Biomedical subjects

A van Lingen

Publications and source records attributed to A van Lingen.

At least 19 recordsLinked to original sources

PubMed1997

Comparison between 360 degrees and 180 degrees data sampling in thallium-201 rest-redistribution single-photon emission tomography to predict functional recovery after revascularization.

Whether 360 degrees or 180 degrees imaging should be used in cardiac thallium-201 single-photon emission tomography (SPET) studies to detect coronary artery disease remains controversial. Moreover, the relative diagnostic accuracy of 360 degrees and 180 degrees 201Tl SPET for the assessment of myocardial viability has never previously been studied. The aim of this study was to perform a direct comparison between 180 degrees and 360 degrees data sampling to detect viable myocardium in patients undergoing revascularization; in order to allow optimal detection of viability a rest-redistribution protocol was used. The 201Tl results were compared with improvement of regional wall motion abnormalities after the revascularization, which was considered as the "gold standard" for myocardial viability. Thirty-two patients, scheduled for revascularization, underwent rest-redistribution 201Tl SPET, using a 360 degrees arc. Raw data along a 180 degrees arc (45 degrees RAO to LPO) were selected from the original 360 degrees data sets (both early an late 201Tl images). All SPET data were analysed semiquantitatively using circumferential profiles of the short-axis images; the data were displayed in polar maps. Criteria for viability included percentage 201Tl redistribution and percentage 201Tl activity on the late image. Regional wall motion was assessed with two-dimensional echocardiography before and 3 months after revascularization. The sensitivities of 360 degrees and 180 degrees imaging for the prediction of functional recovery were 82% and 89%, respectively, whereas the specificities were 51% and 55%, respectively. The diagnostic accuracy of 360 degrees imaging was 62% and that of 180 degrees imaging 67%. This study shows that 360 degrees and 180 degrees imaging have comparable diagnostic accuracy in the prediction of functional recovery after revascularization. With the newer dual-head gamma camera systems with each detector opposing each other, 360 degrees imaging may be preferred.

Angioplasty, Balloon, Coronary↗

PubMed1997

Optimal metabolic conditions during fluorine-18 fluorodeoxyglucose imaging; a comparative study using different protocols.

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) can identify viable myocardium in patients with coronary artery disease. Recently, FDG imaging with single-photon emission tomography (SPET) and 511-keV collimators has been described. To obtain optimal image quality in all patients, cardiac FDG studies should be performed during hyperinsulinaemic glucose clamping. It has been suggested that FDG imaging after the administration of a nicotinic acid derivative may yield comparable image quality to clamping. We studied eight patients and compared the image quality of cardiac FDG SPET studies after oral glucose loading, after administration of a nicotinic acid derivative (acipimox, 250 mg orally) and during hyperinsulinaemic glucose clamping. The image quality was expressed as the myocardial to blood pool (M/B) activity ratio, which is used as a measure of the target-to-background ratio The M/B ratios were comparable after clamping and acipimox (2.8+/-0.8 vs 2.9+/-0.7), whereas the M/B ratio was lower after oral glucose loading (2.2+/-0.3, P<0.05 vs clamp and acipimox). To determine the clearance of FDG from the plasma, blood samples were drawn at fixed time intervals and the FDG activity was measured in a gamma well counter. The FDG clearance was significantly lower after oral glucose loading (T(1/2) oral load=16. 2+/-5.7 min) as compared with clamping (T(1/2) clamp=8.1+/-3.1 min) and acipimox (T(1/2) acipimox=10.7+/-4.0 min, NS vs clamp, P<0.05 vs oral load). It may be concluded that FDG SPET imaging after acipimox administration yields image quality and clearance rates comparable to those obtained during clamping. FDG SPET in combination with acipimox may useful in clinical routine for the assessment of myocardial viability.

Aged↗

PubMed1997

Prediction of improvement of contractile function in patients with ischemic ventricular dysfunction after revascularization by fluorine-18 fluorodeoxyglucose single-photon emission computed tomography.

