Prostate cancer tissue is of greater cell density than benign tissue and thus has altered elasticity. Elastography is a strain imaging technique that provides an assessment of tissue elasticity. Real-time elastography (RTE) visualizes displacements between ultrasound (US) image pairs of tissue under compression. Dr. Pallwein and collaborators [1] used this technique to detect prostate cancer in men prior to radical prostatectomy. Their findings appear in the June 2007 issue of the
BJU International. For the study 15 consecutive patients were examined with RTE prior to RP. Mean age was 56 years and all had clinically organ-confined CaP. Patients had transrectal ultrasound using conventional B-mode and RTE.
Radiologists interpreting the images were blinded to biopsy results. Tissue was compressed and released with the hand-held US transducer and the strain was calculated between pairs of images before and after compression. The compression and decompression was repeated numerous times to obtain reliable elastograms. The stiffness of the lesion was displayed in a color spectrum. The focus was on peripheral zone stiffness to concentrate on areas of potential cancer. Hard lesions with a diameter of >0.5mm and reproducible strain were considered to be cancer. The RTE findings were then compared with the histopathological findings. A contingency coefficient was used to calculate the correlation between RTE and Gleason score.
RTE detected 28 of 35 cancer foci (sensitivity 80 per cent). Seven foci were not detected with RTE and three were in the inner gland. There were four false positive areas. The overall sensitivity, specificity and positive predictive value were 87, 92 and 80 per cent, respectively. The best sensitivity was at the apex and midgland.
RTE has shown promise in detection of breast and thyroid lesions. However, limitations noted in the prostate include an increase in stiffness due to chronic inflammatory tissue, BPH, and small lesions.
[1] Pallwein L, Mitterberger M, Struve P, Pinggera G, Horninger W, Bartsch G, Aigner F, Lorenz A, Pedross F, Frauscher F
