Fetal dose assessment from invasive special procedures by Monte Carlo methods.

The assessment of fetal dose from a special procedure in the clinical environment is difficult as patient size, fluoroscopic beam motion, and imaging sequences vary significantly from study to study. Fetal dose is particularly difficult to estimate when the fetus is exposed partially or totally to scatter radiation from images taken in other locations of the mother's body. A method to reliably estimate fetal dose has been developed by using template based input files for the Monte Carlo radiation transport code MCNP. Female patient phantoms at 0, 3, 6, and 9 months of pregnancy and source terms for common diagnostic tube potentials are used to rapidly build an input file for MCNP. The phantoms can be easily modified to fit patient shape. The geometry and beam location for each type of image acquired (i.e. fluoroscopy, spot filming, etc.) is verified by the use of a 3D visualization code (Sabrina). MCNP is then run to estimate the dose to the embryo/fetus and the exposure to skin entrance (ESE) for the beam being modeled. The actual ESE for the beam is then measured with ion chambers and the fetal dose is determined from the MCNP supplied ratio of ESE to fetal dose. Runs are made for each type of imaging and the doses are summed for the total fetal dose. For most procedures, the method can provide an estimate of the fetal dose within one day of the study. The method can also be used to prospectively model a study in order to choose imaging sequences that will minimize fetal dose.

Genetic risk factors in inflammatory abdominal aortic aneurysms: polymorphic residue 70 in the HLA-DR B1 gene as a key genetic element.

PURPOSE: Evidence of a genetic predisposition to the development of inflammatory abdominal aortic aneurysms (AAAs) exists as a positive family history in 17% of patients. Familial clustering and other similarities between inflammatory AAAs and giant cell arteritis (GCA), which possesses a genetic risk determinant mapped to the HLA-DR molecule, suggest a role of genetic risk factors in inflammatory AAAs. The purpose of this study was to explore whether patients with inflammatory AAAs express disease-relevant genes associated with the HLA-DR region on the short arm of chromosome 6. METHODS: Thirty-seven patients with histomorphologic findings of inflammatory AAA at operation were genotyped for the polymorphism of the HLA-DR B1 and HLA DQ B1 alleles and compared to ethnically matched, healthy control subjects (n = 90). RESULTS: Distribution of HLA-DR B1 alleles was nonrandom in patients with inflammatory AAAs versus control subjects. The HLA-DR B1 alleles B1*15 and B1*0404 were enriched in patients with inflammatory AAAs compared with control subjects (47% versus 27%, and 14% versus 3%; p < 0.05, respectively). Analysis of functionally relevant amino acid polymorphisms encoded by the HLA-DR B1 gene showed relevance at amino acid position 70. HLA-DR B1 alleles overrepresented in patients with inflammatory AAAs express a glutamine substitution at position 70, whereas alleles disfavored in the patient cohort express a negatively charged aspartic acid. Distribution of HLA-DQ B1 alleles were indistinguishable in patients and control subjects. CONCLUSION: These data indicate that a genetic risk determinant can be mapped to the HLA-DR B1 locus in patients with inflammatory AAAs. This association suggests a critical contribution of antigen binding in the pathogenesis of this disease.

Synthesis and evaluation of a boronated nitroimidazole for boron neutron capture therapy.

We postulated that nitroimidazoles, previously used for radiosensitizing solid tumors, may be interesting templates as carriers of 10B for boron neutron capture therapy. To test this hypothesis, we synthesized a 10B-enriched nitroimidazole, 1-2[(undecahydro-closo-dodecaborato)thio]ethyl]-2- methyl-5-nitroimidazole (imidocaptate), by coupling the Cs salt of BSH (Cs2-10B12H11SH) with 1-(2-bromoethyl)-2-methyl-5-nitroimidazole followed by purification of the adduct. Imidocaptate was taken up by V-79 cells in culture and showed no inherent toxicity under euoxic conditions up to 1.05 mM (126 micrograms of 10B/mL of culture medium). Imidocaptate showed a dose-dependent decrease in D0 when the treated cells were irradiated with a thermal neutron beam. At the highest dose tested (126 micrograms of 10B/mL of culture medium), the ratio of control to sample D0 values was 2.6 for both linear quadratic and single-hit multitarget models. At 33 micrograms of 10B/mL, imidocaptate showed a control/treated D0 ration (1.5) equal to that observed with the disulfide form of BSH at 28 micrograms of 10B/mL. Compared to BSH and its disulfide, the reduced toxicity and equipotency of imidocaptate suggest that this agent may be useful for boron neutron capture therapy of cancer.

