A new iterative reconstruction technique for attenuation correction in high-resolution positron emission tomography

A new iterative reconstruction technique (NIRT) for positron emission computed tomography (PET), which uses transmission data for nonuniform attenuation correction, is described. Utilizing the general inverse problem theory, a cost functional which includes a noise term was derived. The cost functional was minimized using a weighted-least-square maximum a posteriori conjugate gradient (CG) method. The procedure involves a change in the Hessian of the cost function by adding an additional term. Two phantoms were used in a real data acquisition. The first was a cylinder phantom filled with uniformly distributed activity of 74 MBq of fluorine-18. Two different inserts were placed in the phantom. The second was a Hoffman brain phantom filled with uniformly distributed activity of 7.4 MBq of¹⁸F. Resulting reconstructed images were used to test and compare a new iterative reconstruction technique with a standard filtered backprojection (FBP) method. The results confirmed that NIRT, based on the conjugate gradient method, converges rapidly and provides good reconstructed images. In comparison with standard results obtained by the FBP method, the images reconstructed by NIRT showed better noise properties. The noise was measured as rms% noise and was less, by a factor of 1.75, in images reconstructed by NIRT than in the same images reconstructed by FBP. The distance between the Hoffman brain slice reconstructed by FBP and the perfect PET Hoffman brain slice created from the MRI image was 0.526, while the same distance for the Hoffman brain slice reconstructed by NIRT was 0.328. The NIRT method suppressed the propagation of the noise without visible loss of resolution in the reconstructed PET images.     

Balo's concentric sclerosis: a variant of multiple sclerosis associated with oligodendroglioma

We report a case of Balo's concentric sclerosis, a rare and acute variant of multiple sclerosis, which coexisted with an oligodendroglioma. The demyelinating lesion was clinically silent and was detected at necropsy. The pathogenesis of concentric sclerosis and the relationship of the demyelinating lesion to the evolution of the glial neoplasm is briefly discussed.     

Concurrent chemotherapy and radiation therapy in advanced head and neck cancer

A combination of radiation therapy and cis-platinum (25 mg/m2 i.v.) day 1, vincristine (1 mg i.v.) day 2, and bleomycin (15 U i.v.) day 4 was given concomitantly to 14 patients with advanced inoperable head and neck cancer and one patient with local recurrence. Radiation therapy consisted of 70 Gy to the involved areas and 50 Gy to adjacent uninvolved areas at 1.8 Gy per fraction. The overall response rate was 100%. Nine patients (60%) achieved a complete response, and six patients achieved a partial response. One patient appeared to have increasing disease, but biopsies have shown only fibrosis. The survival is 8 of 15 (53%), with a median follow-up time of 24 months. Most significant toxicity was anorexia and weight loss. Other toxicity consisted of peripheral neuropathy (1 patient), mild transient elevation of creatinine (1 patient), hypothyroidism (1 patient), and mild pulmonary toxicity (2 patients). Mucositis occurred in all patients, requiring interruption of therapy (2-14 days).     

Rat brain cytochromes P-450: catalytic, immunochemical properties and inducibility of multiple forms

Cytochrome P-450 (P-450) and associated mono-oxygenase activities were estimated in male and female rat brain microsomes. The P-450 concentration in male rat brain was one-tenth the corresponding hepatic levels, which is considerably higher than earlier reports. A distinct sex-related difference was observed in the levels of total P-450 and mono-oxygenase activities known to be mediated by P-450b,e; the female brain levels were 60% of those in the males. Immunoinhibition and immunoblot studies using antisera to P-450b,e and P-450c,d indicated the presence of multiple forms of P-450, immunologically similar to P-450b,e, P-450c and P-450d in the rat brain. Prior treatment with phenobarbital resulted in two-fold increase of total P-450 and selective induction of aminopyrine N-demethylase (APD) and morphine N-demethylase (MND) activities. Administration of 3-methylcholanthrene, selectively induced the levels of ethoxycoumarin O-deethylase (ECD) and arylhydrocarbon hydroxylase, although the levels of total P-450 were not increased. 3-Methylcholanthrene induction was also accompanied by a shift in the absorption maximum of the reduced carbon monoxide difference spectrum from 452 to 448 nm. Immunocytochemical localization using antibodies to P-450b,e indicated the presence of P-450 predominantly in the neuronal cell bodies and to a lesser extent in the fibre tracts in cerebral cortex, cerebellum, thalamus, hypothalamus, hippocampus and brainstem. These studies indicate that the brain contains significant amounts of P-450, which exists in multiple forms and can be selectively induced by prior exposure to phenobarbital or 3-methylcholanthrene.     

