MRI of recurrent rectosigmoid carcinoma

Mediastinal fibrosis as a late and fatal complication of treated tuberculosis mimicking a neoplastic process in a 34-year-old man

Fibrosing mediastinitis, also known as sclerosing mediastinitis, is an uncommon condition marked by abnormal proliferation of fibrous tissue in the mediastinum. This condition may accrue either as an idiopathic condition or as a complication of an underlying disease process. Its pathogenesis remains unknown. However, most reported cases are incriminating abnormal immune-mediated hypersensitivity responses to Histoplasma infection. Other rare causes include tuberculosis, blastomycosis, and an idiopathic form that may be associated with other miscellaneous conditions. CT and MR imaging play a vital role in the diagnosis and management of this disease. We present a rare case of fibrosing mediastinitis as a late complication of tuberculosis in a 34-year-old man with a prior history of mediastinal tuberculosis, mimicking initially a neoplastic mediastinal process. We will describe this clinical case in the light of the literature and point out the contribution of radiological imaging in the diagnosis of this rare pathology.

Radiation risks associated with serial imaging in colorectal cancer patients: Should we worry?

To provide an overview of the radiation related cancer risk associated with multiple computed tomographic scans required for follow up in colorectal cancer patients. A literature search of the PubMed and Cochrane Library databases was carried out and limited to the last 10 years from December 2012. Inclusion criteria were studies where computed tomographic scans or radiation from other medical imaging modalities were used and the risks associated with ionizing radiation reported. Thirty-six studies were included for appraisal with no randomized controlled trials. Thirty-four of the thirty-six studies showed a positive association between medical imaging radiation and increased risk of cancer. The radiation dose absorbed and cancer risk was greater in children and young adults than in older patients. Most studies included in the review used a linear, no-threshold model to calculate cancer risks and this may not be applicable at low radiation doses. Many studies are retrospective and ensuring complete follow up on thousands of patients is difficult. There was a minor increased risk of cancer from ionizing radiation in medical imaging studies. The radiation risks of low dose exposure (< 50 milli-Sieverts) are uncertain. A clinically justified scan in the context of colorectal cancer is likely to provide more benefits than harm but current guidelines for patient follow up will need to be revised to accommodate a more aggressive approach to treating metastatic disease.

Value of diffusion-weighted and gadolinium-enhanced MRI for the diagnosis of pelvic recurrence from colorectal cancer

PURPOSE

To prospectively assess the added value of gadolinium-enhanced and diffusion-weighted (DWI) MRI for the diagnosis of pelvic recurrence from colorectal cancer (CRC).

MATERIALS AND METHODS

Fifty-two patients with suspected pelvic recurrence from CRC underwent pelvic MRI with T2-weighted ("T2"), gadolinium-enhanced fat-suppressed T1-weighted ("gadolinium") and DWI MR sequences. Three readers (senior radiologist: R1, two residents: R2, R3) scored the likelihood of recurrence on "T2," "T2 + DWI," and "T2 + Gadolinium."

RESULTS

Twenty-seven patients had 42 sites of pelvic recurrence. On "T2," R1 achieved AUC of .95, sensitivity 88.4%, specificity 95.2%. For R2, these figures were .89, 81.4%, 90.5%, for R3 .90, 83.7%, 76%. Both Gadolinium injection and DWI significantly improved AUCs for residents but not for the senior radiologist: up to .988 (R2, P = 0.006) and to .98 (R3, P = 0.01) with DWI and to .96 (R2, P = 0.04), .98 (R3, P = 0.01) after gadolinium. All readers achieved slightly better AUCs with "T2 + DWI" than with "T2+Gadolinium" but not significantly (P = 0.68, P = 0.11, P = 0.3; respectively).

CONCLUSION

For diagnosis of pelvic recurrence from CRC, both DWI and gadolinium-enhanced MRI significantly increase diagnostic performances compared with "T2" MRI for residents. DWI may be helpful in patients with contra-indications to intravenous administration of gadolinium.

