Pari Tiwari

Can CT Replace MRI in Preoperative Assessment of the Circumferential Resection Margin in Rectal Cancer

The surgical circumferential resection margin in total mesorectal excision surgery is defined by the relationship of the tumor to the mesorectal fascia. Patients with anticipated tumor invasion of the mesorectal fascia receive neoadjuvant therapy to downstage/downsize the tumor and to obtain tumor-free resection margins. Tumor relationship to the mesorectal fascia is accurately determined by MRI. Compared with MRI, multidetector-row computed tomography is more widely available, faster, less costly, and provides the ability to simultaneously assess the liver, peritoneum, and retroperitoneum for metastases. PURPOSE: The objective of this study was to compare the accuracy of multidetector-row CT with conventional MRI in diagnosis of rectal cancer invasion of the mesorectal fascial envelope. MATERIALS AND METHODS: During a 2-year period, all patients were enrolled in this study who had biopsy-proven rectal carcinoma and were referred, as a part of the routine preoperative staging workup, for a CT scan of the abdomen and pelvis and also an MRI of the pelvis. All examinations were reviewed independently by 2 radiologists who were blinded from one another, from the findings of the other modality, and from clinical information. Both observers were dedicated abdominal radiologists who are experienced in reading pelvic CT and MRI. Categorical agreement between MRI and multidetector-row CT for all the evaluated parameters of the tumor position, mesorectal fascia, and lymph nodes, as well as the interobserver agreement between CT and MRI, was determined by the intraclass correlation weighted kappa statistic to measure the data sets consistency. RESULTS: Among the studys 92 patients, the tumor characteristics suggested by multidetector-row CT agreed with those of MRI, with a weighted &kgr; ranging from 0.488 to 0.748 for the first reader and 0.577 to 0.800 for the second reader. Interobserver agreement ranged from 0.506 to 0.746. Agreement regarding mesorectal fascia characteristics differed significantly between multidetector-row CT and MRI, depending on the level of assessment. In the distal rectum, agreement was 0.207 for the first reader and 0.385 for the second reader. In the mid rectum, agreement was 0.420 and 0.527, respectively, and in the proximal rectum agreement was 0.508 and 0.520. Interobserver agreement was 0.737 at the distal level and 0.700 at the mid and proximal levels. Agreement regarding measurement of the distance from the tumor to the mesorectal fascia was 0.425 for the first reader and 0.723 for the second reader, with interobserver agreement of 0.766. Agreement in assessment of the number of lymph nodes ranged from 0.743 to 0.787 for the first reader and 0.754 to 0.840 for the second reader. Interobserver agreement ranged from 0.779 to 0.841. Agreement in assessment of the size of the lymph nodes ranged from 0.540 to 0.830 for the first reader and 0.850 to 0.940 for the second reader. Interobserver agreement ranged from 0.900 to 0.920. Agreement in assessment of the distance from nodes to the mesorectal fascia was 0.320 for the first reader and 0.401 for the second reader, with interobserver agreement of 0.950. CONCLUSION: The results of this study differ from previously published data by demonstrating substantial agreement between readers in multidetector-row CT assessment of the tumor, mesorectal fascia, and lymph nodes. With the exceptions of mesorectal fascia in the distal rectum and the distance from the nodes to mesorectal fascia, other evaluated parameters were assessed with moderate and substantial agreement between multidetector-row CT and MRI. However, our findings suggest that multidetector-row CT does not correlate well enough with MRI findings to replace it in rectal cancer staging.

Evaluation of MRI for the Diagnosis of Appendicitis During Pregnancy When Ultrasound is Inconclusive

BACKGROUND To retrospectively evaluate the diagnostic performance and clinical utility of magnetic resonance imaging (MRI) in pregnant patients suspected of having acute appendicitis, when an ultrasound study generated an inconclusive result. METHODS The medical records of 19 consecutive women who underwent abdominal and pelvic MRI at a tertiary care referral center (St. Pauls Hospital, Vancouver, Canada), as part of the work up of clinically suspected acute appendicitis, were retrospectively reviewed. MRI was carried out when ultrasound findings were inconclusive. MRI findings were reviewed and compared with surgical findings and clinical follow-up data including pregnancy outcome. RESULTS One of the 19 patients (5.3%) in the study cohort had an appendicitis diagnosed by MRI that was confirmed at operation and by specimen histology. The remaining study patients were diagnosed as not having appendicitis by MRI. These patients were followed until delivery, which was uneventful for all but one patient who was found to have appendicitis during Cesarean section. Overall, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MRI for the diagnosis of appendicitis during pregnancy was 50.0%, 100%, 100%, 94.4%, and 94.7%, respectively. In three patients (16.7%) with no MRI evidence of appendicitis, MRI identified an alternative etiology for their abdominal pain (two patients diagnosed with ovarian cysts, one patient diagnosed with a uterine fibroid). CONCLUSIONS MRI represents a useful diagnostic test for acute appendicitis in pregnant women, and decreases the need for an emergency operation. Its high negative predictive value makes MRI useful for ruling out appendicitis in pregnant patients who have an inconclusive ultrasound. However, the low sensitivity observed in this study suggests that MRI, like other imaging modalities, is not perfect, and may miss an acute appendicitis diagnosis. Thus, future prospective clinical study of MRI as a diagnostic test for the evaluation of women who present with acute abdominal pain and possible appendicitis during pregnancy is warranted.

Abdominal wall desmoid tumors associated with pregnancy: current concepts.

