Bidirectional Association Among the Type of Atrial Fibrillation, Sleep-Disordered Breathing Severity, Heart Failure Progression, and Left Atrial Enlargement, in Patients with Atrial Fibrillation.

This study aimed to clarify (1) the association among the atrial fibrillation (AF) type, sleep-disordered breathing (SDB), heart failure (HF), and left atrial (LA) enlargement, (2) the independent predictors of LA enlargement, and (3) the effects of ablation on those conditions in patients with AF. The study's endpoint was LA enlargement (LA volume index [LAVI] ≥ 78 mL/m2).Of 423 patients with nonvalvular AF, 236 were enrolled. We evaluated the role of the clinical parameters such as the AF type, SDB severity, and HF in LA enlargement. Among them, 141 patients exhibiting a 3% oxygen desaturation index (ODI) of ≥ 10 events/hour underwent polysomnography to evaluate the SDB severity measured by the apnea-hypopnea index (AHI). The LA enlargement and HF were characterized by the LA diameter/LAVI, an increase in the B-type natriuretic peptide level, and a lower left ventricular ejection fraction.This study showed that non-paroxysmal AF (NPAF) rather than paroxysmal AF (PAF), the SDB severity, LA enlargement, and HF progression had bidirectional associations and exacerbated each other, which generated a vicious cycle that contributed to the LA enlargement. NPAF (OR = 4.55, P < 0.001), an AHI of ≥ 25.10 events/hour (OR = 1.55, P = 0.003), and a 3% ODI of ≥ 15.43 events/hour (OR = 1.52, P = 0.003) were independent predictors of an acceleration of the LA enlargement. AF ablation improved the HF and LA enlargement.To break this vicious cycle, AF ablation may be the basis for suppressing the LA enlargement and HF progression subsequently eliminating the substrates for AF and SDB in patients with AF.

Role of Sleep-Disordered Breathing and Epicardial Connections in the Recurrence of Atrial Fibrillation.

The presence of epicardial connections (ECs) between the pulmonary veins (PVs) and atrium may contribute to atrial fibrillation (AF) recurrence. This study aimed to determine the impact of sleep-disordered breathing (SDB) on the presence of ECs and the interplay between SDB and ECs on AF recurrence.We retrospectively reviewed 400 consecutive non-valvular AF patients. Among them, 235 patients exhibiting a 3% oxygen desaturation index (ODI) of ≥ 10 events/hour underwent polysomnography to evaluate the SDB severity, measured by the apnea-hypopnea index (AHI). To facilitate the ablation of AF and ECs, a high-density mapping catheter (HDMC) was employed. AF recurrence was evaluated over a 12-month period post-AF ablation.The key findings included: 1) 63% of AF patients with ECs had SDB with an AHI ≥ 20 events/hour. 2) Despite achieving complete PV isolations and precise EC ablation using an HDMC, SDB presence was associated with an increased AF recurrence. 3) Continuous positive airway pressure therapy for SDB improved AF recurrence among the AF patients with both ECs and SDB (57% versus 73%; P = 0.016). 4) AHI (odds ratio [OR] = 1.91, ≥ 28.4 events/hour) and left atrial volume (LAV) (OR = 1.42, ≥ 128.3 mL) were independent predictors of the presence of ECs, and AHI (OR = 1.44, ≥ 27.8 events/hour) was an independent predictor of the presence of AF recurrence.It is essential for physicians to recognise the potential complexity of ECs and SDB in AF patients. Thus, screening and treating SDB in AF patients presenting with ECs might play a pivotal role in suppressing AF recurrence.

Laser balloon ablation of atrial fibrillation in a patient with a large common inferior trunk: a case report.

