Q a u nt n itta t titve v e 3D D Wh W o h l o e Breast timagi g ng n g with t Trans n mission o n and n d Reflfec e tion o n Ultr t aso s u o n u d

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1 Quantitative 3D Whole Breast Imaging with Transmission and Ultrasound Michael Andre, PhD,James Wiskin, PhD, Haydee Ojeda- Fournier, MD, Linda Olson, MD, David Borup, PhD, Melissa Ledgerwood, B.S., Steven Johnson, PhD, many others University of California, San Diego TechniscanMedical Systems, Inc. Ultrasound Computed Tomography (USCT) Opportunity for Whole Breast Ultrasound Current scanner design Patient findings to date Present Status of Breast Ultrasound Primary adjunctive modality for diagnostic imaging including biopsy guidance but difficult to perform Often limited to clinically assessing solid vs. cystic masses Reader variability Small field of view and range with high-resolution transducers Lacks global view of entire breast Operator dependent Sometimes difficult to reproduce ACRIN 6666: valuable for screening dense breasts, difficult to do Some states now require reporting of fat/gland ratios as risk factor Potential Advantages of Whole Breast USCT Global views of both breasts in standard frame of reference Image is quantitative (c, α, R) Operator independent, standardized scan Whole breast volumetric imaging No image speckle Uniform high resolution independent of range and location M i n i m a l r e f r a c t i o n, d i s t o r t i o n, multiple scattering effects Facilitates review, follow-up Monitor chemo-prevention, therapy Guidance and correction for HIFU R e f l e c t i o n

2 US Computed Tomography INPUT: Known OUTPUT: Measured INTERACTION MAP: Desired Ultrasound Computed Tomography: Inherently Non- L i n e a r 3D Problem Inherently a non-linear 3D problem in ultrasound B-mode US is a form of limited Computed Tomography but assumes 180 backscatter, straight-line propagation, constant sound speed, etc. Unlike x-ray CT or MRI, in US the object size ~wavelength, multiple scattering, refraction, etc., so common 2D CT reconstruction methods are inadequate We use non-linear full-wave 3D inverse scattering algorithm We implement a 3D solution to the inversion TechniScan Medical Systems, Inc., Salt Lake City Johnson, Wiskin, Borup, et al. Current Whole-Breast USCT Scanner Three Transducers angled upward at 12, 5 MHz (80% BW) Recently added a vertically oriented array to better access chest wall Coincident with 2D Transmission Arrays (1536 elements) MHz All data used simultaneously in 3D non-linear full-wave inversion Forward and back-propagation, 4-5 iterations (~45x10 12 operations!) Scan time: sec per slice, ~ 8 min for average breast 3D Reconstruction of c, α, R in minutes using 2 GPUs Resolution: 0.5 mm, 0.9 mm Transmission Sound Speed Sensitivity: m/s, Detection: 7.5 m/s; Atten: 0-4 db/cm/mhz

3 y Full-Wave Inverse-Scatter Image Formation Inversion is an iterative procedure Must first solve the forward problem for ψ sc f or di screte ω sc inc ψ ( r, θ) ψ ( r, θ) ψ ( r, θ) = K( r, θ ) ψ ( r, θ ) g r r, θ θ r dr d ( ) θ φ φ φ φ V Iterative minimization of residual vector must be very efficient We use a Ribiere-Polak conjugate gradient-based minimization FFT Solve Lippmann-Schwinger for scatter potential of each point in 3D Approximately 5-8 iterations are needed to reach 5% residual Data from all levels used simultaneously in 3D inversion (~45x operations!) Full breast 2D reconstruction in seconds, full-wave 3D is ~12 min using very fast algorithm and GPUs Images of sound speed and attenuation are used to correct aberration for Tomograms S i m p l e T i m e of Flight I m a g e Serves as initial estimate at low frequency (600 khz), i t e r a t e t o higher frequenci es x After 3 Iterations: Speed of Sound at 1 MHz 1 mm slice, 394x min for 250 slices Grey scale: m/sec Typically 5-8 iterations Tomography 5.5 MHz Breast Phantom 60 views, 3 transducers (not refraction corrected) Measured Sound Speed Sensitivity m/sec at 30 C ~7.5 m/sec contrast detectability y = x R 2 = Same Data Refraction Corrected using Sound Speed Inverse Scatter Tomography Improved resolution Reduced distortion 1.5 mm slice profile 0.3 mm FWHM in plane Clock views preserved for review by Radiologist U S C T ( m / s e c ) D True Sound Speed (m/sec)

