Randy D. Ernst

MR Imaging for Preoperative Evaluation of Primary Rectal Cancer: Practical Considerations

High-resolution magnetic resonance (MR) imaging plays a pivotal role in the pretreatment assessment of primary rectal cancer. The success of this technique depends on obtaining good-quality high-resolution T2-weighted images of the primary tumor; the mesorectal fascia, peritoneal reflection, and other pelvic viscera; and superior rectal and pelvic sidewall lymph nodes. Although orthogonal axial high-resolution T2-weighted MR images are the cornerstone for the staging of primary rectal cancer, high-resolution sagittal and coronal images provide additional value, particularly in tumors that arise in a redundant tortuous rectum. Coronal high-resolution T2-weighted MR images also improve the assessment of nodal morphology, particularly for superior rectal and pelvic sidewall nodes, and of the relationship between advanced-stage tumors and adjacent pelvic structures. Rectal gel should be used in MR imaging examinations conducted for the staging of polypoid tumors, previously treated lesions, and small rectal tumors. However, it should not be used in examinations performed to stage large or low rectal tumors. Diffusion-weighted imaging is useful for identifying nodes and, occasionally, the primary tumor when the tumor is difficult to visualize with other sequences. Three-dimensional T2-weighted imaging provides multiplanar capability with a superior signal-to-noise ratio compared with two-dimensional T2-weighted imaging.

Quality Initiatives: CT Radiation Dose Reduction: How to Implement Change without Sacrificing Diagnostic Quality

The risks and benefits of using computed tomography (CT) as opposed to another imaging modality to accomplish a particular clinical goal should be weighed carefully. To accurately assess radiation risks and keep radiation doses as low as reasonably achievable, radiologists must be knowledgeable about the doses delivered during various types of CT studies performed at their institutions. The authors of this article propose a process improvement approach that includes the estimation of effective radiation dose levels, formulation of dose reduction goals, modification of acquisition protocols, assessment of effects on image quality, and implementation of changes necessary to ensure quality. A first step toward developing informed radiation dose reduction goals is to become familiar with the radiation dose values and radiation-associated health risks reported in the literature. Next, to determine the baseline dose values for a CT study at a particular institution, dose data can be collected from the CT scanners, interpreted, tabulated, and graphed. CT protocols can be modified to reduce overall effective dose by using techniques such as automated exposure control and iterative reconstruction, as well as by decreasing the number of scanning phases, increasing the section thickness, and adjusting the peak voltage (kVp setting), tube current-time product (milliampere-seconds), and pitch. Last, PDSA (plan, do, study, act) cycles can be established to detect and minimize negative effects of dose reduction methods on image quality.

The efficacy of magnetic resonance cholangiography for the evaluation of patients with suspected choledocholithiasis before laparoscopic cholecystectomy

BACKGROUND Endoscopic retrograde cholangiography is the most commonly utilized tool for the identification of common bile duct stones (CBDS) before laparoscopic cholecystectomy, whereas the role of magnetic resonance cholangiography (MRC) for patient evaluation before laparoscopic cholecystectomy is currently undefined. METHODS We prospectively evaluated the efficacy of MRC for the identification of CBDS among patients with high risk for choledocholithiasis. Patient selection was based on clinical, sonographic, and laboratory criteria. Standard cholangiograms were obtained when possible for verification of MRC results. RESULTS Ninety-nine patients underwent evaluation with preoperative MRC. CBDS was visualized in 30% of patients. MRC sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 85%, 90%, 77%, 94%, and 89%, respectively. CONCLUSIONS MRC is useful for the evaluation of patients with suspected choledocholithiasis. Advantages of MRC include its noninvasive nature, ease of application, and accuracy in identifying and estimating the size of CBDS. Application of MRC in this setting reduces the need for diagnostic endoscopic retrograde cholangiography. Future investigations should be directed at the development of cost-effective utilization strategies for MRC application.

Revisiting MRI for appendix location during pregnancy

OBJECTIVE The purpose of this study is to determine the location of the appendix in pregnant patients by MRI and to investigate the possibility of gradual upward displacement of the appendix during pregnancy. CONCLUSION The gradual upward displacement of the appendix during pregnancy was confirmed. MRI can be used for determination of the appendix localization in pregnant patients. Further studies with a larger number of patients will be helpful to answer this clinically relevant question.