Background: A balloon-based visually guided laser balloon (LB) ablation (LBA) is as effective and safe as radiofrequency ablation and cryoballoon ablation in curing patients with atrial fibrillation (AF). The third-generation LB is so compliant that it can be inflated to any pressure and size change of up to 41 mm with its maximal expansion, which enables maximum balloon/tissue contact regardless of the size or shape of each pulmonary vein (PV) ostium. A large common inferior trunk (CIT) with a structured, completely independent common ostium of both the right and the left inferior PVs completely conjoined prior to the junction with the left atrium is an extremely rare anatomical variant and an important triggering focus in paroxysmal AF. Case summary: We present a case of an LBA of AF in a patient with a large CIT of 34 mm in diameter. The laser energy was individually deployed to the right-sided and left-sided antra of the large CIT with the LB positioned at the ostium of the CIT's right and left branches. The complete electrical isolation of the three PVs was achieved. The patient remained stable without any symptoms or AF recurrence 1 year post ablation. Discussion: The LBA, which is individually deployed to the right-sided and left-sided antra of the large CIT with the third-generation LB positioned at the ostium of the right and left branches of the CIT without laser energy deployment to the posterior wall of the CIT, may be one of the effective strategies for patients with large CITs.

Evaluation of data-driven respiratory gating for subcentimeter lesions using digital PET/CT system and three-axis motion phantom.

Introduction.The application of data-driven respiratory gating (DDG) for subcentimeter lesions with respiratory movement remains poorly understood. Hence, this study aimed to clarify DDG application for subcentimeter lesions and the ability of digital Positron emission tomography/computed tomography (PET/CT) system combined with DDG to detect these lesions under three-axis respiration.Methods.Discovery MI PET/CT system and National Electrical Manufacturers Association (NEMA) body phantom with Micro Hollow Sphere (4, 5, 6, 8, 10, and 13 mm) were used. The NEMA phantom was filled with18F-FDG solutions of 42.4 and 5.3 kBq/ml for each hot sphere and background region. The 3.6 s cycles of three-axis respiratory motion were reproduced using the motion platform UniTraQ. The PET data acquisition was performed in stationary and respiratory-moving states. The data were reconstructed in three PET groups: stationary (NM-PET), no gating with respiratory movement (NG-PET), and DDG gating with respiratory movement (DDG-PET) groups. For image quality, percent contrast (QH); maximum, peak, and mean standardized uptake value (SUV); background region; and detectability index (DI) were evaluated in each PET group. Visual assessment was also conducted.Results.The groups with respiratory movement had deteriorated QHand SUVs compared with NM-PET. Compared with NG-PET, DDG-PET has significantly improved QHand SUVs in spheres above 6 mm. The background region showed no significant difference between groups. The SUVmax, SUVpeak, and QHvalues of 8 mm sphere were highest in NM-PET, followed by DDG-PET and NG-PET. In visual assessment, the spheres above 6 mm were detected in all PET groups. DDG application did not detect new lesions, but it increased DI and visual score.Conclusions. The application of principal component analysis (PCA)-based DDG algorithm improves both image quality and quantitative SUVs in subcentimeter lesions measuring above 6 mm. Although DDG application cannot detect new subcentimeter lesions, it increases the visual indices.

Epicardial Connections After a Conventional Pulmonary Vein Antrum Isolation in Patients With Atrial Fibrillation.

BACKGROUND: The existence of epicardial connection(s) (ECs) between the pulmonary veins (PVs) and atrium may hinder establishing a complete PV antrum isolation (AI) (PVAI) in patients with atrial fibrillation (AF). Thus, the purpose of this study was to determine the prevalence and location of ECs inside the conventional PVAI lines.Methods and Results: Three-hundred consecutive patients with non-valvular AF were evaluated. This study revealed that: (1) the prevalence of patients with ECs and the number of ECs per patient between the PVs and atrium became significantly greater, respectively, in accordance with the progression of paroxysmal to long-lasting AF and left atrial enlargement; (2) some ECs were located at sites far distal to the PVAI lines; (3) 25% of ECs could be detected only by high-density mapping catheters, but not by conventional circular mapping catheters; (4) a B-type natriuretic peptide (BNP) level of 176.6pg/mL and left atrial volume (LAV) of 129.0 mL may be important predictors of the presence of ECs; and (5) the rate of conduction of ECs from the right PVs was dominantly to the atrium and His-bundle, and that from the left PVs to the coronary sinus was most dominant. CONCLUSIONS: The PVAI may not be completed by using only a conventional PVAI method, and additional EC ablation inside the PVAI lines detected using high-density mapping may be able to achieve a more complete PVAI.

Impact of patient body habitus on image quality and quantitative value in bone SPECT/CT.