OBJECTIVES: We evaluated the use of fluorine-18 fluorodeoxyglucose (FDG) and single-photon emission computed tomography (SPECT) to predict improvement of left ventricular ejection fraction (LVEF) after revascularization. BACKGROUND: FDG SPECT has recently been proposed for assessment of myocardial viability. However, FDG SPECT still awaits validation in terms of predicting improvement of contractile function after revascularization in patients with poor left ventricular (LV) function. METHODS: Fifty-five patients with contractile dysfunction (including 22 with LVEF < 30%) underwent FDG SPECT during hyperinsulinemic glucose clamping and early thallium-201 SPECT (to assess perfusion). Improvement of LV function was evaluated 3 months after revascularization with echocardiography and radionuclide ventriculography. RESULTS: The 55 patients were arbitrarily classified into two groups: 19 with three or more viable, dysfunctional segments on FDG SPECT and 36 with less than three viable, dysfunctional segments. LVEF increased significantly in the first group, from 28 +/- 8% (mean +/- SD) before to 35 +/- 9% (p < 0.01) after revascularization. In the second group, LVEF remained unchanged after revascularization (45 +/- 14% vs. 44 +/- 14%, p = NS). The 22 patients with severely depressed LV function were similarly classified into two groups: 14 with three or more viable segments on FDG SPECT in whom LVEF improved significantly (25 +/- 6% vs. 32 +/- 6%) and 8 with less than three viable segments in whom LVEF remained unchanged (24 +/- 6% vs. 25 +/- 6%). CONCLUSIONS: This study shows that FDG SPECT can identify patients in whom LV function improves after revascularization. Because SPECT is widely available, this technique may contribute to more routine use of FDG for determination of viability.

Echocardiography↗

PubMed1997

Metabolic imaging using F18-fluorodeoxyglucose to assess myocardial viability.

Over the past 10 years, F18-fluorodeoxyglucose (FDG) imaging with positron emission tomography (PET) has emerged as an important technique in the delineation of myocardial viability. Using this technique it has become possible to predict recovery of ventricular function after revascularization in patients with chronic coronary artery disease. Data from long-term (although retrospective) follow-up studies have demonstrated that patients with viable myocardium on FDG PET who do not undergo revascularization are prone to cardiac events, including cardiac death and non-fatal infarction. The same studies have pointed out that patients with viable tissue on FDG PET, who do undergo revascularization, improve substantially in symptoms related to congestive heart failure. To allow FDG imaging in centers without PET equipment, recent studies have evaluated the use of FDG imaging with single photon emission computed tomography (SPECT) and 511 keV collimators. Preliminary data using this alternative approach are promising, but need further confirmation. In this review the experience with FDG imaging (using either PET or SPECT) in the assessment of tissue viability in patients with coronary artery disease will be discussed.

Coronary Disease↗

PubMed1997

FDG SPECT in the assessment of myocardial viability. Comparison with dobutamine echo.

The use of 18F-fluorodeoxyglucose (FDG) imaging with single photon emission computed tomography (SPECT) has been introduced recently to assess myocardial viability. Several centres have now gained experience with cardiac FDG SPECT imaging, and this report is a summary of the currently available FDG SPECT data. Three studies have compared FDG SPECT with FDG positron emission tomography and demonstrated good agreement between them. Initial results in patients undergoing revascularization suggest that FDG SPECT can predict improvement in contractile function after revascularization. Although the initial results are promising, larger studies are needed to determine the precise role of FDG SPECT in the assessment of myocardial viability.

Cardiotonic Agents↗

PubMed1997

Prediction of improvement of ventricular function after revascularization. 18F-fluorodeoxyglucose single-photon emission computed tomography vs low-dose dobutamine echocardiography.