Local colorectal cancer recurrence: pelvic MRI evaluation

Surveillance of colorectal cancer is currently based on dosage of tumoral markers, colonoscopy and multidetector row computed tomography. However, pelvic magnetic resonance imaging (MRI) and PET-CT are two second-line useful imaging modalities to assess colorectal cancer local recurrence (LR). The anatomical information derived from MRI combined to the functional information provided by diffusion-weighted imaging currently remain of value. Pelvic MRI is accurate not only for detection of pelvic colorectal recurrence but also for the prediction of absence of tumoral invasion in pelvic structures, and it may thus provide a preoperative road map of the recurrence to allow for appropriate surgical planning. As always, correlation of imaging and clinical findings in the multidisciplinary forum is paramount. MRI can also be used to follow-up LR treated with radiofrequency ablation. The aim of this review is to discuss clinical practice and application of MRI in the assessment or pelvic recurrence from colorectal cancer.

[3.0T MRI with a high resolution protocol for the study of benign disease of the anus and rectum. Part 2: Anorectal inflammatory disease. Postsurgical anatomy and complications after treatment]

Benign anorectal disease comprises a broad group of processes with very diverse origins; these processes may be congenital or acquired as well as inflammatory or tumor related. However, benign anorectal disease has received less attention in the scientific literature than malignant disease. In this second part of this image-based review of benign anorectal disease, we describe the most common inflammatory and fistulous diseases, the postsurgical anatomy, and complications that can occur after surgical treatment or radiotherapy for anorectal disease.

Absence of tumor invasion into pelvic structures in locally recurrent rectal cancer: prediction with preoperative MR imaging

PURPOSE

To retrospectively assess the accuracy of preoperative magnetic resonance (MR) imaging for identification of tumor invasion into pelvic structures in patients with locally recurrent rectal cancer scheduled to undergo curative resection.

MATERIALS AND METHODS

The institutional review board approved this study, and informed consent was waived because of the retrospective nature of the study. Preoperative MR images in 40 consecutive patients with locally recurrent rectal cancer scheduled to undergo curative treatment between October 2003 and November 2006 were analyzed retrospectively. Four observers with different levels of experience in reading pelvic MR images assessed tumor invasion into the following structures: bladder, uterus or seminal vesicles, vagina or prostate, left and right pelvic walls, and sacrum. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated, and a receiver operating characteristic curve was constructed. Surgical and/or histopathologic findings were used as the reference standard. Interobserver agreement was measured by using kappa statistics.

RESULTS

Preoperative MR imaging was accurate for the prediction of tumor invasion into structures with negative predictive values of 93%-100% and areas under receiver operating characteristic curves of 0.79-1.00 for all structures and observers. Positive predictive values were 53%-100%. Disease was overstaged in 11 (observer 1), 22 (observer 2), 10 (observer 3), and nine (observer 4) structures and was understaged in nine (observer 3) and two (observer 4) structures. Assessment failures were mainly because of misinterpretation of diffuse fibrosis, especially at the pelvic side walls. Interobserver agreement ranged between 0.64 and 0.99 for experienced observers.

CONCLUSION

Preoperative MR imaging is accurate for the prediction of absence of tumor invasion into pelvic structures. MR imaging may be useful as a preoperative road map for surgical procedure and may thus increase chances of complete resection. Interpretation of diffuse fibrosis remains difficult.

[Postoperative imaging after colorectal surgery]

Surgery for the treatment of colorectal diseases has been evolving rapidly recently. In addition to classical surgical procedures (colectomy, abdominoperineal resection), new surgical procedures include coloproctectomy with creation of an ileoanal anastomosis and ileal pouch, pelvic reconstructions (omentoplasty, placement of myocutaneous flaps) and creation of different colic anastomoses after anterior rectal resection. Even if computed tomography and fluoroscopic contrast examinations are still commonly used to assess postoperative changes and complications, especially infections, pelvic magnetic resonance imaging is useful to depict postoperative changes, detect complications such as fistulas and tumor recurrence in patients who have undergone surgery for primary or recurrent rectal disease. The main surgical techniques, their respective indications and postsurgical imaging features will be discussed. The main complications and imaging work-up will also be reviewed.