OBJECTIVE: The first edition of guidelines for standardization of bone single photon emission computed tomography (SPECT) imaging was published in 2017, and the optimization and standardization are widely promoted. To the purpose, clarification of the factors related to image quality and quantitative values and their influence are required. The present study aimed to clarify and optimize the influence of patient body habitus on image quality and quantitative values in bone SPECT/CT. METHODS: National Electrical Manufacturers Association body phantom (S-size) and custom-made large body phantoms (M-size and L-size) that simulate the abdomens of Japanese patients weighing 60, 80, and 100 kg, were used. Each phantom was filled with 99mTc-solutions of 108 and 18 kBq/mL for the hot spheres and background, respectively. Dynamic SPECT acquisition was performed for 6000 s (150 s /rotation × 40 rotation). The data were divided into six projection data and reconstructed each acquisition time (150, 300, 450, 600, 750, 900 s, and single projection 6000 s). Image quality was evaluated for contrast (QH, 17 mm), background noise (NB, 17 mm), contrast-to-noise ratio (CNR), maximum standardized uptake value (SUVmax, 17 mm), and visual assessment for a 17 mm hot sphere. RESULTS: Image quality in the 300 s acquisition showed that values of QH, 17 mm, CNR, and SUVmax, 17 mm decreased (-16.7%, -11.8%, and -11.3%) for M-size and (-28.2%, -30.1%, and -21.7%) for L-size compared with S-size, respectively. No significant difference was observed in NB, 17 mm values. M-size and L-size required 1.2 and 2.3 times longer acquisition, to achieve same CNR as S-size. In visual assessment, 17 mm hot sphere could not be detected only in the L-size. When the Japanese bone SPECT guidelines criteria were applied in 600 s, the sphere could be detected between all phantoms. CONCLUSIONS: Patient body habitus significantly affects image quality and decreases the quantitative value in bone SPECT/CT. For the optimization, extend acquisition time according to the patient body habitus is effective for image quality. And for the standardization, it is important to achieve imaging conditions that meet the Japanese bone SPECT guidelines criteria to ensure adequate detectability.

Angiotensin II promotes primary tumor growth and metastasis formation of murine TNBC 4T1 cells through the fibroblasts around cancer cells.

Angiotensin II (Ang II) reportedly facilitates primary tumor growth and distal hematogenous metastasis formation in various murine intravenous metastasis models. However, it is unclear whether Ang II accelerates the initial processes of metastasis formation that begins in primary tumors surrounded by tumor microenvironment. We examined the effects of Ang II on primary tumors and lung metastasis lesions using a murine spontaneous metastasis model, in which triple negative breast cancer 4T1 cells constitutively expressing luciferase (4T1-Luc cells) were injected into the mammary fat pad of BALB/c mice. Subcutaneous injection of Ang II significantly accelerated primary tumor growth and lung metastasis formation. Ang II increased the protein expression levels of c-Myc, cyclin D1, fibronectin, vimentin, αSMA and Snail, and the treatment with the Ang II type 1 receptor blocker valsartan significantly suppressed the Ang II-induced increases of fibronectin and vimentin. Valsartan also significantly reduced lung metastatic lesions. However, Ang II did not have significant effects on 4T1-Luc cells including the proliferation, migration, invasion, or the expressions of proteins related to cell proliferation and epithelial-to-mesenchymal transition. In contrast, when 4T1-Luc cells were co-cultured with dermal fibroblasts, Ang II significantly accelerated cell migration and increased the expressions of fibronectin, vimentin, αSMA and Snail in 4T1-Luc cells. And moreover, Ang II significantly increased the mRNA expression of IL-6 in fibroblasts co-cultured with 4T1-Luc cells. These results suggested that Ang II accelerates surrounding fibroblasts by soluble factors such as IL-6 to promote epithelial-to-mesenchymal transition, which result in the initiation of cancer metastasis.

[Administration Accuracy of Automated Infusion Device for PET Using Improved Disposable Kit].

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.

Evaluation of bone metastatic burden by bone SPECT/CT in metastatic prostate cancer patients: defining threshold value for total bone uptake and assessment in radium-223 treated patients.

