Magnetic resonance imaging of rectal cancer: staging and restaging evaluation.

Magnetic resonance imaging is used to non-invasively stage and restage rectal adenocarcinomas. Accurate staging is important as the depth of tumor extension and the presence or absence of lymph node metastases determines if an individual will undergo preoperative neoadjuvant chemoradiation. Accurate description of tumor location is important for presurgical planning. The relationship of the tumor to the anal sphincter in addition to the depth of local invasion determines the surgical approach used for resection. High-resolution T2-weighted imaging is the primary sequence used for initial staging. The addition of diffusion-weighted imaging improves accuracy in the assessment of treatment response on restaging scans. Approximately 10%-30% of individuals will experience a complete pathologic response following chemoradiation with no residual viable tumor found in the resected specimen at histopathologic assessment. In some centers, individuals with no residual tumor visible on restaging MR who are thought to be at high operative risk are monitored with serial imaging and a "watch and wait" approach in lieu of resection. Normal rectal anatomy, MR technique utilized for staging and restaging scans, and TMN staging are reviewed. An overview of surgical techniques used for resection including newer, minimally invasive endoluminal techniques is included.

Locally Advanced Rectal Cancer Evaluation by Magnetic Resonance Imaging after Neoadjuvant Therapy on Decision Making: Cancer Center Experience and Literature Review.

PURPOSE: An accurate clinical and radiological staging is the pyramid of treatment decisions in locally advanced rectal cancer (LARC). Guidelines recommended neoadjuvant chemoradiation therapy (CRT) followed by surgical resection for fit patients with LARC. Determining the aggressiveness of intervention while avoiding needless morbidity according to patient risk remains an unmet pre-operative decision-making need. With newer magnetic resonance imaging (MRI) techniques and image acquisition available at our Cancer Center, we seek to retrospectively review the correlation between pre- and post-CRT MRI response to the surgical pathological stage in order to aide multidisciplinary team decision making. METHODS: Our Cancer Center Rectal Cancer Registry between 2011 and 2015 included 57 patients with LARC, 20 completed standard CRT with surgery, and of those 10 had repeated MRI after CRT. RESULTS: Our retrospective case series revealed that 90% of the patients had a downstage tumor response on surgical specimen compared to radiological evaluation after CRT, and furthermore, all patients who were re-staged with MRI prior to surgery correlated with the gold standard pathological stage (p = 0.02). CONCLUSIONS: Post-CRT MRI could potentially aide decision making to further avoid 20% of patients with a complete pathological response from a morbid surgery, whereas 10% of patients with an upstaged disease state may require a more aggressive neoadjuvant or planned surgical intervention. We concluded that future multidisciplinary oncology care treatment decision making would benefit from a repeat MRI after neoadjuvant CRT of LARC.

Classification and Diagnosis of Cystic Renal Tumors: Role of MR Imaging Versus Contrast-Enhanced Ultrasound.

Superior soft tissue and contrast resolution of MR imaging benefits sensitivity to kidney cyst features and classification, which may have an impact on patient management and outcomes. Contrast-enhanced ultrasound (CEUS) may have nearly similar sensitivity for detection of cyst features yet is dependent on patient body habitus and adequacy of visualization windows for the kidneys, which does not have the same impact on MR imaging results. Both MR imaging and CEUS may provide superior kidney cyst assessment compared with contrast-enhanced CT; however, further research is needed, particularly for the identification of role of CEUS.

MR Imaging Evaluation of the Kidneys in Patients with Reduced Kidney Function: Noncontrast Techniques Versus Contrast-Enhanced Techniques.

MR imaging has been optimized for the evaluation of a multitude of disease processes affecting the kidneys. A wide variety of noncontrast methods are available for the evaluation of both kidney structure and function, which are especially useful in clinical scenarios that obviate the use of intravenous contrast. Contrast-enhanced methods remain important, especially for tumor evaluation, and are used increasingly for functional analysis of quantitative biometrics, such as glomerular filtration rate and kidney blood flow.

Improved Detection of Pelvic Organ Prolapse: Comparative Utility of Defecography Phase Sequence to Nondefecography Valsalva Maneuvers in Dynamic Pelvic Floor Magnetic Resonance Imaging.

PURPOSE: To evaluate the utility of a defecography phase (DP) sequence in dynamic pelvic floor MRI (DPMRI), in comparison to DPMRI utilizing only non-defecography Valsalva maneuvers (VM). MATERIALS AND METHODS: Inclusion criteria identified 237 female patients with symptoms and/or physical exam findings of pelvic floor prolapse. All DPMRI exams were obtained following insertion of ultrasound gel into the rectum and vagina. Steady-state free-precession sequences in sagittal plane were acquired in the resting state, followed by dynamic cine acquisitions during VM and DP. In all phases, two experienced radiologists performed blinded review using the H-line, M-line, Organ prolapse (HMO) system. The presence of a rectocele, enterocele and inferior descent of the anorectal junction, bladder base, and vaginal vault were recorded in all patients using the pubococcygeal line as a fixed landmark. RESULTS: DPMRI with DP detected significantly more number of patients than VM (p<0.0001) with vaginal prolapse (231/237, 97.5% vs. 177/237, 74.7%), anorectal prolapse (227/237, 95.8% vs. 197/237, 83.1%), cystocele (197/237, 83.1% vs. 108/237, 45.6%), and rectocele (154/237, 65% vs. 93/237, 39.2%). The median cycstocele (3.2cm vs. 1cm), vaginal prolapse (3cm vs. 1.5cm), anorectal prolapse (5.4cm vs. 4.2cm), H-line (8cm vs. 7.2cm) and M-line (5.3cm vs. 3.9cm) were significantly higher with DP than VM (p<0.0001). CONCLUSIONS: Addition of DP to DPMRI demonstrates a greater degree of pelvic floor instability as compared to imaging performed during VM alone. Pelvic floor structures may show mild descent or appear normal during VM, with marked prolapse on subsequent DP images.

Dynamic Pelvic Magnetic Resonance Imaging Evaluation of Pelvic Organ Prolapse Compared to Physical Examination Findings.

OBJECTIVE: To compare dynamic magnetic resonance imaging (dMRI) defecography phase findings with physical examination (PE) grading in the evaluation of pelvic organ prolapse (POP). METHODS: We retrospectively reviewed 274 consecutive patients who underwent dMRI with defecography. Baden-Walker grading of POP, absolute dMRI values, and grading by dMRI were collected for anterior, apical, and posterior compartments. Anatomically significant POP on PE was defined as Baden-Walker Grade ≥3 and on dMRI by dMRI Grade ≥2. A Spearman's Rank correlation was performed between absolute dMRI values and respective POP grades. RESULTS: A total of 178 female patients were included. Anatomically insignificant and significant cystoceles had a 26.4% (19/72) and 84.6% (66/78) agreement respectively. Anatomically insignificant and significant apical prolapse had a 2.0% (2/100) and 62.9% (17/27) agreement respectively. Anatomically insignificant and significant posterior prolapse had a 49.5% (51/103) and 78.7% (59/75) agreement respectively. PE detected only 30% (9/30) of total dMRI detected enteroceles and misdiagnosed 10% (3/30) of these patients with a rectocele. CONCLUSION: The dMRI defecography phase correlated well for anatomically significant prolapse in anterior and posterior compartments. dMRI was superior to PE for enterocele detection and was better able to distinguish an enterocele from a rectocele. Thus, dMRI may have the greatest diagnostic value in cases where the presence of an enterocele is unclear in apical and/or posterior compartments.