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Biomedical subjects

N Chafetz

Publications and source records attributed to N Chafetz.

At least 19 recordsLinked to original sources
PubMed1990

Lumbar spinal fusion. Assessment of functional stability with magnetic resonance imaging.

Segmental spinal instability was evaluated with magnetic resonance (MR) imaging, computed tomography (CT), and conventional radiography in 33 patients who had undergone surgical spinal fusion. In 16 of the 19 patients who had a diagnosis of solid fusion, the immobilized vertebral bodies demonstrated areas of high signal intensity on images with short repetition time (TR) and echo time (TE). The signal intensity of these areas was either less intense or normal on images with long TR and TE. In 10 of the 14 patients with segmental instability at the fusion site, subchondral vertebral bands of low signal intensity were shown on short TR/TE images, which demonstrated high signal intensity on long TR/TE images. All but two of the patients showed vertebral signal changes 12 or more months past fusion or onset of clinical symptoms. The vertebral MR signal intensity in solid lumbar fusions might be related to marrow composition changes resulting from decreased biomechanical stress, while the vertebral signal intensities in patients with unstable fusions might be related to reparative granulation tissue, inflammation, edema, and hyperemic changes. Magnetic resonance imaging appears to be unique in its assessment of functional fusion stability. Magnetic resonance may be most useful in patients symptomatic of fusion pseudarthrosis in whom conventional radiography and CT fail to demonstrate anatomic disruption.

Female↗
PubMed1989

Computed tomography in dental implantation surgery.

High-resolution thin section CT with cross-sectional oblique and panoramic CT reconstructions has been shown to be an excellent tool for the preoperative evaluation of the mandible and maxilla for dental implant surgery. Oblique cross-sections throughout the entire surgical field allow visualization of osseous topography as well as related internal anatomic structures such as the inferior alveolar canal, the mental foramina, the incisive canal, and the maxillary sinuses. Armed with this knowledge, the surgeon-restorative dentist team can plan fixture positioning more effectively, thereby minimizing surprises in the operating room. Cases with inadequate buccolingual bone dimension are not attempted, whereas many other cases that do not appear to have adequate bone, as seen on conventional x-ray films, can be successfully implanted. The ultimate prosthesis is optimized because the surgeon can take full advantage of the available bone to achieve proper fixture alignment. It is quite likely that as future experience is obtained with maxillofacial CT, it may also be useful in diagnosis and treatment for a wide variety of other disorders of the jaw.

Dental Implantation, Endosseous↗
PubMed1988

[3-dimensional computed tomography and multiplanar CT-reformations in lumbar spondylodesis].

Three-dimensional computed tomography (3-D-CT) and multiplanar CT reformations were performed in 42 patients who were clinically suspected of spinal instability following posterior lumbar fusion. Sagittal and coronal CT reformations demonstrated fusion pseudarthrosis more frequently than axial CT or conventional radiography. Three-dimensional CT cuts through the fusion revealed pseudarthrosis in most patients with positive 2-D images. In 5 patients, however, fusion appeared to be artifactually stable or unstable on 3-D cuts contrasting the 2-D images. Three-dimensional surface reconstructions demonstrated the complex anatomy of the fusion and showed superficial breaks. They were helpful in preoperative planning as well as intraoperative localization. 3-D-CT is a clinically useful adjunctive imaging method.

Adult↗
PubMed1988

Three-dimensional computed tomography and multiplanar reformations in the assessment of pseudarthrosis in posterior lumbar fusion patients.