OBJECTIVES: To establish a new three-dimensional quantitative evaluation method for bone metastasis, we applied bone single photon emission tomography with computed tomography (SPECT/CT). The total bone uptake (TBU), which measures active bone metastatic burden, was calculated as the sum of [mean uptake obtained as standardized uptake value (SUV) above a cut-off level] × (the volume of the lesion) in the trunk using bone SPECT/CT. We studied the threshold value and utility of TBU in prostate cancer patients treated with radium-223 (Ra-223) therapy. METHODS: To establish the threshold value of TBU, we compared bone metastatic and non-metastatic regions in 61 prostate cancer patients with bone metastasis and 69 without. Five fixed sites in each patient were selected as evaluation points and divided into bone metastatic and non-metastatic sites. Sensitivity and specificity analysis was applied to establish the threshold level. Using the obtained threshold value, we then calculated the TBU in nine prostate cancer patients who received Ra-223 therapy, and compared the results with the bone scan index (BSI) by BONENAVI® and visual evaluation of bone scintigraphy. RESULTS: Uptake was significantly lower in non-metastatic sites in patients with bone metastasis than in patients without metastasis. Sensitivity and specificity analysis revealed SUV = 7.0 as the threshold level. There was a discrepancy between TBU and BSI change in two of the nine patients, in whom TBU change correlated with visual judgement, but BSI change did not. In two patients, BSI was nearly 0 throughout the course, but the TBU was positive and changed, although the change was not large. These results suggest that TBU may be more accurate and sensitive than BSI for quantitative evaluation of active bone metastatic burden. CONCLUSION: We established a threshold value (SUV > 7.0) for three-dimensional TBU for evaluating active bone metastatic burden in prostate cancer patients using bone SPECT/CT. Despite the small number of patients, we expect the change in TBU could be more accurate and sensitive than the change in BSI among patients who received Ra-223.

[A Comparison of Planar Sensitivity and Spatial Resolution among Different Collimators and Energy Windows on 223Ra Imaging].

OBJECTIVE: The present study aimed to reveal the influence of combination of different collimators and energy windows on the planar sensitivity and the spatial resolution during experimental 223Ra imaging, and to determine optimal imaging parameters. METHODS: A vial type source containing 223Ra solution (4.55 MBq / 5.6 ml) was placed in the air at 100 mm away from the collimator surface. Planar images were acquired with LEHR, LMEGP, ELEGP and MEGP collimators on two dual-head gamma cameras (Symbia intevo (Siemens) and Infinia 3 (GE)). We compared three energy window combinations: 1) single window at 82 keV, 2) double window at 82+154 keV, 3) triple window at 82+154+270 keV. The energy spectrum, the sensitivity and the spatial resolution, such as full-width at half-maximum (FWHM) and full-width at tenth-maximum (FWTM), of each collimator were assessed. RESULTS: Five energy spectra (at around 82, 154, 270, 351 and 405 keV) were essentially observed among four collimators. The sensitivity was high for LEHR collimator, then ELEGP and LMEGP collimator was 3-4 fold, which is greater than MEGP collimator. The 82 keV energy window of four collimators has best spatial resolution. Moreover, the spatial resolution of the 82 keV energy window with LMEGP and ELEGP collimator was almost equal to that of the triple window with MEGP collimator. CONCLUSIONS: Optimal imaging parameters were single energy window using LMEGP or ELEGP, and then triple energy window using MEGP collimator.

Calculation Accuracy of Gross Tumor Volume at the Diaphragm Boundary Evaluated Using Respiratory-gated PET/CT.

OBJECTIVE: The present study aimed to clarify gross tumor volume (GTV) contouring accuracy at the diaphragm boundary using respiratory-gated PET/CT. METHODS: The lung/diaphragm boundary was simulated using a phantom containing 18F solution (10.6 kBq/mL). Tumors were simulated using spheres (diameter, 11-38 mm) containing 18F and located at the positions of the lungs and liver. The tumor background ratios (TBR) were 2, 4, and 8. The phantom was moved from the superior to inferior direction with a 20-mm motion displacement at 3.6 s intervals. The recovery coefficient (RC), volume RC (VRC), and standardized uptake value (SUV) threshold were calculated using stationary, non-gated (3D), and gated (4D) PET/CT. RESULTS: In lung cancer simulation, RC and VRC in 3D PET images were, respectively, underestimated and overestimated in smaller tumors, whereas both improved in 4D PET images regardless of tumor size and TBR. The optimal SUV threshold was about 30% in 4D PET images. In liver cancer simulation, RC and VRC were, respectively, underestimated and overestimated in smaller tumors, and when the TBR was lower, but both improved in 4D PET images when tumors were >17 mm and the TBR was >4. The optimal SUV threshold tended to depend on the TBR. CONCLUSIONS: The contouring accuracy of GTV was improved by considering TBR and using an optimal SUV threshold acquired from 4D PET images.

