Body Coil Magnetic Resonance Imaging Research Articles

Prostate magnetic resonance imaging: The truth lies in the eye of the beholder

PurposeTo determine the diagnostic accuracy and interobserver variability of radiologic interpretation of magnetic resonance imaging (MRI) performed for surgical planning before prostatectomy. Patients and methodsThe records of 233 men undergoing prostatectomy with presurgical multiparametric 3T surface body coil MRI were reviewed. All initial films were read by a fellowship-trained body radiologist provided with relevant clinical information. A senior radiologist then reread all pelvic MRIs blinded to the initial interpretation with findings from both readings compared to final pathology. Kappa (κ) scores as well as sensitivity, specificity, positive predictive values (PPV), negative predictive value (NPV), and accuracy were determined. ResultsWhen considering extraprostatic extension (EPE), there was low concordance comparing the initial vs. repeat MRI interpretation (κ = 0.22). Additionally, when the senior radiologist reread his own initial interpretation (n = 93, blinded to initial result), concordance for EPE was greater (κ = 0.36) albeit similarly low. With regard to EPE, a comparison of initial MRI interpretation vs. reread by senior radiologist noted universal improvements in diagnostic characteristics including sensitivity (30.3% vs. 56.1%), specificity (80.2% vs. 88.6%), PPV (37.7% vs. 66.1%), NPV (74.4% vs. 83.6%), and accuracy (66.1% vs. 79.4%). In contrast, seminal vesicle invasion interpretation was more uniform whereby initial MRI interpretation vs. reread yielded similar sensitivity (18.2% vs. 27.3%), specificity (97.2% vs. 93.8%), PPV (40.0% vs. 31.6%), NPV (91.9% vs. 92.5%), and accuracy (89.7% vs. 87.6%). ConclusionsEven at a tertiary referral center, interobserver variability among radiologists regarding local extent of disease on prostate MRI is high. These observations underscore the importance of uniformity when defining criteria for EPE and seminal vesicle invasion to allow for optimal presurgical planning.

Optimal Methods for Staging Rectal Cancer

At present, several modalities exist for the preoperative staging of rectal lesions, including computed tomography (CT), body coil or endorectal coil magnetic resonance imaging (MRI), endoscopic ultrasonography (EUS) done by rigid or flexible probes, and positron emission tomography (PET). Staging accuracy for CT ranges from 53% to 94% for T-stage accuracy and from 54% to 70% for N-stage accuracy. Improved CT accuracy is observed at higher disease stages. Body coil MRI has shown T- and N-stage accuracy ranging from 59% to 95% and 39% to 95%, respectively. Endorectal coil MRI has shown improved T- and N-stage accuracy, with rates of 66% to 91% and 72% to 79%, respectively. The development of phased-array MRI, combining high spatial resolution with a larger field of view, offers promise to improve on these rates. EUS, considered the current gold standard, has shown T-stage accuracy ranging from 75% to 95%, with N-stage accuracy ranging from 65% to 80%. Flexible EUS probes have the advantage of being able to access and sample iliac nodes. Recent studies also suggest that three-dimensional EUS may provide greater accuracy than conventional two-dimensional EUS. Limited studies exist on the use of PET in primary tumor staging. PET may upstage disease in 8% to 24% of patients and has also been used in posttreatment restaging and surveillance. Postradiation edema, necrosis, and fibrosis seem to decrease restaging accuracy in all modalities. This article reviews the current literature about the staging accuracy of the various modalities and suggests a staging algorithm for rectal cancer.

Endoscopic Ultrasonography and Magnetic Resonance in Preoperative Staging of Rectal Cancer: Comparison With Histologic Findings

