Efficacy of Dynamic Chest Radiography for Chronic Thromboembolic Pulmonary Hypertension.

Background While current guidelines require lung ventilation-perfusion (V/Q) scanning as the first step to diagnose chronic pulmonary embolism in pulmonary hypertension (PH), its use may be limited by low availability and/or exposure to ionizing radiation. Purpose To compare the performance of dynamic chest radiography (DCR) and lung V/Q scanning for detection of chronic thromboembolic PH (CTEPH). Materials and Methods Patients with PH who underwent DCR and V/Q scanning in the supine position from December 2019 to July 2021 were retrospectively screened. The diagnosis of CTEPH was confirmed with right heart catheterization and invasive pulmonary angiography. Observer tests were conducted to evaluate the diagnostic accuracy of DCR and V/Q scanning. The lungs were divided into six areas (upper, middle, and lower for both) in the anteroposterior image, and the number of lung areas with thromboembolic perfusion defects was scored. Diagnostic performance was compared between DCR and V/Q scanning using the area under the receiver operating characteristic curve. Agreement between the interpretation of DCR and that of V/Q scanning was assessed using the Cohen kappa coefficient and percent agreement. Results A total of 50 patients with PH were analyzed: 29 with CTEPH (mean age, 64 years ± 15 [SD]; 19 women) and 21 without CTEPH (mean age, 61 years ± 22; 14 women). The sensitivity, specificity, and accuracy of DCR were 97%, 86%, and 92%, respectively, and those of V/Q scanning were 100%, 86%, and 94%, respectively. Areas under the receiver operating characteristic curve for DCR and V/Q scanning were 0.92 (95% CI: 0.79, 0.97) and 0.93 (95% CI: 0.78, 0.98). Agreement between the consensus interpretation of DCR and that of V/Q scanning was substantial (κ = 0.79 [95% CI: 0.61, 0.96], percent agreement = 0.9 [95% CI: 0.79, 0.95]). Conclusion Dynamic chest radiography had similar efficacy to ventilation-perfusion scanning in the detection of chronic thromboembolic pulmonary hypertension. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Wandtke and Koproth-Joslin in this issue.

Assessment of cerebral perfusion in moyamoya disease with dynamic pseudo-continuous arterial spin labeling using a variable repetition time scheme with optimized background suppression.

PURPOSE: Accurate assessment of cerebral perfusion in moyamoya disease is necessary to determine the indication for treatment. We aimed to investigate the usefulness of dynamic PCASL using a variable TR scheme with optimized background suppression in the evaluation of cerebral perfusion in moyamoya disease. METHODS: We retrospectively analyzed the images of 24 patients (6 men and 18 women, mean age 31.4 ± 18.2 years) with moyamoya disease; each of whom was imaged with both dynamic PCASL using the variable-TR scheme and 123IMP SPECT with acetazolamide challenge. ASL dynamic data at 10 phases are acquired by changing the LD and PLD. The background suppression timing was optimized for each phase. CBF and ATT were measured with ASL, and CBF and CVR to an acetazolamide challenge were measured with SPECT. RESULTS: A significant moderate correlation was found between the CBF measured by dynamic PCASL and that by SPECT (r = 0.53, P < 0.001). The CBF measured by dynamic PCASL (52.5 ± 13.3 ml/100 mg/min) was significantly higher than that measured by SPECT (43.0 ± 12.6 ml/100 mg/min, P < 0.001). The ATT measured by dynamic PCASL showed a significant correlation with the CVR measured by SPECT (r = 0.44, P < 0.001). ATT was significantly longer in areas where the CVR was impaired (CVR < 18.4%, ATT = 1812 ± 353 ms) than in areas where it was preserved (CVR > 18.4%, ATT = 1301 ± 437 ms, P < 0.001). The ROC analysis showed a moderate accuracy (AUC = 0.807, sensitivity = 87.7%, specificity = 70.4%) when the cutoff value of ATT was set at 1518 ms. CONCLUSION: Dynamic PCASL using this scheme was found to be useful for assessing cerebral perfusion in moyamoya disease.

