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Y Takaki

Publications and source records attributed to Y Takaki.

59 records · Page 4Linked to original sources
PubMedDate not supplied

A preliminary phantom study on a proposed model for quantification of renal planar scintigraphy.

A method for estimation of the absolute renal activity within background activity in renal planar scintigraphy will be presented. This method corrects for oversubtraction of background activity with consideration of background activity of the kidney volume, and employs the depth-independent buildup factor (DIBF) method for the correction of attenuation and scatter of photons. This method requires the depth and thickness of the organ and the thickness of background for a background activity correction. The transmission factor (TF) for a volume source is derived from integrating TF for a thin source over the thickness of the organ for the DIBF method. To validate this method, phantom studies with various uniform background activity concentrations were performed and the data were compared with conventional background subtraction that do not consider the organ's volume. The results showed that with the conventional background subtraction method at all depth activity was underestimated with errors of 5%-30% for organ/background concentration ratios of 5-40, while this method estimated the true count rate with errors of less than 5%. More accurate quantifications of renal functions such as renal uptake, glomerular filtration rate (GFR) and renogram may be obtained by this proposed method on the planar images.

Biophysical Phenomena↗
PubMedDate not supplied

Electroretinographic assessment of early changes in ocular siderosis.

We examined a patient with an iron intraocular foreign body and recorded electroretinograms (ERGs) before and after the removal of the foreign body by vitrectomy. The amplitudes of the rod and cone ERGs and the oscillatory potentials (OPs) in the injured eye were reduced before the operation. In addition, the photopic on-responses (b wave) were more reduced than off-responses (d wave). One year after surgery, the amplitudes of the rod, cone and photopic on- and off-responses were markedly improved to within the low normal limit. However, the OP amplitudes remained unchanged with lower values. These findings suggest that iron retinotoxicity leads to a dysfunction of all layers but the changes may be reversible in the early period of the disease. The late period iron toxicity produces more severe damage to the inner retina than the outer retina.

Adult↗
PubMedDate not supplied

Measurement of effective renal plasma flow (ERPF) with 123I-orthoiodohippurate (I-123-OIH).

We evaluated the necessity of attenuation correction for calculating effective renal plasma flow (ERPF) using I-123-orthoiodohippurate (OIH), an agent introduced recently to replace I-131-OIH. From a kidney phantom experiment, the attenuation coefficient (mu) for I-123-OIH in the human body was determined as 0.1262 cm-1. I-123-OIH renal scintigraphy was performed in 23 patients with urinary diseases with blood sampling for calculation of ERPF by Tauxe's method. Calculated renal uptake, with or without attenuation correction, was compared with ERPF determined by Tauxe's method. There was good correlation between renal uptake without attenuation correction and ERPF obtained by Tauxe's method (r = 0.737), while much better correlation was found between attenuation-corrected renal uptake and ERPF calculated by Tauxe's method (r = 0.816). In conclusion, attenuation correction for renal uptake is an important technique for estimating ERPF using I-123-OIH renal scintigraphy.

Adolescent↗