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Biomedical subjects

D S Schauwecker

Publications and source records attributed to D S Schauwecker.

At least 19 recordsLinked to original sources
PubMed2003

Melanoma patients evaluated by four different positron emission tomography reconstruction techniques.

One hundred and nineteen patients with malignant melanoma were studied using 2-[ F]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET). The images were reconstructed using ordered subset expectation maximization with and without attenuation correction and filtered backprojection with and without attenuation correction. The most probable draining lymph node chains were surgically explored and the tumour volume was quantified at histology. The four different reconstructions of the PET images were retrospectively graded on a five-point scale by two blind readers and compared with the tumour volume. The readers agreed within +/-1 grade 93% (529/568) of the time. Comparing the areas under the receiver operating characteristic (ROC) curves gave 0.698, 0.668, 0.694 and 0.684 for the four reconstruction techniques. The lowest value comparing any pair of the four reconstruction techniques was P=0.371. Thus, none of the reconstruction techniques gave significantly better results than any of the others. The sensitivity of detection was 85% for tumour volumes of 113 m or more (about 6 mm in diameter), but only 4% for tumours less than this size. It can be concluded that the use of attenuation correction gives aesthetically more pleasing images, but the sensitivity and specificity are not significantly improved.

Adult↗
PubMed2001

FDG-PET sensitivity for melanoma lymph node metastases is dependent on tumor volume.

BACKGROUND AND OBJECTIVES: The purpose of this study is to determine the tumor volume threshold for successful positron emission tomography (PET) imaging of melanoma nodal metastases. METHODS: Review of a clinical series of patients who had FDG-PET imaging of regional lymph node basins followed by lymphadenectomy. Lymph node tumor volumes were calculated from direct measurements of metastatic nodule(s) in formalin fixed specimens. PET scan interpretations were correlated with histology to determine sensitivity. Sensitivity was correlated with the aggregate lymph node tumor volume in the nodal basin and with AJCC stage group. RESULTS: Forty-five patients with 49 pathologically positive regional nodal basins comprised the study group. Median total basin tumor volume was 28.3 mm(3)(range 0.004-22,879 mm(3)). FDG-PET sensitivity for detection of all tumor volumes was 0.49. The observed 90% sensitivity threshold for detection of nodal metastases was > or = 78 mm(3). PET sensitivity was 0.14 for detection of tumor volumes < 78 mm(3). PET sensitivity differed by prescan AJCC stage: I-0.0; II-0.24; III-0.81; IV-1.0 (P < 0.001). CONCLUSIONS: FDG-PET reliably detects lymph node tumor deposits greater than approximately 80 mm(3) volume, but sensitivity falls rapidly below this. This amount of tumor is most likely to occur in patients with AJCC stage III or IV disease.

Fluorodeoxyglucose F18↗
PubMed1997

Scrotal pathology as the cause for hip pain. Diagnostic findings on bone scintigraphy.

Scrotal scintigraphy has become a relatively uncommon examination in many nuclear medicine departments. However, scrotal perfusion is visualized during three-phase bone imaging of the pelvis and hips. The authors present a compilation of three cases of hip pain secondary to unsuspected scrotal pathology documented on routine three-phase bone scintigraphy, discussing this topic for the first time in the literature. A short review of the pathophysiology of referred hip pain, differential diagnosis, and imaging alternatives emphasize the unique contribution of nuclear imaging.

Adolescent↗
PubMed1997

Bone scintigraphy in the canine cruciate deficiency model of osteoarthritis. Comparison of the unstable and contralateral knee.

OBJECTIVE: To examine the effects on 99mTc medronate (MDP) bone scintigraphy of unilateral anterior cruciate ligament (ACL) transection in the unstable and contralateral knee of dogs. METHODS: Bone scintigraphy was performed in 5 dogs at baseline and 6 and 12 weeks after ligament transection, with images of both knees obtained 3-4 h after intravenous injection of the radionuclide. An image of the T4-T5 vertebral region was also acquired as an internal standard. In 3 additional dogs, scintigraphy was performed at baseline and 5 1/2 weeks after sham ACL transection. RESULTS: A marked increase in uptake of 99mTc MDP was seen in the unstable knee. In contrast, in all but one case uptake in the contralateral knee did not increase significantly. Sham ligament transection had no effect on uptake of the radionuclide. CONCLUSION: Changes occur in subchondral bone as well as in articular cartilage in the unstable knee in this model. The bony changes, which could be either primary or secondary to early changes in the biomechanical properties of the cartilage, may contribute to the pathogenesis of cartilage damage. No appreciable effects on bone turnover in the contralateral knee could be proved in this study.

Animals↗
PubMed1996

Pulmonary emboli from pulse-spray and mechanical thrombolysis: evaluation with an animal dialysis-graft model.

PURPOSE: To compare pulmonary emboli resulting from pulse-spray pharmacomechanical thrombolysis (PSPMT) and mechanical thrombolysis performed to declot dialysis-access grafts. MATERIALS AND METHODS: Polytetrafluoroethylene arteriovenous shunts were created in eight dogs and were deliberately clotted at monthly intervals. Animals were randomly assigned to treatment with pulse-spray urokinase thrombolysis or a low-speed rotational percutaneous thrombolytic device. Perfusion imaging, pulmonary-artery pressure measurements, and pulmonary arteriography were performed before and after each procedure. RESULTS: A total of 22 procedures were performed (11 PSPMT and 11 mechanical thrombolysis). Declotting was successful in all procedures, with 100% 30-day patency. Segmental defects were seen on perfusion images after 10 (91%) of 11 PSPMT procedures and two (18%) of 11 mechanical thrombolysis procedures (P < .002). Transient increases in pulmonary-artery pressure occurred in the PSPMT group. Complete resolution of emboli and return to baseline pressures were seen in all cases, even after multiple (up to four) procedures in the same animal. There was no histologic evidence of pulmonary infarction in either group. CONCLUSION: The percutaneous thrombolytic device is effective for declotting dialysis grafts in dogs and results in statistically significantly fewer pulmonary emboli compared with PSPMT.