The desmoid tumors (DTs) are unusual soft-tissue tumors that have a propensity for aggressive local growth and may develop during, or soon after pregnancy. Pregnancy-associated DTs are uncommon and optimal management of this tumor has yet to be defined. Currently, controversy centers on the timing of surgical resection and is influenced by the potential for tumor growth and the effects of a gravid uterus. A review of current literature in which DTs were managed either during pregnancy or in the postpartum period, was carried out. Surgical resection of these tumors has been performed successfully both during and soon after delivery, and the role of postpartum radiotherapy, chemotherapy and other medical intervention remains controversial. Management of DTs diagnosed during pregnancy is complex and treatment must be individualized.

Dual-energy computed tomography: a promising novel preoperative localization study for treatment of primary hyperparathyroidism

BACKGROUND The objective of this study was to evaluate dual-energy computed tomography (DE-CT) for preoperative parathyroid tumor (PT) localization in individuals undergoing parathyroidectomy for treatment of primary hyperparathyroidism (PHP). METHODS DE-CT was evaluated by retrospective review of the clinical and biochemical characteristics, imaging, operative findings, and outcomes for PHP cases undergoing an initial operation at a single center. RESULTS The accuracy of each preoperative imaging test, based on operative findings and pathological confirmation of removal of a PT from the localized site was: 58% for ultrasound, 75% Tc-99m sestamibi noncontrast single photon emission noncontrast CT, and 75% for DE-CT. DE-CT was able to correctly localize a PT in a 3rd of cases that were nonlocalized. All study patients had normalization of serum calcium and parathyroid hormone levels postoperatively. CONCLUSIONS DE-CT shows promise for the preoperative PT localization, especially in nonlocalized PHP cases, and warrants further investigation.

Does training and experience influence the accuracy of computed tomography colonography interpretation

AIM To evaluate the effect of experience on the accuracy rate of computed tomography colonography (CTC) interpretation and patient preferences/satisfaction for CTC and colonoscopy. METHODS A prospective, non-randomized, observational study performed in a single, tertiary care center involving 90 adults who underwent CTC followed by colonoscopy on the same day. CTC was interpreted by an abdominal imaging radiologist and then a colonoscopy was performed utilizing segmental un-blinding and re-examination as required. A radiology resident and two gastroenterology (GI) fellows blinded to the results also interpreted the CTC datasets independently. Accuracy rates and trend changes were determined for each reader to assess for a learning curve. RESULTS Among 90 patients (57% male) aged 55 ± 8.9 years, 39 polyps ≥ 6 mm were detected in 20 patients and 13 polyps > 9 mm in 10 patients. Accuracy rates were 88.9% (≥ 6 mm) and 93.3% (> 9 mm) for the GI Radiologist, 89.8% (≥ 6 mm) and 98.9% (> 9 mm) for the Radiology Resident and 86.7% and 95.6% (≥ 6 mm) and 87.8% and 94.4% (> 9 mm) for each of the GI fellows respectively. The readers accuracy rate did not change significantly with the percentage change rate ranging between -1.7 to 0.9 (P = 0.12 to 0.56). Patients considered colonoscopy more satisfactory than CTC (30% vs 4%, P < 0.0001), they felt less anxiety during colonoscopy (36% vs 7%, P < 0.0001), they experienced less pain or discomfort during colonoscopy compared to CTC (69% vs 4%, P < 0.0001) and colonoscopy was preferred by 77% of the participants as a repeat screening test for the future. CONCLUSION No statistically significant learning curve was identified in CTC interpretation suggesting that further study is required to identify the necessary training to adequately interpret CTC scans.

Utility of Transient Elastography in Estimating Hepatic Iron Concentration in Comparison to Magnetic Resonance Imaging in Patients Who are Transfusion-Dependent: A Canadian Center Experience

Abstract Transfusion-dependent hereditary anemias such as β-thalassemia (β-thal), predispose patients to iron overload and its numerous clinical sequelae. Accurate assessment of overall iron status and prompt initiation of chelation therapy to prevent irreversible end-organ damage can be achieved using magnetic resonance imaging (MRI) to measure liver iron concentration (LIC) as a surrogate marker of total body iron; however, its access may be associated with long wait times and delay in treatment. We report an observational cohort study at a single tertiary care center assessing the theoretical role of transient elastography (TE), which measures liver stiffness, in estimating LIC compared to other established diagnostic measures. While regression analyses confirm a moderate correlation between LIC per R2 MRI and serum ferritin level (pooled estimate of correlation = 0.55), there was no significant correlation between TE reading and LIC based on R2 MRI (pooled estimate of correlation = −0.06), and only a weak correlation was observed with serum ferritin level (pooled estimate of correlation = 0.45). These results suggest TE may not be sensitive enough to detect subtle changes in the hepatic parenchymal stiffness associated with liver iron deposition.

Utility of Magnetic Resonance Imaging for the Diagnosis of Appendicitis During Pregnancy: A Canadian Experience

Purpose The objective of the study was to evaluate the performance of magnetic resonance imaging (MRI) for the diagnosis of appendicitis during pregnancy. Methods We conducted a retrospective review of all MRI scans performed at our institution, between 2006 and 2012, for the evaluation of suspected appendicitis in pregnant women. Details of the MRI scans performed were obtained from the radiology information system as well as details of any ultrasounds carried out for the same indication. Clinical and pathological data were obtained by retrospective chart review. Results The study population comprised 63 patients, and 8 patients underwent a second MRI scan during the same pregnancy. A total of 71 MRI scans were reviewed. The appendix was identified on 40 scans (56.3%). Sensitivity of MRI was 75% and specificity was 100% for the diagnosis of appendicitis in pregnant women. When cases with right lower quadrant inflammatory fat stranding or focal fluid, without appendix visualization, were classified as positive for appendicitis, MRI sensitivity increased to 81.3% but specificity decreased to 96.4%. Conclusions MRI is sensitive and highly specific for the diagnosis of appendicitis during pregnancy and should be considered as a first line imaging study for this clinical presentation.