Non-contrast-enhanced MRA of renal artery stenosis: validation against DSA in a porcine model.

OBJECTIVES: To compare 3D-inversion-recovery balanced steady-state free precession (IR-bSSFP) non-contrast-enhanced magnetic resonance angiography (MRA) with 3D-contrast-enhanced MRA (CE-MRA) for assessment of renal artery stenosis (RAS) using digital subtraction angiography (DSA) as the reference standard. METHODS: Bilateral RAS were surgically created in 12 swine. IR-bSSFP and CE-MRA were acquired at 1.5 T and compared to rotational DSA. Three experienced cardiovascular radiologists evaluated the IR-bSSFP and CE-MRA studies independently. Linear regression models were used to calibrate and assess the accuracy of IR-bSSFP and CE-MRA, separately, against DSA. The coefficient of determination and Cohen's kappa coefficient were also generated. RESULTS: Calibration of the three readers' RAS grading revealed R(2) values of 0.52, 0.37 and 0.59 for NCE-MRA and 0.48, 0.53 and 0.71 for CE-MRA. Inter-rater agreement demonstrated Cohen's kappa values ranging from 0.25 to 0.65. Distal renal artery branch vessels were visible to a significantly higher degree with NCE-MRA compared to CE-MRA (p < 0.001). Image quality was rated excellent for both sequences, although image noise was higher with CE-MRA (p < 0.05). In no cases did noise interfere with image interpretation. CONCLUSIONS: In a well-controlled animal model of surgically induced RAS, IR-bSSFP based NCE-MRA and CE-MRA accurately graded RAS with a tendency for stenosis overestimation, compared to DSA. KEY POINTS: • IR-bSSFP and CE-MRA are accurate methods for diagnosis of renal artery stenosis • IR-bSSFP and CE-MRA demonstrate excellent agreement with DSA • Both IR-bSSFP and CE-MRA have a tendency to overestimate renal artery stenosis.

Computed tomography appearance of a right cervical aortic arch.

The clinical diagnosis of cervical aortic arch rests on the detection of a pulsatile mass in the supraclavicular fossa. Unfortunately, clinical differentiation of a cervical arch from an aneurysm of the great vessels can be difficult. Dynamic computed tomography (CT) can aid in this differentiation and avert the need for angiography.

MRI of Askin's tumor. Case report at 1.5 T.

This represents the first case of an Askin's tumor demonstrated on MRI. It showed a large pleural-based mass which trapped pleural fluid in large pseudotumors. The disease was unilateral and involved the mediastinum as well. Magnetic resonance imaging was helpful in demonstrating extrathoracic disease in the area of the right brachial plexus.

Efficacy of prostate-specific antigen and magnetic resonance imaging in staging stage C adenocarcinoma of the prostate.

OBJECTIVES: The authors compared the two most common presurgical tests now used for the preoperative staging of adenocarcinoma of the prostate, prostate-specific antigen (PSA) and magnetic resonance imaging (MRI). METHODS: One hundred consecutive radical retropubic prostatectomy patients were imaged at 1.5 Tesla before surgery with routine T1-weighted and T2-weighted transaxial images. The images were analyzed by two experienced radiologists for evidence of extracapsular disease. Radiologists rated each gland on a scale of 0 to 100 for the percentage likelihood of extracapsular disease based on its MRI appearance. Receiver operator characteristic (ROC) curves were plotted, and areas were calculated for the two radiologists and the preoperative PSA values. RESULTS: Comparison of the areas of the ROC curves generated from the two radiologists and those from the preoperative PSA values showed no statistical difference. CONCLUSIONS: In this series, radiologic interpretation of body coil MRI studies in those patients chosen for a radical retropubic prostatectomy was no better in staging adenocarcinoma of the prostate than simply using the preoperative PSA values.

Magnetic resonance angiography of the pelvis and lower extremities. Works in progress.

