Accuracy of contrast-enhanced MDCT and MRI for identifying the severity and cause of neural foraminal stenosis in cervical radiculopathy: a prospective study.

OBJECTIVE: The purpose of this study was to determine the accuracy of IV contrast-enhanced MDCT and MRI for evaluation of the severity and cause of neural foraminal stenosis in patients with cervical radiculopathy. SUBJECTS AND METHODS: Eighteen patients with cervical radiculopathy prospectively underwent contrast-enhanced MDCT and MRI. Contrast-enhanced MDCT scans were acquired at 1-mm thickness and reconstructed in oblique axial (parallel to disk) and sagittal (perpendicular to neural foramen) 2-mm sections without a gap. The MRI sequences used were sagittal T1-weighted, fast spin-echo T2-weighted, 3D fast spin-echo T2-weighted, axial T2-weighted, and 3D gradient-recalled echo. Three neuroradiologists independently and blindly rated the severity and cause of neural foraminal stenosis on a 4-point scale. Using the same scale at surgery, one of three surgeons rated the severity and cause of neural foraminal stenosis, and the results were used as the reference standard. Interobserver and intraobserver agreement (kappa) was calculated. RESULTS: For severity of neural foraminal stenosis, the sensitivities of contrast-enhanced MDCT (50/55, 91%) and MRI (55/57, 96%) were similar, as were their specificities (contrast-enhanced MDCT, 13/24, 54%; MRI, 11/24, 46%). For cause of neural foraminal stenosis, the accuracies of contrast-enhanced MDCT (46/54, 85%) and MRI (45/57, 79%) were similar. Interobserver agreement on severity of neural foraminal stenosis was moderate to almost perfect for contrast-enhanced MDCT (kappa=0.50-1.00) and MRI (kappa=0.43-1.00). For cause of neural foraminal stenosis, interobserver agreement was moderate to substantial for contrast-enhanced MDCT (kappa=0.52-0.76) but only fair for MRI (kappa=0.23-0.39). Intra observer agreement was very high for severity of neural foraminal stenosis (contrast-enhanced MDCT, kappa=0.85; MRI, kappa=0.80) and cause of neural foraminal stenosis (contrast-enhanced MDCT, kappa=0.86; MRI, kappa=1.00). CONCLUSION: Contrast-enhanced MDCT is as accurate as MRI in evaluation of the severity and cause of neural foraminal stenosis and may have better interobserver agreement.

Routine isotropic computed tomography scanning of chest: value of coronal and sagittal reformations.

OBJECTIVE: We sought to evaluate the usefulness of coronal and sagittal reformations from isotropic chest computed tomography (CT) examinations. METHODS: A total of 30 chest CT examinations were reconstructed into 2 sets of axial source images: 0.9-mm slice width with 0.45-mm reconstruction interval (isotropic) and 4-mm slices with 3-mm reconstruction interval. The isotropic dataset was reformatted into coronal and sagittal stacks with 4-mm slices. Three readers reviewed the image sets with 4-mm slice widths. Coronal and sagittal reformations were compared at the same sitting to axial images for depiction of anatomy and disease in the aorta, pulmonary arteries, hilar regions, mediastinum, lung parenchyma, pleura, diaphragm, thoracic spine, ribs, and trachea. A 5-point scale was used to determine whether nonaxial reformations showed anatomy and disease significantly better, somewhat better, same, somewhat worse or significantly worse than equivalent thickness axial source images. A 3-point scale was used to score if nonaxial image sets showed no, some, or significant additional information compared with the axial plane regarding the main diagnosis. RESULTS: There was better visualization of the hilar regions, diaphragm, spine, and trachea on the coronal reformations compared with source axial images (P < 0.05). Sagittal reformations scored better than axial source images for aorta, pleura, diaphragm, spine, and ribs (P < 0.05). The coronal and sagittal series showed significant additional information in 11% and 9% of patients, respectively. CONCLUSION: Radiologists should consider the use of one or both of coronal and sagittal planes in addition to the axial series in routine interpretation of chest CT.

Pathologic characteristics of exophytic renal masses.

OBJECTIVE: Pathologic grade is an important prognostic factor for renal-cell carcinoma (RCC). The objective of this study was to determine if there is any association of radiologic characteristics with pathologic grade and type of small renal tumors. PATIENTS AND METHODS: We retrospectively reviewed the records of 500 patients who underwent extirpative renal surgery. Fifty-one patients met the inclusion criteria of solitary RCC <6 cm and adequate radiologic imaging available for review. The axial images with the largest area of tumor growing into the kidney were evaluated by a single radiologist to determine the percent of tumor that was exophytic. RESULTS: Nine patients had tumors that were >67% exophytic, and 42 patients had tumors <67% exophytic. There is a statistically significant difference in the mean Fuhrman grade for these 2 groups (1.78 v 2.25, P < 0.01). The distribution of histologic subtype was as follows: 34 patients with clear cell, 15 with papillary, and one each with chromophobe and unclassified tumors. Papillary RCC comprised 78% (7 of 9) of tumors that were >67% exophytic and 15% (3 of 20) that were <33% exophytic. The relative risk of a >67% exophytic tumor being papillary v nonpapillary is 4.1. CONCLUSIONS: Exophytic renal tumors are more likely to be of lower pathologic grade and of the papillary RCC subtype when compared with endophytic renal tumors. A larger prospective study is required to confirm these findings and determine the implications. This information may be useful when small tumors are being considered for watchful waiting or ablative therapies.

