Improvements on a patient-specific dose estimation system in nuclear medicine examination.

The purpose of this paper is to develop a patient-specific dose estimation system in nuclear medicine examination. A dose deposition routine to store the deposited energy of the photons during their flights was embedded in the widely used SimSET Monte Carlo code and a user-friendly interface for reading PET and CT images was developed. Dose calculated on ORNL phantom was used to validate the accuracy of this system. The ratios of S value for (99m)Tc, (18)F and (131)I computed by this system to those obtained with OLINDA for various organs were ranged from 0.93 to 1.18, which were comparable to that obtained from MCNPX2.6 code (0.88-1.22). Our system developed provides opportunity for tumor dose estimation which cannot be known from the MIRD. The radiation dose can provide useful information in the amount of radioisotopes to be administered in radioimmunotherapy.

Assessment of macular retinal thickness and volume in normal eyes and highly myopic eyes with third-generation optical coherence tomography.

PURPOSE: To compare the macular retinal thickness and macular volume between subjects with high myopia and non-myopia. METHODS: This prospective nonrandomized, comparative study recruited healthy subjects with high myopia subjects, defined as a spherical equivalence (SE) over -6 dioptres (D) or AXL>or=26.5 mm and the best corrected visual acuity better than 20/25, and subjects with non-myopia, defined as an with SE between 1.5D and -1.5 D and the BCVA better than 20/25. Optical coherence tomography was performed in each eye. RESULTS: Eighty high myopic eyes and 40 non-myopic eyes were included. The mean age of the high myopic group and non-myopia group was 29.6 and 27.5 years old, respectively. The mean refraction was -9.27 D in the high myopia group and -0.22 D in the non-myopia group. The high myopia group had significantly greater mean retinal thickness in the foveola and fovea 1 mm area than the non-myopia group (166 vs149 microm, P<0.0001, 199 vs188 microm, P=0.0063, respectively). However, the mean retinal thickness in the inner and outer macular area (superior, nasal, inferior, or temporal) of the high myopia group was significantly less than in the non-myopia group. In addition, the high myopia group had significantly smaller macular volume than the non-myopia group (P<0.0001). CONCLUSION: This study demonstrated that the retinal thickness in individuals with high myopia is thicker in the foveola and fovea, but thinner in the inner and the outer macular region. The retina of individuals with high myopia had smaller macular volume than those with non-myopia.

Uncovering the relation between betel quid chewing and cigarette smoking in Taiwan.

OBJECTIVE: To describe the characteristics of betel quid chewers and to investigate the behavioural and mortality relations between betel quid chewing and cigarette smoking. METHOD: Prevalence and mortality risks of betel quid chewers by smoking status were calculated, based on the National Health Interview Survey in 2001 and a community based cohort, respectively. Cox's proportional hazards model was used to adjust mortality risks for age, alcohol use, and education. RESULTS: Almost all betel quid chewers were smokers, and most started chewing after smoking. Chewers were predominantly male, mostly in their 30s and 40s, more likely being among the lowest educational or income group, and residing in the eastern regions of Taiwan. On average, betel quid chewers who smoked consumed 18 pieces of betel quid a day, and smoked more cigarettes per day. Far more smokers use betel quid than non-smokers (27.5% v 2.5%), but ex-smokers quit betel quid more than smokers (15.1% v 6.8%). The significantly increased mortality of betel quid users who also smoked, for all causes, all cancer, oral cancer, and cancer of the nasopharynx, lung, and liver, was the result of the combined effects of chewing and smoking. Smokers who chewed betel quid nearly tripled their oral cancer risks from a relative risk of 2.1 to 5.9. Increasing the number of cigarettes smoked among betel quid chewers was associated with a synergistic effect, reflective of the significant interaction between the two. CONCLUSION: To a large extent, the serious health consequences suffered by betel quid chewers were the result of the combined effects of smoking and chewing. Betel quid chewing should not be considered as an isolated issue, but should be viewed conjointly with cigarette smoking. Reducing cigarette smoking serves as an important first step in reducing betel quid chewing, and incorporating betel quid control into tobacco control may provide a new paradigm to attenuate the explosive increase in betel quid use in Taiwan.