Magnetic resonance imaging in locoregional staging of rectal adenocarcinoma

A comprehensive overview of the current status of magnetic resonance imaging (MRI) in the locoregional assessment and management of rectal adenocarcinoma is presented. Staging systems for rectal cancer and treatment strategies in its management are discussed to give the reader the context that shapes MRI acquisition techniques and interpretation. Findings on MRI are detailed and their accuracy reviewed based on currently available evidence. Optimization of MRI acquisition and relevant pelvic anatomy are reviewed. A detailed description of our approach in interpreting MRI for locoregional staging of rectal cancer is given and future directions are also introduced.

Significance of perivascular soft tissue around the common hepatic and proximal superior mesenteric arteries arising after pancreaticoduodenectomy: evaluation with serial MDCT studies

PURPOSE

To evaluate the interval change of perivascular soft tissue (PVST) around the common hepatic and proximal superior mesenteric arteries arising after pancreaticoduodenectomy (PD) and to compare the difference between post operative change (benign PVST) and recurrence (malignant PVST).

MATERIALS AND METHODS

Serial multidetector CT (MDCT) studies in 44 patients who underwent PD for periampullary carcinomas were retrospectively reviewed (Group A). The incidence and interval change of PVST were evaluated and compared to control group (Group B, 21 patients with PD for benign diseases).

RESULTS

PVST was seen in all the 44 patients in Group A, and it was noted in 12 of 21 (57.1%) patients in Group B. Thirteen of 44 (29.5%) patients showed interval enlargement of PVST (malignant PVST), and 12 of 13 developed within 2 years after PD. There was higher incidence of malignant PVST in patients with lymph node metastasis (p < 0.01) and those with pancreas head carcinoma (p < 0.05).

CONCLUSION

PVST is common after PD regardless of whether patients had malignant or benign diseases. PVST should be monitored for at least 2 years to distinguish recurrence from post operative change. Patients with lymph node metastasis and pancreas head carcinoma had a higher incidence of malignant PVST.

Evaluation of locally recurrent pelvic malignancy: performance of T2- and diffusion-weighted MRI with image fusion

PURPOSE

To evaluate the performance of T2- and diffusion-weighted magnetic resonance imaging (MRI) with image fusion for detection of locally recurrent pelvic malignancy.

MATERIALS AND METHODS

The study group consisted of 28 patients (27 female, 1 male) who underwent pelvic MRI at 1.5 T after treatment of pelvic malignancy. MR images were reviewed independently by three blinded readers. The performance of the four sequences for detecting local recurrence was evaluated using receiver operating characteristic analysis: T2-weighted fast spin-echo (FSE), diffusion-weighted echo-planar imaging (DWI), dynamic contrast-enhanced (DCE) fat-suppressed T1-weighted spoiled gradient echo (SPGR), and T2-DWI with image fusion, the latter created using OsiriX Medical Imaging Software.

RESULTS

Local recurrence was confirmed at biopsy in 16 patients. Twelve patients showed no evidence of recurrence on two consecutive MRI studies. The Az value for T2-DWI with image fusion (0.949) was statistically greater than that for T2-weighted FSE (0.849) (P<0.05). The sensitivity and specificity was 87.5% and 47.2%, respectively, for T2-weighted FSE, 100.0% and 50.0% for DWI, 95.8% and 58.3% for DCE fat-suppressed T1-weighted SPGR, and 93.8% and 72.2% for T2-DWI with image fusion.

CONCLUSION

For depicting locally recurrent pelvic malignancy, T2-DWI with image fusion outperforms standard T2-weighted FSE and DWI and is comparable to DCE fat-suppressed T1-weighted SPGR.

3-T MRI of rectal carcinoma: preoperative diagnosis, staging, and planning of sphincter-sparing surgery

OBJECTIVE

The purpose of this study was to assess the accuracy of 3-T MRI in the preoperative diagnosis, staging, and planning of surgical management of rectal carcinoma.

SUBJECTS AND METHODS

Thirty-eight patients (23 men, 15 women) with clinically suspected rectal carcinoma underwent 3-T MRI. Coronal, axial, and sagittal T2-weighted sequences with and without fat suppression; axial T1-weighted spin-echo sequences; axial T1-weighted gradient-echo sequences with and without fat suppression; oblique 2D MR hydrography; and 3D fat-suppressed dynamic contrast-enhanced MRI were performed. Image quality with these sequences was evaluated by three radiologists experienced in body MRI. The significance of difference in results with the sequences was tested. The manner in which MRI staging and feasibility of sphincter-sparing surgery agreed with operative and pathologic findings was evaluated with kappa statistics.