Anaesthesia in Barbados

Purpose  To describe the anaesthesia services in Barbados: to present the major challenges confronting the Anaesthesia Department of the govemment-owned Queen Elizabeth Hospital (QEH): and to describe the Department’s approaches to optimise safety and cost-effectiveness of anaesthesia at QEH. Source of Information  Authors (KBS, HSLM. RAH), who collectively provided more than 50 yr of anaesthesia at QEH; the Dean (ERW) of the University of West Indies Medical School (Barbados campus); archives of Barbados; and records of QEH. Principal findings  The government of Barbados provides modem health care services to all of its citizens, primarily at QEH. Barbados, however, has tight financial constraints, infrastructura) limitations, and a bureaucratic administration that predispose QEH’s Anaesthesia Department to unexpected depletions of drugs and disposable supplies, sporadic shortages of personnel and functioning equipment, and occasional quality assurance problems. To deal with such problems, the Anaesthesia Department has implemented several pro-active measures; establishing an audit system to prevent depletion of imported drugs and supplies: training local personnel to maintain equipment: purchasing an oxygen concentrator to reduce oxygen costs: decreasing nitrous oxide use (expensive m Barbados): and initiating its own quality and safety standards. Conclusion  Continuous delivery of high quality, cost-effective anaesthesia care requires thoughtful planning by administrators and judicious resource allocations. Health care administrators and clinical departments need to work together closely to establish a framework that enables departments to play a major role in determining how the institution’s limited financial resources are best allocated to meet the departmental pnonties.

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Résumé Objectif  Decnre I’organisation de I’anesthesie a la Barbade; presenter les problemes considerables auxquels doit faire face le departement d’anesthesie de I’hdpital d’etat Queen Elizabeth (QEH) et decnre les efforts du departement pour optimahser la securite et lefficabte en fonction des couts. Source de l’information  Les auteurs (KBS. HSLM. RAH) qui ont collectivement foumi plus de 50 ans d’anesthesie au QEH; le doyen de la faculte de medecine des Antilles (campus de la Barbade); les archives de la Barbade; les dossiers du QEH. Principales constatations  Le gouvemement de la Barbade procure des services sanrtaires modemes a tous ses citoyens, pnncipalement au QEH. La Barbade subit toutefois des contraintes financieres tres severes. des limitations dans son infrastructure et une bureaucratie qui predispose le departement d’anesthesie du QEH a des penunes imprevisibles de medicaments et de materiel jetabte. a I’absenteisme du personnel et au manque d’equipement spoi adique. et a des problemes occasionnels d’assurance-qualite. Raur regler ces genres de problemes, le departement d’anesthesie a mis en vigueur plusieurs mesures simultanees; I’etablissement d’un systeme de comptabilite pour prevemr les penunes de medicaments et du materiel importes; la formation de personnel pour la maintenance de r^quipement; I’achat dun concentrateurpour reduire lecout de I’oxygene; la rationnement du protoxyde d’azote (cher a la Barbade); et le mise en vigueur de ses propres standards de qualrte et de seurrte. Conclusion  La prestation continue de sans anesthestque efficients et de haute qualrte requiert une plantation soignee et I’allocation judicieuse de ressources. Les administrateurs en soins de sante et les departements dmiques doivent travailler de concert pour etablir un encadrement permettant aux departements de jouer un role majeur dans I’allocation de ressources financieres limitees en tenant compte des pnorites etabhes par les departements.

     

Evaluation of the role of second messenger systems in tumor necrosis factor-stimulated resorption of fetal rat limb bones

Tumor necrosis factor (TNF) actions in target tissues are mediated by various signalling pathways. The effect of TNF to stimulate resorption in fetal rat limb bones is not inhibited by indomethacin. The current studies were designed to assess the role of cyclic AMP (cAMP) and calcium as second messengers in this prostaglandin-independent action of TNF on bone resorption. TNF alone failed to increase cyclic AMP in fetal rat limb bones after either brief (15 min) or long-term (72 h) treatment. TNF-stimulated resorption in fetal rat limb bones was enhanced by the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX). In short term incubations, the combination of TNF + IBMX did not elicit increases in cAMP in the limb bones. In 72 h cultures, addition of IBMX revealed a dose-dependent effect of TNF to increase cAMP. TNF produced a significant increase in inositol phosphate turnover in limb bones, with a greater response at 5 min than at 1 or 20 min. The calcium channel blocker nitrendipine inhibited TNF-stimulated resorption in the fetal rat limb bones. TNF-stimulated resorption was attenuated by pretreatment with pertussis toxin (PTx). PTx did not inhibit the effect of TNF to increase inositol phosphate turnover. TNF did not increase cAMP, intracellular calcium, or inositol phosphates in the UMR-106 cells. The data suggest the following: (a) cyclic mucleotides may play a role in TNF-stimulated resorption, although an increase in cAMP is not a direct rapid effect of TNF per se; (b) inositol phosphates could also play a signalling role in the action of TNF; (c) a pertussis toxin-sensitive step is required for TNF action on bone resorption.     