The development of new surgical techniques and use of neoadjuvant therapy have increased the need for accurate preoperative staging of rectal cancer. We compared the ability of endoscopic ultrasonography (EUS) and two magnetic resonance imaging (MRI) coils to locally stage rectal carcinoma before surgery. Forty-nine patients with histologically proven rectal carcinoma were T and N staged by EUS and either body coil MRI or phased-array coil MRI. After radical surgery, the preoperative findings were compared with histologic findings on the surgical specimen. For T stage, accuracies were 70% for EUS, 43% for body coil MRI, and 71% for phased-array coil MRI. For N stage, accuracies were 63% for EUS, 64% for body coil MRI, and 76% for phased-array coil MRI. For T stage, EUS had the best sensitivity (80%) and the same specificity (67%) as phased-array coil MRI. For N stage, phased-array coil MRI had the best sensitivity (63%) and the same specificity (80%) as the other methods. EUS and phased-array coil MRI provided similar results for assessing T stage. No method provided satisfactory assessments of local N stage, although phased-array coil MRI was marginally better in assessing this important parameter. Although none of the results differed significantly, phased-array coil MRI seems to be the best single method for the preoperative staging of rectal cancer.

Clinical Examination, Endosonography, and MR Imaging in Preoperative Assessment of Fistula in Ano: Comparison with Outcome-based Reference Standard

To prospectively evaluate the relative accuracy of digital examination, anal endosonography, and magnetic resonance (MR) imaging for preoperative assessment of fistula in ano by comparison to an outcome-derived reference standard. Ethical committee approval and informed consent were obtained. A total of 104 patients who were suspected of having fistula in ano underwent preoperative digital examination, 10-MHz anal endosonography, and body-coil MR imaging. Fistula classification was determined with each modality, with reviewers blinded to findings of other assessments. For fistula classification, an outcome-derived reference standard was based on a combination of subsequent surgical and MR imaging findings and clinical outcome after surgery. The proportion of patients correctly classified and agreement between the preoperative assessment and reference standard were determined with trend tests and kappa statistics, respectively. There was a significant linear trend (P < .001) in the proportion of fistula tracks (n = 108) correctly classified with each modality, as follows: clinical examination, 66 (61%) patients; endosonography, 87 (81%) patients; MR imaging, 97 (90%) patients. Similar trends were found for the correct anatomic classification of abscesses (P < .001), horseshoe extensions (P = .003), and internal openings (n = 99, P < .001); endosonography was used to correctly identify the internal opening in 90 (91%) patients versus 96 (97%) patients with MR imaging. Agreement between the outcome-derived reference standard and digital examination, endosonography, and MR imaging for classification of the primary track was fair (kappa = 0.38), good (kappa = 0.68), and very good (kappa = 0.84), respectively, and fair (kappa = 0.29), good (kappa = 0.64), and very good (kappa = 0.88), respectively, for classification of abscesses and horseshoe extensions combined. Endosonography with a high-frequency transducer is superior to digital examination for the preoperative classification of fistula in ano. While MR imaging remains superior in all respects, endosonography is a viable alternative for identification of the internal opening.

Role of dynamic pelvic floor magnetic resonance imaging (MRI) in the assessment of patients with idiopathic combined faecal and urinary incontinence

The aetiology of combined urinary and faecal incontinence (UFI) are interrelated and remain poorly understood; affecting appropriate patient selection, thus accountmg for sub-optimal surgical outcome. A potential variable in this process is Global pelvic floor dysfunction (GPFD). The aim of this study was to prospectively assess whether use of phased array body coil MRI could identify global pelvic floor dysfunction in these patients with multisystem dysfunctional symptoms. Symptomatic parncipants were selected from patients presenting with complaints of combined urinary and faecal incontinence either in the colorectal or urology outpatient clinics. Patients who have had previous pelvic floor surgery were excluded from this study. All underwent standard urodynamics and anorectal physiology assessment. Voiding cystometry, coIonoscopy and endoanal ultrasound were also performed. A standardised protocol was used for the MRI imaging. Thirty individual parameters were measured using buih-in-sofiware (callipers, compass and densitometer). Statistical analysis was performed using SPSS software Nineteen consecutive patients were assessed. Patiems were age, sex and parity matched with asymptomatic controls (n= 11). The MRI procedure was tolerated well by all the participants. Results are shown in the table. Body coil MRI is a non-invasive, well-tolerated imaging modafity. The novel use of MR1 in these patients has demonstrated for the first time distinct anatomical features evident in the levator plate, Urethrovesical angle and anal sphincter complex in patients with GFPD. Our data suggests that body coil dynamic MR1 may have a potential role in identifying patients with global perineal muscle dysfunction, thus facilitating definitive surgical management.