Optimization of MR Imaging for Pretreatment Evaluation of Patients with Endometrial and Cervical Cancer

Endometrial and cervical cancer are the most common gynecologic malignancies in the world. Accurate staging of cervical and endometrial cancer is essential to determine the correct treatment approach. The current International Federation of Gynecology and Obstetrics (FIGO) staging system does not include modern imaging modalities. However, magnetic resonance (MR) imaging has proved to be the most accurate noninvasive modality for staging endometrial and cervical carcinomas and often helps with risk stratification and making treatment decisions. Multiparametric MR imaging is increasingly being used to evaluate the female pelvis, an approach that combines anatomic T2-weighted imaging with functional imaging (ie, dynamic contrast material-enhanced and diffusion-weighted imaging). MR imaging helps guide treatment decisions by depicting the depth of myometrial invasion and cervical stromal involvement in patients with endometrial cancer and tumor size and parametrial invasion in those with cervical cancer. However, its accuracy for local staging depends on technique and image quality, namely thin-section high-resolution multiplanar T2-weighted imaging with simple modifications, such as double oblique T2-weighting supplemented by diffusion weighting and contrast enhancement.

The role of MR cholangiopancreatography in the evaluation of pregnant patients with acute pancreaticobiliary disease

This study aimed to determine the usefulness of MR cholangiopancreatography (MRCP) in the evaluation of pregnant patients with acute pancreaticobiliary disease and its additional value over ultrasound. MRI studies of pregnant patients who were referred because of acute pancreaticobiliary disease were included. MR images and patient charts were reviewed retrospectively to determine clinical outcome and the results of other imaging studies. 18 pregnant patients underwent MRCP because of right upper quadrant pain (n = 6), pancreatitis (n = 9), cholangitis (n = 1) or jaundice (n = 2). 15 patients were also evaluated with ultrasound. Biliary dilatation was detected in eight patients by ultrasound, but the cause of biliary dilatation could not be determined by ultrasound in seven patients. MRCP demonstrated the aetiology in four of these patients (choledocholithiasis (n = 1), Mirizzi syndrome (n = 1), choledochal cyst (n = 1) and intrahepatic biliary stones (n = 1)) and excluded obstructive pathology in the other four patients. MRCP was unremarkable in the seven patients who had no biliary dilatation on ultrasound. Three patients underwent only MRCP; two had choledocholithiasis and one cholelithiasis and pancreatitis. Choledocholithiasis diagnosed with MRCP (n = 3) was confirmed by endoscopic retrograde cholangiopancreatography. Mirizzi syndrome (n = 1) and a choledochal cyst (n = 1) were confirmed by surgery. The patients with normal MRCP (n = 12) and one patient with intrahepatic stones improved with medical treatment. MRCP appears to be a valuable and safe technique for the evaluation of pregnant patients with acute pancreaticobiliary disease. Especially when ultrasound shows biliary dilatation, MRCP can determine the aetiology and save the patient from unnecessary endoscopic retrograde cholangiopancreatography by excluding a biliary pathology.

MR imaging of ectopic pregnancy with an emphasis on unusual implantation sites

Ectopic pregnancy (EP) is a life-threatening condition and remains the leading cause of death in the first trimester of pregnancy, although the mortality rate has significantly decreased over the past few decades because of earlier diagnoses and great improvements in treatment. EP is most commonly located in the ampullary portion of the fallopian tube and rarely in unusual sites such as the interstitium, cervix, cesarean scar, anomalous rudimentary horn of the uterus and peritoneal abdominal cavity. MRI may confirm or give additional information to ultrasonography, which is the most user-dependent imaging modality. Magnetic resonance imaging can accurately localize the site of abnormal implantation. It could be helpful for EP patient treatment by distinguishing the ruptured and unruptured cases before methotrexate treatment. MRI is quite sensitive to blood and can identify the hemorrhage phase.

Pretreatment high-resolution rectal MRI and treatment response to neoadjuvant chemoradiation

BACKGROUND: Use of rectal MRI evaluation of patients with rectal cancer for primary tumor staging and for identification for poor prognostic features is increasing. MR imaging permits precise delineation of tumor anatomy and assessment of mesorectal tumor penetration and radial margin risk. OBJECTIVE: The aim of this study was to evaluate the ability of pretreatment rectal MRI to classify tumor response to neoadjuvant chemoradiation. DESIGN: This study is a retrospective, consecutive cohort study and central review. SETTING: This study was conducted at a tertiary academic hospital. PATIENTS: Sixty-two consecutive patients with locally advanced (stage cII to cIII) rectal cancer who underwent rectal cancer protocol high-resolution MRI before surgery (December 2009 to March 2011) were included. MAIN OUTCOME MEASURES: The primary outcomes measured were the probability of good (ypT0–2N0) vs poor (≥ypT3N0) response as a function of mesorectal tumor depth, lymph node status, extramural vascular invasion, and grade assessed by uni- and multivariate logistic regression. RESULTS: Tumor response was good in 25 (40.3%) and poor in 37 (59.7%). Median interval from MRI to surgery was 7.9 weeks (interquartile range, 7.0–9.0). MRI tumor depth was <1 mm in 10 (16.9%), 1 to 5 mm in 30 (50.8%), and >5 mm in 21 (33.9%). Lymph node status was positive in 40 (61.5%), and vascular invasion was present in 16 (25.8%). Tumor response was associated with MRI tumor depth (p = 0.001), MRI lymph node status (p < 0.001) and vascular invasion (p = 0.009). Multivariate regression indicated >5 mm MRI tumor depth (OR = 0.08; 95% CI = 0.01–0.93; p = 0.04) and MRI lymph node positivity (OR = 0.12; 95% CI = 0.03–0.53; p = 0.005) were less likely to achieve a good response to neoadjuvant chemoradiotherapy. LIMITATIONS: Generalizability is uncertain in centers with limited experience with MRI staging for rectal cancer. CONCLUSION: MRI assessment of tumor depth and lymph node status in rectal cancer is associated to tumor response to neoadjuvant chemoradiotherapy. These factors should therefore be considered for stratification of patients for novel treatment strategies reliant on pathologic response to treatment or for the selection of poor-risk patients for intensified treatment regimens.