RESULTS

Rectal carcinoma was identified on MRI and confirmed histologically in all 38 patients. MRI findings were correctly predictive of T category in 35 cases (accuracy, 92.1%). In 31 (96.9%) of 32 resectable cases,sphincter-sparing surgical approaches were accurately chosen on the basis of MRI findings. Among the 11 sequences, 3D fat-suppressed dynamic contrast-enhanced MRI best delineated tumor margins. Coronal and axial T2-weighted images also well depicted tumor margins with minimal artifact. T2-weighted images were superior to unenhanced T1-weighted images.

CONCLUSION

MRI of rectal cancer at 3 T is accurate for prediction of T category and the feasibility of sphincter-sparing surgery. The best images were obtained with coronal, sagittal, and axial T2-weighted sequences and 3D fat-suppressed dynamic contrast-enhanced MRI.

Detection of recurrent rectal cancer with CT, MRI and PET/CT

Computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) all have the potential to directly visualize local and distant relapse of colorectal cancer (CRC). Nevertheless, the role of diagnostic imaging for routine follow-up of CRC patients remains controversial. Although MRI and PET have advantages over CT in the detection of local recurrence, until now only a few surveillance programs recommend the use of annual CT for routine follow-up. The objective of this review is to elucidate the current status of diagnostic imaging for the detection of recurrent rectal cancer based on the recent literature and our own experience. Furthermore, an insight into contemporary surveillance programs and an outlook concerning a novel technical approach to moving-table MRI at 1.5 Tesla for staging purposes are given.

Anatomic and pathologic findings at external phased-array pelvic MR imaging after surgery for anorectal disease

Pelvic magnetic resonance (MR) imaging is useful for identification of postoperative changes, complications, and disease recurrence in patients who have undergone surgery for primary or recurrent anorectal disease. Commonly used interventions include treatment for anorectal carcinoma: anterior rectal resection with or without creation of different colic anastomoses and abdominoperineal excision with or without pelvic reconstruction (omentoplasty, placement of myocutaneous flaps). Other common interventions include treatment for inflammatory bowel disease (coloproctectomy with or without creation of an ileoanal anastomosis and ileal pouch) and treatment for fistulas (placement of flaps or setons). Postoperative anatomic changes and formation of scar tissue can usually be identified with consecutive MR imaging examinations. Pelvic MR imaging is an accurate technique for assessment of complications including anastomotic leakage, septic complications such as fistulas and abscesses, neoplastic recurrence, and other less common complications (perineal hernia, peritoneal pseudocyst). The sophisticated surgical procedures used in rectal surgery can alter normal anatomy and make image interpretation difficult. Thus, familiarity with the appearances of postoperative anatomic changes, complications, and tumor recurrence is essential for accurate MR imaging evaluation after surgery for anorectal disease.

Surgery for recurrent rectal carcinoma: The role of preoperative magnetic resonance imaging

Despite apparent curative resection of rectal carcinoma, local recurrence rates of between 3 and 32% have been reported. For those patients, radical surgical resection offers the only hope of cure. We present a review of the magnetic resonance imaging (MRI) findings and contraindications to curative surgery demonstrated using imaging.

Routine follow-up by magnetic resonance imaging does not improve detection of resectable local recurrences from colorectal cancer

OBJECTIVE

To determine if routine follow-up by magnetic resonance imaging (MRI) improves the detection of resectable local recurrences from colorectal cancer.

SUMMARY BACKGROUND DATA

Surgical treatment offers the best prospect of survival for patients with recurrent colorectal cancer. Unfortunately, most cases are often diagnosed at an unresectable stage when traditional follow-up methods are used. The impact of MRI surveillance on the early diagnosis of local recurrences has yet to be ascertained.

METHODS

Patients who underwent curative surgery for rectal and left-sided colon tumors were included in a program of pelvic surveillance by routine MRI, in addition to the standard follow-up protocol. Cases were then analyzed for mode of diagnosis, resectability, and overall survival.

