Stereological estimation of the total number of ventilatory units in mice lungs.

We present an unbiased estimator of the total number of alveolar structures distal to the transition from a bronchiole to an alveolar duct system ('ventilatory units', VUs). In species without respiratory bronchioles, including mice, the number of VUs is equivalent to the number of acini. The acinus is a functional unit of gas exchange, defined as a parenchymal unit distal to a terminal bronchiole in which all airways contain alveoli and thus participate in gas exchange. The estimator combines two different estimators of the number of VUs: (1) an estimator derived from the Euler number of all the openings of the bronchial tree and (2) an estimator derived from direct counts of topological changes occurring at bronchiole-alveolar duct junctions. Combining the two estimators eliminates the requirement to be able to identify even vanishingly small pieces of bronchial tissue in physical disectors. We implemented the fractionator estimator in five adult mice lungs using physical fractionators with varying but known sampling fractions (Horvitz-Thompson estimator). We obtained total values of about 4200 VUs (CV = 0.05) in 21-day-old and 4480 (CV = 0.06) in 69-day-old animals. Being fractionator estimates, these total numbers are independent of shrinkage. The densities of VUs per unit volume of tissue (values corrected for tissue shrinkage) were similar in left and right lungs.

124I-PET dosimetry in advanced differentiated thyroid cancer: therapeutic impact.

PURPOSE: This study evaluated the impact of (124)I-positron emission tomography (PET) dosimetry on post-primary surgery therapy in radioiodine-naïve patients with advanced differentiated thyroid cancer (DTC). PATIENTS, MATERIAL, METHODS: In each of 28 thyroidectomized patients with high-risk DTC (one or more of pT4, pN1 or pM1), we gave 23-50 MBq of (124)I as an oral capsule and performed PET dosimetry to calculate the individualized therapeutic (131)I activity that would, insofar as possible, achieve a radioiodine dose >or=100 Gy to all metastases without exceeding 2 Gy to the blood (a surrogate for bone marrow toxicity). We thus determined the absorbed lesion dose per GBq of administered 131I activity (LDpA) based on serial PET (4, 24, 48, 72 and 96 h after oral 124I intake) and PET/computed tomography (25 h after (124)I intake) and the critical blood activity (CBA) based on blood and whole-body radiation counting (2, 4, 24, 48, 72, 96 h after 124I intake). We compared the dosimetry-based interventions with our standard empirical protocol. RESULTS: 25 patients had a total of 126 iodine-positive metastases. 18 (72%) of the 25 had solely iodine-avid metastases, while seven (28%) had both iodine-avid and -non-avid metastases. In two patients (8%), none of the iodine-avid metastases could have been practically treated with a sufficient radiation dose. Relative to the empirical protocol, (124)I-PET dosimetry findings changed management in 7 (25%) patients, e.g. allowing application of activities >11 GBq (131)I. Further changes included implementation of hematological back-up in a patient found to be at risk of life-threatening marrow toxicity, and early multimodal therapy in 9 (32%) patients. CONCLUSION: 124I-PET dosimetry is a useful routine procedure in advanced DTC and may allow safer or more effective radioiodine activities and earlier multimodal interventions than do standard empirical protocols.

Value of (124)I-PET/CT in staging of patients with differentiated thyroid cancer.

The aim of this study is to evaluate the clinical significance of (124)I positron emission tomography (PET) using a combined PET/CT tomograph in patients with differentiated thyroid carcinoma and to compare the PET/CT results with (131)I whole-body scintigraphy (WBS), dedicated PET and CT alone. Twelve thyroid cancer patients were referred for diagnostic workup and entered complete clinical evaluation, including histology, cytology, thyroglobulin level, ultrasonography, fluorine-18 fluorodeoxyglucose (FDG)-PET, FDG-PET/CT and CT. Lesion-based evaluation showed a lesion delectability of 56, 87 and 100% for CT, (124)I-PET, and combined (124)I-PET/CT imaging, respectively. Lesion delectability of (131)I-WBS was 83%. We conclude that (124)I-PET/CT imaging is a promising technique to improve treatment planning in thyroid cancer. It is particularly valuable in patients suffering from advanced differentiated thyroid cancer prior to radio-iodine therapy and in patients with suspected recurrence and potential metastatic disease.

