Errors in the measurements of T2 using multiple-echo MRI techniques. II. Effects of static field inhomogeneity

The accurate estimation of the spin-spin relaxation time T2 is an important goal in magnetic resonance imaging particularly because it can be used for quantitative tissue characterization. The spin-spin relaxation time T2 may be estimated using multiecho pulse sequences, but the accuracy of the estimate is dependent on the fidelity of the spin-echo amplitudes, which may be severely compromised by rf pulse and static field imperfections. In this paper, the effects of static field inhomogeneities are investigated. The propagation of the errors introduced by off-resonance effects are analyzed through computer simulations and analytical solutions of the Bloch equations. A series of experiments performed on a simple tissue phantom using a whole-body imaging system operating at 6.35 MHz corroborates the simulation and analytical results. For accurate measurements of T2 using a whole-body imaging system it is necessary to correct for these inhomogeneities. A correction scheme which would enable a more accurate estimate of T2 is currently under investigation.     

Cancer of the hypopharynx — A clinical study of 290 cases

Between 1986–1990, 290 patients with squamouscell carcinoma of the hypopharynx were assessed at the S. S. K. M. Hospital Calcutta, out of the total of 1460 number of Head Neck cancer, (19.8%). The most frequent initial symptom was a foreign body sensation in the throat (70%), and males were affected more than females (9.8 : 1.2). The peak age incidence was found between 40 and 50 years (24%). Most of the patients came in advanced stages with cervical lymph node metastases (60%). One interesting fact that came out from the present study is the Right pyriform fassa was more commonly affected than the left in righthanded persons (56.9%). Though the reason is not clear it could be due to right — sided swallow, as one side may be predominant in funtion.     

Synthesis and biological activities of novel 5-(2-acylethynyl)uracils

5-(2-Acylethynyl)-2,4-dimethoxypyrimidines (3-6) were synthesized in excellent yields from 2,4-dimethoxy-5-[2-(trimethylsilyl)ethynyl]pyrimidine (2) by treatment with acid chlorides in the presence of anhydrous aluminum chloride. Compounds 3-6 were deblocked with chlorotrimethylsilane and sodium iodide in acetonitrile to the corresponding 5-[(2-acyl-1-iodo)vinyl]uracils (7-10), which on treatment with potassium hydroxide in dioxane yielded the corresponding 5-(2-acylethynyl)uracils (11-14). The 5-(2-acylethynyl)uracils were found to be active against Ehrlich ascites carcinoma (EAC) cells in vivo, the most active compounds being 5-(2-benzoylethynyl)uracil (11) and 5-(2-p-toluoylethynyl)uracil (12). The T/C values of 281 and 300 were obtained for compounds 11 and 12, respectively, in the case of mice bearing EAC cells. The 5-(2-acylethynyl)uracils have also shown in vitro activity against CCRF-CEM and L1210/0 tumor cell lines. The lead compound 5-(2-p-toluoylethynyl)uracil effectively inhibited thymidylate synthetase.     

Physiological analysis to quantify training load in badminton.

OBJECTIVE: To estimate the training load of specific on court training regimens based on the magnitude of variation of heart rate-lactate response during specific training and to determine the magnitude of variation of biochemical parameters (urea, uric acid, and creatine phosphokinase (CPK)) 12 hours after the specific training programme so as to assess training stress. METHODS: The study was conducted on six national male badminton players. Maximum oxygen consumption (VO2), ventilation (VE), heart rate, and respiratory quotient were measured by a protocol of graded treadmill exercise. Twelve training sessions and 35 singles matches were analysed. Heart rate and blood lactate were monitored during technical training routines and match play. Fasting blood samples collected on two occasions--that is, during off season and 12 hours after specific training--were analysed for serum urea, uric acid, and CPK. RESULTS: Analysis of the on court training regimens showed lactate values of 8-10.5 mmol/l in different phases. The percentage of maximum heart rate ranged from 82% to 100%. Urea, uric acid, and CPK activity showed significant changes from (mean (SD)) 4.93 (0.75) mmol/l to 5.49 (0.84) mmol/l, 0.23 (0.04) to 0.33 (0.06) mmol/l, and 312 (211.8) to 363 (216.4) IU/l respectively. CONCLUSION: Maximum lactate reported in the literature ranges from 3-6 mmol/l. Comparatively high lactate values and high percentage of maximum heart rate found in on court training show a considerable stress on muscular and cardiovascular system. The training load needs appropriate monitoring to avoid over-training. Workouts that are too intensive may interfere with coordination, a factor that is important in sports requiring highly technical skill such as badminton.     