Long-term follow up after sentinel node biopsy alone for early-stage cervical cancer.

OBJECTIVE: Sentinel node biopsy alone (SNB) reduces the postoperative complications of pelvic lymphadenectomy, such as lymphedema and lymphangitis; however, the long-term prognosis after SNB is unclear. The objective of this study was to evaluate the long-term outcome and complications of patients with early-stage cervical cancer who underwent SNB for hysterectomy or trachelectomy. METHODS: We performed SNB for cervical cancer using a radioisotope method in 181 patients between 2009 and 2017. If the intraoperative sentinel lymph node evaluation was negative for metastasis, no further lymph nodes were removed. RESULTS: The median age of the patients was 34 years (range, 21-73 years). The International Federation of Gynecology and Obstetrics 2008 stage was IA1 in 6 patients, IA2 in 18, IB1 in 154, and IIA1 in 3. Of the 181 patients (44 with hysterectomy, 137 with trachelectomy), 8 did not undergo pelvic lymphadenectomy because of a false-negative intraoperative diagnosis, 20 received adjuvant therapy after surgery, and 4 (2.2%) experienced recurrence over a median follow-up period of 83.5 months (range, 25-145 months). In the four recurrent cases, recurrence occurred in the pelvis, lung, and bone in one patient each, while the remaining patient developed pelvic and para-aortic lymph node metastases. Of these four patients, one died, and the remaining three are alive without disease after multidisciplinary therapy. The 5-year progression-free and overall survival rates were 98.8% and 99.4%, respectively. Postoperative complications, such as lymphedema, were very low rate. CONCLUSIONS: SNB for early-stage cervical cancer might be safe and effective, with no increase in the recurrence and postoperative complications rate.

Diagnostic accuracy for the epileptogenic zone detection in focal epilepsy could be higher in FDG-PET/MRI than in FDG-PET/CT.

OBJECTIVES: To examine the utility of FDG-PET/MRI in patients with epilepsy by comparing the diagnostic accuracy of PET/MRI and PET/CT in epileptogenic zone (EZ) detection. METHODS: This prospective study included 31 patients (17 males, 14 females) who underwent surgical resection for EZ. All patients were first scanned using FDG-PET/CT followed immediately with FDG-PET/MRI. Two series of PET plus standalone MR images were interpreted independently by five board-certified radiologists. A 4-point visual score was used to assess image quality. Sensitivities and visual scores from both PETs and standalone MRI were compared using the McNemar test with Bonferroni correction and Dunn's multiple comparisons test. RESULTS: The EZs were confirmed histopathologically via resection as hippocampal sclerosis (n = 11, 35.5%), gliosis (n = 8, 25.8%), focal cortical dysplasia (n = 6, 19.4%), and brain tumours (n = 6, 19.4%) including cavernous haemangioma (n = 3), dysembryoplastic neuroepithelial tumour (n = 1), ganglioglioma (n = 1), and polymorphous low-grade neuroepithelial tumour of the young (n = 1). The sensitivity of FDG-PET/MRI was significantly higher than that of FDG-PET/CT and standalone MRI (FDG-PET/MRI vs. FDG-PET/CT vs. standalone MRI; 77.4-90.3% vs. 58.1-64.5% vs. 45.2-80.6%, p < 0.0001, respectively). The visual scores derived from FDG-PET/MRI were significantly higher than those of FDG-PET/CT, as well as standalone MRI (2.8 ± 1.2 vs. 2.0 ± 1.1 vs. 2.1 ± 1.2, p < 0.0001, respectively). Compared to FDG-PET/CT, FDG-PET/MRI increased the visual score (51.9%, increased visual scores of 2 and 3). CONCLUSIONS: The diagnostic accuracy for the EZ detection in focal epilepsy could be higher in FDG-PET/MRI than in FDG-PET/CT. KEY POINTS: • Sensitivity of FDG-PET/MRI was significantly higher than that of FDG-PET/CT and standalone MRI (FDG-PET/MRI vs. FDG-PET/CT vs. standalone MRI; 77.4-90.3% vs. 58.1-64.5% vs. 45.2-80.6%, p < 0.0001, respectively). • Visual scores derived from FDG-PET/MRI were significantly higher than those of FDG-PET/CT and standalone MRI (2.8 ± 1.2 vs. 2.0 ± 1.1 vs. 2.1 ± 1.2, p < 0.0001, respectively). • Compared to FDG-PET/CT, FDG-PET/MRI increased the visual score (51.9%, increased visual scores of 2 and 3).

