A potential error in the quantitation of fecal blood loss: concise communication.

Chromium-51-labeled red cells were used to quantitate fecal blood loss in a patient with chronic upper gastrointestinal hemorrhage. On Day 1, the stool guaiac was positive but the blood loss indicated by 51Cr was less than 1 cm3. Blood loss in the stool by 51Cr did not become significant until Day 3, when it measured 23 cm3. The failure to detect abnormal blood loss on Day 1, and probably on Day 2, appears to be due to a long intestinal transit time from a proximal bleeding site. The problem of slow intestinal transit is not uncommon and could lead to a false-negative study or falsely low estimates of fecal blood loss. This problem could be minimized by beginning stool collection on Day 3 or by delaying stool collection until the appearance in the stool of an oral nonabsorbable marker swallowed when the 51Cr-tagged red cells are injected.

Imaging the bowel with technetium--an aid in gallium studies.

Three cases are present to demonstrate the usefulness of oral or rectal technetium-99m preparations in locating the stomach and bowel in relation to abnormal accumulation of gallium-67 within the abdomen. In this way, the concentration of gallium in an abscess or a tumor may be distinguished from its physiologic excretion into the bowel.

Femoral prosthesis subsidence in asymptomatic patients. A stereophotogrammetric assessment.

A radiographic stereophotogrammetric technique (SPG) was used to evaluate quantitatively the presence of early femoral prosthesis subsidence after total hip arthroplasty (THA). This paper focuses on the measurement of subsidence in 12 patients who remained asymptomatic during the first two years after surgery. Only one of these had SPG estimated subsidence in excess of one millimeter at any timepoint. These findings are consistent with the conclusion that early postoperative subsidence is not a common finding among asymptomatic THA patients.

Differentiation between postoperative scar and recurrent disk herniation: prospective comparison of MR, CT, and contrast-enhanced CT.

Twenty-five symptomatic postlumbar surgery patients had findings on lumbar spinal noncontrast CT that were equivocal for distinguishing recurrent disk herniation from postoperative epidural fibrosis (scar). Contrast-enhanced CT and lumbar MR imaging were performed to differentiate these two conditions. Of the 14 levels, surgically explored, the diagnosis of scar or recurrent disk herniation was correct with contrast-enhanced CT at 10 levels and with MR imaging at 11 levels. At the levels operated on less than 2 years prior to MR imaging, scar more frequently demonstrated intermediate than low signal intensity. Scar older than 2 years most often showed low signal intensity. These preliminary findings suggest that MR may be useful in differentiating postoperative fibrosis from recurrent disk herniation in a significant proportion of patients whose unenhanced CT scans are equivocal.

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.

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.

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.

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.

[Magnetic resonance tomography in the determination of the functional stability of posterolateral lumbar spondylodeses]. / Magnetresonanztomographie bei der Beurteilung funktioneller Stabilität posterolateraler lumbaler Spondylodesen.

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.

[3-dimensional computed tomography and multiplanar CT-reformations in lumbar spondylodesis]. / Dreidimensionale Computertomographie und multiplanare CT-Reformationen bei lumbalen Spondylodesen.

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.

High-resolution computerized tomography and nuclear bone scanning in the diagnosis of postoperative stress fractures of the mandible: a clinical report.

Root-form titanium dental implants are the treatment of choice for many partially and totally edentulous patients. The overall success rate is greater than 95%. Postoperative pain is usually the result of infection. This report presents two cases involving a sudden onset of jaw pain. Computerized tomographic scanning revealed that the pain was caused by stress fracture of the mandible.

CT in low back pain syndrome.

CT has become the imaging modality of choice for diagnosing the specific cause of low back pain syndrome. This article describes and illustrates those abnormalities commonly associated with low back pain: disk herniation, spinal stenoses, facet joint abnormalities, spondylosis, inflammatory conditions of the lumbar spine, and sacroiliitis.

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.

Magnetic resonance imaging: skeletal applications.

It has been assumed that magnetic resonance imaging (MRI) would have limited utility in visualizing bones, due to the lack of hydrogen atoms in cortical bone. Nonetheless, that same lack makes it possible to clearly distinguish cortical bone from soft tissue and from marrow. Thus, roles are described for magnetic resonance imaging in depicting bone and soft tissue tumors, the spine (including the spinal cord and vertebral discs), and appendicular soft tissue, as well as the detection of avascular necrosis in the hip.

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.