4 P re -Clinical Study of Whole Breast Ultrasound Measure range of tissue properties and masses in patients Determine equivalence to breast sonography 172 subjects to date at UCSD (target 300 total accrual including Mayo Clinic) 19 to 78 years old All referred for diagnostic breast sonography (findings on mammography or physical exam) Study designed to assess equivalence to sonography (93% power) Determine reproducibility Sound Speed Attenuation WBU: Subject Right Breast Right: 6 Simple Cysts, 2 reported on US Left: 4 Simple Cysts, none reported on US Axial Sagittal Corrected for c Intermediate SOS (1530 m/s), distinct margins, spherical Very low Atten (<0.1 d B / c m / M H z ) Anechoic, circumscribed spherical WBU: Subject Left Breast Biopsy-Confirmed Fibroadenoma, 40 yo WBU: Subject Left Breast 40 yo with biopsy-confirmed Fibroadenoma Sound Speed Patient had series of Diagnostic US for palpable mass: 3:00, 5 cm FN,10 mm solid, hypoechoic mass, posterior shadowing, distinct margins WBU: 3:00 Left breast 8 x 9 x 6 mm mass. Intermediate sound speed (1560 m/sec), intermediate attenuation (1.6 db/cm/mhz), hypoechoic, distinct margins

5 Subject Left Breast 70 yo with palpable finding in upper-inner quadrant Sound Speed WBU: Subject Left Breast C-C Sagittal Attenuation Mammo: Left breast 14 x 14 x 19 mm spiculated high density mass anterior zone, UIQ, mildly dense fibroglandularpattern. U S : 10:00 Irregular, hypoechoic, posterior shadowing, abrupt interface, architectural distortion, 16 x 12 mm. Note angular shape. Pathology: Biopsy confirmed invasive ductal carcinoma WBU: Subject Left Breast Subject Left Breast 33 yo seen for lump or thickening no family history of cancer Sound Speed Attenuation WBU: 10:00 Left breast 14 x 14 x 16 mm irregular mass. Very high sound speed (1610 m/sec), high attenuation (2.6 db/cm/mhz),hypoechoic, same angular shape as sonogram, architectural distortion Mammo: Heterogeneously dense, left breast 2 cm spiculated mass, malignant appearing calcifications, MOQ. U S : 1:00, 2 cm from nipple, 1.9 x 1.2 cm irregular, highly suspicious, heterogeneous, abrupt interface. Pathology: Biopsy confirmed invasive ductal carcinoma

6 Sound Speed WBU: Subject Left Breast -- IDC C-C Sagittal WBU: Subject Left Infiltrating Ductal Carcinoma 1:00 Left breast,3 cm from nipple, 2.2 x 1. 1 x 1. 6 c m. High sound speed (mean 1570 m/sec), irregular shape, hyper to water. Highattenuation (2.3 db/cm/mhz). RT hypoechoic, spiculated margins, similar irregular shape as sonogram and mammogram WBU Sound Speed Whole Breast Ultrasound Computed Tomography MG Sonogram IDC MRI: 2.1 x 1.7 x 1.8 cm WBU: 2.21 x 1.65 x 1.82 cm MRI: 2.1 x 1.7 x 1.8 cm T1 MIP ( V i d ) Sound Speed T1 Fused + Sound Speed WBU: 2.21 x 1.65 x 1.82 cm

7 Potential Value of 3D Volumetric W BU P yo : Infiltrating cancer with mixed ductal and lobular features WBU scan before surgery Both have high Sound Speed and Attenuation Two lumpectomies Specimens did not have cl ear m argi ns Patient returned to surgery to remove connecting residual tumor Illustrates a potential advantage of global view of breast WBU (cm) WBU (cm) Minimum Diameter y = x R ² = Sonography (cm) Maximum Diameter y = x R ² = Sonography (cm) Work in Progress Reader Classification: WBU and Sonography Teaching File of 35 cases with known findings 47 subjects with masses visualized on sonography 12 cancer, 17 FA, 8 complicated cysts, 10 simple cysts 98% Agreement, mass present in correct location BI-RADS by Sonography: Sensitivity=100%, Specificity=46%, and Accuracy=53% W BU: Sensitivity=100%, Specificity=54%, and Accuracy=60% No significant difference between two modalities Summary WBU image resolution is 0.8 mm (reflection) and 1.2 mm (transmission) Slice thickness and spacing is 1 mm, 3D IST algorithm improves image quality 8-10 minutes scan time per breast (size dependent) Independent quantitative images of speed, attenuation, reflectivity are produced (other parameters feasible) Potentially new information for characterizing masses Simple cysts: low to intermediate sound speed, low attenuation Solid masses: higher sound speed and attenuation Malignancies: highest sound and attenuation Also: 3D shape, margins, texture, echogenicity, posterior pattern, etc. 300 patients on two prototypes at UCSD and Mayo

8 Acknowledgements NIH/NCI 1 R44 CA A2 01A2 Avon Foundation UCSD CTA #