The Effect of Oral Laxatives on Rectal Distension and Image Quality in Magnetic Resonance Imaging of the Prostate.

Introduction Increasing rectal size is associated with increased artefacts on magnetic resonance imaging (MRI) of the prostate and has the potential to degrade image quality. The objective of this study was to analyse the effect of oral laxative medication on rectal distension and image quality in prostate MRI. Methods Eighty patients prospectively received either 15 mg of oral senna (laxative group) or no medication (control group). Patients underwent prostate MRI according to standard local protocol and seven rectal dimensions on axial and sagittal images were measured. A subjective assessment of rectal distension was also made using a five-point Likert scale. Finally, artefacts on diffusion-weighted sequences were assessed using a four-point Likert scale. Results There was a small reduction in rectal diameter on sagittal images in the laxative group compared to the control group, with mean diameters of 27.1 mm and 30.0 mm respectively, p=0.02. There was no significant difference in rectal measurements of anteroposterior diameter, transverse diameter, or rectal circumference on axial imaging. Subjective scoring also demonstrated no significant difference in diffusion-weighted imaging quality between the laxative group and control group, p=0.82. Conclusion Bowel preparation with the oral laxative, senna, provided only a marginal decrease in rectal distension on one measure and no reduction in artefacts on diffusion-weighted sequences. The findings of this study do not support the routine use of this medication in patients undergoing prostate MRI.

Proton magnetic resonance spectroscopy as a potential tool for differentiating between abdominal fluid collections.

PURPOSE: To determine the utility of proton magnetic resonance spectroscopy (MRS) in distinguishing abdominal fluid types. MATERIALS AND METHODS: Abdominal fluid samples were obtained from patients undergoing therapeutic percutaneous drainage. In vitro spectroscopy was performed using a 1.5-T scanner and a head coil. Single voxel spectra were obtained using a point resolved spin-echo sequence with water suppression (TR/TE 2000 msec/35 msec). The peak pattern for each sample was examined and the signal-to-noise ratio (SNR) estimated (ratio of tallest peak to noise at <0 ppm). RESULTS: Thirty-five samples were analyzed: purulent collection (eight), serosanguinous collection (eight), non-chylous ascites (six), chylous ascites (one), bile (seven), and bile with iodinated contrast media (five). The mean SNR of the dominant peak was: purulent collection, 12.7; serosanguinous collection, 3.2; non-chylous ascites, 2.4; chylous ascites, 8.8; bile, 1.4; and bile with contrast media, 60.8. Pus samples had a broad based peak pattern with continuous signal of >1.5 ppm width situated within the range 0.2-2.5 ppm, not found in other samples. Chylous ascites (one sample) had a distinctive peak at 1.2 ppm. Bile with contrast had three peaks at 3.5/3.6, 2.6, and 2.1 ppm. No other patterns were found to be discriminatory. Common non-specific patterns seen included a bifid peak at 1.1-1.3 ppm and a broad based peak situated between 3 and 4 ppm. CONCLUSIONS: The H1 spectra of purulent fluid has a higher SNR than common non-purulent abdominal fluids and a distinct broad based peak pattern from 0.2-2.5 ppm. Proton spectroscopy may be a useful tool for distinguishing purulent from non-purulent intra-abdominal collections.

Abdominal computed tomographic findings of Mycobacterium tuberculosis and Mycobacterium avium intracellulare infection in HIV seropositive patients.

OBJECTIVE: To compare the computed tomographic (CT) findings of abdominal Mycobacterium tuberculosis (MTB) infection and Mycobacterium avium intracellulare (MAI) infection in patients with human immunodeficiency virus (HIV) infection. METHODS: A retrospective review of the CT findings of 30 patients with HIV and proven MTB (n = 9) or MAI (n = 21) infection was conducted. Images were reviewed by a radiologist blinded to the diagnosis, and the radiologic findings involving the abdominal viscera, peritoneum and lymph nodes were compared. RESULTS: The following were more frequent in patients with MAI infection: hepatomegaly (MAI 71% v. MTB 44%, p < 0.05), uniform attenuation of lymph nodes (MAI 90% v. MTB 55%, p < 0.05) and clustered pattern of lymph nodes (MAI 57% v. MTB 22%, p < 0.05). In patients with MTB infection, lymph nodes with low attenuation centrally were more common (MAI 10% v. MTB 44%, p < 0.05), and mesenteric lymph nodes were significantly larger (MAI mean = 20 mm v. MTB mean = 40 mm, p < 0.05). CONCLUSION: Although nonspecific, CT may be useful in the early diagnosis of MTB and MAI infection, allowing for presumptive treatment before microbiologic confirmation.

Role of gadolinium-enhanced magnetic resonance imaging in retroperitoneal fibrosis.

PURPOSE: To determine if the gadolinium-enhancement characteristics of magnetic resonance images (MRI) differ for acute and chronic benign retroperitoneal fibrosis (RPF). METHOD: Seven male subjects, 3 with newly diagnosed nontreated RPF (acute group) and 4 with long-standing stable RPF (chronic group) who had been treated with steroids, ureteric stents or both, underwent MRI examinations with gadolinium enhancement. Patients in the acute group were examined again after treatment. Mean dynamic gadolinium-enhancement ratios (both dynamic and delayed) were calculated for each group. RESULTS: The initial mean dynamic enhancement ratio for the acute group (mean 1.86, range 1.80-1.95) was significantly different (p = 0.005) from that of the chronic group (mean 1.37, range 1.26-1.61). The mean dynamic enhancement ratio for the acute group after treatment (4-8 months duration) was 1.40 (range 1.26-1.51). The mean delayed enhancement ratio (RPF/psoas muscle signal intensity) for the acute group was 1.41 (range 1.38-1.43, data from 2 patients) and for the chronic group was 1.29 (range 1.13-1.44). CONCLUSION: Dynamic gadolinium enhancement was useful in differentiating newly diagnosed RPF from treated chronic disease and may have a role in assessing disease activity, monitoring response to treatment and detecting relapse.