Simplifying the exploration of volumetric images: development of a 3D user interface for the radiologist's workplace.

Volumetric imaging (computed tomography and magnetic resonance imaging) provides increased diagnostic detail but is associated with the problem of navigation through large amounts of data. In an attempt to overcome this problem, a novel 3D navigation tool has been designed and developed that is based on an alternative input device. A 3D mouse allows for simultaneous definition of position and orientation of orthogonal or oblique multiplanar reformatted images or slabs, which are presented within a virtual 3D scene together with the volume-rendered data set and additionally as 2D images. Slabs are visualized with maximum intensity projection, average intensity projection, or standard volume rendering technique. A prototype has been implemented based on PC technology that has been tested by several radiologists. It has shown to be easily understandable and usable after a very short learning phase. Our solution may help to fully exploit the diagnostic potential of volumetric imaging by allowing for a more efficient reading process compared to currently deployed solutions based on conventional mouse and keyboard.

Evaluation of femur length during the second and third trimesters in fetuses with myelomeningocele.

OBJECTIVES: To determine if the femur length of fetuses with myelomeningocele is shorter in the second and third trimesters compared with that of normal fetuses. METHODS: We retrospectively collected measurements of femur length, head circumference, biparietal diameter and abdominal circumference from detailed obstetric ultrasound studies performed during the second and third trimesters in 31 fetuses with myelomeningocele and 43 fetuses with no detectable anomaly. The gestational age predicted by each parameter (based on Hadlock's tables) was compared with the true gestational age (based on last menstrual period), using the ANCOVA test to determine if there was a statistically significant difference between the two groups of fetuses. RESULTS: There was no significant difference in femur length (P = 0.60) or in abdominal circumference (P = 0.85) between fetuses with myelomeningocele and normal fetuses. Fetuses with myelomeningocele did have a significantly lower biparietal diameter and head circumference (P < or = 0.001). CONCLUSIONS: Myelomeningocele is not associated with reduced femur length in the second and third trimesters, suggesting that the known postnatal lower extremity foreshortening in patients with myelomeningocele develops late in gestation or after birth.

Comparison of CT localization radiography and high-kilovoltage chest radiography.

Twenty-five patients had localization radiography before chest computed tomography (CT) for evaluation of pulmonary nodules, staging of lung carcinoma, or suspected metastatic disease. Evaluation of the localization radiograph and the 140 k Vp frontal chest radiograph were performed independently and without history by a CT and chest radiologist, respectively. These interpretations were compared to a reference standard compiled from the full CT and chest radiographic reports. Significant abnormalities in the soft tissues, bones, mediastinum, hila, and pleura were detected with about equal frequency by chest and localization radiography. Chest radiography detected all 16 of the lung nodules greater than 1 cm in diameter, while localization radiography detected 12; however, this was not statistically significant. Both the sensitivity and specificity of nodule detection by chest radiography exceeded that of localization radiography. The performance of localization radiography in the detection of chest abnormalities in this and other studies encourages further development of computed chest radiography.

Clinical value of coronary bypass graft evaluation with CT.

Computed tomography (CT) has a reported accuracy of 45%-97% in assessment of patency of coronary artery bypass grafts. Dynamic CT was done in 26 patients (47 grafts) with recurrent cardiac symptoms after graft surgery. Although CT was 79% accurate (with selective angiography as the standard), the authors do not believe that it provides sufficient information for the assessment of symptomatic patients. Four patients had high-grade stenoses in their grafts, and 50% of patients had significant progression of atherosclerosis in their native coronary arteries. Neither of these conditions could be detected by CT. The clinical contribution of CT will probably be greatest for routine screening of asymptomatic patients soon after operation. Technical problems with CT scanning for graft patency are discussed.

Evaluation of the grafted ascending aorta with computed tomography. Complications caused by suture dehiscence.

Patients who have undergone surgery on the thoracic aorta and placement of a synthetic tubular graft need close, long-term radiological follow-up, as they are at risk of not only complications and progression of the underlying disease (atherosclerosis, dissection, or cystic medial necrosis) but also complications of the procedure, notably suture dehiscence leading to formation of an aneurysm around the graft. In a series of 14 asymptomatic postoperative patients studied by computed tomography (CT), the authors detected leakage of contrast material around the graft in 6 patients, 2 of whom required re-operation to correct suture dehiscence. CT is a noninvasive and sensitive method of postoperative evaluation of patients who have undergone an aortic graft.

Problems and pitfalls in the evaluation of thoracic aortic dissection by computed tomography.

Several conditions can lead to either false positive or false negative diagnoses of aortic dissection by computed tomography (CT) with intravenous administration of contrast medium. Insufficient contrast enhancement may cause intimal flaps to be missed, leading to a false negative diagnosis. False positive diagnoses result when extraaortic structures (e.g., mediastinal veins, pericardium, thickened pleura, and lung) are mistaken for false channels in the aorta. Superimposition of structures in thick CT slices may cause intimal calcifications to appear displaced. Streak artifacts across the descending aorta can resemble double aortic channels or intimal flaps. Fusiform aneurysms with thrombus are often hard to distinguish from thrombosed dissections by CT as well as by aortography.

Distinguishing benign from malignant pulmonary nodules by computed tomography.

Investigators have been able to distinguish benign pulmonary nodules from malignant ones in about two-thirds of the cases studied by detecting high computed tomography (CT) numbers (attributed to microscopic calcifications) within many benign nodules. This paper reports a similar analysis on a series of 22 benign and 14 malignant pulmonary nodules. Although about one-third of the benign nodules gave high CT numbers, all but one of the nodules diagnosed as benign by CT could also be diagnosed by detection of calcification on plain radiographs or conventional tomograms.

CT demonstration of subcutaneous venous collaterals.