Two-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) of the lower extremities has recently been rediscovered as a technique that can be used to find small vessels in the foot and leg for surgical revascularization in patients with severe peripheral vascular disease. The purpose of this article is to acquaint the reader with some of the common problems that may be encountered in this imaging technique and to show their derivations and solutions were applicable. In addition, the authors show receiver operator curve analysis of one radiologist's ability to determine the location and patency of arteries using this technique to be outstanding (AZ, 0.9737). This represents a promising new technique for imaging the arterial system in patients with severe peripheral vascular disease.

Enhanced pancreatic CT imaging utilizing a geometric magnification technique.

Computed tomography (CT) using a geometric magnification technique was found to improve spatial resolution in phantom studies when compared with conventional third-generation geometry images. The clinical feasibility of using geometric magnification, small focal spot size, and dynamic contrast enhancement was studied in 143 patients referred to CT for clinically suspected pancreatic disease. This population included 46 patients with a normal pancreas and 36 patients subsequently proven to have primary pancreatic carcinoma. Using this new technique in conjunction with dynamic contrast enhancement resulted in high quality pancreatic images. Despite the limitations in tube current associated with a small focal spot size and low total heat capacity of the system, clinical imaging was not adversely affected. Use of the geometric magnification technique is recommended in departments where it is technically feasible.

Strategies for musculoskeletal magnetic resonance imaging.

There is a broad range of clinical applications for MRI in the diagnosis of musculoskeletal disease, and the emphasis in this article is on the evaluation of the joints and extremities. A discussion of basic principles, including radiofrequency coils, positioning, pulsing sequences, imaging planes, and technical parameters is followed by discussions of tailored approaches to the evaluation of mass lesions and joint pathology for specific regions of the musculoskeletal system. In the final section, consideration is given to the overall role of MRI in the diagnosis of musculoskeletal disorders with respect to other established imaging modalities.

Imaging approach to the suspected renal mass.

The authors present their algorithmic approach to the detection, characterization, and staging of renal masses. Based on classification of urographic findings, the patient may be triaged to the appropriate cross-sectional or invasive imaging modality that will result in the most cost-effective management.

Hepatic imaging: current status.

The radiologist needs to be aware of the varied appearance of hepatic mass lesions and be prepared to recommend the most cost-effective imaging approach. In this article, the authors discuss their hepatic imaging experience, common pitfalls, and current recommendations.

Common artifacts encountered in thoracic magnetic resonance imaging: recognition, derivation, and solutions.

The article discusses the many types of thoracic magnetic resonance imaging artifacts, their derivations, and their current solutions. Magnetic resonance imaging artifacts of the thorax can be divided into two major categories. First, there are machine-related artifacts related to the machine's hardware: the intrinsic magnetic field, chemical shift, magnetic susceptibility, radio frequency leaks, metal artifacts, B1-homogeneity, gradient coils, truncation, aliasing, zipper artifacts, artifacts related to the surface coil profiles, pulse profiles, and crosstalk. Second, there are artifacts related to motion: voluntary patient motion, involuntary motion, and physiologic motions. Each one of these artifacts, and their solutions, will be discussed.

Metastasizing chordoma in early childhood: report of a case at 1.5 T.

We present here the first report of an extraskeletal metastasizing presacral chordoma found in a child. MRI of this large lesion showed heterogeneous signal intensity on both the SE 550/30 and on SE 2440/100 images. MRI demonstrated this mass to be separate from the sacrum and provided nonionizing cross-sectional imaging prior to attempted surgical resection.

In vivo and ex vivo magnetic resonance imaging evaluation of early disc degeneration with histopathologic correlation.

