R B Jeffrey

Surface normal overlap: a computer-aided detection algorithm with application to colonic polyps and lung nodules in helical CT

We developed a novel computer-aided detection (CAD) algorithm called the surface normal overlap method that we applied to colonic polyp detection and lung nodule detection in helical computed tomography (CT) images. We demonstrate some of the theoretical aspects of this algorithm using a statistical shape model. The algorithm was then optimized on simulated CT data and evaluated using a per-lesion cross-validation on 8 CT colonography datasets and on 8 chest CT datasets. It is able to achieve 100% sensitivity for colonic polyps 10 mm and larger at 7.0 false positives (FPs)/dataset and 90% sensitivity for solid lung nodules 6 mm and larger at 5.6 FP/dataset.

STS-MIP: a new reconstruction technique for CT of the chest.

The authors present sliding thin-slab maximum intensity projection (STS-MIP) as a technique for improved visualization of blood vessels and airways from rapidly acquired thin-section CT data. The STS-MIP reconstructions can be computed rapidly and without operator intervention directly from the transaxial sections. The resulting images retain the high contrast resolution of thin-section (1-3 mm) CT while providing vascular or airway visibility within a sequence of overlapping thin-slabs (3-10 mm). Examples are presented of pulmonary vessels and airways derived from spiral CT and of pulmonary vessels and coronary arteries derived from electron-beam CT.

Visualization modes for CT colonography using cylindrical and planar map projections.

PURPOSE The purpose of this study was to demonstrate the limitations to the effectiveness of CT colonography, colloquially called virtual colonoscopy (VC), for detecting polyps in the colon and to describe a new technique, map projection CT colonography using Mercator projection and stereographic projection, that overcomes these limitations. METHOD In one experiment, data sets from nine patients undergoing CT colonography were analyzed to determine the percentage of the mucosal surface visible in various visualization modes as a function of field of view (FOV). In another experiment, 40 digitally synthesized polyps of various sizes (10, 7, 5, and 3.5 mm) were randomly inserted into four copies of one patient data set. Both Mercator and stereographic projections were used to visualize the surface of the colon of each data set. The sensitivity and positive predictive value (PPV) were calculated and compared with the results of an earlier study of visualization modes using the same CT colonography data. RESULTS The percentage of mucosal surface visualized by VC increases with greater FOV but only approaches that of map projection VC (98.8%) at a distorting, very high FOV. For both readers and polyp sizes of > or =7 mm, sensitivity for Mercator projection (87.5%) and stereographic projection (82.5%) was significantly greater (p < 0.05) than for viewing axial slices (62.5%), and Mercator projection was significantly more sensitive than VC (67.5%). Mercator and stereographic projection had PPVs of 75.4 and 78.9%, respectively. CONCLUSION The sensitivity of conventional CT colonography is limited by the percentage of the mucosal surface seen. Map projection CT colonography overcomes this problem and provides a more sensitive method with a high PPV for detecting polyps than other methods currently being investigated.

Computed tomography of cervical infections.

Computed tomography of 31 patients with infections of the face and neck was reviewed and correlated with the clinical and surgical results. Computed tomography was found to be valuable for (a) distinguishing cellulitis from abscess, (b) defining the precise location and extent of complex infections, (c) demonstrating secondary complications, and (d) occasionally suggesting the etiology of infection. Based on this review, we concluded that CT provides important diagnostic information that aids clinical assessment and guides medical and surgical management of cervical infections. The anatomic relationships of selected cervical spaces are reviewed with respect to pathways of spread and potential complications of cervical infections.

Multidetector-row helical CT and advanced postprocessing techniques for the evaluation of pancreatic neoplasms

AbstractAn important feature of multidetector-row helical computed tomography (CT) is the increased speed of scanning that permits routine use of very thin collimation and acquisition of near isometric imaging data of the abdomen within the time span of a single breath-hold. The parallel escalation in the capabilities of workstations makes feasible the practical use of advanced postprocessing techniques to create high quality volumetric imaging. This article highlights the unique contributions of multidetector-row CT and advanced postprocessing techniques to the evaluation of the pancreas and peripancreatic vascular structures and their value in the diagnosis and staging of pancreatic neoplasms.