AIMS: To compare assessment of myocardial flow and glucose metabolism by single-photon emission computed tomography (SPECT) with low-dose dobutamine echocardiography in predicting improvement in regional and global left ventricular function after coronary artery bypass grafting. METHODS AND RESULTS: Thirty patients with regional wall motion abnormalities (mean ejection fraction 32 +/- 19%) were studied with low-dose dobutamine echocardiography (5 and 10 micrograms. kg-1 min-1) and thallium-201/ 18F-fluorodeoxyglucose(FDG) SPECT prior to surgery. For comparative analysis, a 13-segment model was used. Postoperative improvement was predicted if the echocardiogram showed that wall motion abnormalities were reversible during the dobutamine infusion and there was normal perfusion or relatively increased FDG uptake in perfusion defects (mismatch) in dyssynergic segments on SPECT. After surgery, ventricular function was reassessed. An echocardiogram was taken at the 3 month follow-up with the patient at rest. Regional wall motion had improved in 62/168 (37%) revascularized segments. In predicting functional outcome, low-dose dobutamine echocardiography reached a sensitivity of 89% and a specificity of 82%, with a positive predictive value of 74% and a negative predictive value of 93%, whereas for thallium-201/FDG SPECT these values were 84%, 86%, 78% and 90%, respectively. In patients with more than two viable segments on either technique, the wall motion score index, a surrogate of global ventricular function, improved significantly. CONCLUSION: For the optimal prediction of functional outcome, combined assessment of flow and FDG imaging is needed. Both thallium-201/FDG SPECT and low-dose dobutamine echocardiography appear comparable and similarly accurate in predicting improvement of left ventricular function after surgical revascularization.

Analysis of Variance↗

PubMed1996

Course of impaired left ventricular function after acute myocardial infarction predicted with planar thallium-201 chloride and F18-fluorodeoxyglucose imaging.

UNLABELLED: Planar reset myocardial thallium-201 chloride (201Tl)/F18-fluorodeoxyglucose (FDG) imaging has been shown to distinguish between viable and non-viable tissue. Twenty-five patients (60 +/- 9 years) with acute myocardial infarction were studied using this technique within 6 +/- 2 days (T1) after infarction and again after 42 +/- 4 days (T6). Serial assessment of wall motion with 2D-echocardiography was performed to determine the predictive value of radionuclide indices for the course of impaired regional left ventricular function. No revascularization procedure was performed. Segmental 201Tl and FDG uptake was evaluated using circumferential profiles. Echocardiographic wall motion was scored as normal, hypokinetic or akinetic. Myocardial segments were considered non-viable if a match between 201Tl and FDG uptake was present, which is a concordant reduction in 201 Tl and FDG uptake (Group A). Myocardial segments were considered viable if: a mismatch was present between 201Tl and FDG uptake which was defined as a segmental FDG uptake exceeding 201Tl uptake by > or = 20% in a segment with reduced 201Tl uptake (Group B); a normal FDG uptake (> or = 75%) was present without a mismatch pattern in a segment with reduced 201Tl uptake (201Tl < 75% of peak activity) (Group C); a normal 201Tl uptake was present in the area of wall motion abnormality (Group D). Corresponding scintigraphic images obtained at T1 and T6 were compared. RESULTS: 51 segments were normokinetic, 37 were hypokinetic and 6 were akinetic at T1. Of the 63 segments with wall motion abnormalities at T1, 18 regions showed a match (FDG-201Tl < 20%) (Group A). Regional function improved in only one (6%) of these segments. In 19 regions a mismatch was present (FDG-201Tl > 20%) (Group B) of which three (16%) showed spontaneous improvement in function (p = NS vs. matched segments), although recovery varied considerably among patients. Regional function in two segments deteriorated. In 14 regions with reduced 201Tl uptake, FDG uptake was normal (Group C) of which five (36%) were improved after 6 weeks (p < 0.05 vs. match; p = NS vs. mismatched segments). Of the 12 segments with normal 201Tl uptake (Group D), seven (58%) showed improvement in function, whereas five (42%) did not show improvement (p < 0.05 vs. match). In addition, all scintigraphically selected viable segments were grouped (Group B + C + D) and compared with the non-viable segments (Group A). The predictive value of a positive viability test for spontaneous functional improvement was 33%. The predictive value of a negative viability test for lack of functional improvement was 94%. CONCLUSIONS: absence of residual FDG uptake shortly after infarction is associated with irreversible injury, while preservation of metabolic activity identifies segments with variable outcome. Wall motion alone is not a good indicator for the presence of viable tissue. Planar 201Tl/FDG imaging allows early identification of viable but jeopardized tissue and may help select patients who will benefit from aggressive therapy to salvage endangered myocardium.

Deoxyglucose↗

PubMed1996

Absorbed dose distribution of the auger emitters 67GA and 125I and the beta-emitters 67CU, 90Y, 131I, and 186RE as a function of tumor size, uptake, and intracellular distribution.