Combined PET/CT with iodine-124 in diagnosis of spread metastatic thyroid carcinoma: a case report.

Iodine-124 positron emission tomography (PET) is a useful 3D imaging technique for diagnosis and management of thyroid diseases. The difficulty in interpretation of the PET scans with highly selective tracers, such as iodine-124, is the lack of identifiable anatomical structures, so an accurate anatomical localization of foci presenting abnormal uptake is problematic. Consequently, a combined PET/CT scanner can resolve these difficulties by co-registering PET and CT data in a single session allowing a correlation of functional and morphologic imaging. A case is presented where iodine-124 produced by a clinical cyclotron and FDG were used to acquire images with a combined PET/CT scanner for clinical staging. On the basis of the PET/CT exams the treatment of the patient was modified.

Intraoperative treatment strategy to reduce the incidence of postcardiopulmonary bypass atrial fibrillation.

PURPOSE: Postcardiopulmonary bypass atrial fibrillation remains a constant complication associated with coronary revascularization, the incidence of which occurs from 20% to 35%. Previous studies have addressed this problem in the postoperative setting utilizing pharmacological agents, but the results have been variable. The purpose of this study was to evaluate a novel intraoperative strategy to reduce the incidence of postcardiopulmonary bypass atrial fibrillation. We theorized that leukocyte depletion by filtration with the addition of aprotinin would reduce the systemic inflammatory effects of bypass and reduce the incidence of atrial fibrillation. METHODS: One hundred and twenty-two patients participated in this randomized study. Only isolated primary coronary revascularization procedures on cardiopulmonary bypass were included. The control group (n=55) received standard moderate hypothermic blood cardioplegia cardiopulmonary bypass. The treatment group (n=65) received similar cardiopulmonary bypass with the addition of strategic leukocyte depletion with Pall Biomedical Products (East Hills, NY) leukodepletion filters and full-dose aprotinin. RESULTS: The intraoperative addition of leukocyte depletion by filtration with aprotinin reduced the incidence of postcardiopulmonary bypass atrial fibrillation by 72%. The incidence.of atrial fibrillation in the control group was 27% (15 of 55). In contrast, the occurrence of atrial fibrillation in the treated group was only 7.6% (5 of 65) (p<0.025). CONCLUSIONS: This novel intraoperative treatment strategy of both mechanical (leukocyte filtration) and pharmacological (aprotinin) intervention appears to markedly reduce the incidence of postcardiopulmonary bypass atrial fibrillation. To our knowledge, this is the first study to combine these two treatment strategies. A previous study has noted a decline in atrial fibrillation with aprotinin in the animal model, but not to the extent observed in our study. The beneficial effects of the reduction of atrial fibrillation include reduced risk of emboli formation and the incidence of ischemia in the heart, lung and brain. In addition, a decrease in length of hospital stay, recovery time and overall cost occurred.

Metabolism of 15 (p 123I iodophenyl-)pentadecanoic acid in heart muscle and noncardiac tissues.

The uptake and turnover of omega(p 123I iodophenyl-)pentadecanoic acid (I-PPA), a radioiodinated free-fatty-acid analog, was examined in the heart, lung, liver, kidneys, spleen, and skeletal muscle of rats. At 2 min post injection, a high cardiac uptake of 4.4% dose per gram had already been achieved; this was followed by a rapid, two-component, tracer clearance. The kinetics of tissue concentrations of labeled hydrophilic catabolites indicated a rapid oxidation of I-PPA and the subsequent washout of I-PPA catabolites from heart-muscle tissue. The fractional distribution of the labeled cardiac lipids compared favorably with previously reported values for 3H-oleic- or 14C-palmitic-acid-labeled myocardial lipids. Typical patterns of I-PPA metabolism were observed in tissues depending on primary fatty-acid oxidation, lipid metabolism regulation, or I-PPA-catabolite excretion. The tissue concentrations and kinetics of I-PPA and its metabolites in the heart muscle indicated that general pathways of cardiac-lipid metabolism are traced by this new gamma-emitting isotope-labeled radiopharmaceutical.