Thermal analysis of the bone surface induced by laser radiation

High energy laser has emerged to be an important surgical tool in medical technology. However, the application of laser energy to drill or cut a bone is still in an experimental state. In order to estimate the adequacy of laser heating of bone surface and at the same time minimize the damage to the bone tissue, we developed a mathematical model of the temperature distribution in bone due to laser irradiation. The thermal analysis shows that the temperature distribution depends on several parameters, including the density, the specific heat, and the thermal conductivity of the osseous tissue.     

Stimulation of enzyme secretion from isolated pancreatic acini by Clostridium difficile toxin B

Exposure of isolated rat pancreatic acini to increasing concentrations (10 ng - 800 ng/ml) of toxin B from Clostridium difficile produced a biphasic effect on the rate of secretion of amylase, trypsinogen, and chymotrypsinogen. Whereas doses of toxin B from 10-30 ng/ml increased enzyme secretion by 15-20%, doses between 30 ng and 60 ng/ml showed a regression of this effect, whereafter the rate of secretion of amylase, trypsinogen, and chymotrypsinogen increased with increasing concentrations of the toxin. Toxin B concentration of 800 ng/ml enhanced amylase, trypsinogen and chymotrypsinogen secretion by 119%, 185% and 195%, respectively, when compared with the basal level. Stimulation of enzyme secretion by toxin B was not affected by the presence of either actinomycin-D or cycloheximide, at a concentration which inhibited acinar RNA or protein synthesis by 80-90%. Although toxin B as well as CCK8, carbachol and secretin by themselves caused significant stimulation in amylase, trypsinogen and chymotrypsinogen secretion from isolated pancreatic acini, toxin B together with either CCK8, carbachol or secretin produced no further augmentation in enzyme secretion than what was observed with the secretagogues alone. It is concluded that toxin B of Cl. difficile exerts a direct effect on pancreatic acinar cells as evidenced by stimulation of enzyme secretion.     

A clinical and genetic study of 56 Saudi Wilson disease patients: identification of Saudi-specific mutations

Wilson disease (WD) is a hereditary disorder, with recessive transmission and genetic heterogeneity. Several mutations of ATP7B, the gene underlying WD, were reported in many ethnic groups. In this study, mutation screening in ATP7B of 56 Saudi Arabian WD patients was undertaken. The clinical data of all patients were recorded. The entire ATP7B coding sequence, including intron-exon boundaries were screened for mutation by the polymerase chain reaction (PCR)-based mutation detection technique and DNA sequencing. Thirty-nine patients were symptomatic at presentation and 17 subjects were pre-symptomatic siblings of affected patients. Fourteen patients had neurological, 11 patients had mixed (hepatic and neurological), and 14 patients had hepatic presentations. Family history suggestive of WD was present in 72% of cases and 68% had consanguineous parents. Genetic analysis showed disease-causing mutations in three exons (exons 8, 19 and 21) of the ATP7B gene in 28 patients (50%). Mutations in exons 21 (18 cases) and 19 (one case) were unique for Saudis. This large series of Saudi patients with WD has shown wide variability in the genomic substrate of WD. There is no correlation between genotype and clinical presentation.