Validation of Cross-calibration Schemes for Quantitative Bone SPECT/CT Using Different Sources under Various Geometric Conditions.

PURPOSE: Several cross-calibration schemes have been proposed to produce quantitative values in bone SPECT imaging. Differences in the radionuclide sources and geometric conditions can decrease the accuracy of cross-calibration factor (CCF). The present study aimed to validate the effects of calibration schemes using different sources under various geometric conditions. METHODS: Temporal variations as well as variations in acquisition counts and the shapes of 57Co standard and 99mTc point sources and a 99mTc disk source were determined. The effects of the geometric conditions of the source-to-camera distance (SCD) and lateral distance on the CCF were investigated by moving the camera or source away from the origin. The system planar sensitivity of NEMA incorporated into a Symbia Intevo SPECT/CT device (Siemens®) was defined as reference values. RESULTS: The temporal variation in CCF using the 57Co source was relatively stable within the range of 0.7% to 2.3%, whereas the 99mTc source ranged from 2.7% to 7.3%. In terms of source shape, the 57Co standard point source was the most stable. Both SCD and lateral distance decreased as a function of distance from the origin. Errors in the geometric condition were higher for the 57Co standard point source than the 99mTc disk source. CONCLUSIONS: Different calibration schemes influenced the reliability of quantitative values. The 57Co standard point source was stable over a long period, and this helped to maintain the quality of quantitative SPECT/CT imaging data. The CCF accuracy of the 99mTc source decreased depending on the preparative method. The method of calibration for quantitative SPECT should be immediately standardized to eliminate uncertainty.

Relationship among multifaceted factors including blood pressure at discharge and long-term clinical outcome in patients with cardiovascular diseases.

The relationship among blood pressure (BP) levels at discharge, other multifaceted factors assessed in cardiac rehabilitation programs, and prognosis for up to 2 years was examined in 154 consecutive cases (132 patients; 69 males; 79 ± 12 years, mean ± SD). A total of 72 composite events occurred (58 rehospitalizations from cardiovascular causes and 14 all-cause death events). The relationship between the systolic BP (SBP) at discharge and the long-term prognosis formed a J-shaped curve, with the event rate being lowest in patients with SBP of 115-125 mmHg. This relationship was still significant after adjustment of multifaceted factors assessed in cardiac rehabilitation programs.

Trends in blood pressure control and medication use during 20 years in a hypertension clinic in Japan.

Guidelines for the management of hypertension have recommended strict control of blood pressure to help prevent cardiovascular disease. The aim of the present study was to evaluate the current status of blood pressure control and trends over the past two decades. Four hundred patients treated for hypertension at Kyushu University Hospital were included in the present study. Blood pressure levels and prescribed antihypertensive drugs were examined in 2011. The average blood pressure was 129/74 mmHg, and the number of prescribed antihypertensive drugs was 2.2. Angiotensin II receptor antagonists, angiotensin-converting enzyme inhibitors, calcium channel blockers, diuretics, alpha-blockers, and beta-blockers were prescribed in 66%, 5%, 78%, 21%, 12%, and 27% of the cases, respectively. Systolic blood pressure was significantly higher, and diastolic blood pressure was significantly lower in patients aged 80 years or older compared with the younger patients (<80 and ≥80 years, 128/75 mmHg and 133/68 mmHg, respectively). The number of prescribed antihypertensive drugs was similar between the two groups. Sixty-five patients were continuously treated for 20 years. The average blood pressure of these patients significantly decreased from 142/87 mmHg in 1991 to 128/71 mmHg in 2011, accompanied with an increase in the number of antihypertensive drugs from 1.6 in 1991 to 2.7 in 2011. These findings suggest that the revised guidelines for the management of hypertension may have contributed to increased awareness and better management of blood pressure levels.

Evaluation of a computer-assisted diagnosis system, BONENAVI version 2, for bone scintigraphy in cancer patients in a routine clinical setting.