The in vivo and ex vivo microanatomic appearance of early disc degeneration were identified by magnetic resonance imaging and correlated with their respective histopathologic findings. Five cadaver spines (18 discs) and 25 patient studies (122 discs) all imaged at 1.5 Tesla were studied. Two signs of early degenerative disc disease were found: infolding and the central dot. Infolding of the central fibers of the outer annulus coalesced into a central dot of low signal intensity that was seen on both the ex vivo and in vivo images. Infolding was seen 29 of 122 times, and the central dot was observed 15 to 122 times on the in vivo images. A later form of degenerative disc disease was identified as a separation of the nucleus pulposus from the hyaline cartilage end-plate. This separation was seen as a linear area of either low or high signal intensity on the ex vivo images but only as a band of high signal intensity on the in vivo spin-echo 2,500-msec/80-msec images. Only 7 of 122 in vivo discs showed this separation. Internal herniation of nucleus pulposus into the outer annulus was seen only on the ex vivo images. Early degenerative disc disease may exist before there is loss of disc height or signal intensity on the long time-to-repetition (TR)/time-to-echo (TE) magnetic resonance images.

The spleen and its vasculature in pancreatitis: CT findings.

The spleen and its vasculature are susceptible to damage from pancreatic inflammatory exudates. Fourteen patients were identified who demonstrated splenic or splenic vascular involvement from pancreatitis on computed tomography. Findings included intra- and perisplenic inflammatory fluid collections (n = 6), acute splenic hematomas (n = 3), splenic infarction (n = 1), splenic artery pseudoaneurysm (n = 1), and splenic vein thrombosis (n = 6). Eight of the 14 patients went on to urgent interventions including percutaneous catheter drainage (n = 2) and transcatheter embolotherapy (n = 6) based on the CT findings.

Magnetic resonance imaging of the ovary.

The authors present the newer MR imaging techniques and how to use them to diagnose the common benign and malignant causes of adnexal masses. Specific features on MR imaging for adnexal lesions that are stressed include morphologic features, specific chemical shift, magnetic susceptibility, and enhancement pattern.

Contributions of magnetic resonance imaging in the evaluation of optic gliomas.

Eleven patients with gliomas in the optic chiasm were studied using a 0.5 Tesla superconducting system and third generation computed tomography scanners. All tumors were identified with both modalities, but in the majority of cases, the posterior extension of the tumor and its relationship to adjacent brain, important to both prognosis and management, were shown better by magnetic resonance imaging.

Intrahepatic extramedullary hematopoiesis: MR, CT, and sonographic appearance.

A 45-year-old patient with focal intrahepatic extramedullary hematopoiesis is presented in which the liver was imaged by CT, ultrasound, and MR. The appearance of the lesions on MR consisted of slightly increased signal on T2-weighted images with heterogeneous enhancement of some of the lesions during bolus infusion of gadolinium. The T1-weighted images postgadolinium showed no delayed enhancement.

Normal anatomy of the thoracic inlet as seen on transaxial MR images.

The thoracic inlet can now be studied with high-resolution MR imaging. Recent advances in fold-over suppression (antialiasing software) allow for small fields of view without the usual problems of aliasing from the shoulders. This pictorial assay shows the normal anatomy that can be seen in this area on transaxial MR images. The vagus, phrenic, and recurrent laryngeal nerves can be seen as discrete entities. MR imaging can be used more often for pathologic conditions involving the lower portion of the neck and the thoracic inlet.

MR imaging of vaginal agenesis with hematocolpos.

Magnetic resonance imaging of a 14-year-old girl with abdominal pain and known vaginal agenesis revealed massive hematocolpos with a normal cervix and uterine body. Prior ultrasound of this area was significantly limited by bowel loops anterior to the retroflexed uterine body and cervix, which were displaced cephalad out of the pelvic inlet and were not seen. Magnetic resonance is the examination of choice in patients with symptomatic vaginal agenesis prior to surgical correction.

Intraabdominal desmoplastic small cell tumor: CT and MR findings.

The pertinent radiologic findings in two cases of a recently described tumor, intraabdominal desmoplastic small cell tumor, are presented. This is an aggressive, usually lethal malignant neoplasm of the peritoneum occurring in boys and young men with a marked predilection for intraperitoneal spread. In both cases, CT or MR demonstrated a necrotic intraperitoneal mass with peritoneal metastases. Given the limited differential diagnosis, intraabdominal desmoplastic small cell tumor should be strongly considered as a diagnosis of an intraperitoneal neoplasm in young males.