Evaluation of chest and abdominal exposure dose appropriate for a digital image reader system incorporating a columnar-crystal structured phosphor plate and a contrast-detail phantom.

We evaluated a newly developed digital image reader incorporating a columnar-crystal structured phosphor plate (CPP) to determine its effectiveness for chest and abdominal exposures by assessing contrast-detail (C-D) curves and image quality figure values obtained from a C-D phantom. With the help of five radiologic technologists with 5 years or more of experience in the interpretation of plain radiographs, we assessed chest and abdominal radiographic films that had undergone image processing. The exposure dose required for obtaining the same image quality under chest exposure conditions (110 kV) was 66% of that necessary for a conventionally used computed radiography system incorporating a powder phosphor plate, whereas the percentage under abdominal exposure conditions (85 kV) was 82%. The rate of dose reduction varied depending on the anatomic region radiographed, the exposure conditions applied, and the method of image processing employed. Because the CPP has a higher X-ray detection efficiency than the hitherto-used powder phosphor plate, its use has to potential to reduce the patients' radiation exposure dose.

Analysis of medical accidents using the "Why Why Why Analysis" (questions): comparison with conventional analytical techniques.

Techniques such as 4M-4E matrices and the SHEL model have been proposed in recent years as tools for analyzing medical accidents and developing countermeasures. There have been hardly any reports, however, describing their use for the development of risk strategies in the medical setting. After using the SHEL model, Toranomon Hospital is currently using "Why Why Why Analysis" and has had several successes as a result of its use. With this in mind, a comparative study was conducted between "Why Why Why Analysis" and several previously reported accident countermeasure tools, root cause analysis (RCA), used at Veterans Hospitals in the US, and quality control (QC), used in the industrial sector. As a result, "Why Why Why Analysis" as applied in radiology work was determined to be easy to deploy even for beginners as compared with the other tools, able to accommodate complaints as well as accidents, and useful on the basis of having both practical and expandable functions for improving radiology work.

[Thyroid uptake error in four different gamma camera systems].

The thyroid uptake of (123)I and (131)I is generally measured by a gamma camera system. We evaluated the error in determining thyroid uptake caused by different methods of calculation among four gamma camera systems with various collimators. We first designed an original thyroid phantom that consisted of the thyroid and a body containing various levels of radioiodine activity. The applications for thyroid uptake equipped in two gamma camera systems performed calculations by the automatic method with background counts not subtracted from the capsule counts. When the size of the rectangular region of interest (ROI) for the capsule was set at 10x8 cm (a typical ROI size for the thyroid), percentages of thyroid uptake as calculated by the manual method with background counts subtracted from the capsule counts and thyroid counts were 52% to 57% when the value was set at 55% for (123)I; and 54.2% and 58.7%, respectively, when the value was set at 60% for (131)I. On the other hand, the percentages of thyroid uptake calculated by the automatic method with the application using two gamma camera systems with non-subtraction of background counts from the capsule counts were 46% and 50.5% when the value was set at 55%; and 49.6% when the value was set at 60%. The values calculated by the automatic method were underestimated as a result of background counts that were not subtracted from the capsule counts. When ROI size for the capsule was set at 4x4 cm, which is slightly larger than the capsule size, even thyroid uptake as determined by the automatic method using the application showed a difference of less 2% from the set values. There was no difference in thyroid uptake among the various kinds of collimators, high-resolution collimators, all-purpose collimators, and a suitable collimator for gamma-ray energy of (123)I.