PURPOSE: The influence of tumor volume, uptake of radioactive compounds in cells of tumors and normal tissues, and characteristics of the emitted ionizing particles on the efficacy of systemic radiation were studied. METHODS AND MATERIALS: The influence of these variables was assessed using a point kernel approach combined with a distance histogram technique. Simulation calculations were performed to assess dose distributions for three tumor sizes (phi = 200 microns, 2 mm, or 2 cm) and six radionuclides: 67Ga, 125I, 67Cu, 90Y, 131I, and 186Re. RESULTS: The energy deposition patterns depended on the relation of the tumor size and range of the emitted particles. Selective uptake was especially important in cases where the range was short compared to the dimension of the tumor. CONCLUSION: To attain a high dose for treatment of micrometastases, the use of Auger and conversion electron emitters (67Ga and 125I) or beta-emitters with emission spectra including low energetic electrons (67Cu and 131I) was recommended. The results demonstrated the complementary nature of selectivity of energy deposition and crossfire. This implied that for tumor cells or areas with reduced uptake, crossfire from radioactivity in surrounding cells or areas with selective uptake would be provided by intermediate (conversion electrons) or long-range (beta-particles) emissions.

Dose-Response Relationship, Radiation↗

PubMed1996

Prediction of recovery of myocardial dysfunction after revascularization. Comparison of fluorine-18 fluorodeoxyglucose/thallium-201 SPECT, thallium-201 stress-reinjection SPECT and dobutamine echocardiography.

OBJECTIVES: We compared three techniques to predict functional recovery after revascularization. BACKGROUND: Recently, fluorine-18 (F-18) fluorodeoxyglucose in combination with single-photon emission computed tomography (SPECT) has been proposed to identify viable myocardium, Thallium-201 reinjection and low dose dobutamine echocardiography are used routinely for this purpose. METHODS: Seventeen patients (mean [+/- SD] left ventricular ejection fraction 36 +/- 11%) were studied. Regional and global ventricular function were evaluated before and 3 months after revascularization by echocardiography and radionuclide ventriculography, respectively. Myocardial F-18 fluorodeoxyglucose uptake (during hyperinsulinemic glucose clamping) was compared with rest perfusion assessed with early thallium-201 SPECT. On a separate day, low dose dobutamine echocardiography and post-stress thallium-201 reinjection SPECT were simultaneously performed. RESULTS: The sensitivities for F-18 fluorodeoxyglucose/thallium-201, thallium-201 reinjection and low dose dobutamine echocardiography to assess recovery were 89%, 93% and 85%, respectively; specificities were 77%, 43% and 63%, respectively. Stepwise logistic regression indicated that F-18 fluorodeoxyglucose/ thallium-201 was the best predictor. In hypokinetic segments, the combination of F-18 fluorodeoxyglucose/thallium-201 and low dose dobutamine echocardiography was the best predictor. Global function improved (left ventricular ejection fraction increased > 5%) in 6 patients and remained unchanged in 11. All three techniques correctly identified five of six patients with improvement. Fluorine-18 fluorodeoxyglucose/thallium-201 identified all patients without improvement; low dose dobutamine echocardiography identified 9 of 11 without improvement; and thallium-201 reinjection identified 6 of 11 patients without improvement. CONCLUSIONS: Fluorine-18 fluorodeoxyglucose/thallium-201 SPECT was superior to the other techniques in assessing functional recovery. Integration of metabolic and functional data is necessary, particularly in hypokinesia, for optimal prediction of improvement of regional function.

Adult↗

PubMed1996

Dual X-ray absorptiometry for alveolar bone: precision of peri-implant mineral measurements ex vivo.

The precision of measurements of minor mineral changes in alveolar bone mineral content (ABMC) and alveolar bone mineral density (ABMD) on implant surfaces was determined in small regions (0.03 +/- 0.005 cm2) using dual X-ray absorptiometry (DXA). Dog hemimandibles with alveolar processes containing 17 implants were studied ex vivo. The precision was expressed as the coefficient of variation in percent (c.v. %). The ultra-high resolution protocol was applied to the mesial, distal and apical subregions of each implant. The line spacing was 0.0254 cm and the point resolution was 0.0127 cm. The mean c.v. (%) +/- s.d. for the ABMC in the mesial, distal and apical regions were 0.42 +/- 17, 0.47 +/- 0.21 and 0.48 +/- 0.18, respectively. For the ABMD these values were 0.42 +/- 0.16, 0.47 +/- 0.19 and 0.48 +/- 0.16. For each region approximately 68% of the 17 c.v. values were distributed within 1 s.d. from the mean c.v. These results indicate that measurements are highly reproducible (better than 0.48%) and that there are no differences in precision between several peri-implant regions. Changes as small as 0.85% in ABMC and ABMD in small areas adjacent to implant surfaces are measurable with a confidence level of 95%. Therefore the DXA technique will be expedient for our research evaluating the efficacy of the ceramic hydroxyapatite implant releasing agents affecting or inducing alveolar bone- and root cementum-like materials on its surface.