Detection of colonic polyps in a phantom model : Implications for virtual colonoscopy data acquisition

PURPOSE Virtual colonoscopy is a new method of colon examination in which computer-aided 3D visualization of spiral CT simulates fiberoptic colonoscopy. We used a colon phantom containing various-sized spheres to determine the influence of CT acquisition parameters on lesion detectability and sizing. METHOD Spherical plastic beads with diameters of 2.5, 4, 6, 8 and 10 mm were randomly attached to the inner wall of segments of plastic tubing. Groups of three sealed tubes were scanned at 3/1, 3/2, 5/1 collimation (mm)/pitch settings in orientations perpendicular and parallel to the scanner gantry. For each acquisition, image sets were reconstructed at intervals from 0.5 to 5.0 mm. Two blinded reviewers assessed transverse cross-sections of the phantoms for bead detection, using source CT images for images for acquisitions obtained with the tubes oriented perpendicular to the gantry and using orthogonal reformatted images for scans oriented parallel to the gantry. RESULTS Detection of beads of > or = 4 mm was 100% for both tube orientations and for all collimator/pitch settings and reconstruction intervals. For the 2.5 mm beads, detection decreased to 78-94% for 5 mm collimation/pitch 2 scans when the phantom sections were oriented parallel to the gantry (p = 0.01). Apparent elongation of beads in the slice direction occurred as the collimation and pitch increased. The majority of the elongation (approximately 75%) was attributable to changing the collimator from 3 to 5 mm, with the remainder of the elongation due to doubling the pitch from 1 to 2. CONCLUSION CT scanning at 5 mm collimation and up to pitch 2 is adequate for detection of high contrast lesions as small as 4 mm in this model. However, lesion size and geometry are less accurately depicted than at narrower collimation and lower pitch settings.

CT evaluation of mediastinal infections.

Of 104 patients evaluated for thoracic sepsis by CT, 22 patients had both CT and clinical evidence of mediastinal infections. The CT findings in these patients were reviewed and compared with a control group of seven postoperative patients following uncomplicated median sternotomy. Based on CT appearance, patients were classified into one of three groups: (a) diffuse soft tissue infiltration with or without gas (i.e., mediastinitis) (10 patients); (b) focal mediastinal abscess (four patients); (c) mediastinal infection associated with empyema or subphrenic abscess (eight patients). Computed tomography proved reliable in distinguishing diffuse mediastinitis from a localized drainable abscess. However, in the absence of mediastinal gas, CT could not differentiate mediastinitis from benign postoperative changes. Computed tomography was helpful in identifying associated empyemas and a variety of other secondary complications. In five of six patients with mediastinal abscess, CT demonstrated communication or contiguity with four empyemas and one subphrenic abscess. Closed chest tube drainage of the empyemas and percutaneous drainage of the subphrenic abscess combined with antibiotic therapy were successful in treating the mediastinal abscess in these five patients. Although overall mortality for mediastinal infection in this series was 27%, there was a 50% mortality for patients with diffuse mediastinitis.

Uterine adenomyosis. A difficult sonographic diagnosis.

In an effort to distinguish the appearance of generalized uterine adenomyosis from leiomyoma, a retrospective study was performed on 80 patients who had preoperative uterine sonography. A diagnosis of adenomyosis (eight patients) was suggested if the uterus was diffusely enlarged, but the myometrial texture, contour, and central cavity echoes were each normal. Leiomyoma, or other focal uterine pathology (72 patients) was characterized by focal or globular uterine enlargement with abnormal echo texture and contour, as well as nonvisualization or displacement of the central cavity echo complex. Using these criteria, ultrasound was able to suggest adenomyosis with a sensitivity of 63%, a specificity of 97%, and a positive predictive value of 71%. Focal pathology was diagnosed with a sensitivity of 97%, a specificity of 63%, and a positive predictive value of 96%. Although irregular myometrial sonolucent zones have previously been reported as characteristic for adenomyosis, this study did not confirm this finding.

Computed Tomography of Psoas Abscesses

Nine surgically proven cases of pyogenic psoas abscesses are presented. The most common finding on computed tomography was diffuse enlargement of the psoas with a central low density area corresponding to an abscess cavity. This was noted in seven patients. The anatomy of the psoas muscle and retrofascial area is discussed, as well as the changing etiology and bacteriology of psoas abscesses

CT evaluation of invasive lesions of the bladder.

Abstract: The role of computed tomography (CT) in defining the extent of local tumor invasion was reviewed retrospectively in 22 patients with biopsy proven malignant lesions of the bladder. These included 14 cases of primary bladder carcinoma and 8 cases of pelvic malignancies with secondary invasion of the bladder. Computed tomography proved accurate in detecting lymph node enlargement, obvious extravesical masses, and relatively small mural or mucosal lesions of the bladder. However, CT was not able to reliably predict microscopic invasion of either the serosal surface of the bladder by pelvic malignancies or microscopic invasion of the perivesical fat by intrinsic bladder carcinoma. These factors, in addition to the inability of CT to detect metastases in normal sized lymph nodes, appear to limit the overall accuracy of CT in the evaluation of locally invasive pelvic malignancies. Nevertheless, CT appears to be a useful noninvasive screening technique to avoid needless radical surgery in advanced lesions with bladder invasion.