Mitigation of elevated indoor radon gas resulting from underground air return usage.

Underground air returns have been found to be active transportation pathways for radon gas entry into homes. Several homes for which underground air returns were contributing to elevated indoor 222Rn concentrations were evaluated for possible mitigation. Two houses with such problems were successfully mitigated by inserting flexible ducts into the returns. In one of these houses, the initial mitigation attempt resulted in an exacerbation of the problem due to leakage of the ducting. This was solved by re-sleeving the returns using a stronger material. Mitigation of elevated indoor radon gas caused by use of underground air returns by inserting flexible ducts is not possible for all situations, especially those for which the returns are small, filled with debris, misaligned, or inaccessible.

Underground air returns as active transportation pathways for radon gas entry into homes.

Levels of elevated 222Rn in homes can fail to correlate with measured radium concentrations in soils and surrounding rocks for reasons which can include water sources, building materials, and unusual variations in climate or building construction. Several homes were identified in the Phoenix, AZ metropolitan area with soil radium concentrations of < 0.074 Bq g-1 (2.0 pCi g-1) which had elevated radon concentrations unexplained by geological sources alone. Continuous monitoring of eight houses under different conditions of cooling system usage revealed a definite role of the underground air returns as active transport pathways contributing to the enhancement of the indoor concentration of 222Rn in six of the houses. The ratio of indoor 222Rn concentrations on days when the cooling system was operated continuously compared to days the system was off ranged from essentially one up to a factor exceeding 10.

Worry changes decision making: the effect of negative thoughts on cognitive processing.

The present studies demonstrate that daily worry level is predictive of cognitive processing differences and that these differences are an effect of negative thoughts. In Study 1, worriers (those who reported 50% or greater daily worry) and non-worriers performed a categorization task. The groups did not differ when the stimulus was a clear member or non-member of the category. Worriers showed a significant disruption in processing as the ambiguity of the category membership increased. Study 2 demonstrated that the disruption arose as a result of increased levels of negative thoughts. Worriers and non-worriers were assigned to two conditions, either O-worry ("Relax and let your mind wander for 15 minutes") or 15-worry ("Worry as you typically would for 15 minutes"). Non-worriers evidenced the same disruptive effects in the 15-worry condition as worriers in that condition and worriers in Study 1. Similarly, worriers in the O-worry condition showed a reduction in disruptive effects. The findings are taken as indicating that worry is accompanied by changes in cognitive processing and that these changes are similar for worriers and non-worriers.

Development and validation of the Penn State Worry Questionnaire.

The present report describes the development of the Penn State Worry Questionnaire to measure the trait of worry. The 16-item instrument emerged from factor analysis of a large number of items and was found to possess high internal consistency and good test-retest reliability. The questionnaire correlates predictably with several psychological measures reasonably related to worry, and does not correlate with other measures more remote to the construct. Responses to the questionnaire are not influenced by social desirability. The measure was found to significantly discriminate college samples (a) who met all, some, or none of the DSM-III-R diagnostic criteria for generalized anxiety disorder and (b) who met criteria for GAD vs posttraumatic stress disorder. Among 34 GAD-diagnosed clinical subjects, the worry questionnaire was found not to correlate with other measures of anxiety or depression, indicating that it is tapping an independent construct with severely anxious individuals, and coping desensitization plus cognitive therapy was found to produce significantly greater reductions in the measure than did a nondirective therapy condition.

Use of visual training for reading disabilities: a review.

Visual training continues to be used as a remediation technique for reading disabilities despite consistent evidence that it does not provide effective treatment. A review of the ophthalmologic, optometric, and psychological literature relating to the assumption that a relationship exists between reading failure and perceptual ability has found no evidence to support this assumption.

Sex and coding strategy effects on reaction time to hemispheric probes.

Two experiments were conducted to investigate the influence of coding instructions on cerebral laterality differences. Experiment I required 20 subjects (10 female) to use either rehearsal or imagery coding strategies in a recognition task with word probes to the right and left hemispheres. No hemispheric differences were found, but sex of subject was found to be related to coding strategy. Ten subjects (5 female) in Experiment II performed a similar task, except picture probes were used. Subjects using rehearsal coding responded faster to left-hemisphere probes, but faster to right-hemisphere probes when imagery coding was employed. The differing laterality effects in these experiments were attributed to naming responses implicitly required in Experiment II.