Animals↗
PubMed1995

Differentiation of infected from noninfected rapidly progressive neuropathic osteoarthropathy.

Differentiation of infected from noninfected rapidly progressive neuropathic osteoarthropathy can be difficult in a combined bone/111In-leukocyte study. We present two cases: one infected and one not infected. By examining the distribution of the 111In leukocyte activity and the change in the lesion-to-background ratios from the 4-hr to the 24-hr image, it may be possible to determine if the rapidly progressive neuropathic osteoarthropathy is infected.

Adult↗
PubMed1995

Direct comparison of fluorine-18-FDG SPECT, fluorine-18-FDG PET and rest thallium-201 SPECT for detection of myocardial viability.

UNLABELLED: Twenty consecutive patients were evaluated for presumptive myocardial viability using rest TI-SPECT, FDG-PET and FDG-SPECT. The FDG studies were performed after rest TI-SPECT to guide intervention or medical management. METHODS: Twenty patients with proven coronary artery disease, either known or suspected to have previous myocardial infarction and persistent perfusion defects shown by rest reinjection TI-SPECT, underwent FDG-PET and subsequent FDG-SPECT with a three-detector SPECT camera. FDG-PET and SPECT images were compared by five observers to determine if any fixed thallium segments were visualized by either FDG imaging method. RESULTS: Thirteen of 60 fixed segments were shown probably viable by FDG-SPECT (8 of 20 patients) and 14 of 60 by FDG PET (7 of 20 patients). Two patients had fixed thallium segments found probably viable with FDG by SPECT alone and one by PET alone. CONCLUSION: FDG is shown to provide additional information about myocardial viability. Both SPECT, using a three-detector camera, and PET with a specialized instrument are equally effective for imaging FDG in this application.

Coronary Disease↗
PubMed1992

Comparison of gallbladder ejection fraction with histopathologic changes in acalculous biliary disease.

This selective retrospective study was undertaken to establish whether the gallbladder contraction (ejection fraction) calculated during cholescintigraphy correlates with the histopathologic changes in the surgical specimen. The medical records of 243 patients who underwent hepatobiliary scintigraphy were reviewed. Of these, 215 patients had cholecystokinin cholescintigraphy and 100 went on to cholecystectomy. The original histologic slides from 67 gallbladders were available and reviewed by a pathologist who graded each specimen based on presence and severity of changes associated with "chronic" cholecystitis. There was no significant correlation between the severity of histopathologic change and cholecystokinin-induced gallbladder emptying.

Adult↗
PubMed1992

The scintigraphic diagnosis of osteomyelitis.

Osteomyelitis is a serious health problem that results in multiple limb amputations annually. This article reviews the current scintigraphic procedures used in the diagnosis of osteomyelitis and discusses some of the newer radiopharmaceuticals now being developed. The goal is to understand the strengths and weaknesses of each method so that the procedure most effective for specific clinical settings can be selected. In general, the three-phase bone scan is the procedure of choice if the suspected osteomyelitis is not superimposed on another disease that causes increased bone remodeling (i.e., findings on the radiograph are normal). If the suspected osteomyelitis is superimposed on a disease that causes increased bone remodeling, the combined 111In-labeled leukocyte-99mTc bone scan is the procedure of choice in the non-marrow-containing skeleton and the 111In-labeled leukocyte and 99mTc bone marrow scans are the procedures of choice in the marrow-containing skeleton.

Citrates↗
PubMed1991

Comparison of indium-111 nonspecific polyclonal IgG with indium-111-leukocytes in a canine osteomyelitis model.

Osteomyelitis was surgically produced in the proximal tibia of ten dogs. A sham operation was performed on the other tibia. Early (3 hr) and late (20 hr) imaging was performed 1, 4, 7, 10, and 13 wk later, while the osteomyelitis progressed from acute to chronic. Indium-111-IgG had a significantly greater accumulation at the osteomyelitis site than 111In-leukocytes, both during early (p = 0.001) and late (p = 0.03) imaging, and at each of the weeks studied (p less than 0.001). During early imaging, both agents gave equivalent lesion to background ratios. On the late images, the 111In-leukocytes gave significantly higher lesion-to-background ratios than 111In-IgG (p less than 0.001) and higher ratios than they did during the early images (p less than 0.001). Both agents had greater accumulation in acute osteomyelitis than in chronic osteomyelitis (p less than 0.02). Osteomyelitis in the surgical site can be distinguished from the uptake in the sham surgery site using 111In-leukocytes, but not when using 111In-IgG.

Animals↗
PubMed1990

Diagnostic imaging of osteomyelitis.

There are many imaging procedures for diagnosing osteomyelitis, each with unique strengths and weaknesses. Plain radiographs are inexpensive and can be very accurate but may provide a delayed diagnosis. Computed tomography and magnetic resonance imaging are both excellent at differentiating soft tissue infection from osteomyelitis. Computed tomography, magnetic resonance imaging, and bone scans are accurate diagnostic tools for use when the bone has not be violated by surgery, trauma, or other structural alterations. When such changes are present, an Indium-111 leukocyte or Indium-111 polyclonal antibody study may be necessary for accurate diagnosis.

Bone and Bones↗