Clinical results of carbon-ion radiotherapy with separation surgery for primary spine/paraspinal sarcomas.

PURPOSE: To evaluate the clinical outcome of combination of carbon-ion radiotherapy with separation surgery (CIRT-SS) in patients with primary spinal/paraspinal sarcoma (PSPS) and epidural spinal cord compression (ESCC). METHODS: CIRT-SS was performed in 11 consecutive patients. Patients treated in the primary and salvage settings were categorized into Group A (n = 8) and Group B (n = 3), respectively. Clinical results and imaging findings were collected, with a particular focus on ESCC grade, treatment-associated adverse events (AEs), and the locoregional control (LRC) rate and overall survival (OS). RESULTS: The median follow-up period from the start of CIRT-SS was 25 months (7-57 months). ESCC was improved by SS in all cases. No patients exhibited radiation-induced myelopathy (RIM), but three developed Grade 3 vertebral compression fracture (VCF) during follow-up. Locoregional recurrences were observed in four patients [Group A: 1 (12.5%), Group B: 3 (100%)]. Over the entire follow-up period, three patients developed distant metastases and two patients died. The 2-year LRC rate and OS were 70% and 80%, respectively. CONCLUSION: CIRT-SS in the primary setting achieved acceptable LRC and OS without RIM in patients with PSPS and with ESCC. VCF was the most frequent AE associated with CIRT-SS.

Value of Intraoperative Cytological and Pathological Sentinel Lymph Node Diagnosis in Fertility-Sparing Trachelectomy for Early-Stage Cervical Cancer.

BACKGROUND AND OBJECTIVES: Trachelectomy, a fertility-sparing surgery for early-stage cervical cancer, can be performed only when there is no extrauterine extension present. Therefore, identifying the sentinel lymph nodes (SLNs) and using them to obtain an intraoperative pathologic diagnosis can provide information on the feasibility and safety of trachelectomy. Our aim was to assess the value of an intraoperative SLN diagnosis. METHODS: We retrospectively analyzed the accuracy of intraoperative imprint cytology and frozen-section examination in 201 patients at our institution in whom trachelectomy was planned. RESULTS: All patients could be evaluated for SLNs; a total of 610 SLNs were analyzed. Although the specificity of both imprint cytology and frozen-section examination was 100.0%, the sensitivity was only 58.6 and 65.5%, respectively. The diagnostic sensitivity was higher in 2-mm slices along the short axis than on bisection along the longitudinal axis. Imprint cytology correctly diagnosed 2 patients who had false-negative results on frozen section. The nature of the metastatic foci that caused an intraoperative false-negative diagnosis was either micrometastasis or isolated tumor cells. CONCLUSIONS: The accuracy of intraoperative SLN diagnosis requires improvement, especially when small metastatic foci are present.

Prognostic outcome and complications of sentinel lymph node navigation surgery for early-stage cervical cancer.

