The present study aimed to prepare a small acute-phase cerebral infarction phantom made of gelatin and sucrose to simulate brain parenchymal cells, and a phantom made of collagen peptides and sucrose to simulate cerebral infarction for diffusion-weighted imaging (DWI). During the preparation of gelatin and sucrose mixture (17.0 wt% gelatin, 20.0 wt% sucrose), a cylindrical wooden bar was placed in the center of the phantom and covered with a heat-shrinkable film to ensure space remained after gelling. A mixed solution composed of collagen peptide and sucrose (16.0 wt% collagen peptide, 27.5 wt% sucrose) was then enclosed within the space. The T₂ relaxation time and apparent diffusion coefficient (ADC) of the phantom were set equal to those observed in actual patients with acute-phase cerebral infarction. The mixture was selected based on the signal intensity of both the healthy brain tissue and that subjected to acute cerebral infarction, such that no contrast was observed during T₂-weighted imaging (T₂WI). T₂WI and DWI were performed using a 1.5 T scanner. Although contrast between the mixed gel and mixed solution was obscure on T₂WI, cerebral infarction was clearly visible on DWI. However, the phantom exhibited mono-exponential changes in the ADC value at b values of 0 and 1,000 (s/mm²), and was affected by the proton density and T₁ value depending on the imaging condition.

Purpose: The AI-300 automated infusion device (Sumitomo Heavy Industries, Ltd., Tokyo, Japan) is subject to administration error as a function of smaller volumes of ¹⁸F-FDG dispensed via a three-way cock supplied with a disposable kit. The present study aimed to validate the administration accuracy of the AI-300 using an improved disposable kit for quantitative positron emission tomography (PET) assessment. Methods: We determined administration accuracy between the improved and previous disposable kits by measuring variations in dispensed volumes and radioactive concentrations of ¹⁸F-FDG according to the criteria of the Japanese Society of Nuclear Medicine. A reference value was generated by measuring radioactivity using a standard dose calibrator. Results: The values obtained using the previous kit deviated from the reference values by a maximum of −10.6%, and the deviation depended on dispensed volumes of ¹⁸F-FDG<0.25 mL. In contrast, the values were relatively stable when using the improved kit with dispensed ¹⁸F-FDG volumes < 0.25 mL. Variations in radioactive concentrations were relatively stable using the improved kit, whereas that of the previous kit was slightly unstable at high radioactive concentrations. Conclusion: The administration accuracy of the AI-300 using the previous kit varied considerably according to smaller dispensed volumes, but the improved kit might alleviate this problem. The present results indicated that the improved disposal kit should be immediately implemented to eliminate uncertainty surrounding quantitative PET findings.

In Japan, medical liquid-crystal display (LCD) and general LCD monitors have color temperatures of 7500 and 6500 K, respectively. The differences in color temperature make it difficult for radiologists to judge whether the same color is being displayed on the monitor. Therefore, the radiologist may overlook lesions. We examined chromaticity on a color scale test pattern to determine the relationships between color temperature (6500–12,500 K) of the medical color LCD monitors, there are three types of fluorescent light and three types of illuminance LCD monitors. As the color temperature of the monitor increased, the variation in chromaticity for grayscale test patterns increased and those variations for the blue scale test patterns decreased in a dark room and at 600 lux. In addition, even if the color temperature of the monitor was changed, the variation in chromaticity showed no change under fluorescent lighting with light bulb color and daylight color. The results of this study will be useful for quality control and quality assurance of medical LCD monitors in terms of illuminance and color temperature of the monitor.

Purpose: We examined whether early delayed scanning is useful for differentiation of liver lesion and heterogenous physiological accumulation in positron emission tomography (PET) examination. Methods: The subjects of the study were 33 patients with colorectal cancer who underwent PET examination and were added early delayed scanning to distinguish between liver lesions and heterogenous physiological accumulation to conventional early images. We placed same regions of interest (ROI) in the tumor and hepatic parenchyma for early delayed and conventional early images. Then, we measured SUVmax of the ROIs and calculated tumor to liver parenchyma uptake ratio (TLR). In addition, change rates between early and early delayed images were calculated for the SUVmax and TLR. Results: The receiver operating characterstic (ROC) analysis result of SUVmax showed the highest SUVmax change rate, and the ROC analysis result of TLR showed the highest early delayed scanning. The SUVmax of the lesions did not change between early scan and early delayed scanning (p=0.98), but it decreased significantly in the normal group (p<0.001). TLR of the lesion group was significantly increased (p<0.001) in early delayed images compared to early scan and TLR significantly decreased in the normal group (p<0.001). The AUC of the ROC curve showed the highest SUVmax change rate (0.99). Conclusion: Early delayed scanning could distinguish between liver lesions and heterogenous physiological accumulation in colon cancer patients.

