The myocardial blood flow (MBF) was measured with PET and the15Osteady-state method using a continuous infusion ofH215Oin 8 normal volunteers. The intra-vascular radioactivities were corrected by blood volume measured with a single inhalation ofC15O.The MBF values were obtained both invasively and non-invasively. As the15Osteady-state method is susceptible to a partial volume effect due to a relatively thin myocardial wall thickness and wall motion, the MBF values were corrected for the partial volume effect by tissue fraction measured with transmission scan. The MBF values obtained non-invasively were 90.7±20.6, 65.1±21.6 and 104.4±44.5ml/min/ml in the septum, anterior wall and lateral wall, respectively. They were close to the previously reported MBF values of 100 ml/min/100 ml. Therefore, we were able to obtain reasonably accurate MBF values non-invasively.
We developed an automatic device to measure etch pit density on cellulose nitrate film, which consisted of microscope, monochrome video camera, image processing device, monochrome display and personal computer. For 1-3 MeV energy alpha particle, high reproducibility of automatic counting was confirmed. In case of 4 MeV energy alpha particle, results of automatic counting were unstable. Counting efficiency for 4 MeV energy alpha particle can be decreased with increasing threshold level which was used when image data was converted into binary data. Correction for loss of etch pit density due to overlapping etch pit image was not necessary up to about 8000 tracks cm-2in case of about 10μm diameter etch pits. Radon concentration can be estimated up to 120 Bq m-3without correction due to overlapping etch pit image, when the measurement was carried out for 2 months with an electrostatic integrated radon monitor.