Exploration of tumor size measurement methods in preoperative breast cancer assessment using whole-body silicon photomultiplier PET: feasibility and first results.

PURPOSE: Whole-body silicon photomultiplier positron emission tomography (WB SiPM PET) could be used to diagnose breast cancer spread before lumpectomy. We aimed to investigate the method of measuring the tumor size by WB SiPM PET as a basis for diagnosing breast cancer spread in the breast. MATERIALS AND METHODS: We retrospectively reviewed 35 breast cancer lesions in 32 patients who underwent WB SiPM PET/CT in the prone position as preoperative breast cancer examinations from September 2020 to March 2022. In all cases, a 20-mm spherical VOI was placed in the normal mammary gland to measure the mean standardised uptake value (SUVmean) and the standard deviation (SD) of 18F-fluorodeoxyglucose (FDG) uptake. We prepared four types of candidates (SUVmean + 2 SD, SUVmean + 3 SD, 1.5 SUVmean + 2 SD, 1.5 SUVmean + 3 SD) for thresholds for delineating tumor contours on PET images. On the semiautomatic viewer soft, the maximum tumor sizes were measured at each of the four thresholds and compared with the pathological tumor sizes, including the extensive intraductal component (EIC). RESULTS: The lesion detection sensitivity was 97% for WB SiPM PET. PET detected 34 lesions, excluding 4-mm ductal carcinomas in situ (DCIS). PET measurements at the '1.5 SUVmean + 2 SD' threshold demonstrated values closest to the pathological tumor sizes, including EIC. Moreover, '1.5 SUVmean + 2 SD' had the highest concordance (63%). CONCLUSIONS: The study demonstrated that among various PET thresholds, the '1.5 SUVmean + 2 SD' threshold exhibited the best performance. However, even with this threshold, the concordance rate was limited to only 63%.

Administered dosage and effective dose estimated from 81Rb-rubidium hydroxide for lung ventilation scintigraphy using 81mKr noble gas.

The aim of this study was to estimate the administered dosage of 81mKr noble gas as calculated by the radioactivity of 81Rb-rubidium hydroxide (81RbOH). The administered dosage was regarded as the total amount of 81mKr noble gas. The radioactivity of 81mKr was calculated using the radioactivity of 81RbOH at the examination, the beginning of inhalation, the inhalation duration and the attenuation volume from the generator to the patient for 81mKr noble gas. In addition, we created an Internet survey and asked National University Hospital in Japan to respond to questions regarding the parameters of concern. Survey responses were provided by 38 hospitals (response rate was 90.5%). Twenty-seven hospitals (64.3%) examined lung ventilation scintigraphy using 81mKr noble gas. The mean administered dosage and the effective dose of lung ventilation scintigraphy using 81mKr noble gas were 35.8 ± 22.1 GBq and 0.97 ± 0.60 mSv, respectively.

Effect of resolution recovery using graph plots on regional cerebral blood flow in healthy volunteers.

PURPOSE: We evaluated the effect of resolution recovery (RR) using graph plots on regional cerebral blood flow (rCBF) in brain perfusion single-photon emission computed tomography (SPECT) images derived from healthy volunteers and patients diagnosed with probable Alzheimer's disease. METHOD: We acquired brain perfusion SPECT images with scatter correction (SC), computed tomography-based attenuation correction (CTAC), and RR from a three-dimensional brain phantom and from healthy volunteers. We then compared contrast-to-noise ratio, count density ratios, increase maps, and rCBF using statistical parametric mapping 8. RESULTS: Regional brain counts were significantly increased from 20-24% with SC, CTAC, and RR compared with SC and CTAC. Mean CBF in healthy volunteers was 42.5 ± 5.4 mL/100 g/min. Average rCBF determined using SC, CTAC and RR increased 7.5, 2.0, and 3.7% at the thalamus, posterior cingulate, and whole brain, respectively, compared with SC and CTAC. CONCLUSION: Resolution recovery caused variations in normal rCBF because counts increased in cerebral regions.