Absorptiometry, Photon↗

PubMed1996

Comparison of myocardial uptake of fluorine-18-fluorodeoxyglucose imaged with PET and SPECT in dyssynergic myocardium.

UNLABELLED: PET with 18F-fluorodeoxyglucose (FDG) can detect viable myocardium and predict functional recovery after revascularization. The use of PET for clinical routine, however, is limited. Recently, imaging FDG with SPECT was proposed. The aim of this study was to compare the diagnostic value of FDG-PET and FDG-SPECT in the detection of viable myocardium in segments with abnormal wall motion. METHODS: Twenty patients with previous myocardial infarction were studied. All underwent FDG-PET and FDG-SPECT during hyperinsulinemic glucose clamping. Regional perfusion was assessed with 13N-ammonia PET and early resting 201TI- SPECT. Regional wall motion was assessed with two-dimensional echocardiography. The agreement between FDG/13N-ammonia PET and FDG/201TISPECT to detect viability in dyssynergic myocardium was 76%. On a patient basis, PET and SPECT yielded comparable results in 17 of 20 patients. In a subgroup of patients with LVEF < or = 35% (n = 12), all PET and SPECT viability data were identical. CONCLUSION: This study shows a good correlation between the detection of viability in dyssynergic myocardium with FDG/13N-ammonia PET and FDG/201TI SPECT, both on a segmental and patient basis.

Ammonia↗

PubMed1995

Influence of high and low plasma insulin levels on the uptake of fluorine-18 fluorodeoxyglucose in myocardium and femoral muscle, assessed by planar imaging.

The aim of this study was to optimize the metabolic conditions for planar myocardial fluorine-18 fluorodeoxyglucose (FDG) imaging. The effects of high and low insulin levels during euglycaemic clamping on myocardial and femoral muscle FDG uptake were compared since insulin plays a major role in glucose metabolism. FDG uptake in 11 patients was studied using planar scintigraphy. Patients were studied twice: in the low-dose insulin protocol (LDI), insulin was infused at a rate of 20 mU/kg per hour, starting 1 h before FDG administration, while in the high-dose insulin protocol (HDI) it was infused at a rate of 100 mU/kg per hour. Glucose infusion rate was adjusted according to frequently determined blood glucose levels. Somatostatin was infused to block endogenous insulin release. Planar images were obtained from the thorax region and femoral muscles. Regions of interest were drawn over normal and abnormal myocardial areas (based on angiographic and thallium-201 data) and over lung, liver and muscle areas. After clamping, insulin levels during LDI and HDI at t = 60 were 30.6 +/- 13.3 and 129.6 +/- 30.5 mU/l respectively (P < 0.0001). Femoral muscle uptake was significantly higher during HDI (P < 0.001). Uptake in normal and abnormal myocardial areas did not differ between the two protocols. Heart/lung ratios (NS) and heart/liver ratios (P < 0.05) increased during HDI. It may be concluded that planar FDG imaging is influenced by plasma insulin levels. The euglycaemic hyperinsulinaemic clamp technique, although more demanding, gives an adjustable metabolic steady state without significantly altering the FDG uptake patterns in normal and abnormal myocardial regions. The image quality of planar FDG images improves due to lower background uptake of FDG during clamping with high plasma insulin levels.

Case-Control Studies↗

PubMed1995

Relation between myocardial uptake of thallium-201 chloride and fluorine-18 fluorodeoxyglucose imaged with single-photon emission tomography in normal individuals.

