The aim of this study was to characterise brain tumour type and treatment response in relation to the uptake of thallium-201. 201T1 single photon emission tomography (SPET) was performed in 58 patients with brain tumours. Fifty-six patients were utilised for the statistical comparison of the early and delayed 201T1 indices expressed as the ratio of tumour to contralateral cerebral hemisphere uptake. The retention index of 201T1 in the tumour tissue calculated from the early and delayed scans was also analysed. Furthermore, in 56 patients with 58 brain tumours, a comparison was made of the diagnostic value of high 201T1 uptake and gadolinium diethylene triamine penta-acetic acid (Gd-DTPA) enhancement on MRI scans. Although high 201T1 uptake was observed in viable malignant gliomas, brain metastases, meningiomas and malignant teratoma, the viable malignant gliomas could not be differentiated from brain metastases and extracerebral tumours by means of 201T1 indices. 201T1 SPET failed to diagnose a viable ring-enhanced tumour with a thin rim and small tumours of less than 1.5 cm in diameter visualised by Gd-DTPA-enhanced MRI. In spite of this, 201T1 SPET appears to be effective for determination of the malignant viability of tumours.

Precise correction for γ-ray attenuation in skull bone has been a significant problem in obtaining quantitative single photon emission computed tomography (SPECT) images. The correction for γ-ray attenuation is approximately proportional to the density and thickness of the bone under investigation. If the acoustic impedance and the speed of sound in bone are measurable using ultrasonic techniques, then the density and thickness of the bone sample can be calculated. Whole bone usually consists of three layers, and each layer has a different ultrasonic character. Thus, the speed of sound must be measured in a small section of each layer in order to determine the overall density of whole bone. It is important to measure the attenuation constant in order to determine the appropriate level for the ultrasonic input signal. We have developed a method for measuring the acoustic impedance, speed of sound, and attenuation constant in a small region of a bone sample using a fused quartz rod as a transmission line. In the present study, we obtained the following results: impedance of compact bone; 5.30(±0.40)×106 kg/(m2s), speed of sound; 3780±250 m/s, and attenuation constant; 2.70±0.50 Np/m. These results were used to obtain the densities of compact bone, spongy bone and bone marrow in a bovine bone sample and as well as the density of pig skull bone, which were found to be 1.40±0.30 g/cm3, 1.19±0.50 g/cm3, 0.90±0.30 g/cm3 and 1.26±0.30 g/cm3, respectively. Using a thin solid transmission line, the proposed method makes it possible to determine the density of a small region of a bone sample. It is expected that the proposed method, which is based on ultrasonic measurement, will be useful for application in brain SPECT.

In this report, I describe an experimental analysis of the acoustic mechanism of the suikinkutsu. The sound of the suikinkutsu consists of an original sound generated by water drops striking the surface of the water in the suikinkutsu and a reverberant sound generated by the original sound. The reverberant sound is the sound we hear through the observation holes of the suikinkutsu. The body of the suikinkutsu also has its own natural frequencies and vibrates in synchronism with the natural frequencies of the oscillation modes of air inside it, affecting the tonal quality of the sound emitted from the suikinkutsu. If all of the natural frequencies and time constants of the reverberant sound are optimized, the suikinkutsu can produce a sound of good tonal quality. In this study, we investigate the relationships between the original sound and the reverberant sound emitted from the suikinkutsu. We propose an experimental formula representing the natural frequencies of the suikinkutsu and examine the validity of this formula.

Precise correction for γ ray attenuation in the skull bone is essential when obtaining quantitative single-photon emission computed tomography (SPECT) images of the brain. Correction for γ ray attenuation is approximately proportional to the density and thickness of the bone under investigation. Therefore, if the acoustic impedance and speed of sound in the bone are measurable using ultrasonic techniques, then the density and thickness of the bone sample can be calculated. We propose a method for determining simultaneously the thickness of and speed of sound in the skull bone through in vivo measurements; the principle being that the time delay between two discrete transmission paths will yield the desired information. Thus, it is necessary to distinguish between the responses of these two transmission paths. The proposed method incorporates the pulse compression method to measure the time delay between detected transmission paths and reduce dispersion in the transmission line, thus increasing the signal-to-noise (S/N) ratio and significantly improving measurement accuracy. Using the proposed pulse compression method, the speed of sound in a number of materials was obtained, with the following results: 5 mm-thick poly methyl methacrylate(PMMA) plate, 2620±130 m/s; compact bone, 3820±250 m/s; spongy bone, 1930±90 m/s. The errors in thickness indicated by these measurements were 5.6%, 7.2% and 12% for the PMMA plate, compact bone and spongy bone, respectively. Thus, using a thin transmission line, the proposed method makes it possible to determine the thickness of a bone sample with sufficient accuracy. It is anticipated that this method, which is based on ultrasonic measurements, will be useful for application in brain SPECT.

No abstract