Subcutaneous collateral veins were identified by computed tomography (CT) in 12 patients. These were seen as enhancing round or tubular structures surrounded by subcutaneous fat, and most were associated with occlusion of a major vein in the abdomen or thorax. The CT appearance of deep vein occlusions included an intraluminal thrombus with an enhancing rim, a mass replacing the nonvisualized vein and distortion of the vein by an adjacent mass. The subcutaneous fat was examined on the CT scans of 50 patients not suspected of having deep venous occlusions. The appearance of normal subcutaneous structures and the differential diagnosis are discussed.

Thymoma detection by mediastinal CT: patient with myasthenia gravis.

The precise role of computed tomography (CT) in evaluating the mediastinum for thymomas in patients with myasthenia gravis is not defined. The only published CT accuracy assessment reports a false-positive rate of 90%. Mediastinal CT was performed in 23 consecutive unselected patients with myasthenia gravis who underwent thymectomy independent of their neurologic status or diagnostic imaging results. Four patients had discrete thymomas; all were detected by CT. Conventional chest radiography and tomography were positive in three and falsely negative in one. In the remaining 19 patients with a normal or atrophic thymus or microscopic hyperplasia, CT was falsely positive in two; conventional chest radiography and tomography were falsely positive in three. Mediastinal CT is an accurate technique for evaluation of thymoma in patients with myasthenia gravis.

Volume determinations using computed tomography.

Computed tomography potentially offers the most accurate noninvasive means of estimating in vivo volumes. Contiguous 1-cm-thick CT scans were obtained through phantoms, dog kidneys in vivo, and human spleens before splenectomy. Cross-sectional areas were calculated for each individual scan and volumes then determined with each of four mathematical integration techniques. Volume estimations were compared to volumes determined by water displacement. The simplest, most practical means of calculating volumes, using the summation-of-areas technique with scans obtained at 2 cm intervals, was similar in accuracy to more complex methods. The mean percentage error of volume calculations using the sum-of-areas technique was 4.95% for five immobile phantoms, 3.86% for eight dog kidneys, 3.59% for eight human spleens in vivo at 1 cm scan spacing, and 3.65% for the same human spleens at 2 cm scan spacings. Difficulties in visual recognition and manual tracking of object boundaries seem to be more significant sources of error than patient-related factors.

Recurrent rectal carcinoma in an asymptomatic patient.

Pelvic recurrence is a common cause of symptoms and mortality in patients who have undergone surgical resection of rectal carcinoma. Diagnosis by physical examination and standard radiologic techniques is usually only possible when the recurrence becomes symptomatic because of its advanced state. Previous reports have documented the ability of computed tomography (CT) to depict accurately pelvic recurrence of rectal carcinoma in the symptomatic patient. Surgical resection of recurrence is usually noncurative but appears to result in a more prolonged survival if performed in the asymptomatic patient. We report a case of pelvic lymph node recurrence suggested by CT and confirmed by CT guided needle biopsy in an asymptomatic patient. Diagnosis of recurrence at this early stage by CT, supplemented with CT guided biopsy, may offer the patient an increased chance of survival following surgical resection.

CT detection of intraosseous gas: a new sign of osteomyelitis.

In three patients the diagnosis of osteomyelitis was made when computed tomography (CT) demonstrated gas within the medullary cavity of the involved bone. The diagnosis was clinically unsuspected in two of the patients before the CT examination, and none showed bone abnormalities on plain radiographs. Two patients had evidence of infection of the deep soft tissues adjacent to bone, and the third developed the lesion in an allograft. In all three patients CT detection of intraosseous gas resulted in significant alteration of patient management.

Splenic abscess due to Salmonella typhimurium bacteremia.

We have described a case of splenic abscess due to Salmonella typhimurium bacteremia. We believe abdominal roentgenograms and computed tomography are most effective in the preoperative evaluation of splenic abscess. Salmonella infections should be considered in the differential diagnosis of splenic abscess.

Gated cardiac computed tomography with a motion phantom.

CT images of the heart are significantly degraded by the effects of motion during the scanning interval. The use of electrocardiographic (ECG) gating to provide "stop-action" cardiac images remains limited by artifacts. A motion phantom has been constructed to allow systematic study of the artifact structure of ECG-gated images and to isolate the origins of these artifacts. "Stop-action" reconstructed images are presented demonstrating two classes of artifacts: (a) pinwheel artifacts that appear at the edges of high-contrast moving objects; and (b) linear streaks occurring in relation to missing views when an incomplete angular set of projections is used for image reconstruction with the convolution back-projection algorithm. These results underscore the use of the motion phantom for the analysis of image artifacts and stress the need for new CT reconstruction algorithms which are optmized for "stop-action" scanning.

CT-pathologic correlations in Hodgkin's disease and non-Hodgkin's lymphoma.

In order to assess its potential uses in the staging and treatment planning of lymphoma, CT was performed in 27 newly diagnosed, previously untreated patients with Hodgkin's disease or non-Hodgkin's lymphoma; 18 staging laparotomies provided pathologic correlations. CT detected and defined disease in areas not well evaluated by conventional techniques (high para-aortic, mesenteric, splenic hilar nodes). CT interpretation of splenic size and weight correlated well with splenic weight confirmed at pathology. Nodules were identified in several spleens containing foci of lymphoma.

Early experience with the Varian Six Second body scanner in the diagnosis of hepatobiliary tract disease.

Thirty-four patients with liver disease were studied with a research model of the Varian Six Second body scanner. Useful information was gained in patients with a variety of hepatic disorders. This scanner permits resolution of normal hepatic parenchymal detail which has not been reported previously and has reduced the streak artifacts originating from high- and low-CT objects which have been a major source of image degradation with other units.