Effects of the Obesity Type on FDG-PET Image Quality.

PURPOSE: The aim of our study is to evaluate whether an 18F-FDG PET/CT image quality is influenced by the obesity type visceral fat or subcutaneous fat. METHODS: We chose continuously 68 patients with obesity (35 subcutaneous fats and 33 visceral fats) who underwent an 18F-FDG PET/CT scan at our clinic from January 3, 2015 to June 30, 2015. And then, we calculated the noise equivalent count (NECdensity), the signal to noise ratio of the liver (SNRliver), and the ratio of random coincidence counts to total prompt (random/prompt countrate) on each PET/CT image. RESULTS: We observed that NECdensity was decreased as the body mass index (BMI) and the abdominal circumference increased regardless of the obesity type. When the BMI was on the same degree between two types, however, NECdensity of a visceral fat was 21.6% that is inferior to that of subcutaneous fat on the average. A similar relation was satisfied also in abdominal circumference. Conversely, random/prompt countrate of a visceral fat was more than that of subcutaneous fat when the abdominal circumference and BMI were on the same degree, respectively. Overall, random/prompt countrate tended to increase as BMI and the abdominal circumference increased. With respect to SNRliver, the value of a visceral fat was inferior to that of subcutaneous fat unconditionally. CONCLUSION: When the BMI and abdominal circumference are on the same degree, respectively, the 18F-FDG PET/CT image quality of visceral fat is inferior to that of subcutaneous fat. The measure is to extend the collection time by about 20% in the pelvic area from the abdomen of visceral fat type obesity.

Effects of Non-radioactive Material around Radioactive Material on PET Image Quality.

PURPOSE: Subcutaneous fat is a non-radioactive material surrounding the radioactive material. We developed a phantom, and examined the effect of subcutaneous fat on PET image quality. METHODS: We created a cylindrical nonradioactive mimic of subcutaneous fat, placed it around a cylindrical phantom in up to three layers with each layer having a thickness of 20 mm to reproduce the obesity caused by subcutaneous fat. In the cylindrical phantom, hot spheres and cold spheres were arranged. The radioactivity concentration ratio between the hot spheres and B.G. was 4:1. The radioactivity concentration of B.G. was changed as follows: 1.33, 2.65, 4.00, and 5.30 kBq/mL. 3D-PET images were collected during 10 minutes. RESULTS: When the thickness of the mimicked subcutaneous fat increased from 0 mm to 60 mm, noise equivalent count decreased by 58.9‒60.9% at each radioactivity concentration. On the other hand, the percentage of background variability increased 2.2‒5.2 times. Mimic subcutaneous fat did not decrease the percentage contrast of the hot spheres, and did not affect the cold spheres. CONCLUSION: Subcutaneous fat decreases the noise equivalent count and increases the percentage of background variability, which degrades PET image quality.

Predictive Value of 18F-Sodium Fluoride Positron Emission Tomography in Detecting High-Risk Coronary Artery Disease in Combination With Computed Tomography.

Background Application of 18F-sodium fluoride (18F-NaF) positron emission tomography ( PET ) to coronary artery disease has attracted interest. We investigated the utility of 18F-NaF uptake for predicting coronary events and evaluated the combined use of coronary computed tomography (CT) angiography ( CCTA ) and 18F-NaF PET /CT in coronary artery disease risk assessment. Methods and Results This study included patients with ≥1 coronary atherosclerotic lesion detected on CCTA who underwent 18F-NaF PET / CT . High-risk plaque on CCTA was defined as plaque with low density (<30 Hounsfield units) and high remodeling index (>1.1). Focal 18F-NaF uptake in each lesion was quantified using the maximum tissue:background ratio ( TBR max), and maximum TBR max per patient (M- TBR max) was determined. Thirty-two patients having a total of 112 analyzed lesions were followed for 2 years after 18F-NaF PET / CT scan, and 11 experienced coronary events (acute coronary syndrome and/or late coronary revascularization [after 3 months]). Patients with coronary events had higher M- TBR max than those without (1.39±0.18 versus 1.19±0.17, respectively; P=0.0034). The optimal M- TBR max cutoff to predict coronary events was 1.28 (area under curve: 0.79). Patients with M- TBR max ≥1.28 had a higher risk of earlier coronary events than those with lower M- TBR max ( P=0.0062 by log-rank test). In patient-based (n=41) and lesion-based (n=143) analyses of CCTA findings that predicted higher coronary 18F-NaF uptake, the presence of high-risk plaque was a significant predictor of both M- TBR max ≥1.28 and TBR max ≥1.28. Conclusions 18F-NaF PET / CT has the potential to detect high-risk coronary artery disease and individual coronary lesions and to predict future coronary events when combined with CCTA . Clinical Trial Registration URL : www.umin.ac.jp . Unique identifier: UMIN 000013735.

18F-sodium fluoride positron emission tomography for molecular imaging of coronary atherosclerosis based on computed tomography analysis.

