An 84-year-old man, who had had a colostomy and abdominopermeal resection for rectal carcinoma 3 years earlier, was being evaluated for possible recurrent tumor in the presacral space. The CT scan showed an irregular soft-tissue mass in the operative bed suspicious for recurrent tumor (fig. 1A). MRI using a Fonar 0.3-T nonsuperconductive magnet was performed with a slice thickness of 9 mm and slice interval of 12 mm. Transverse scans were obtained using the spin-echo (SE) pulse sequence with a repetition time (TA) of 2000 msec and echo times (TE) of 28 and 56 msec. Sagittal views wereobtained using SE 2000/28, SE 2000/56, and inversion recovery (IA) with 1500 msec TA, 310 msec TI (inversion time), and 28 msec TE. A discrete nodule 2.0 cm in diameter, which was hypointense in comparison with the surrounding parenchyma, was seen in the left lateral lobe of the prostate on the SE 2000/28 scan only (fig. 1B). The nodule could not be identified retrospectively on the CT scan at comparable transverse levels. The patient was already scheduled for CT-9uided fine-needle aspiration for cytology of his suspected recurrent tumor mass, so we decided to do a biopsy of the prostatic nodule at the same time, even though we could not see it on CT. Using the bony and soft-tissue landmarks from the transverse MA scan at the level ofthe nodule, we placed the needle into the expected location of the mass using CT guidance (fig. 1A). Cytology on the aspirates were conclusive for malignancy from both locations. The recurrent tumor mass was well differentiated adenocarcinoma, and the prostatic nodule was moderate to poorly differentiated adenocarcinoma.
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Herman et al. (1986) studied this question.