RESULTS

Pelvic recurrence was found in 30 (13%) of the 226 patients studied. MRI detected 26 of 30 (87%) and missed 4 of 30 (13%) cases with local recurrence. Of the latter, 3 were anastomotic recurrences. In 28 (14%) patients, local recurrence was suspected by an initial MR scan but cleared by subsequent MRI or CT-guided biopsy. Recurrent pelvic cancer was diagnosed by MRI with 87% sensitivity and 86% specificity. In 19 (63%) cases, CEA was abnormally elevated, and 9 patients (30%) were symptomatic. Surgical resection was possible in only 6 patients (20%). There was no difference between MRI and conventional follow-up tests in their ability to detect cases suitable for surgery.

CONCLUSIONS

Pelvic surveillance by MRI is not justified as part of the routine follow-up after a curative resection for colorectal cancer and should be reserved for selectively imaging patients with clinical, colonoscopic, and/or biochemical suspicion of recurrent disease.

Preoperative radiotherapy improves outcome in recurrent rectal cancer

PURPOSE

When local recurrent rectal cancer is diagnosed without signs of metastases, a potentially curative resection can be performed. This study was designed to compare the results of preoperative radiotherapy followed by surgery with surgery only.

METHODS

Between 1985 and 2003, 117 patients with recurrent rectal cancer were prospectively entered in our database. Ninety-two patients were suitable for resection with curative intent. Preoperative radiation with a median dosage of 50 Gy was performed in 59 patients; 33 patients did not receive preoperative radiotherapy. The median age of the patients was respectively 66 and 62 years.

RESULTS

The median follow-up of patients alive for the total group was 16 (range, 4-156) months. Tumor characteristics were comparable between the two groups. Complete resections were performed in 64 percent of the patients who received preoperative radiation and 45 percent of the nonirradiated patients. A complete response after radiotherapy was found in 10 percent of the preoperative irradiated patients (n = 6). There were no differences in morbidity and reintervention rate between the two groups. Local control after preoperative radiotherapy was statistically significantly higher after three and five years (P = 0.036). Overall survival and metastases-free survival were not different in both groups. Complete response to preoperative radiotherapy was predictive for an improved survival.

CONCLUSIONS

Preoperative radiotherapy for recurrent rectal cancer results in a higher number of complete resections and an improved local control compared with patients treated without radiotherapy. Preoperative radiotherapy should be standard treatment for patients with recurrent rectal cancer.

Suspected local recurrence after radical prostatectomy: endorectal coil MR imaging

PURPOSE

To evaluate endorectal coil magnetic resonance (MR) imaging in the depiction of local recurrence after radical prostatectomy.

MATERIALS AND METHODS

Endorectal MR images were reviewed retrospectively in 82 patients who underwent prostatectomy. The interval between prostatectomy and MR imaging ranged between 0.5 and 13.0 years (mean, 3.25 years). Local recurrence was considered present if there was no evidence of distant metastases and there was a positive biopsy result, subsequent reduction in prostate-specific antigen (PSA) level after radiation therapy of the pelvis, or serial MR imaging findings of increased tumor size. Local recurrence on MR images was assessed for location, size, signal intensity, and invasion of adjacent structures. All images were reviewed independently by two readers who were blinded to clinical information.

RESULTS

Thirty-four of 82 patients did not meet inclusion criteria. Forty-one of 48 remaining patients had clinically documented local recurrence, which MR imaging depicted in 39 of 41 (95%) patients. Seven of 48 patients had no evidence of local or distant metastases, and none had positive MR imaging findings. Sensitivity of MR imaging was 95%, and specificity was 100%. Local recurrences were perianastomotic in 12 (29%) patients and retrovesical in 17 (40%), within retained seminal vesicles in nine (22%), and at anterior or lateral surgical margins in four (9%). All local recurrences were hyperintense to adjacent pelvic muscles on T2-weighted MR images. The mean diameter of tumors was 1.4 cm (range, 0.8-4.5 cm). PSA levels at MR imaging in patients with clinically proved recurrences ranged from undetectable to 10 ng/mL (mean, 2.18 ng/mL).

CONCLUSION

MR imaging depicts a high proportion of local recurrence after prostatectomy. The authors propose incorporation of endorectal coil MR imaging in the diagnostic paradigm of patients who have undergone prostatectomy and are suspected of having local recurrence.