Evaluation of the role of pre-operative magnetic resonance imaging in the management of rectal cancer.

This study assesses the ability of body coil magnetic resonance imaging (MRI) to pre-operatively stage mural penetration, nodal status and circumferential resection margin (CRM) involvement of rectal cancer. Between 1995 and 1997, MRI using a body coil was performed in consecutive patients with primary rectal carcinomas. Group A: 67 patients underwent surgery without long course neo-adjuvant therapy. Predicted tumour stage was compared to the histology of the specimen. Group B: 21 patients with MRI evidence of advanced disease, underwent long course neo-adjuvant therapy followed by repeat MRI prior to surgery. The second scan assessed response to treatment and likelihood of CRM involvement at subsequent surgery. Group A: Accuracy of pre-operative staging was: 'T' stage - 54%, 'N' stage - 77%, involvement of CRM by tumour - 97%. Group B: After long course neo-adjuvant therapy the second MRI scan was 95% accurate in predicting CRM involvement by tumour. In this study pre-operative rectal cancer staging with MRI and a body coil lacks accuracy in predicting mural penetration and nodal involvement. Body coil MRI can accurately predict the potential for CRM involvement. This technique may help determine which patients require long course neo-adjuvant therapy.

Endoanal ultrasound or magnetic resonance imaging for preoperative assessment of anal fistula: a comparative study.

To compare endoanal ultrasound (EUS) with a 10-MHz probe vs. bodycoil magnetic resonance imaging (MRI) in the preoperative evaluation of anal fistula. 23 patients with fistula in the anal region underwent preoperative 0.5 T bodycoil MRI and 10 MHz EUS which included probing in 6 patients. The results of the EUS and MRI were compared against the surgical findings as a reference method. In classification of the primary tract there was agreement between EUS and surgical findings in 14 (61%) and between MRI and surgery in 11 (48%). Concerning the presence of an internal opening the corresponding figures were 17 (74%) and 10 (43%) and in judging the presence of an extension or an abscess 15 (65%) vs. 11 (48%), respectively. In three out of eight patients with nonhealing or recurrence after surgery preoperative imaging had shown an extension and/or an abscess that was not identified by the surgeon. EUS, sometimes complemented with probing, is well comparable to bodycoil MRI in classifying and describing the topography of an anal fistula.

Endoluminal MR imaging of anorectal diseases.

Endoluminal magnetic resonance imaging (MRI) has become an important technique in the diagnostic work-up of patients with anorectal diseases. The high spatial resolution of endoluminal MRI gives a detailed demonstration of the anal and rectal anatomy and pathology. This technique has been demonstrated to be superior to endoluminal sonography and body coil MRI. Endoanal MRI and phased-array coil MRI seem to have comparable results in perianal fistulas, but comparative data are lacking. Phased-array coil MRI is the imaging technique of choice for imaging rectal tumors, while endoluminal MRI is the alternative technique for imaging rectal tumors and the preferred technique for imaging anal tumors. Endoluminal MRI is superior to phased-array coil MRI in fecal incontinence, as phased-array coil MRI does not give the detailed spatial resolution required for evaluation of anal sphincter lesions.

Comparison of the digital rectal examination, endorectal ultrasound, and body coil magnetic resonance imaging in the staging of adenocarcinoma of the prostate

A series of 25 patients with biopsy proven adenocarcinoma of the prostate underwent preoperative staging evaluation with a digital rectal examination, endorectal ultrasound, and body coil magnetic resonance imaging (MRI) before their radical retropubic prostatectomy. The sensitivity and specificity of the digital rectal examination for the detection of extracapsular disease were 17 and 100%, respectively. The sensitivity and specificity of endorectal ultrasound for the detection of extracapsular disease were 35 and 89%, respectively. The sensitivity and specificity of body coil MRI for the detection of extracapsular disease by adenocarcinoma of the prostate were 47 and 63%, respectively. Microscopic disease of the capsule and seminal vesicles was the principle reason for understaging by both imaging modalities. This small series suggests that both imaging modalities are marginally more sensitive, albeit less specific, for extracapsular disease of the prostate than the digital rectal examination, with ultrasound having a slight edge in specificity and MRI having a slight edge in sensitivity.