BACKGROUND AND AIMS: We aimed at evaluating the relation of 18F-sodium fluoride (18F-NaF) uptake on positron emission tomography (PET) to coronary atherosclerosis detected and assessed by computed tomography (CT). METHODS: Thirty-two patients with one or more coronary atherosclerotic lesions detected on cardiac CT underwent 18F-NaF PET/CT. Each coronary atherosclerotic lesion was evaluated on CT angiography for plaque types (calcified plaque [CP], non-calcified plaque [NCP], partially calcified plaque [PCP]), and the presence of CT-based high-risk features (minimum CT density <30 Hounsfield units and vascular remodeling index >1.1). Focal 18F-NaF uptake of each lesion was quantified using maximum tissue-to-background ratio (TBRmax). RESULTS: A total of 111 lesions were studied. In a patient-based analysis, logarithmically transformed coronary calcium score correlated positively with maximum TBRmax per patient, and 15 patients with myocardial infarction or unstable angina history showed a higher maximum TBRmax per patient than those without (1.36 ± 0.15 versus 1.15 ± 0.15, p = 0.0006). In a lesion-based analysis, PCP showed a higher TBRmax than CP and NCP (1.17 ± 0.19 versus 1.00 ± 0.24 and 0.92 ± 0.18, respectively, p < 0.0001), and the lesions with high-risk features had a higher TBRmax than those without (1.20 ± 0.21 versus 1.02 ± 0.20, p = 0.0011). CONCLUSIONS: Coronary arterial 18F-NaF uptake is related to total plaque burden, coronary event history, and specific features of coronary atherosclerosis based on CT analysis. 18F-NaF PET/CT, in combination with cardiac CT, may provide a new molecular imaging approach to identify high-risk patients and coronary atherosclerotic lesions.

Data on analysis of coronary atherosclerosis on computed tomography and 18F-sodium fluoride positron emission tomography.

This article contains the data showing illustrative examples of plaque classification on coronary computed tomography angiography (CCTA) and measurement of 18F-sodium fluoride (18F-NaF) uptake in coronary atherosclerotic lesions on positron emission tomography (PET). We divided the lesions into one of three plaque types on CCTA (calcified plaque, non-calcified plaque, partially calcified plaque). Focal 18F-NaF uptake of each lesion was quantified using maximum tissue-to-background ratio. This article also provides a representative case with a non-calcified coronary plaque detected on CCTA and identified on 18F-NaF PET/non-contrast computed tomography based on a location of a vessel branch as a landmark. These complement the data reported by Kitagawa et al. (2017) [1].

Apparent diffusion coefficient values in peripheral and transition zones of the prostate: comparison between normal and malignant prostatic tissues and correlation with histologic grade.

PURPOSE: To investigate the utility of apparent diffusion coefficient (ADC) values for discriminating tumor in patients with prostate cancer from normal prostatic tissues in healthy adult men, and to identify correlations between ADC and histologic grade of prostate cancer. MATERIALS AND METHODS: A total of 125 healthy male volunteers (mean age, 60 years; range, 50-86 years) and 90 prostate cancer patients (mean age, 71 years; range, 51-88 years) underwent diffusion-weighted imaging (DWI) of the prostate with a single-shot echo-planar imaging sequence using b-factors of 0 and 800 sec/mm2. ADC was measured from two locations in the peripheral zone (PZ) and two locations in the central gland (CG) in normal subjects, and tumor locations of PZ or transition zone (TZ) in patients with prostate cancer. RESULTS: Mean ADC values of tumor regions in both PZ (1.02+/-0.25x10(-3) mm2/sec) and TZ (0.94+/-0.21x10(-3) mm2/sec) were significantly lower than those in the corresponding normal regions (1.80+/-0.27x10(-3) mm2/sec and 1.34+/-0.14x10(-3) mm2/sec, respectively) (P<0.0001 each). Furthermore, a significant negative correlation was identified between ADC in PZ cancer and tumor Gleason score (rho=-0.497, P<0.0001). CONCLUSION: ADC values appear to provide acceptable diagnostic accuracy in both PZ and TZ.

Age-related and zonal anatomical changes of apparent diffusion coefficient values in normal human prostatic tissues.

PURPOSE: To identify age-related changes and differences in the diffusion of water molecules within the prostate, through diffusion-weighted imaging (DWI) of the prostate gland in healthy adult Japanese men. MATERIALS AND METHODS: A total of 114 healthy male volunteers (mean age, 55 years; range, 24-81 years) underwent DWI of the prostate with a single-shot echo-planar imaging (EPI) sequence using b-factors of 0 and 1000 seconds/mm(2). Apparent diffusion coefficient (ADC) values of six locations in the peripheral zone (PZ) and two locations in the central gland (CG) were measured and correlations between region and age were examined. RESULTS: ADC values measured within both PZ and CG regions of the prostate showed a uniform distribution, and no significant differences were found between evaluated regions. However, mean ADC values were 1.64 +/- 0.27 x 10(-3) mm(2)/second for PZ and 1.26 +/- 0.12 x 10(-3) mm(2)/second for CG, representing a significant difference. In addition, significant positive correlations were identified between ADC values for both PZ and CG regions and subject age (r = 0.526, P < 0.0001; r = 0.190, P = 0.0431, respectively). CONCLUSION: ADC values within both PZ and CG regions of the prostate increase with age, and this must be taken into consideration when using DWI in the diagnosis of prostate cancer.