BACKGROUND: To evaluate the prognostic outcome and surgical complications in patients with early-stage cervical cancer who underwent sentinel node navigation surgery (SNNS) for hysterectomy or trachelectomy. METHODS: A total of 139 patients who underwent SNNS using 99mTc phytate between 2009 and 2015 were evaluated. No further lymph node dissection was performed when intraoperative analysis of the sentinel lymph nodes (SLNs) was negative for metastasis. We compared the surgical complications between the SNNS group and 67 matched patients who underwent pelvic lymph node dissection (PLND) after SLN mapping between 2003 and 2008. We also examined the clinical outcomes in the SNNS group. RESULTS: The mean number of detected SLNs was 2.5 per patient. Fourteen of the 139 patients in the SNNS group underwent PLND based on the intraoperative SLN results. The amount of blood loss, the operative time, and the number of perioperative complications were significantly less in the SNNS group than in the matched PLND group. There was no recurrence during a follow-up period ranging from 2 to 88 months (median 40 months) in the SNNS group. CONCLUSIONS: Using SNNS for early-stage cervical cancer is safe and effective and does not increase the recurrence rate. A future multicenter trial is warranted.

The Effect of Interim FDG-PET-guided Response-Adapted Therapy in Pediatric Patients with Hodgkin's Lymphoma (HL-14) : Protocol for a Phase II Study.

This trial enrolls patients with untreated Hodgkin's lymphoma aged<20 years at diagnosis and examines the effects of omitting radiation therapy if the FDG-positron emission tomography (PET) findings after two completed cycles of combination chemotherapy are negative. It thereby aims to determine whether patients who truly require radiation therapy can be identified by FDG-PET. If so, this modality could be used to omit radiation therapy for all other patients, decreasing the risk of serious long-term complications without affecting survival rates. The outcomes of patients for whom FDG-PET is used to assess early treatment response will also be determined.

Structural changes in Parkinson's disease: voxel-based morphometry and diffusion tensor imaging analyses based on 123I-MIBG uptake.

OBJECTIVE: Patients with Parkinson's disease (PD) may exhibit symptoms of sympathetic dysfunction that can be measured using 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy. We investigated the relationship between microstructural brain changes and 123I-MIBG uptake in patients with PD using voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) analyses. METHODS: This retrospective study included 24 patients with PD who underwent 3 T magnetic resonance imaging and 123I-MIBG scintigraphy. They were divided into two groups: 12 MIBG-positive and 12 MIBG-negative cases (10 men and 14 women; age range: 60-81 years, corrected for gender and age). The heart/mediastinum count (H/M) ratio was calculated on anterior planar 123I-MIBG images obtained 4 h post-injection. VBM and DTI were performed to detect structural differences between these two groups. RESULTS: Patients with low H/M ratio had significantly reduced brain volume at the right inferior frontal gyrus (uncorrected p < 0.0001, K > 90). Patients with low H/M ratios also exhibited significantly lower fractional anisotropy than those with high H/M ratios (p < 0.05) at the left anterior thalamic radiation, the left inferior fronto-occipital fasciculus, the left superior longitudinal fasciculus, and the left uncinate fasciculus. CONCLUSIONS: VBM and DTI may reveal microstructural changes related to the degree of 123I-MIBG uptake in patients with PD. KEY POINTS: • Advanced MRI methods may detect brain damage more precisely. • Voxel-based morphometry can detect grey matter changes in Parkinson's disease. • Diffusion tensor imaging can detect white matter changes in Parkinson's disease.

Comparison of positron emission tomography diffusion-weighted imaging (PET/DWI) registration quality in a PET/MR scanner: Zoomed DWI vs. Conventional DWI.