Contrast-enhanced MR imaging of postoperative scars and VX2 carcinoma in rabbits: comparison of macromolecular contrast agent and gadopentetate dimeglumine

PURPOSE

To compare the magnetic resonance (MR) imaging enhancement patterns of a blood pool contrast agent, SH L 643A, with those of gadopentetate dimeglumine in postoperative scars and VX2 carcinomas in rabbits and to compare these enhancement patterns with microvessel density in pathologic specimens.

MATERIALS AND METHODS

Eighteen rabbits with experimentally induced postoperative scars (n = 12) or VX2 carcinoma (n = 6) in the thighs underwent sequential MR imaging first with gadopentetate dimeglumine and then, 24 hours later, with SH L 643A. The enhancement ratios (ie, the ratios of postcontrast to precontrast signal intensity) and the microvessel densities of postoperative scars and VX2 carcinomas were assessed. Differences were tested for by using the Mann-Whitney U and Wilcoxon signed rank tests.

RESULTS

In postoperative scars, enhancement ratios were consistently lower with injection of SH L 643A than with injection of gadopentetate dimeglumine for up to 30 minutes (P <.05). In postoperative scars, mean peak enhancement ratios were 1.29 +/- 0.15 (SD) with injection of SH L 643A and 1.61 +/- 0.31 with injection of gadopentetate dimeglumine (P <.01). In VX2 carcinomas, the enhancement ratios were not significantly different with injection of SH L 643A than with injection of gadopentetate dimeglumine at all time points. The mean difference between the enhancement ratios of the VX2 carcinomas and postoperative scars was 0.64 +/- 0.10 (range, 0.50-0.77) with SH L 643A and 0.36 +/- 0.16 (range, 0.17-0.66) with gadopentetate dimeglumine (P <.01). The mean microvessel density (in terms of vessels per field of view) was 10.7 +/- 5.5 for postoperative scars and 30.0 +/- 7.7 for VX2 carcinoma (P <.001).

CONCLUSION

The difference between the enhancement ratios of postoperative scars and VX2 carcinomas with SH L 643A was greater than that with gadopentetate dimeglumine. Enhancement ratios at SH L 643A-enhanced MR imaging corresponded well with microvessel density in postoperative scars and VX2 carcinomas.

Imaging of rectal cancer

Radiologic evaluation of rectal cancer is invaluable in aiding the surgeon, gastroenterologist, and oncologist in the initial and follow-up management of patients with this malignancy. This review highlights recent developments in computed tomography; ultrasonographic, metabolic, and magnetic resonance imaging of rectal cancer; its clinical ramifications; and the direction of future efforts.

Colorectal carcinoma: radiological diagnosis and staging

Colorectal carcinomas are the most common gastrointestinal tract tumors. 50-60% of the colorectal carcinomas originate in rectum and sigmoid colon. The new developments in imaging modalities have brought improvements in therapeutic aspects. The survival rates in these patients depend on the tumor penetration and the presence of regional lymph node or distant metastasis. The recurrence rates have decreased with the new operation techniques and preoperative radiotherapy, thus increasing the importance of accurate tumor staging. Double contrast barium enema studies enable the diagnosis while staging and follow-up is best done by topographic imaging techniques.

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.

Colon diseases: MR evaluation using combined T2-weighted single-shot echo train spin-echo and gadolinium-enhanced spoiled gradient-echo sequences

This study demonstrates the appearance of large bowel diseases on magnetic resonance (MR) images using breath-hold T2-weighted half-Fourier acquisition snapshot turbo spin-echo (HASTE), breath-hold T1-weighted spoiled gradient-echo (SGE), and breath-hold gadolinium-enhanced T1-weighted SGE with and without fat-suppression sequences. The study represents a collective experience using a generalized combined abdominal-pelvic imaging protocol. Of 29 patients, 27 had surgical, endoscopic, microbiological, and/or histopathological correlation, and 2 had a diagnosis based on characteristic imaging findings. Fifteen patients had neoplastic disease including colon adenocarcinoma (n = 11), rectosigmoid carcinoid (n = 1), familial adenomatous polyposis (n = 2), and cecal lipoma (n = 1). Fourteen patients had non-neoplastic disease including diverticulosis (n = 6), ischemic colitis (n = 2), pseudomembranous colitis (n = 2), acute appendicitis with periappendiceal abscess (n = 2), Mycobacterium avium intracellulare (MAI) colitis (n = 1), and Crohn's proctocolitis (n = 1). In all 15 patients with neoplastic diseases, MR imaging depicted the primary lesions and demonstrated local extent. Mass lesions were best shown on T2-weighted HASTE and gadolinium-enhanced fat-suppressed SGE images. Of 14 patients with non-neoplastic diseases, inflammatory changes were best shown on gadolinium-enhanced fat-suppressed T1-weighted SGE images in all cases. MR imaging with fast scanning breath-hold techniques and intravenous gadolinium enhancement provided good depiction and characterization of large bowel diseases.