OBJECTIVE: To evaluate a computer-assisted diagnosis system, BONEVAVI version 2 for bone scintigraphy, this study examined the performance of the software in patients with and without skeletal metastasis. METHODS: Bone scans of various patients were analyzed by BONENAVI version 2. Patients with skeletal metastasis from prostate cancer, lung cancer, breast cancer, and other cancers were included in the study as true positive cases. Patients with normal bone scans, consecutive patients with several days of no skeletal metastasis (regardless of hot spots), and patients with abnormal bone scans but no skeletal metastasis were included as negative cases. Patient artificial neural network (ANN) values equal to or above 0.5 were regarded as positive, and those below 0.5 as negative. This study also analyzed cases according to primary cancer factors, osseous metastasis type, and bone tumor burden. RESULTS: The sensitivity of patient ANN values was 121/142 (85 %) for all cancers, 25/29 (86 %) for prostate cancer, 35/40 (88 %) for lung cancer, 37/45 (82 %) for breast cancer, and 24/28 (86 %) for other cancers. The specificity of ANN values was 40/49 (82 %) for normal bone scans, 99/122 (81 %) for consecutive patients with several days of no skeletal metastasis, and 44/81 (54 %) for patients with abnormal bone scans but no skeletal metastasis. Patients showing false negatives included: 10 patients with small lesions (6 of whom showed positive lesion ANN values), 4 patients with osteolytic lesions, 5 patients with intertrabecular osseous metastasis, and 1 patient with a metastatic lesion adjacent to the urinary bladder. The correlation between manually counted lesion numbers and Bone Scan Index was excellent for prostate cancer, and was good for lung cancer, breast cancer, and other cancers. CONCLUSION: BONENAVI version 2 is an effective computer-assisted diagnosis system for bone scanning, but the drawbacks of bone scanning remain unresolved.

[Improvement of quantitative accuracy using phase-based respiratory-gated PET/CT in phantom and clinical studies].

OBJECTIVE: The present study aimed at determining the quantitative accuracy of phase-based respiratory-gated PET/CT imaging using phantom and clinical studies. METHODS: The effects of target size, target-to-background ratio (TBR), and respiratory motion on PET images were estimated using a NEMA body phantom comprising six spheres (diameter 10-37mm) in a solution of F-18 of three different TBRs (4, 6, 8). The phantom was moved in a superior-inferior direction at motion displacements of 0, 10, 20 and 30 mm. Stationary images of the phantom as well as non-gated (3D) and gated (4D) images of the phantom while moving were reconstructed and the recovery coefficient (RC) of individual spheres was calculated from each image. We then determined the RC improvement rate to evaluate improvements conferred by 4D-PET/CT. We retrospectively analyzed data from 14 patients with lung cancer who were examined by 3D- and 4D-PET/CT. Each lesion on the 3D-PET/CT and each of the five phases of the 4D-PET/CT were analyzed. RESULTS: Larger motion displacement and TBR resulted in increased RC degradation for small spheres. The RC improvement rate showed that 4D acquisition improved the RC of spheres with larger motion displacement exceeding 13 mm in diameter. 4D-PET/CT alone can reduce the effects of motion blurring, but partial volume effects may still be the dominant source of quantitative inaccuracy for small lesions. The trends of phantom and clinical studies for evaluating the improvement rate were similar. CONCLUSIONS: 4D-PET/CT significantly improved the quantitative accuracy of PET images particularly when larger motion displacement exceeded 17mm in diameter such as in lung cancer.

Optimal radiation shielding for beta and bremsstrahlung radiation emitted by (89)Sr and (90)Y: validation by empirical approach and Monte Carlo simulations.

