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SUMMARY:“Breast MRI by  the Shutter-Speed Method: Elimination of Unneces
 sary Breast Biopsies" - Dr Charles S. Springer\, Jr.\, Advanced Imaging Re
 search Centre. Oregon Health & Science University
DTSTART:20101221T120000Z
DTEND:20101221T130000Z
UID:TALK27635@talks.cam.ac.uk
CONTACT:Mala Jayasundera
DESCRIPTION:Abstract: \nThere is growing public health concern over the be
 nefits of X-ray mammography in breast cancer screening. Though it accompli
 shes early detection with high sensitivity\, the consequent large number o
 f false positive readings leads to a high fraction (typically\, 70%) of bi
 opsy procedures yielding benign pathology reports. These biopsies\, unnece
 ssary in this sense\, have negative (morbid) consequences: pain\, anxiety\
 , possible harm\, and expense (biopsy procedures cost typically ten times 
 more than mammography or sonography). It has long been wished that MRI pro
 vide a more accurate diagnosis of breast disease. For 15 years a particula
 r protocol\, quantitative (Dynamic-Contrast-Enhanced) DCE-MRI\, has held p
 romise because it is a form of generalized "functional MRI\," focusing on 
 tumor vascular properties. However\, DCE-MRI hasn't proven significantly b
 etter than mammography and\, since it is also more expensive\, has not com
 e into wide practice. The mathematical model generally used for quantitati
 ve DCE-MRI analysis was adopted from well-known tracer pharmacokinetic der
 ivations. However\, its unedited translation for DCE-MRI has the unreasona
 ble consequence of treating all inter-compartmental equilibrium water exch
 ange processes as effectively infinitely fast. This is because\, though th
 e DCE-MRI contrast agent (CA\, a monomeric Gd(III) chelate) plays the trac
 er molecule role\, the signal molecule is water\, and these have different
  tissue compartmentalizations. We have modified the model to accommodate w
 ell-known water inter-compartmental transfer rate constants. We conduct an
  analysis designed to detect tumor foci exhibiting precisely water exchang
 e kinetics effects ("shutter-speed" effects) on pharmacokinetic parameters
 \, particularly the CA extravasation rate constant\, Ktrans. In a populati
 on now reaching 137 positive-screening breast lesions\, we have found that
  malignant tumor capillaries are sufficiently more CA-permeable to trigger
  focal Ktrans biomarker shutter-speed effects (ΔKtrans) that are essentia
 lly zero for benign lesions. The molecular basis for this is quite reasona
 ble. Lesion region-of-interest and pixel-by-pixel ΔKtrans mapping allows 
 complete specificity between biopsy/pathology-proven malignant (32) and be
 nign (105) tumors. The biopsy procedures on the latter could have been avo
 ided\, and with cost savings since they are more expensive than MRI. This 
 discrimination is independent of the screening modality\, the MRI instrume
 nt vendor (platform/software)\, and the magnetic field strength. A signifi
 cant sub-population of 95 lesions occurred in 93 high-risk women who were 
 mammographically-negative but positively screened by clinical MRI approach
 es. Twenty malignant tumors in this population were missed by mammography.
  The MR shutter-speed is a fundamental concept that applies not only in qu
 antitative MRI studies of many different cancers\, but also of other patho
 logies and of physiological conditions.
LOCATION:CRI Lecture Theatre
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