Objective: This study aimed to establish a methodology for obtaining visually equivalent image quality regardless of patient size by controlling the acquisition time of positron emission tomography (PET) studies. Methods: In Part 1, we determined the physical image quality index with the highest correlation with visual assessment in 30 patients. In Part 2, 100 patients were scanned to identify the patient-dependent parameters that were most correlated with the physical image quality index. These parameters were calculated from the combination of the administered activity of ¹⁸F-FDG and weight. We drew an approximate curve from these parameters and prepared a scatter plot of the physical image quality index. In Part 3, we checked whether the image quality was constant by controlling the acquisition time in 189 patients. The approximation formula we obtained under (2) was used to control the acquisition time. The physical image quality index was a constant value, and the patient-dependent parameter was calculated from the patient’s physique. Results: The physical image quality index with the highest correlation with visual evaluation was the noise equivalent count weight (NEC_weight) (correlation coefficient: 0.90). The patient-dependent index most correlated with NEC_weight was activity/weight³ (A/W³) (coefficient of determination: 0.978). The verification of the acquisition time to obtain a certain image quality showed an average of 0.60 ± 0.034 Mcounts/m∙kg, and a similar image quality was obtained independent of the individual physiques. Conclusions: Calculating NEC_weight and A/W³ enable the determination of the appropriate acquisition time for stable image quality before the PET study.

Practical image retrieval systems must fully use image databases. We investigated the accuracy of our content-based computer tomography (CT) image retrieval system (CB-CTIRS) for classifying lesion patterns and retrieving similar cases in patients with diffuse lung diseases. The study included 503 individuals, with 328 having diffuse lung disease and 175 having normal chest CT scans. Among the former, we randomly selected ten scans that revealed one of five specific patterns [consolidation, ground-glass opacity (GGO), emphysema, honeycombing, or micronodules: two cases each]. Two radiologists separated the squares into six categories (five abnormal patterns and one normal pattern) to create a reference standard. Subsequently, each square was entered into the CB-CTIRS, and the F-score used to classify squares was determined. Next, we selected 15 cases (three per pattern) among the 503 cases, which served as the query cases. Three other radiologists graded the similarity between the retrieved and query cases using a 5-point grading system, where grade 5 = similar in both the opacity pattern and distribution and 1 = different therein. The F-score was 0.71 for consolidation, 0.63 for GGO, 0.74 for emphysema, 0.61 for honeycombing, 0.15 for micronodules, and 0.67 for normal lung. All three radiologists assigned grade 4 or 5 to 67.7% of retrieved cases with consolidation, emphysema, or honeycombing, and grade 2 or 3 to 67.7% of the retrieved cases with GGO or micronodules. The retrieval accuracy of CB-CTIRS is satisfactory for consolidation, emphysema, and honeycombing but not for GGO or micronodules.

Identifying the electrical properties of cancer relies on the understanding of the electric potential (EP) of cancer tissues. This study aimed to investigate the EP properties in 49 pancreatic head cancer tissues using a digital multimetre. The anode was placed at the central side of the tumour, and the electric potential differences (EPDs) between cancerous and cancerous, cancerous and noncancerous, and noncancerous and noncancerous lesions at approximately 1-cm intervals following resection were evaluated. Pathological evaluation identified 30 of these samples as pancreatic invasive ductal carcinoma (PIDC, 10 without preoperative chemotherapy and 20 after chemotherapy), seven other pancreatic cancers, three tumours of Vater’s ampulla (VA), and eight extrahepatic cholangiocarcinoma (EHCC) samples. We also evaluated the differences in pH for cancerous and noncancerous lesions in nine PIDC samples. Our data suggest that the EP of pancreatic cancerous tissues is higher than that of noncancerous tissues, especially in PIDCs. We also noted that EPD was the highest when comparing cancerous and noncancerous lesions. Additionally, PIDC tissues presented with low pH; the pH difference between cancerous and noncancerous sites was significantly correlated with EPD (P = 0.011). These EPDs were also correlated with tumour size in PIDCs and inversely correlated with their response to chemotherapy. The EP values for both the cancerous and noncancerous sites in both the VA tumours and EHCC samples were not significantly different, whereas EPD in PIDC correlated with tumour extension and viable tumour content, suggesting that EPD might be useful for evaluating the viability and effectiveness of neoadjuvant chemotherapy.

Malignant hyperthermia (MH) is an anaesthetic complication that causes an abnormal hypermetabolic state. RYR1 encoding ryanodine receptors of the sarcoplasmic reticulum and CACNA1S encoding α subunits of dihydropyridine receptors are known to be associated with MH pathogenicity. We performed genetic screening using next-generation sequencing to evaluate the prevalence of genes associated with MH pathogenicity and clinical symptoms. This was a retrospective cohort study wherein next-generation sequencing data of 77 families diagnosed with MH predisposition by calcium-induced calcium release (CICR) tests from 1995 to 2019 was used to search for RYR1 and CACNA1S variants. Furthermore, the clinical symptoms and predisposition tests in participants with RYR1 and CACNA1S variants were compared. In the 77 families, 44.2%, 7.8%, and 48.1% individuals had RYR1, CACNA1S, and neither RYR1 nor CACNA1S variants, respectively. Clinically significant differences were found in the maximum body temperature, maximum elevated body temperature for 15 min, creatinine kinase level, and CICR rate between the RYR1 and CACNA1S groups. The prevalence of pathogenic CACNA1S variants appears to be prominent in Japan. The severity of clinical symptoms and the CICR rate were greater in individuals with RYR1 variants than in those with CACNA1S variants, likely due to more direct regulation of calcium levels by ryanodine receptors than by dihydropyridine receptors. Genetic analysis of MH in future studies may help identify other genes associated with MH, which will further clarify the relationship between genotypes and MH symptoms and contribute to safer anaesthesia practice.