[Measurement of Absorbed Dose in the Air in X-ray CT Examination Rooms Using a Special Protective Shield for CT].

PURPOSE: X-ray CT examinations are required not only in routine medical examinations but also in various situations such as emergency medical care. Although medical staff may be exposed to radiation when assisting patients, the distribution of air-absorbed doses in the CT examination room when using a special protective shield for CT has not been clarified. Here, we measured air-absorbed doses at several points simultaneously to clarify the distribution of these doses and the effect of a special protective shield for CT in reducing them. METHOD: A human phantom was imaged with an X-ray CT system. The absorbed dose in the air dose profile distribution was measured with an OSL dosimeter in the presence and absence of a special protective shield for CT. RESULTS: The highest air absorbed doses of 4.27 mGy were at 0 cm in the horizontal direction, 120 cm in the vertical direction, and 50 cm in the body axis direction. The largest reduction in air absorbed dose following installation of the special protective shield for CT was 91.7%, obtained at 0 cm in the horizontal direction, 150 cm in the vertical direction, and 50 cm in the body axis direction. CONCLUSION: A 91.7% reduction in air-absorbed dose was o directly behind the special protective shield for CT. The reduction in air-absorbed dose was 65.8% at the location of a gap between the special protective shield for CT and gantry.

PHANTOM STUDY OF THE ENTRANCE SURFACE DOSE OF A NEW CT SCOUT ACQUISITION THAT ALSO SERVES AS A TUBE WARM-UP.

We determined the effect of a new scout image acquisition technique ('smart scout'), which also serves as a tube warm-up, on radiation dose and automatic exposure control (AEC) mA settings. The entrance surface dose (ESD) of a chest phantom with and without the smart scout was measured. A conical AEC phantom was scanned in the setting for abdominal CT, and AEC curves were generated. ESD when the smart scout was not used was 0.75 mGy at 120 kV, 50 mA. ESD when using the smart scout was 0.24 mGy for a body habitus setting of 'Less', 0.54 mGy for 'Moderate' and 0.95 mGy for 'More'. When the diameter of the subject was ≥32 cm, the mA setting became lower in 'Less'. The smart scout reduced exposure at the 'Less' and Moderate' settings compared to the conventional scout scan.

Performance of using opposing homozygotes for paternity testing in Japanese Black cattle.

Genome-wide single nucleotide polymorphism (SNP) markers in Japanese Black cattle enable genomic prediction and verifying parent-offspring relationships. We assessed the performance of opposing homozygotes (OH) for paternity testing in Japanese Black cattle, using SNP genotype information of 50 sires and 3,420 fattened animals, 1,945 of which were fathered by the 50 genotyped sires. The number of OH was counted for each sire-progeny pair in 28,764 SNPs with minor allele frequencies of ≥0.05 in this population. Across all pairs of animals, the number of OH tended to increase as the pedigree-based coefficient of relationship decreased. With a threshold of 288 (1% of SNPs) for paternity testing, most sire-progeny pairs were detected as true relationships. The frequency of Mendelian inconsistencies was 2.4%, reflecting the high accuracy of pedigree information in Japanese Black cattle population. The results indicate the utility of OH for paternity testing in Japanese Black cattle.