OBJECTIVE: High-energy beta emitters such as Strontium-89 ((89)Sr) and Yttrium-90 ((90)Y) are becoming increasingly popular nuclear therapy sources in Japan for treating cancer. Various characteristics of materials must be considered when designing radiation protection device for high-energy beta emitters. We empirically measured and simulated dose equivalents of beta and bremsstrahlung radiation arising from (89)Sr and (90)Y radiation shielded with various materials and determined optimal shielding materials against these sources. METHODS: The dose equivalents of (89)Sr and (90)Y determined experimentally using an ionization chamber survey meter were compared with those of Monte Carlo simulations. The relative dose equivalents of beta and bremsstrahlung radiation separately transmitted by changing the thickness of acrylic, aluminum, iron, lead and tungsten shielding materials were simulated. RESULTS: Dose equivalents were consistent between the empirical measurements and the simulation to within ±5%. Shielding ability was more effective in the order of tungsten, lead, iron, aluminum and acrylic against both (89)Sr and (90)Y. The amount of beta and bremsstrahlung radiation transmitted through tungsten and lead was relatively small. Although such high-density material generates much bremsstrahlung radiation, it absorbs the bremsstrahlung radiations. CONCLUSIONS: Tungsten was the optimal material for efficient shielding against (89)Sr and (90)Y radiation and preferable among operators. The present findings provide useful information about how to define an appropriate shielding strategy for high-energy beta emitters.

[Comparison of (18)F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography image quality between commercial and in-house supply of FDG radiopharmaceuticals].

OBJECTIVE: PET images are affected by scanner model, reconstruction conditions, injected dose, scan duration, patient health status and FDG radiopharmaceutical supply systems. The present study compares images of 40 patients using commercial and in-house FDG systems with one PET scanner (Aquiduo). METHODS: The PET images were evaluated using the physical indexes of NECpatient, NECdensity and SNRliver proposed by the Japanese guidelines for oncological FDG-PET/CT, and by visual assessment. RESULTS: There were no significant differences in the physical indexes between PET images generated using commercial and in-house FDG. The physical indexes were also acceptable according to the recommended Japanese guidelines. NECdensity was higher when a higher dose/body weight of commercial FDG was injected (correlation coefficient: r=0.576, p<0.001) and lower when BMI was lower and in-house FDG was injected (r=-0.786, p<0.0001). These results suggest that scan duration should be increased if the injected dose of commercial FDG/body weight is <5.5 MBq/kg, and if individuals with BMI >21.4 kg/m(2) are injected with in-house FDG. CONCLUSIONS: Scan duration should be varied depending on FDG supply systems to ensure more accurate image quality and quantitative values during evaluations of response to therapy and prognostic prediction.

[Technical features and roles of cobalt-57 flood sources for daily quality control of gamma cameras].

Quality control (QC) detects changes in the performance of gamma cameras that could adversely affect interpretations of clinical studies. We used plate and sheet (57)Co flood sources to measure extrinsic uniformity during daily QC. Each source, when placed on the top of a collimated detector, allowed the acquisition of uniform images from both detectors, thus reducing the amount of time needed to perform daily QC. No serious problems with the gamma camera system were revealed by visual checks, and changes in detector sensitivity were rapidly determined by observing daily variations in the measured values of extrinsic uniformity. Furthermore, (57)Co flood sources confer advantages in that they shorten the time required for preparation of flood sources and reduce the consequent exposure of medical staff to radiation.

[Quality control of dose calibrator using a traceable syringe-type (68)Ge/(68)Ga calibration source].

OBJECTIVES: Accurate calibration of dose calibrators (DC) is required for quantitative positron emission tomography (PET) studies to generate meaningful information. Values measured by DC depend not only on the radioactive nuclide but also the environment where measurements are taken. Therefore, DC must be calibrated at each location. The present study aimed to determine appropriate calibration values, and evaluate the performance of DC using a traceable (68)Ge/(68)Ga calibration source that is available as a surrogate (18)F source. METHODS: We used a (68)Ge/(68)Ga calibration source to determine the optimal DC value for measuring (18)F activity in the operating environment. Variations in sensitivity and geometry as well as measurement uncertainty were evaluated using the (68)Ge/(68)Ga source. We adopted the criteria of the Guide for the expression of uncertainty in measurement (GUM) to evaluate DC performance. RESULTS: Although the manufacturer's recommended (18)F calibration number for the CRC-25PET is 480, we found that the optimal number was 482. Over a period of one year, the sensitivity of the DC varied <0.1%, and the expanded uncertainty of DC measurements was 2.2%. CONCLUSION: Measurements of the certified activity of a traceable national standard were corrected, and the uncertainty of measurements as well as the accuracy of a DC were determined. Calibration numbers for DC should be regularly determined using (68)Ge/(68)Ga calibration sources at each location to ensure the most accurate results.