ARRS 2019: Detecting prostate cancer with contrast-enhanced subharmonic imaging

Contrast-enhanced subharmonic imaging (CE-SHI) offers a new technique for imaging of microbubble ultrasound contrast agents for detection of prostate cancer not found by multiparametric magnetic resonance imaging (MRI), according to research presented in a scientific session of the 2019 annual meeting of the American Roentgen Ray Society (ARRS) held May 5-10 in Honolulu, HI. Radiologists from Thomas Jefferson University Hospitals in Philadelphia described a pilot study representing the first in vivo application of this technique.

The study included 55 patients referred for prostate biopsy. Thirty-one patients had had a prior negative MRI or negative MRI-guided biopsy of the prostate. The patients were imaged using conventional grayscale, color, and power Doppler, conventional contrast HI, SHI, and flash replenishment in combination with SHI (MIP-SHI). SHI represented a new technique enabling imaging of microbubble ultrasound contrast agents with up to a 10-fold increase in contrast-to-background signal ratio relative to conventional harmonic imaging (HI).

Interpreting radiologists rated Doppler flow and contrast enhancement on a 5-point subjective scale for each sextant of the prostate. Prostate biopsy was subsequently performed with up to six targeted cores by use of CE imaging, followed by a 12-part systemic biopsy.

Session presenter Ethan J. Halpern, MD, vice chair for research and co-director of the Prostate Diagnostic Center, said that prostate cancer was identified in 24 of the patients, including nine patients with a prior negative MRI or negative MRI-guided biopsy. He noted that contrast enhancement was clearly observed with both HI and SHI techniques in all participants, but that SHI provided improved contrast signal and tissue suppression relative to conventional HI. Microvascular architecture and increased vascularity were best delineated with MIP-SHI.

Arguing for ultrasound, Dr. Halpern said, “Although multi-parametric MRI is currently used for this purpose, ultrasound has numerous advantages. Ultrasound systems are portable. Ultrasound studies are far less expensive and more widely available as compared with MRI. Contrast enhanced ultrasound studies can be performed at the same sitting as the ultrasound-guided biopsy, while mp-MRI requires two visits, one for the diagnostic MR study and a second for the fusion biopsy. There is no need for a fusion imaging system when using contrast enhanced ultrasound. No additional effort is required to properly register the CE ultrasound diagnostic study with the targeting system for biopsy.

“Diagnosis of clinically significant prostate cancer with non-invasive means is a real clinical challenge,” said Dr. Halpern. “Combining contrast enhanced ultrasound with subharmonic imaging has the potential to provide a new, non-invasive method for diagnosis and characterization of prostate cancer.”