Satoshi Sasayama

Increased uptake of iodine-131 in metastases of differentiated thyroid carcinoma associated with less severe hypothyroidism following total thyroidectomy.

Background. In an attempt to determine possible factors affecting the efficacy of iodine‐131 (I‐131) treatment for metastatic thyroid carcinoma, the authors focused their efforts on thyroid functions after total thyroidectomy.

Development of optoelectronic monitoring system for ear arterial pressure waveforms

Invasive intra-arterial blood pressure measurement is the most accurate method but not practical if the subject is in motion. The apparatus developed by Wesseling et al., based on a volume-clamp method of Penaz (Finapres), is able to monitor continuous finger arterial pressure waveforms noninvasively. The limitation of Finapres is the difficulty in measuring the pressure of a subject during work that involves finger or arm action. Because the Finapres detector is attached to subjects finger, the measurements are affected by inertia of blood and hydrostatic effect cause by arm or finger motion. To overcome this problem, the authors made a detector that is attached to subjects ear and developed and optoelectronic monitoring systems for ear arterial pressure waveform (Earpres). An IR LEDs, photodiode, and air cuff comprised the detector. The detector was attached to a subjects ear, and the space adjusted between the air cuff and the rubber plate on which the LED and photodiode were positioned. To evaluate the accuracy of Earpres, the following tests were conducted with participation of 10 healthy male volunteers. The subjects rested for about five minutes, then performed standing and squatting exercises to provide wide ranges of systolic and diastolic arterial pressure. Intra- and inter-individual standard errors were calculated according to the method of van Egmond et al. As a result, average, the averages of intra-individual standard errors for earpres appeared small (3.7 and 2.7 mmHg for systolic and diastolic pressure respectively). The inter-individual standard errors for Earpres were about the same was Finapres for both systolic and diastolic pressure. The results showed the ear monitor was reliable in measuring arterial blood pressure waveforms and might be applicable to various fields such as sports medicine and ergonomics.

Optimal dose of injection in activation study with O-15 water and PET.

In activation studies with the bolus method for O-15 water and PET, the radiotracer concentration may reach the limits of the system in terms of dead time correction and accidental coincidence. To obtain the optimal injection dose of O-15 water, we performed a normal volunteer study to evaluate the relationship between the injected dose and the radioactivity concentration in the brain and a phantom study to evaluate the performance of the PET scanner (PCT3600W) under high count rate conditions and the effect of averaging on the signal to noise ratio for the PET images.A linear relationship was noted between the injected dose (normalized for each body weight: x) and the mean radiotracer concentration in the brain measured by PET (y) (y = 2.52 + 30.1x, n = 64, r = 0.87, p < 0.001). The percent error in the measurement of radioactivity with PET was within ± 5% in the 100 to 2000 nCi/m/ (3.7–74 KBq/mZ) range. Below 100 nCi/mZ (3.7 KBq/mZ), the percent error increased due to the rapid increase in noise in the reconstructed images. Over 1000 nCi/ mZ (37 KBq/mZ), on the other hand, the noise was almost unchanged.With our PET scanner, the optimal range of the radiotracer concentration in the brain is below 1000 nCi/mZ (37 KBq/mZ), corresponding to an injection dose of 33 mCi (1.22 GBq)/60 kg body weight. With the same total dose, the increment of number of repeated measurements for averaging provided the better signal to noise ratio. In designing a paradigm for an activation PET study, the injection dose and the number of repeated measurements for averaging should be considered.

Off-line image exchange between two PACS modules using the "ISAC" magneto-optical disk

In order to exchange digital imaging data between two independent PACS modules, the ISAC (Image Save And Carry: JPACS/MEDIS-DC) formatted 130-mm magneto-optical disk (MOD) was used as an interchangeable off-line data transferring and recording medium. This system can provide the means for connecting distributed image databases and is useful for clinical studies.

Validation of optoelectronic monitoring system for ear arterial pressure waveforms in practical use

A newly developed optoelectronic monitoring systems for ear arterial pressure waveform (Earpres) was tested in ergonomics and sports science. Changes in systolic and diastolic blood pressures and heart rate were continuously measured by the system during VDT operations such as word processing and computer games, and during two different styles of weight lifting, one-hand and two-hands curls, with three different weights respectively. Statistical analysis of the results showed that systolic and diastolic blood pressures and heart rate increased during VDT operation, and in the extreme case the increments of those were as high as 78 mmHg and 50mmHg respectively during computer game operation and 50 bpm during word processor operation. It was also statistically clarified that systolic and diastolic blood pressures and heart rate increased in accordance with weight during one-hand and two-hands curls. It was ascertained that the results obtained by Earpres agreed for the most part with physiological knowledge; some results might be new findings. Earpres was thus validated as a physiologically and ergonomically useful apparatus. Additionally, an apparatus was constructed to detect the exact location of an artery in the ear, composed of a halogen lamp, a band-pass filter, a bundle of optical fibers, and a CCD device. With the apparatus, Earpres became much easier to handle.