Purpose: The purpose of this research is to clarify the effects of low monitor unit (MU) on multileaf collimator (MLC) position accuracy and dose distribution in intensity modulated radiotherapy (IMRT) using respiratory gated. Method: In the phantom experiment, irradiation without respiratory gated and respiratory gated with low MU (3, 5, and 7 MU) were performed, and positional accuracy and dose distribution of MLC were analyzed. MLC positional accuracy was calculated from the log-files and the MLC position error, gap size error, MLC leaf speed were calculated and compared with the planned value. Gamma analysis of the dose distribution obtained from the irradiated films and the dose distribution of the treatment plans were carried out. Results: Without respiratory gated and respiratory gated, the frequency of gap size error that did not exceed 0.2 mm were more than 93% under all conditions. MLC position error increased with increasing MLC leaf speed. The determination coefficient of respiratory gated irradiation was lower by about 20% compared with that without respiratory gated, and variation from the approximate straight line occurs. The output difference due to low MU irradiation during respiratory gated was within 1% of the planned value. Although, the pass rate of gamma analysis differed in tumor size, the dose distribution well conformity at 96% or more for both without respiratory gated and respiratory gated. However, in the comparison of the profile in the MLC movement direction, respiratory gated irradiation at 3 MU showed a difference of about 9% at the edge of the irradiated field and about 6% at the point where the dose rapidly changed. Conclusion: It was shown that MLC position accuracy due to stop and go of MLC leaf can be secured even with low MU irradiation of about 3 MU. However, attention should be paid to the dose of risk organs adjacent to the tumor margin.

Background: Assessment of left ventricular (LV) diastolic function is important because it is possible to detect early sign of myocardial ischemia by this assessment. The purpose of this study was to compare between electrocardiogram (ECG) -gated myocardial perfusion single photon emission computed tomography (G-SPECT) and ultrasound echocardiography in assessment of LV diastolic function in the small heart (SH). Methods: The study population consisted of 144 patients who underwent both G-SPECT and ultrasound echocardiography. Peak filling rate (PFR), one-third mean filling rate (1/3 MFR) and the ratio of time to PFR to the RR interval (TPFR/RR) were calculated by quantitative gated SPECT (QGS) and heart risk view-F (HRV-F). Peak early mitral annular velocity (e′) was used as the reference standard of LV diastolic function. Results: There were 33 patients with end-systolic volume (ESV) of ≤10 ml (SH10), 51 patients with ESV of 11–20 ml (SH 20) and 60 patients with ESV of >20 ml (normal-sized heart: NH). In SH10, PFR calculated by QGS was not correlated with e′. However, that by HRV-F was significantly correlated with e′ (r=0.47, p=0.006). On the other hand, 1/3 MFR and TPFR/RR calculated by QGS and HRV-F were not correlated with e′ in SH10 and SH20. PFR, 1/3 MFR and TPFR/RR calculated by QGS and HRV-F were correlated with e′ in NH.

As the use of filmless examination images, using various systems, has increased, and became common to perform KAKUTEI and save the images. In particular, the use of quality assurance system for images (Kenzo system) has increased to ensure the efficient performance of confirmed image. However, there has been no report showing what kind of function should be used or how to write the specifications of such a function in introducing the Kenzo system. Therefore, this study conducted a survey to the in-charge medical staff of medical institutions to provide “information included in the specifications when introducing medical systems”. As a result, it is possible, through analyzing and clarifying the necessary functions of the Kenzo system, to apply it in medical institutions with various scales and workflows. The results indicate the person in charge was looking for functions, such as “coordination of information and image processing, securing the consistency of the information, and clarifying responsibility using the records of confirmed persons”. We showed examples of how to describe these in the specifications.