Association between regularity in dapsone (DDS) treatment and development of deformity

The existence of an association between regularity in dapsone intake and the development of deformity was investigated in 5746 leprosy patients under treatment in South India. The incidence of deformity, year by year over a 5-year period, increased significantly with increasing levels of drug collection. The excess incidence in "more regular" patients was significant at all ages and in both sexes in nonlepromatous (N) cases. The same was true in intermediate (N?L) cases except in patients under 15 years of age. The evidence in lepromatous (L) cases was not so consistent. Independent confirmation of the presence of the association was sought through a matched case-control type of analysis with 140 N, 48 N?L, and 81 L cases, matching being undertaken with respect to sex, age, type of leprosy, year of starting treatment, and observation period. This showed that the mean regularity in cases (deformed patients) before the development of deformity was significantly higher than the mean regularity in the corresponding matched controls, the differences being particularly large among the N and N?L types. These findings raise the possibility of a causal link between regular dapsone intake and the development of deformity.     

CT-Cephalometry—A study in Indian population

Determination of obstructive site in obstructive sleep apnoea (OSA) is of paramount importance is planning the management. Cephalometric evaluation of lateral X-rays when combined with clinical assessment and fibreoptic examination of the airway helps in locating the site of obstruction. The usual technique of cephalometry has been modified so as to give a better delineation of the soft tissues. Holding a 2mm card board in the mouth and using barium paste helped in more accurate calculations. Using our technique, various parameters have been quantified and a number of controls were studied and normal range derived. Further improvement in cephalometry has been done by using C.T. cephlometry topogram technique. A topogram is a scan done on a running table top cranio-caudally. Using the topogram technique 38 OSA patients were evaluated for all the parameters. The technique, its advantages over traditional cephalometry and the values obtained in the study are discussed in this paper.     

Association of initial tuberculin sensitivity, age and sex with the incidence of tuberculosis in south India: a 15-year follow-up.

OBJECTIVE: To determine the association of initial tuberculin sensitivity, age and sex with the development of tuberculosis. METHODS: A 15-year follow-up of 280000 subjects in south India, where new cases of tuberculosis were detected mainly by periodic population surveys. Life-table technique was employed to estimate tuberculosis incidence and disease risk in survivors. The independent effect of tuberculin sensitivity, sex and age at intake was determined using Cox's proportional hazard model. RESULTS: Taking subjects with reaction size 0-7 mm to 3 IU PPD-S as reference group, the adjusted relative risk (RR) for developing culture-positive tuberculosis was 1.1, 1.9, 2.9, 3.6 and 3.3 for those with indurations of 8-11, 12-15, 16-19, 20-24 and > or = 25 mm (P < 0.01). Considering subjects aged 0-4 years as reference group, the adjusted RR for the other groups increased from 1.7 to 10.8 (P < 0.01). Males had a substantially higher incidence (adjusted RR 3.0, P < 0.001). The risk of culture-positive tuberculosis over 15 years in survivors was 3.3% (5.0% in males and 1.6% in females), and increased substantially with tuberculin sensitivity at intake. In those with > or = 12 mm at intake, the approximate lifetime risk was 6.1% (8.6% in males and 3.1% in females). CONCLUSION: The incidence of tuberculosis increased steadily with tuberculin sensitivity to PPD-S and age at intake. Males had a significantly higher risk than females in every PPD-S group and the overall risk was three-fold higher.     

Evaluation of a collapsed-cone convolution algorithm for esophagus and surface mold 192Ir brachytherapy treatment planning

PurposeTG43 does not account for a lack of scatter and tissue and applicator heterogeneities. The advanced collapsed-cone engine (ACE) algorithm available for use in the Oncentra Brachy treatment planning system (Elekta AB, Stockholm, Sweden) can model these conditions more accurately and is evaluated for esophageal and surface mold brachytherapy treatments.Methods and MaterialsACE was commissioned for use then compared against TG43 for five esophageal and five surface mold treatment plans. Dosimetric differences between each algorithm were assessed using superimposed comparisons and dose-volume histogram statistics.ResultsEsophagus (6 Gy per fraction): Compared with TG43, ACE demonstrated up to a 0.63% and 0.05 Gy reduction in planning target volume (PTV) V100% and PTV D98, respectively. Lung D2cc and bone D2cc deviated by up to 0.09 Gy and 0.03 Gy, respectively. Lung D0.1 cc and bone D0.1 cc both deviated by up to 0.12 Gy.Surface mold (4.5 Gy per fraction): Compared with TG43, ACE demonstrated up to a 12.5% and 0.18 Gy reduction in PTV V80% and PTV D98, respectively. Bone D2cc and D0.1 cc both reduced by up to 0.2 Gy when modeled with ACE. Increasing mold size laterally increased the dosimetric differences between TG43 and ACE.ConclusionsTG43 generally overestimated dose delivered to the target volume and organs at risk for the sites investigated. Dosimetric differences observed for esophageal treatments were minimal; however, surface mold treatments would benefit from the increased dosimetric accuracy offered by ACE.Implementation should be considered for surface mold ¹⁹²Ir treatment planning, but increased calculation time, additional contouring, and mass density assignment requirements should be scrutinized with regard to their potentially negative impact on current clinical practice.     