Isotropic CT examination of abdomen and pelvis diagnostic quality of reformat.

RATIONALE AND OBJECTIVES: To evaluate the image quality of axial and coronal reformats obtained from isotropic resolution abdomino-pelvic computed tomography (CT) examinations. MATERIALS AND METHODS: Thirty consecutive patients with intravenous contrast-enhanced abdomino-pelvic CT examinations (Brilliance 40, Philips Medical Systems, Cleveland, OH) were enrolled for the study. The raw data were reconstructed into two sets of source axial images: 0.9-mm slice widths with 0.45-mm reconstruction interval (isotropic resolution) and 4-mm slice widths with 3-mm reconstruction interval (anisotropic resolution: group A). Isotropic data set was reformatted into axial and coronal stacks (groups B and C, respectively) with 4-mm slice width and 3-mm interval. Three independent readers evaluated stacks A to C using a 3-point scale for resolution of hepatic vessels, edge sharpness of kidneys, respiratory motion artifact, reconstruction artifact, noise, and overall image quality. RESULTS: There was no statistical difference among the groups A to C for vessel resolution, motion artifact, noise, and overall quality. The scores given to group C were significantly lower than those to groups A and B for reconstruction artifacts. There was no difference among groups A to C for overall impression of image quality. The interreader agreements were excellent for axial images (groups A and B) and moderate for coronal reformats. CONCLUSION: Isotropic scanning of the abdomen and pelvis allows creation of reformats with similar image quality as similar thickness axial source images. These reformats are of sufficient quality to form the basis of clinical interpretation.

Multichannel CT: evaluating the spine in postoperative patients with orthopedic hardware.

Evaluating the spine in patients with metal orthopedic hardware is challenging. Although the effectiveness of conventional computed tomography (CT) can be limited by severe beam-hardening artifacts, the evolution of multichannel CT in recent years has made available new techniques that can help minimize these artifacts. Multichannel CT allows faster scanning times, resulting in reduced motion artifacts; thinner sections, with which it is possible to create a scanned volume of isotropic voxels with equivalent image resolution in all planes; and the generation of a higher x-ray tube current, which may result in better penetration of metal hardware and reduction of artifacts. Although 140 kVp and high milliamperage-second exposure are recommended for imaging patients with hardware, caution should always be exercised, particularly in children, young adults, and patients undergoing multiple examinations. The acquisition of multiplanar reformatted images in the axial, sagittal, coronal, and oblique planes and of three-dimensional volume-rendered images optimizes image interpretation. Wide window settings are best for reviewing images when hardware is present. The integrity of hardware is best assessed with multiplanar average intensity projection. Soft-tissue structures are best visualized by interactively varying the window width and level settings. Implementation of these techniques can yield diagnostic-quality images and aid in patient treatment.

Gastrointestinal stromal tumors: CT and MRI findings.

The objective of this study was to report the CT and MRI appearances of primary and metastatic gastrointestinal stromal tumor (GIST). The clinical and imaging findings of 31 patients with histological and immunohistochemical diagnosis of GIST were reviewed. The CT and MRI findings were assessed independently for size, location, enhancement characteristics, and pattern of metastatic disease. The tumors were of enteric (n=13), gastric (n=12), duodenal (n=2), and rectal (n=3) origin. In one case the primary site was the mesentery, without involvement of bowel. Primary tumors were typically exophytic (79%), larger than 5 cm (84%), and inhomogeneously enhancing (84%). Central necrosis of all tumors (37%) and aneurysmal dilation of enteric tumors (33%) were less common. Metastases were most commonly to mesentery (26%) or liver (32%). Less common findings were ascites (7%) and omental caking (3%). Liver metastases were hypervascular in 92% of patients and rapidly became cystic following therapy with imatinib mesylate (Gleevec; Novartis, East Hanover, NJ, USA). Lung metastases, bowel obstruction, vascular invasion, and significant lymphadenopathy were not seen in any patient. GISTs have some specific CT findings which could help differentiate them from other gastrointestinal tumors. Liver metastases became cystic following therapy, mimicking simple cysts. MRI was better than single-phase CT for assessing liver metastases, while CT was more sensitive for mesenteric metastases.

Characterization of endoleaks by dynamic computed tomographic angiography.