Recently, we have demonstrated the feasibility of imaging myocardial uptake of fluorine-18 fluorodeoxyglucose (FDG) with single-photon emission tomography (SPET) using a specially designed collimator. Thallium-201 was used to determine distribution of perfusion for comparison with FDG uptake. However, regional 201Tl and FDG activities may be different, based on differences in tracer attenuation and the use of different collimators. To study the relation between tracer activities imaged with SPET, nine healthy individuals underwent resting 201Tl SPET and FDG SPET during a hyperinsulinaemic euglycaemic clamp. The SPET data were analysed semiquantitatively, using circumferential profiles. Mean profiles of midventricular short-axis slices showed no significant difference between 201Tl and FDG activity. Regional fluctuations were similar for FDG and 201Tl; the highest tracer activities were observed in the lateral wall and the lowest activities in the septum. Finally, pooled data (n = 1620 segmental activities) in nine individuals showed a linear correlation (P < 0.0001) between 201Tl and FDG activity: FDG = 0.76 201Tl + 0.23 (r = 0.70). These data demonstrate the absence of major differences between regional 201Tl and FDG activity in normal myocardium, suggesting that no separate 201Tl and FDG SPET reference values are needed for comparison with patient studies.

Adult↗

PubMed1995

Radiotoxicity of 67-gallium on myeloid leukemic blasts.

Promising clinical results are obtained with radiolabeled antibodies in leukemia patients. 67Gallium (67Ga) is a radionuclide that accumulates in many malignant tissues without need for a monoclonal antibody. For this reason, the use of 67Ga as a therapeutic agent is appealing. In the present we study, we report data about the radiotoxicity of 67Ga on peripheral blast cells of 23 patients with acute myelogenous leukemia (AML) in vitro. Isolated blast cells were incubated for 4 days with 0.74 MBq/ml (20 microCi/ml), 1.48 MBq/ml (40 microCi/ml) or 2.96 MBq/ml (80 microCi/ml) 67Ga. Compared with non-irradiated control cells proliferation during incubation was almost abolished. Clonogenic survival was measured by a colony forming unit assay (CFU-assay). In 13 of the 23 patients (56%) sufficient colony growth was observed for evaluation. The mean clonogenic survival of blasts after incubation with 0.74 MBq/ml and 2.96 MBq/ml 67Ga was 22.5, 11.3 and 3.5%, respectively. In some cases colony growth was completely abolished after incubation with only 0.74 MBq/ml 67Ga. No correlation was found between cellular 67Ga-uptake, (micro)dosimetry and transferrin receptor density (CD-71) via which 67Ga enters the cell. In vitro the blasts received a dose of > 10 Gy in 9 of the 2.96 MBq/ml, in 3 of the 1.48 MBq/ml and in 2 of the 0.74 MBq/ml incubations. In one patient, even a radiation dose > 40 Gy was reached. Low dose rate irradiation is known to arrest cells in G2/M-phase of the cell cycle, but no such arrest was observed during incubation with 67Ga. Thus, 67Ga induces clonogenic cell death in leukemic blasts. Cellular uptake of 67Ga in vitro varies between patients and can be very high in some patients. The easy availability, low costs and absence of immunological problems warrant further investigation of the therapeutic potential of 67Ga in refractory or relapsed AML patients.

Acute Disease↗

PubMed1995

Myocardial F-18 fluorodeoxyglucose imaging by SPECT.

F-18 fluorodeoxyglucose (FDG) in combination with positron emission tomography (PET) is used in patients with coronary artery disease to detect viable myocardium. It was shown that FDG PET is highly accurate in predicting reversibility of cardiac function after revascularization when viable tissue is present. Because PET centers are not widely available, the clinical use of FDG is limited. The authors have shown in another study that imaging 511 keV with planar scintigraphy and a special collimator is feasible. Furthermore, they have studied myocardial FDG uptake in normal volunteers and in patients with coronary artery disease using SPECT. Recently, they have studied the value of FDG SPECT to predict recovery of contractile function before revascularization in patients undergoing bypass surgery. It appears that the FDG SPECT approach is feasible and can predict reversibility of wall motion abnormalities. Further studies are needed to compare FDG SPECT with other techniques for the detection of viable myocardium.

Coronary Disease↗

PubMed1995

Additional weight-bearing during exercise is more important than duration of exercise for anabolic stimulus of bone: a study of running exercise in female rats.

