Biomedical subjects

Alfred Buck

Publications and source records attributed to Alfred Buck.

40 records · Page 3Linked to original sources

PubMed2002

Autoradiographic quantification of 18F-FDG uptake in experimental soft-tissue abscesses in rats.

PURPOSE: To use semiquantitative autoradiography to investigate fluorodeoxyglucose (FDG) uptake, distribution, and cellular localization in acute, early chronic, and late chronic soft-tissue infections. MATERIALS AND METHODS: Unilateral calf-muscle abscesses were induced in 12 Sprague-Dawley rats by means of intramuscular inoculation of 0.1 mL of bacterial suspension (Staphylococcus aureus, 1.2 x 10(9) CFU/mL). Following injection of 130-180 MBq of fluorine 18 FDG, autoradiography of the abscess and contralateral muscle was performed (10-microm section thickness) on days 2, 5, and 9 after infection. Detailed spatial correlation of autoradiographs and histopathologic samples was performed by means of image fusion. Regions of interest were placed in the abscess wall, and measured gray values were converted to kilobecquerels per cubic centimeter according to kilobecquerels of injected activity per gram of body weight, which yielded standardized uptake values (SUVs). RESULTS: Acute abscess formation was characterized by central necrosis predominantly surrounded by neutrophils and a second necrotic tissue layer that bordered neutrophil infiltrates peripherally. Areas with increased FDG uptake corresponded to cellular inflammatory infiltrates, mainly granulocytes. The corresponding SUV was calculated to be 4.08 +/- 0.65 (mean +/- SD). Early chronic phase showed mixed cellular infiltrate of granulocytes and macrophages that surrounded central necrosis with interspersed fibroblasts and only residual muscle necrosis layer within the abscess wall. FDG uptake was located where granulocytes and macrophages were present, as in acute infection (SUV = 5.32 +/- 2.30). Late chronic infection was characterized by a prominent layer of macrophages around residual central necrosis and fibroblast-enriched granulation tissue delineating the infection from muscle tissue. FDG uptake clearly coincided with the macrophages, and no substantial increase of FDG uptake was detected within fibroblast-enriched granulation tissue. The SUV was calculated as 7.97 +/- 0.21. Results of Kruskal-Wallis ANOVA demonstrated that the change in SUV with time was statistically significant (chi(2) = 7.42, P <.05). CONCLUSION: The highest FDG uptake coincides with areas of inflammatory cell infiltrates, predominantly in neutrophils in the acute phase and in macrophages in the chronic phase of soft-tissue infection.

Abscess↗

PubMed2002

PET diagnostic accuracy: improvement with in-line PET-CT system: initial results.

The authors describe the initial application for tumor staging with an in-line system with a positron emission tomographic (PET) scanner and a multi-detector row helical computed tomographic (CT) scanner combined in one machine. Fifty-three patients underwent imaging with four CT tube currents and PET emission and transmission data acquisition. Stepwise analysis of coregistered images revealed a significant (P <.05, McNemar test) improvement in lesion classification between PET images alone and coregistered images from the PET-CT examination.

Abdominal Neoplasms↗

PubMed2002

Evaluation of the reference tissue models for PET and SPECT benzodiazepine binding parameters.

Recently, reference tissue methods have been proposed to estimate binding potential from PET data. A reference region without specifically bound ligand is used as an indirect input function to enable the expression of the time-concentration curve of a region of interest using a compartment model. However, PET dopaminergic and serotoninergic studies have shown differences between binding potential (BP) values obtained with reference tissue methods and those obtained with conventional kinetic modeling using an arterial input function. In this study, we measured the BP values for the benzodiazepine receptors in seven subjects using PET [(11)C]flumazenil and SPECT [(123)I]iomazenil radioligands. We compared the BP values obtained using the reference tissue methods with those obtained using the conventional kinetic method. These values were also compared with the absolute value of receptor density, B'(max). For the PET studies, a multi-injection approach employing labeled and unlabeled flumazenil was used to estimate the main binding parameters, BP and B'(max). For SPECT studies, a single injection protocol of [(123)I]iomazenil was used to estimate BP values. The BP values were estimated using one- and two-tissue compartment models for the target region. Similar BP values were obtained using either the one- or two-tissue compartment model. This is probably due to the rapid equilibrium between tissue compartments reached with these radioligands. For PET and SPECT, these BP values were highly correlated (r > 0.960) to the BP values obtained using the arterial input function. We also found high correlations between the BP values obtained using the simplified reference tissue method and the receptor density parameter B'(max) (r > 0.884). However, the reference tissue methods yielded lower BP values than those obtained using the conventional approach. Moreover, there was a bias on BP values that was not a simple scaling. It seems that the physiological values found in gray matter structures using these radioligands give acceptable BP values. We conclude that the reference tissue methods should be carefully evaluated for each radioligand.

Adult↗

PubMed2002

Accuracy of image coregistration of pulmonary lesions in patients with non-small cell lung cancer using an integrated PET/CT system.

UNLABELLED: The purpose of this study was to evaluate the accuracy of image coregistration of PET and CT (PET/CT) images in patients with lung lesions and the influence of the breathing protocol during CT. METHODS: Seventy-five patients with a solitary and well-circumscribed pulmonary lesion (non-small cell lung cancer; size, 10-30 mm) underwent PET/CT on a combined scanner. CT was acquired during shallow breathing in 37 patients and during normal expiration (i.e., the level reached when the patient exhaled without forcing expiration and then held the breath) in 38 patients. The volume of interest of each lesion was defined separately on PET and CT images, and the geometric center of gravity (COG) was assessed. The distance of COGs between the PET image and the CT image was measured. All lesions were classified according to 4 lung regions: apical, peripheral, central, and lung base. The mismatch between COG(PET) and COG(CT) was compared between regions and patient groups using a 2-way ANOVA with the Bonferroni-Dunn test for post hoc comparisons. RESULTS: The range of COG distance between PET and CT was 1.7-5.4 mm in the apex, 0.5-14.7 mm in the periphery, 0.7-5.9 mm centrally, and 2.9-11.3 mm in the lung base. The match between PET and CT was significantly better in patients who had the CT scan obtained during normal expiration than in patients who performed shallow breathing during CT scanning (P = 0.024). No reciprocal effects were found (interaction P = 0.76). The mismatch of lesions depends significantly on lung region (P < 0.0001). Post hoc analysis showed a significant difference between the upper 2 regions and the lower 2 regions (all P < or = 0.002) but not between the apex and the central region (P = 0.95) and between the peripheral region and the lung base (P = 0.15). The lesion size had no influence on the COG mismatch. CONCLUSION: The match of lung lesions in coregistered PET/CT images is better when acquiring the CT scan during normal expiration. The coregistration accuracy is better in the upper and central parts of the lung. The normal expiration protocol is suggested to be superior to shallow breathing during CT scanning.

Adolescent↗