BACKGROUND: Current imaging modalities may not be able to detect endoleaks, differentiate between type II and type III, or localize inflow and outflow sources. We describe a new technique that can characterize endoleaks to guide secondary intervention. METHODS: One hundred four patients with Zenith (Cook, Inc.) endograft repair of abdominal aortic aneurysms (AAAs) were monitored by serial computed tomographic angiography (CTA). Endoleaks were evaluated with a dynamic CTA using a stationary table position, 24-mm beam collimation, and continuous scanning over 30 to 40 seconds to create a cine. RESULTS: Twelve patients (12%) had endoleaks that persisted or appeared more than 30 days post-deployment. Five patients in whom the standard CT surveillance protocol could not differentiate type II versus type III endoleaks underwent dynamic CTA. This technique accurately characterized the endoleaks and localized inflow and outflow branches to guide the subsequent successful secondary interventions. CONCLUSIONS: Dynamic CTA is a useful technique to evaluate endoleaks for characterization and precise localization to guide secondary interventional therapy.

Suspected acute pulmonary embolism: evaluation with multi-detector row CT versus digital subtraction pulmonary arteriography.

PURPOSE: To determine diagnostic accuracy of four-channel multi-detector row computed tomography (CT) in emergency room and inpatient populations suspected of having acute pulmonary embolism (PE) who prospectively underwent both CT and pulmonary arteriography (PA). MATERIALS AND METHODS: Patients referred for PA to assess suspected PE were eligible. Institutional review board approval and written informed consent were obtained. All patients underwent CT and PA within a 48-hour period. For CT, 4 x 2.5-mm collimation was used. Three readers independently evaluated each study for PE presence. PE status, vessel level, and lobar location were determined by means of majority rule, and interobserver agreement (kappa) was calculated for PE status, as assessed with each modality. Sensitivity and specificity of CT were calculated by using PA as the reference standard. Two radiologists later reviewed false-positive CT studies. RESULTS: The study group comprised 93 patients (median age, 56 years; range, 19-88 years). Sensitivity, specificity, and accuracy of CT were 100%, 89%, and 91%, respectively. kappa values were 0.71 and 0.83 for CT and PA, respectively, and were not significantly different between modalities. At PA, 18 patients (19%) had PE at 50 vessel levels (five main and/or interlobar, 24 segmental, and 21 subsegmental), 17 (94%) of which had PE at multiple sites. At CT, 26 patients (28%) had PE at 71 vessel levels (24 main and/or interlobar, 33 segmental, and 14 subsegmental). Twenty patients (77%) had PE at multiple sites. Review of eight false-positive CT studies showed an appearance highly suggestive of acute PE in three patients, chronic PE in one, and no PE in three; one study was inconclusive. CT better demonstrated large-level vessel involvement (P < .01), while PA better demonstrated small-level vessel involvement (P < .01). CONCLUSION: Multi-detector row CT has an accuracy of 91% in the depiction of suspected acute PE when conventional PA is used as the reference standard.

Fundamentals of multichannel CT.

Multichannel computed tomography (MCCT) has created a technical revolution in CT scanning. Following the introduction of single-channel helical scanning in 1989, 4-channel systems were introduced in 1998 and 16-channel systems in 2002. The core of this new technique is the X-ray detector array design, which allows for multiple simultaneous registration of slice information during gantry rotation. This design allows for faster scanning and acquisition of thinner slice widths. The high-speed scanning also minimizes motion artifacts. The ability to scan with very thin slice thickness creates a scanned volume with isotropic voxels. This allows for two- and three-dimensional reconstructions with similar resolution as the source images. MCCT also allows for higher X-ray tube currents, which create better penetration of metallic orthopedic fixation devices. Musculoskeletal imaging benefits from MCCT because large anatomic areas may be covered with thin slices. When needed, high tube currents can be applied for scanning areas of interest in the presence of metal. Thin slice acquisition allows isotropic viewing, which we use routinely.

CT with 3D rendering of the tendons of the foot and ankle: technique, normal anatomy, and disease.

Three-dimensional rendering of computed tomographic data with volume rendering (VR), shaded surface display (SSD), and maximum intensity projection has been performed for over 20 years. In the foot and ankle, no one image reformatting technique is satisfactory for displaying every anatomic relationship or disease process. Two-dimensional multiplanar reformatted (MPR) images are the basic images used for diagnosis. MPR images are especially useful for identifying small fractures. VR is useful for demonstrating the relationships between ankle tendons and the underlying osseous structures, and SSD is useful when fractures extend to the articular cortex and a disarticulated view is desired. Three-dimensional images are helpful in patients with congenital deformities, arthritis, and trauma.

Fundamentals of multichannel CT.

Multichannel CT has become a very valuable tool in diagnostic imaging. It provides a combination of fast and long coverage in conjunction with thin slices. The fast scanning allows for single-breathhold scanning, fewer motion artifacts, and better use of intravenous contrast media. The brains of the MCCT scanners are the sophisticated detector arrays packed with electronics to handle the flow of image information. The submillimeter detectors rows offer isotropic properties to the image voxels, thereby creating viewing in any plane and better three-dimensional renderings.