Contrast enhanced subharmonic breast imaging: work in progress

Abstract

Contrast enhanced subharmonic imaging (SHI) may enable combined imaging and estimation of quantifiable flow parameters such as perfusion. A modified Logiq 9 scanner (GE Healthcare, Milwaukee, WI) operating in grayscale SHI mode was used to measure in vivo SHI time intensity curves in 4 dogs. Renal SHI was performed following IV injections of the contrast agent Optison (GE Healthcare, Princeton, NJ). Following 3 contrast injections a neutron activation assay technique (BioPhysics Assay Laboratory Inc, Worcester, MA) was employed to quantify the degree of perfusion in 8 sections of each kidney. Digital clips were transferred to a PC and SHI time intensity curves acquired in each section. SHI fractional blood volumes (FBVs) were calculated and the perfusion estimated from the initial slope of the FBV uptake. SHI perfusion data was compared to the gold standard using linear regression analysis. As part of an ongoing study, women with breast lesions participated in a study of contrast enhanced breast SHI. Following baseline scans of grayscale ultrasound and power Doppler, Optison was administrated for power Doppler and grayscale SHI (0.5 and 4.0 ml dosages, respectively). Digital clips were acquired of each injection and SHI time intensity curves were determined within each lesion. In the dogs 270 SHI time intensity curves were acquired. SHI perfusion estimates correlated significantly with microsphere results (r = 0.57; p < 0.0001). To date six patients with seven benign breast masses have been studied. The internal morphology of the vascularity associated with the breast masses was visualized better with SHI than with power Doppler. SHI perfusion estimates of the breast lesions ranged from 1.67 to 2.46 ml/min/g. In conclusion, a new contrast specific imaging techniques, SHI, has been investigated for in vivo breast imaging and perfusion estimation, but further studies are required to substantiate these preliminary results.