 149 151 154 0.29 154 156 158 159 0.30 158 160 162 162 163 0.31 163 164 166 166 167 167 0.32 167 169 171 171 171 172 172 0.33 171 173 175 176 176 176 176 177 0.34 176 178 179 179 180 180 180 181 181 0.35 180 181 183 183 184 185 185 186 187 0.36 185 186 187 187 188 188 189 190 191 191 0.37 189 190 191 191 192 193 193 194 195 195 0.38 193 194 196 196 197 197 197 198 199 199 200 0.40 202 203 204 204 205 205 206 207 208 208 208 0.41 206 207 208 208 209 209 210 211 212 212 212 0.42 211 211 212 212 213 213 214 215 216 216 217 0.43 215 216 217 217 218 218 219 219 220 220 221 0.44 220 220 221 221 222 222 223 223 224 224 225 0.45 224 224 225 225 226 226 227 227 228 228 229 0.46 228 229 229 230 231 231 232 233 233 234 0.47 233 233 234 235 235 236 237 237 238 0.48 238 238 239 240 240 241 241 242 242 0.49 242 243 243 244 244 245 245 246 0.50 247 247 248 248 249 250 251 0.51 251 252 253 254 254 255 0.52 257 257 258 258 259 0.53 261 261 262 263 264 0.54 265 266 267 268 0.55 269 270 271 272 0.56 275 276 276 0.57 279 280 281 0.58 284 285 0.59 288 289 0.60 293 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
Mammography Equipment - MQSA QA Mammography Equipment - MQSA QA Mammography Equipment - MQSA QA Mammography Equipment - MQSA QA
Mammography Equipment - MQSA QA Mammography Equipment - MQSA QA Mammography Equipment - MQSA QA Mammography T.R. Nelson, Ph.D. x41433 tnelson@ucsd.edu ACR Phantom ACR insert (no scatter)