Imaging of anorectal disease

BACKGROUND

Over the past two decades developments in imaging have changed the assessment of patients with anorectal disease.

METHODS

The literature on imaging techniques for anorectal diseases was reviewed over the period 1980-1999.

RESULTS

For the staging of primary rectal tumours, phased array magnetic resonance imaging (MRI) may be regarded as the most appropriate single technique. The combination of endosonography or endoluminal MRI with ultrasonography or spiral computed tomography yields similar results. All techniques have limitations both for local staging and in the assessment of distant metastases. MRI or positron emission tomography is preferable for tumour recurrence. For perianal fistula, high-resolution MRI (phased array or endoluminal) is the technique of choice. For constipation, defaecography is the preferred technique, nowadays with emphasis on functional information. The role of magnetic resonance defaecography is currently being evaluated. For faecal incontinence, endosonography and endoluminal MRI give similar results in detecting sphincter defects; endoluminal MRI has the advantage of detecting external sphincter atrophy.

CONCLUSION

High-resolution MRI, endosonography and defaecography are currently the optimal imaging techniques for anorectal disease.

Tissue characterization in the female pelvis by means of MR imaging

Pelvic imaging techniques such as computed tomography and ultrasonography provide a limited capability for tissue characterization. Fat, fluid, and calcification, for example, can be identified on the basis of parameters such as x-ray attenuation, echogenicity, and sound attenuation. Because of the many tissue parameters, such as T1, T2, magnetic susceptibility, and chemical shift, that contribute to signal intensity, magnetic resonance (MR) imaging may afford an ability to identify a wider array of specific tissues. The purpose of this article is to review the ability of MR imaging to help identify various types of soft tissue and to provide an approach to interpretation of MR images of the female pelvis through tissue characterization. Lipid, fluid, hemorrhage, smooth muscle, fibrosis, solid malignant tissue, and hydrated soft tissue (including edema, mucin, and myxomatous tissue) have typical MR imaging properties, and their presence in a mass can often be established on MR images. Consideration of the tissue composition of various pathologic processes in the pelvis can result in more systematic approaches to image interpretation and thus narrow the differential diagnosis.

Fibrosing mediastinitis: CT and MR findings

The aim of this study is to present the computed tomography (CT) and magnetic resonance (MR) findings in three cases of fibrosing mediastinitis, probably secondary to tuberculosis. Two patients had diffuse involvement of the mediastinum and one patient presented with a posterior mediastinal mass. On CT, the patients with diffuse involvement showed infiltrating soft-tissue masses with multiple foci of dense calcifications. One of these lesions enhanced mildly with contrast and one did not enhance. On MR examination, diffuse masses were of heterogeneous, intermediate and low signal on T1-weighted images (n = 2) and were of homogeneous low signal (n = 1) or heterogeneous (n = 1) signal intensity on T2-weighted images. After administration of Gd-DTPA, these mediastinal masses showed heterogeneous enhancement. The posterior mediastinal mass showed homogeneous pronounced enhancement on CT and was homogeneous with intermediate T1 signal intensity and hypointense T2 signal intensity. The CT findings of an infiltrative or well-defined mediastinal mass with scattered calcifications should suggest the diagnosis of fibrosing mediastinitis in the appropriate clinical setting. Although the appearance of calcification on MR are not specific, this technique provides further information than CT especially in those cases in which the lesions appear noncalcified, because MR imaging revealed areas of low signal intensity characteristic of fibrous tissue.

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.