Three-dimensional (3-D) surface reconstructions and multiplanar computed tomography (CT) reformations were obtained in 30 patients with clinically suspected spinal fusion pseudarthrosis. The imaging studies were blind-reviewed and the results were compared with the clinical and surgical findings. Sagittal, planar, and curved coronal two-dimensional (2-D) reformations were more useful in the detection of bony nonunion than were axial CT scans, as the latter required more extensive analysis. Three-dimensional surface "cuts" adequately demonstrated pseudarthrosis in most cases. In some instances, however, segmentation artifacts created artifactual clefts or implied solidity, which contrasted with the interpretation of the 2-D images. Sagittal 3-D cuts were helpful in demonstrating bony central and lateral stenosis. Three-dimensional surface reconstructions demonstrated superficial clefts and outlined the complex anatomy of the spinal fusions, thus facilitating pre- and intraoperative planning. The amount of bone stock available for pseudarthrosis repair at the fusion site and the need for additional harvesting of bone from the iliac crest also could be assessed easily. 3-D CT proved to be useful as an adjunctive imaging method in the evaluation of posterior lumbar fusion patients suspected of pseudarthrosis.

Adult↗
PubMed1988

Neuromuscular thermography of the lumbar spine with CT correlation.

Fifteen asymptomatic volunteers and 19 patients with current CT (GE 8800 CT/T) scans demonstrating either thecal sac contour distortion or nerve root displacement from disc rupture or spinal stenosis of the L4-L5 or L5-S1 levels judged to be at least moderate in severity underwent lumbar thermography. All patients were studied with an infrared telethermographic unit (AGA model 720M) employing the technical standards recommended by the Academy of Neuromuscular Thermography. The thermographic exams were interpreted independently and in a blind fashion by two radiologists. Of the 15 exams of asymptomatic patients, six were interpreted as positive and consistent with nerve fiber irritation. Of the 19 exams of patients with demonstrated CT abnormalities, all had positive thermograms for nerve fiber irritation (specificity 60%, sensitivity 100%). It is concluded that lumbar thermography is a sensitive examination for detecting those patients who will demonstrate lumbar spinal CT abnormalities and should play an important role in the diagnostic screening of low-back pain syndrome patients.

Adult↗
PubMed1987

[Magnetic resonance tomography in the determination of the functional stability of posterolateral lumbar spondylodeses].

MR tomography was used to assess functional lumbar stability in 30 patients with posterolateral fusions. The vertebral bodies of 9 of the 12 patients with unstable lumbar fusions presented with areas of decreased signal intensity on T1- and intermediately weighted images, which increased on T2-weighting. The vertebrae of 15 of the 18 patients with stable fusions demonstrated zones of increased signal intensity on T1- and intermediately weighted images, which were less intense or invisible on T2-weighing. Surgical correlation was available in 11 of the 30 patients studied. Hyperemia and inflammation appear to be responsible for the abnormal signal intensities in the patients with stable fusions, whereas an increase in adipose marrow due to decreased biomechanical stress is thought to account for the atypical signal intensities in the vertebral bodies of the patients with stable fusions. MR tomography seems to be a potential method for evaluating functional lumbar fusion stability. MR tomography may be particularly helpful in those patients with multiple back surgeries and possible instability, recurrent disc herniation, or postoperative fibrosis. MR is recommended in the patient, who appears clinically unstable, whose radiographs and CT, however, do not demonstrate fusion failure.

Adult↗
PubMed1987

Pseudarthrosis following lumbar fusion: detection by direct coronal CT scanning.

Twenty patients with fusions of the lumbar spine (seven with pseudarthrosis, 11 with solid bony fusions, and two with fusions that appeared solid but assessment was complicated by the presence of surgical hardware) underwent computed tomographic (CT) scanning in the supine position in the axial plane and, employing a specially designed seat, in the coronal plane. Three-millimeter contiguous sections were acquired. The direct coronal images were compared with those reformated from the axial images. The higher-resolution direct coronal images facilitated the diagnosis of pseudarthrosis and increased confidence in interpretation of normal studies. Direct coronal imaging is easy to perform and in many cases requires fewer scans and less radiation than reformations. Because it provides more useful diagnostic information, direct coronal imaging should replace current methods for evaluating fusions of the lumbar spine.

Adult↗
PubMed1985

Stereophotogrammetry of the lumbar spine. A technique for the detection of pseudarthrosis.

