Magnetic resonance imaging with Gadolinium-DTPA for assessment of bladder carcinoma and its response to treatment

[Follow-up after radiotherapy of anal canal carcinoma]

Anal canal carcinoma is a rare and curable disease for which the standard of care is radiation therapy with concurrent 5-fluoro-uracil and mitomycine-based chemotherapy. Post-treatment follow-up however is rather poorly defined. This article offers a review of the various post-treatment surveillance options both for early diagnosis of relapse and care for late treatment effects. While follow-up remains mostly clinical, we will discuss morphologic (endorectal echoendoscopy, pelvic magnetic resonance imaging, tomodensitometry and positron emission tomography) and biologic (squamous cell carcinoma antigen and pathology) follow-up so as to determine their diagnostic and prognostic value.

Magnetic resonance imaging (MRI) contrast agents for tumor diagnosis

This review focuses on MRI contrast agents for tumor diagnosis. Several types of low molecular weight Gd3+-based complexes and dextran-coated superparamagnetic iron oxide (SPIO) nanoparticles have been used for clinical tumor diagnosis as longitudinal relaxation time (T1) and transverse relaxation time (T2) MRI contrast agents, respectively. To further improve the sensitivity of MRI, new types of chelates for T1 MRI contrast agents and combination of low molecular weight T1 MRI contrast agents with different types of carriers have been investigated. Different types of materials for forming secure coating layers of SPIO and novel superparamagnetic particles with higher relaxivity values have been explored. Various types of ligands were applied to improve the capability to target tumor for both T1 and T2 contrast agents. Furthermore, MRI contrast agents for detection of tumor metabolism were also pursued.

Recurrent or residual pelvic bowel cancer: accuracy of MRI local extent before salvage surgery

PURPOSE

To determine pre-operative MRI accuracy in assessing local disease extent in recurrent/residual pelvic bowel cancer by comparing MRI assessment and staging examination under anaesthesia (EUA), with laparotomy/histopathological findings.

MATERIALS AND METHODS

Twenty-seven consecutive patients with recurrent (n = 21) or residual (n = 6) pelvic bowel cancer (13 of the rectum, eleven of the anus and three of the colon) underwent EUA and pelvic MRI (1T) using a phased array pelvic coil. Retrospective analysis of eight specific anatomical regions for tumour involvement on MRI was performed. Findings at EUA and biopsy were recorded. The MRI and EUA findings were correlated with findings at surgery and histopathology. Statistical comparison between MRI and EUA results was performed using the chi-squared test.

RESULTS

Overall MRI accuracy in determining tumour invasion for all sites assessed was 452/499 (91%), sensitivity was 95/109 (87%), specificity was 357/390 (92%), positive predictive value (PPV) was 95/128 (74%) and negative predictive value (NPV) was 357/371 (96%). PPV and NPV for specific areas were 21/38 (55%) and 134/136 (99%) for genitourinary tract, 4/6 (67%) and 61/65 (94%) for pelvic side wall, 21/26 (81%) and 40/41 (98%) for pelvic floor, 1/6 (17%) and 40/43 (93%) for the posterior pelvis pre-sacrum/sacrum. For those anatomical sites evaluated by both EUA and MRI, MRI was superior to EUA, with an accuracy of 89% vs 73% (P < 0.05).

CONCLUSION

MRI is an accurate technique for assessing disease extent in recurrent/residual pelvic bowel cancer.

The assessment of irradiated bladder carcinoma using dynamic contrast-enhanced MR imaging

AIM

To evaluate the role of dynamic contrast-enhanced magnetic resonance imaging (DCEMRI) in distinguishing residual or recurrent tumour from radiation change in patients with bladder carcinoma.

MATERIALS AND METHODS

Forty patients with biopsy proven bladder carcinoma were imaged before and at 4 and 12 months after radiotherapy (XRT) using conventional and dynamic contrast-enhanced magnetic resonance imaging at 0.5 Tesla. An enhancement of >1.54 times above baseline at 80 s post-contrast injection proved a reliable indicator of tumour before radiotherapy and was therefore applied to the assessment of patients after XRT. Conventional MR images and dynamic enhancement profiles (DEPs) from the site of previous tumour were scored by three radiologists for the presence of tumour at 4 and 12 months after XRT. Findings were compared with cystoscopic biopsy.

RESULTS

Dynamic contrast-enhanced magnetic resonance imaging had negative predictive values of 100% and 93% for tumour recurrence at 4 and 12 months, respectively. The positive predictive values, sensitivity and specificity were 48, 100 and 48% at 4 months and 50, 80 and +76% at 12 months post XRT, respectively.

CONCLUSION

Dynamic contrast-enhanced magnetic resonance imaging may prove reliable in excluding the presence of persistent or recurrent tumour up to 12 months after XRT.

Quantitative dynamic contrast enhanced MRI of recurrent pelvic masses in patients treated for cancer

Recurrent tumour and post-treatment inflammatory masses may be difficult to differentiate on T2 weighted and post-contrast T1 weighted MR sequences. The purpose of this study was to assess the value of quantitative analysis of enhancement patterns in improving the separation of tumour recurrence from benign post-treatment masses in the pelvis. 32 patients with a total of 44 benign or malignant pelvic masses arising more than 6 months after treatment by surgery and/or radiotherapy were studied. After localizing the lesion on T1 and T2 weighted sequences, sequential T1 weighted spoiled gradient recalled echo (SPGR) images were obtained through the mass during bolus intravenous injection of 0.1 mmol kg-1 of Gd-chelate. Analysis of the maximum enhancement and proportion of maximum enhancement by 30, 60 and 90 s after onset of injection was performed prospectively by radiologists using standard manufacturer's software. Semi-automated analyses using software to provide irregular regions of interest and automated signal intensity measurements were also performed. Maximum enhancement was significantly greater in tumour recurrence than fibrosis following surgery, with better separation between the two groups using computer assisted analysis (p < 0.001) than manual analysis (p < 0.05). Separation between post-radiotherapy tumour recurrence and benign post-radiotherapy masses reached statistical significance for manual measurements of maximum enhancement (p < 0.05) but not for computer assisted analysis. There was no significant difference in enhancement rates between benign and malignant masses in post-radiotherapy patients. Measurement of the maximum enhancement of a mass alone does not reliably separate lesions in the post-radiotherapy patient but may be helpful when considered together with signal intensity and morphology on conventional MRI sequences.