Localization of appendix with MDCT and influence of findings on choice of appendectomy incision

OBJECTIVE The purpose of this study was to show the relation between McBurneys point and the appendix in patients undergoing 3D MDCT and to investigate the effect of this information on a surgeons choice of appendectomy incision. MATERIAL AND METHODS Among 142 adults undergoing consecutive MDCT studies, 100 patients (35 women, 65 men; mean age, 52.1 years) with an identifiable appendix on abdominopelvic MDCT examinations were selected for the study group. The presence of intraabdominal mass or a history of abdominal surgery were the exclusion criteria. Three-dimensional reconstruction of the CT data was performed with a surface shaded display algorithm. The locations of the base of the appendix and McBurneys point were marked on a single 3D image that allowed display of the skin surface markings for each patient. The superoinferior and mediolateral distances from the level of the appendix to the level of McBurneys point were measured, and the radial distance was calculated from these measurements. A surgeon experienced in emergency abdominal surgery reviewed 3D CT images and one axial image showing the appendix, and his choice of incision for each patient based on the CT information was recorded. The influence of the superoinferior and mediolateral distances of the appendix from McBurneys point on the surgeons decision was analyzed with a multivariate logistic regression model. RESULTS The appendix was exactly at McBurneys point in only 4% of the patients. In 36% of the cases, the appendix was within 3 cm, in 28% of cases it was 3-5 cm, and in 36% of the cases it was more than 5 cm away from McBurneys point. Mean +/- SD superoinferior, mediolateral, and radial distances between the appendix and McBurneys point were 33.0 +/- 24.1, 20.8 +/- 19.3, and 42.1 +/- 26.7 mm, respectively. After reviewing the images, the surgeon would have altered his incision site in 35% of the cases. The surgeon preferred a higher incision in 28% and a lower incision in 7% of the cases. Both positive and negative superoinferior displacement away from McBurneys point were significant factors regarding the surgeons decision to alter the incision (p = 0.005), and the superoinferior distance was more than 3 cm in 94% of the cases in which the surgeon would have altered the incision. CONCLUSION The location of the appendix varies widely among individuals, and McBurneys point has limitations as an anatomic landmark. Three-dimensional MDCT findings can be useful to surgeons customizing appendectomy incisions. Additional information about the location of the appendix in the CT report (if possible, together with a 3D image showing the location of the appendix) may be beneficial for surgeons performing appendectomy.

Intraoperative Sonography During Open Partial Nephrectomy for Renal Cell Cancer: Does It Alter Surgical Management?

OBJECTIVE The purpose of this study is to evaluate whether intraoperative ultrasound (IOUS) during open partial nephrectomy alters the surgical management for renal cell cancer (RCC). MATERIALS AND METHODS One hundred ninety-eight consecutive patients undergoing IOUS during open partial nephrectomy for RCC were selected for retrospective review of clinical and imaging data. Patient age and sex, the local extent of the primary lesion, and the presence of additional lesions were recorded. Ultrasound findings were compared with preoperative CT or MRI to determine whether the IOUS findings changed surgical management. Summary statistics were performed to assess what percentage of patients with additional IOUS findings had a change in their surgical management. The Kaplan-Meier method was used to estimate 5-year overall survival (OS) and event-free survival (EFS) rates for all patients. Patients were followed for 9-12 years to assess survival and measure recurrence rates. RESULTS Twenty-one of 198 patients (10.6%; 95% CI, 6.7-15.8%) had additional findings on IOUS not seen on preoperative imaging. As a result, surgery was modified in 15 of these 21 patients (71.4%; 95% CI, 47.8-88.7%). The 5-year OS rate was 81%, and the EFS rate was 76% for the whole group; most deaths were due to unrelated causes. There was no statistically significant difference in OS (p = 0.867) and EFS (p = 0.069) rates among patients who had a change of management because of additional lesions seen by IOUS. CONCLUSION IOUS performed during open partial nephrectomy for resection of RCC shows additional findings compared with preoperative cross-sectional imaging that may alter surgical management.