Mechanical loading is necessary for maintenance of skeletal integrity, but the most effective type, intensity, and duration of exercise are not known. In vivo experiments have indicated that the strain generated by the stimulus is more important than the duration of the stimulus. To elucidate this question, we studied 5-month-old female Wistar rats exercised on a motor-driven exercise belt for 17 weeks, 5 days per week (average velocity 20 m/min). Group 1 served as controls, group 2 was trained for 30 min, group 3 was trained for 30 min with a 50-g backpack, and group 4 was trained for 15 min with a 50-g backpack. Total body bone mineral content (BMC), bone mass of the lower extremities (LEBMC), total body lean soft-tissue mass (LSTM), and total body fat-tissue mass (FTM) were measured by dual-energy absorptiometry (DXA) at 0, 6, and 17 weeks. The BMC increased more in group 4 than in controls (15% vs. 8%, p < 0.03). In the other two intervention groups, no significant increases of total body BMC occurred compared with controls, although a trend was observed (12%). The LEBMC increased significantly in all exercising groups after 17 weeks, being 16% in group 2, 15% in group 3, and 20% in group 4, compared with 6% in controls (p < 0.05). The increase in LSTM after 6 weeks was most pronounced in group 3, at 20%, compared with 10% in the control group (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗

PubMed1995

Feasibility of planar fluorine-18-FDG imaging after recent myocardial infarction to assess myocardial viability.

UNLABELLED: The aim of this study was to define the clinical feasibility of planar myocardial 18F-fluorodeoxyglucose (FDG) imaging and to assess the relation between 201Tl, FDG and left ventricular function early after myocardial infarction. METHODS: Fifty-one patients were studied 5 +/- 2 days after infarction. Scintigraphic images were visually and quantitatively analyzed using a circumferential profiles technique. FDG uptake was normalized to the area with maximal 201Tl uptake. Scintigraphic data were compared with left ventricular wall motion as assessed by ventriculography in 22 patients. Relative regional 201Tl uptake was categorized as normal (> or = 75% of peak activity), moderately reduced (50%-75%) or severely reduced (< 50%). These tracer defects were considered viable if FDG uptake exceeded 201Tl uptake by > or = 20% and/or if FDG uptake was normal (> or = 75%). All regions with FDG uptake 20% less than 201Tl uptake were considered nonviable. RESULTS: Four hundred forty-one myocardial regions were analyzed; 200 showed normal 201Tl uptake, 241 had reduced uptake, 191 had moderately reduced 201Tl uptake and 50 regions had severely reduced uptake. Viability for moderately and severely reduced regions was observed in 62% and 48%, respectively. A concordance between flow and metabolism was observed in 38% and 52%, respectively. CONCLUSION: Myocardial FDG imaging is feasible with standard gamma camera systems and enables the identification of regions with preserved glucose metabolism in patients shortly after infarction.

Coronary Angiography↗

PubMed1994

A dosimetric model for intrathecal treatment with 131I and 67Ga.

PURPOSE: Calculations were performed of absorbed dose distributions of the beta-emitter 131I and the Auger emitter 67Ga for intrathecal administration. METHODS AND MATERIALS: The proposed dosimetric model accounts for the macroscopic distribution of the activity, by means of a Medical Internal Radiation Dose Committee approach, and for the microscopic distribution of activity, by means of a point kernel technique. This point kernel approach was used in combination with a distance histogram technique, to study in more detail the absorbed dose distribution in the cerebro-spinal fluid, in the surface of the central nervous system, and in tumor sites. We simulated decreased uptake, as well as highly selective uptake in free-floating tumor cells and in meningeal lesions (1-16 cells thick). RESULTS: In case of limited access to lesions adherent to the pia mater, the beta-emitter 131I provides crossfire from the CSF, resulting in a higher absorbed dose (Gy/MBq) in these lesions as compared with the Auger emitter 67Ga. In case of increasing radionuclide uptake, the increment of the absorbed dose in the adherent lesions and the free floating cells from 67Ga is considerable because of the local deposition of energy by this radionuclide. CONCLUSIONS: The model might be useful to select the optimal emission characteristics of radionuclides applicable for intrathecal therapy, which is demonstrated in a comparison of the Auger emitter 67Ga and the beta-emitter 131I.

Gallium Radioisotopes↗