Endorectal Coils, Contrast Media Boost Accuracy of Magnetic Resonance Techniques for Prostate Cancer Diagnosis

CHICAGO-Endorectal coil studies presented at the 90th Scientific Assembly and Annual Meeting of the Radiological Society of North America show unequivocally that the devices boost the diagnostic confidence of imaging to determine management of prostate disease. Also, new studies of magnetic resonance spectroscopic imaging (MRSI), dynamic contrastenhanced MR imaging, and ultrasmall paramagnetic contrast media reveal that these approaches improve diagnosis and provide useful information for patient management. Under the guidance of Hedvig Hricak, MD, PhD, chairman of the department of radiology at Memorial Sloan-Kettering Cancer Center (MSKCC), radiologist Liang Wang, MD, confirmed that an endorectal coil boosts the resolution and diagnostic confidence of MRI and multivoxel MRSI for determining whether prostate cancer is confined within the borders of the organ (abstract SSA07-01). Based on experience with 411 patients, including 268 cases in which both MRI and MRSI were used, Dr. Wang found that examinations employing a coil enabled the clinician to stage cancer with significantly increased accuracy. The average Partin nomogram score for imaging results obtained using of a coil was 0.8327, compared with 0.7769 without a coil. Exams performed with MRSI were even more accurate. Figure 1 shows use of an endorectal coil with MRI for assessing organ confinement in a patient with prostate cancer. Radiologist Joan Vilanova, MD, from Clinica Girona, in Girona, Spain, showed the value of endorectal coilassisted MRI and 3D MRSI for reevaluating patients with elevated prostate- specific antigen (PSA) persisting after a negative biopsy (abstract SSA07- 03). Prostate cancer was positively identified in 10 of 27 cases. Cancer was found in the transitional zone of four patients and the peripheral gland of six. In the positive cancer cases, the choline + creatine/ citrate (CC/Ci) ratio and choline/creatine (Ch/Cr) ratios for voxels in the transitional zone were significantly different (P > .01) from ratios in the voxels with benign prostatic hyperplasia. For the peripheral gland, the CC/Ci and Ch/Cr ratios for cancer voxels were significantly different from the ratios in voxels sampled in normal tissue, Dr. Vilanova said. The protocol's overall accuracy, sensitivity, and specificity were 85%, 75%, and 87%, respectively. Dr. Vilanova recommended that 3D MRSI should be routinely prescribed for patients whose PSA levels continue to be elevated after negative biopsy. He cautioned radiologists, however, to carefully survey the entire gland as well as the transitional and peripheral zones when performing the procedure. Contrast Tools Detect Recurrence, Nodal Involvement Dynamic contrast-enhanced (DCE) MRI can assist follow-up therapeutic planning for recurrent prostate cancer after radiation therapy, according to Masoom A. Haider, MD, an assistant professor of radiology at Princess Margaret Hospital in Toronto, Ontario, Canada (abstract SSA07-04). A study of 37 patients demonstrated that early intense enhancement on DCEMRI uncovers locally recurrent prostate cancer. The DCE-MRI was performed using a 1.5T MRI and a four-element torso phased-array coil. Sensitivity and positive predictive value rates of 72% and 88%, respectively, confirmed that the dynamic contrast technique is far superior to conventional T2-weighted MRI for this role. The enhancement pattern also aids in planning for follow-up of minimally invasive therapy. Ultrasmall iron-oxide contrast continues to show promise for detecting nodal involvement in prostate cancer. Using ferumoxtran-10, M.G. Harisinghani, MD, a researcher at the Center for Molecular Imaging Research at Massachusetts General Hospital, Boston, discovered that metastatic prostate cancer usually first involves lymph nodes located within 2.5 cm of the anterior surface of lumbar vertebral bodies (abstract SSG19-03). Dr. Harisinghani's study of 21 prostate cancer patients also found that all positive nodes were localized within 1.2 cm of the aorta. These results may aid biopsy and therapeutic planning, he said.