Approximation of the expected value of the harmonic mean and some applications

Although the harmonic mean (HM) is mentioned in textbooks along with the arithmetic mean (AM) and the geometric mean (GM) as three possible ways of summarizing the information in a set of observations, its appropriateness in some statistical applications is not mentioned in textbooks. During the last 10 y a number of papers were published giving some statistical applications where HM is appropriate and provides a better performance than AM. In the present paper some additional applications of HM are considered. The key result is to find a good approximation to E(H_n), the expectation of the harmonic mean of n observations from a probability distribution. In this paper a second-order approximation to E(H_n) is derived and applied to a number of problems.The harmonic mean H_n of n observations Z₁, …, Z_n drawn from a population is defined byHn=n∑i=1n1Zi.[1]There have been a number of applications of the harmonic mean in recent papers. A more general version of H_n with weights w₁, …, w_n isHn(w)=∑i=1nwi∑i=1nwiZi.[2]where w = (w₁,…,w_n)^T. The harmonic mean H_n is used to provide the average rate in physics and to measure the price ratio in finance as well as the program execution rate in computer engineering. Some statistical applications of the harmonic mean are given in refs. 1–4, among others. H_n(w) has been used in evaluation of the portfolio price-to-earnings ratio value (ref. 5, p. 339) and the signal-to-interference-and-noise ratio (6) among others. The asymptotic properties of H_n including the asymptotic expansion of E(H_n) are investigated in refs. 7 and 8 by either assuming that some moments of 1/Z_i are finite or that Z_i s follow the Poisson distribution. It is noted that recent papers (9, 10) enable one to use saddle-point approximation to give the asymptotic expansion of E(H_n) to any given order of 1/n for some constants c₀, c₁, c₂, …, i.e.,E(Hn)=c0+c1n+c2n2+⋯.[3]However, such methods are not applicable for obtaining the asymptotic expansion of H_n when the first moment of 1/Z_i is infinite. In ref. 3, Z_i s are assumed to follow a uniform distribution in the interval (0,1), i.e., U(0,1), motivated by learning theory. Using the property that the inverse of H_n converges to the stable law, ref. 3 showed thatE(Hn)∼1log(n),[4]where the symbol “∼” means asymptotic equivalence as n → ∞. Our interest in this paper is to determine the second term in the asymptotic expansion of E(H_n) or the general version E(H_n(w)) under more general assumptions on distributions of Z_i s. We show that under mild assumptions,E(Hn)∼1log(n){1+c1log(n)},[5]where the constant c₁ will be given. In addition, we use the approach for obtaining [5] to the case that the first moment of 1/Z_i is finite, motivated by evaluation of the marginal likelihood in ref. 11.     

Circumferential Stent Fracture: novel detection and treatment with the use of StentBoost

Circumferential stent fracture is extremely uncommon, and in rare cases, it can cause stent thrombosis. Recognizing stent fracture can be difficult on conventional fluoroscopy because of poor stent radiopacity. We found that StentBoost image acquisition yields improved visibility of stent struts, enabling the identification of stent fracture and the precise positioning of new stents over previously stented segments.We report the case of a 50-year-old man who presented with acute myocardial infarction and subacute stent thrombosis a week after percutaneous transluminal coronary angioplasty and placement of a bare-metal stent. The new lesion was crossed with a guidewire, but multiple attempts to advance a balloon catheter were unsuccessful. Live StentBoost image acquisition revealed circumferential stent fracture into 2 separate sections, with abnormal angulation between the proximal and distal portions of the stent. With StentBoost guidance, the wire and balloon catheter were both easily manipulated to cross the lesion, and angioplasty and restenting were completed with good results.StentBoost can be a useful adjunctive tool for the cardiac interventionist during complex percutaneous transluminal coronary angioplasty, and it was invaluable in this challenging situation. We discuss stent fracture and the benefits of using StentBoost in such situations.