A computer-assisted photogrammetric method for the detection of pseudarthrosis following spinal fusion is described. This radiologic method is quantitative and noninvasive and requires a minimum of clinician time. Results of tests with a phantom specimen are presented. Preliminary indications are that the method may prove to be a useful adjunct to the clinician in monitoring the postoperative course of patients requiring fusion procedures.

Lumbar Vertebrae↗
PubMed1985

Multinuclide digital subtraction imaging in symptomatic prosthetic joints.

One hundred eleven patients with symptomatic prosthetic joints (86 hips, 23 knees, and two shoulders) were evaluated for prosthetic loosening and infection by combined technetium-99m-MDP/gallium-67 digital subtraction imaging. Clinical correlation was based on the assessment of loosening and bacterial cultures obtained at the time of surgery in 54 patients, joint aspiration cultures obtained in 37 patients, and long-term clinical follow-up for greater than 1.5 years in an additional 15 patients. Results revealed an 80%-90% predictive value of a positive test for loosening, and a 95% predictive value of a negative test for infection. However, because of the low sensitivities and specificities observed, this approach to the evaluation of symptomatic prosthetic joints does not seem cost effective.

Adult↗
PubMed1985

Subsidence of the femoral prosthesis. A stereophotogrammetric evaluation.

A quantitative three-dimensional measurement method, radiographic stereophotogrammetry (SPG), was employed to assess the relation between early subsidence of the femoral prosthesis after total hip arthroplasty (THA) and subsequent clinical course. The SPG technique and the authors' error control mechanisms are described in 15 patients in the early postoperative period, and the findings are correlated with those of follow-up clinical examinations. Among the 12 patients who remained clinically asymptomatic with respect to pain, only one had an SPG estimate of subsidence in excess of 1 mm at any point in time. Each of the three patients who later became symptomatic had SPG estimates of subsidence in excess of 1.75 mm within six months of the operation. Thus far, the patient with the largest estimate of subsidence is the only one who required surgical revision.

Evaluation Studies as Topic↗
PubMed1981

Detection of bone-marrow metastases using quantitative computed tomography.

A method is described for using quantitative computed tomography (CT) to detect subtle skeletal metastases not readily identified or precisely located by conventional methods. Four patients with intramedullary metastases are presented along with data from 13 control subjects. The results indicate that CT may demonstrate intramedullary changes that occur in skeletal metastases and that cannot be detected by other techniques. A difference in medullary CT number greater than 20 HU between limbs is abnormal. This asymmetry, however, is not specific for metastatic disease, and clinical judgment must be exercised in interpreting this finding.

Adenocarcinoma↗
PubMed1979

The heterogeneous liver scan: ultrasound correlation.

Fifty-five heterogeneous technetium-99m sulfur colloid liver scans of 48 patients with suspected metastatic disease were compared with gray scale ultrasound results. Of the 52 ultrasound scans corresponding to the nuclear scans with mild to moderate heterogeneity, 35 (67%) were normal, 11 (21%) were consistent with hepatocellular disease, 3 were incomplete because of abdominal gas, and 2 were false positive studies interpreted as suspicious for tumor. Ultrasound is not recommended for searching for space-occupying lesions when the nuclear scan is mild to moderately heterogeneous; it did detect the presence of tumor in 1 of 3 patients with severely "mottled" nuclear scans.

Diagnostic Errors↗
PubMed1979

Portal and hepatic veins: accuracy of margin echoes for distinguishing intrahepatic vessels.

One hundred randomly selected sonograms were retrospectively reviewed to determine the accuracy of employing the margin characteristics of intrahepatic venous radicals to distinguish portal from hepatic veins; 99% of intrahepatic portal veins demonstrated high amplitude acoustic margins. However, one or more hepatic veins also had high amplitude acoustic margins in 29% of patients in whom intraparenchymal hepatic veins were identified. The authors conclude that an intrahepatic venous structure without an echogenic border is almost invariably an hepatic vein, although other anatomical features should be considered for proper classification of intrahepatic venous structures which demonstrate high amplitude echoes surrounding the lumen.

Adolescent↗