Evaluation of four radiopharmaceuticals for imaging inflammation in a rabbit model of arthritis

We compared the utility of four radiopharmaceuticals;¹¹¹In-chloride,⁶⁷Ga-citrate,¹¹¹In labeled leukocytes (WBCs) and^99mTc-MDP for assessing the inflammatory response in antigen induced arthritis in a rabbit model. A total of 20 rabbits, divided into four equal groups, were included in this study. Each group was studied twice with a single radiotracer: a baseline study and a follow-up study after induction of the arthritis. Knee to knee, knee to whole body, and knee to liver (except for the group studied with^99mTc-MDP) ratios were generated. Knee to knee ratios showed no significant change from baseline to arthritis studies in any of the four groups. Significantly increased knee to total body ratios were seen in all of the groups, except for the group studied with^99mTc-MDP. The greatest increase was seen in the group studied with¹¹¹In-chloride. Significantly increased knee to liver ratios were observed in all three groups for which these ratios were generated and again the greatest increase was observed in the group studied with¹¹¹In-chloride. In summary, based on the higher uptake observed in this group, of the four radiotracers evaluated,¹¹¹In-chloride is probably the most useful for monitoring the inflammatory response in antigen induced arthritis. The symmetry of the response suggests that it may also be useful in monitoring the response to therapy.     

67Ga-transferrin and 67Ga-lactoferrin binding to tumor cells: Specific versus nonspecific glycoprotein-cell interaction

In order to evaluate the mechanisms which facilitate the transfer of ⁶⁷Ga from transferrin in plasma to intracellular binding sites, lactoferrin, a glycoprotein with high affinity for ⁶⁷Ga, was used as a probe to study the effect of protein binding on gallium uptake by tumor cells. The in vivo effect of transferrin and lactoferrin on the biodistribution of ⁶⁷Ga was studied in nude mice bearing human malignant mesothelioma. Tumor uptake of ⁶⁷Ga was reduced 30% by transferrin and 57% by lactoferrin compared with ⁶⁷Ga-citrate alone. Liver uptake of ⁶⁷Ga, however, was significantly increased by binding to lactoferrin. The in vitro binding of ⁶⁷Ga to tumor cells (Burkitt's lymphoma) was apparently promoted by the addition of transferrin or lactoferrin to the incubation medium, but this glycoprotein enhancement of gallium uptake by the cells was dependent on the albumin level, decreasing in absolute uptake as the albumin concentration was increased, suggesting nonspecific binding of glycoproteins to cells. Because of the significant amount of nonspecific binding of ⁶⁷Ga-labeled glycoprotein complexes in cell culture experiments, in vitro experiments should be used with caution in developing a hypothesis on the mechanisms of cellular uptake of radiogallium. In vivo experiments suggest different mechanisms for cellular uptake of ⁶⁷Ga in neoplastic tissue and in liver.     

Preoperative risk assessment in cardiac surgery: comparison of predicted and observed results

In the present climate of quality-assurance policies, rigorous requirements for informed consent, and a constantly changing patient population, a system of preoperative risk assignment and postoperative correlation was developed to monitor and evaluate surgical performance. Patients were categorized by operation, priority (emergent, urgent, elective), New York Heart Association Functional Class, and risk. Risk was assigned before operation using data from the Coronary Artery Surgery Study (CASS) and the recent literature. Data were collected by a full-time data manager and were stored and analyzed by computer. From January 1, 1984, to July 1, 1985, 1,303 patients underwent operation for acquired disease. This group included 913 patients undergoing isolated primary coronary artery bypass grafting (CABG). The comparison of predicted and observed results showed: (Table: see text). For patients undergoing isolated primary CABG, the elective group had an operative mortality of 0.6% (2/329); the urgent group, 1.1% (5/450); and the emergent group, 5.2% (7/134). Preoperative risk assignment is an effective method of quality assurance. Female sex and age older than 60 years, which predicted an operative mortality of 2 to 5% in the CASS study and other recent series, did not predict a similar risk in our series.