Fast spin-echo MR images of the pelvis obtained with a phased-array coil: value in localizing and staging prostatic carcinoma

Abstract

Objective: The fast spin-echo pulse sequence allows T2-weighted MR images to be acquired more rapidly than is possible with conventional spin-echo sequences, and phased-array coils can provide a higher signal-to-noise ratio than is possible with the body coil. The combination of these methods permits higher resolution images to be obtained with more signal averages despite shorter imaging times. In this study, initial technical comparisons designed to confirm the advantage of combining fast spin-echo pulse sequences with a pelvic phased-array multicoil were followed by an assessment of the value of these methods for the localization and staging of prostatic carcinoma.

Subjects and methods: Seventy-one men with known (60) or suspected (11) prostatic carcinoma were imaged with T2-weighted fast spin-echo pulse sequences in the axial and coronal planes with a phased array of four surface coils (multicoil) for signal reception. Four of these men also were imaged with fast spin-echo sequences and the body coil, and six of these men also were imaged with T2-weighted conventional spin echo sequences and the multicoil; image qualities achieved with these techniques were compared. The use of IV glucagon (42 of 71 studies) before fast spin-echo sequences was correlated with the subsequent presence or absence of peristaltic artifacts on MR images. MR images were analyzed for the presence or absence of prostatic cancer in the right and left sides of the gland and for evidence of spread either through the capsule, into the seminal vesicles, or to lymph nodes or bone. Findings at MR imaging were compared with results of radical prostatectomy (20), lymph node dissection without prostatectomy (seven), and biopsy (67).

Results: Image quality obtained with the combination of the fast spin-echo sequence with the multicoil was judged superior to that obtained with either the conventional spin-echo sequence with the multicoil or the fast spin-echo sequence with the body coil. Significant motion artifacts were noted in 45% of studies (13/29) performed without glucagon vs 7% of studies (3/42) performed with glucagon. In the 58 patients for whom information concerning the location of tumor in either the right or left side of the gland was obtained from biopsy (39) or surgery (19), MR images allowed cancer to be detected with 89% sensitivity and 77% specificity. Among the 20 patients undergoing prostatectomy and seven others undergoing lymph node dissection, MR imaging permitted high accuracies in predicting involvement of the seminal vesicles (100%), local transcapsular spread (85%), and involvement of pelvic lymph nodes (85%).

Conclusion: Fast spin-echo imaging with a pelvic phased-array multicoil provides high-resolution images of the prostate that may obviate an endorectal coil for the detection, localization, and staging of prostatic carcinoma.