[Examination of three-detector high-speed-rotation SPECT acquisition under breathhold in body: clinical application of 99mTc-MAA].

In traditional pulmonary perfusion single photon emission computed tomography (SPECT), respiratory lung motion and cyclically varying changes in lung volume during image acquisition inherently degrade the image sharpness of ill-defined perfusion defects. However, because of the lack of an adequate fast imaging technique, perfusion SPECT has never been acquired under breathhold conditions, whereas breathhold images are commonly used for pulmonary magnetic resonance (MR) and computed tomographic (CT) images. Although a high-speed imaging technique combined with a multidetector SPECT system may enable SPECT images to be obtained during a short period of breathholding, image quality would be degraded owing to decreased radioactivity counts and increased statistical noise. To resolve this problem, we developed an innovative SPECT imaging technique using a triple-head SPECT system and the high-speed-detector rotation-multiplied projection (HSRMP) technique, where a single SPECT image was reconstructed from multiple respiratory dimensional breathhold projection data obtained at the same angle. HSRMP provided noiseless high-quality perfusion SPECT images by compensating for decreased radioactivity counts caused by high-speed imaging, and significantly improved image quality and perfusion defect clarity compared with traditional non-breathhold SPECT images.

[Measurement of effective dose of the assisting person in diagnostic X-ray examination].

We measured the effective dose received by the person assisting the patient at diagnostic X-ray examination. Measurement was done when a patient's chest, abdomen, lumbar vertebrae, hip joint, skull, cervical vertebrae, or knee joint was examined by radiography. A body phantom including human bones exposed to radiation was used in the role of the patient. Some exposure conditions for these measurements were the same as those used routinely in computed radiography. Effective dose was measured directly with an ionization survey meter. As a result, the effective dose of the person assisting with axial projection of the hip joint was 124 microSv, which was higher than that for other regions and projections. If the assisting person helped a patient without using any protective device, the effective dose would be low enough to ignore. However, because medical staff are frequently exposed to radiation, optimal protection is crucial to prevent unnecessary radiation.