PURPOSE: To compare zoomed diffusion-weighted imaging (z-DWI) with reduced field of view (FOV) by spatially selective radiofrequency pulses and conventional echo planar imaging (EPI) DWI (c-DWI) with regard to registration quality using positron emission tomography / magnetic resonance (PET/MR) in patients with malignant tumors. MATERIALS AND METHODS: Fludeoxyglucose (18(F) ) PET imaging, c-DWI, and z-DWI were conducted simultaneously in 21 patients with known or suspected malignancy using a PET/MR system. A fusion image showing the largest tumor area was generated for analysis. Registration accuracy between PET and DWI was assessed based on the area of maximum overlap and central point displacement of the tumor. EPI factor, echo time (TE), matching area, and displacement were compared between c-DWI and z-DWI by paired t-test. Agreement of apparent diffusion coefficient (ADC) acquired by the two sequences were also assessed with linear regression s and Bland-Altman plot analysis. RESULTS: Thirty-two lesions were detected on both PET and DWI (mean size 536.3 ± 471.8 mm(2) ). At least one lesion was found in all subjects. In all cases, EPI factor was smaller with z-DWI than c-DWI (43.1 ± 15.6 vs. 62.0 ± 10.0, P < 0.0001), and TE was also shorter for z-DWI (53.6 ± 3.6 msec vs. 65.2 ± 3.6 msec, P < 0.0001). Registration accuracy was better with z-DWI in 30 of 32 lesions (93.8%), and both average matching area and central point displacement were significantly improved (79.8 ± 18.1% vs. 61.8 ± 22.9%, P < 0.0001 and 3.92 ± 2.69 mm vs. 7.51 ± 4.07 mm, P < 0.0001). ADC values calculated with c-DWI and z-DWI showed good agreement. CONCLUSION: Zoomed DWI reduces image distortion and provides better registration accuracy with PET images.

Diagnostic utility of intravoxel incoherent motion mr imaging in differentiating primary central nervous system lymphoma from glioblastoma multiforme.

PURPOSE: To evaluate the diagnostic performance of intravoxel incoherent motion (IVIM) MR imaging and 18 F-fluorodeoxyglucose positron emission tomography (FDG-PET) in differentiating primary central nervous system lymphoma (PCNSL) from glioblastoma multiforme (GBM). MATERIALS AND METHODS: Fifty patients, 17 with PCNSL and 33 with GBM, were retrospectively studied. From the 3 Tesla IVIM data, the perfusion fraction (f) and diffusion coefficient (D) were obtained. In addition, the maximum standard uptake value (SUVmax ) was obtained from the FDG-PET data. Each of the three parameters was compared between PCNSL and GBM using Mann-Whitney U-test. The performance in discriminating between PCNSL and GBM was evaluated using receiver-operating characteristics analysis and area-under-the-curve (AUC) values for the three parameters. RESULTS: The fmax and Dmin values were significantly higher in GBM than in PCNSL (P < 0.01 and P < 0.0001, respectively). In addition, the SUVmax value was significantly lower in GBM than in PCNSL (P < 0.0005). The AUC values for fmax , Dmin , and SUVmax were 0.756, 0.905, and 0.857, respectively. The combination of the fmax and Dmin increased the diagnostic performance (AUC = 0.936) of fmax (P < 0.05), but this value was not significantly different from the values for Dmin (P = 0.30). CONCLUSION: IVIM-MR imaging noninvasively provides useful quantitative information in distinguishing between PCNSL and GBM. J. Magn. Reson. Imaging 2016;44:1256-1261.

Decontamination of the Activation Product Based on a Legal Revision of the Cyclotron Vault Room on the Non-self-shield Compact Medical Cyclotron.

The non-self-shield compact medical cyclotron and the cyclotron vault room were in operation for 27 years. They have now been decommissioned. We efficiently implemented a technique to identify an activation product in the cyclotron vault room. Firstly, the distribution of radioactive concentrations in the concrete of the cyclotron vault room was estimated by calculation from the record of the cyclotron operation. Secondly, the comparison of calculated results with an actual measurement was performed using a NaI scintillation survey meter and a high-purity germanium detector. The calculated values were overestimated as compared to the values measured using the NaI scintillation survey meter and the high-purity germanium detector. However, it could limit the decontamination area. By simulating the activation range, we were able to minimize the concrete core sampling. Finally, the appropriate range of radioactivated area in the cyclotron vault room was decontaminated based on the results of the calculation. After decontamination, the radioactive concentration was below the detection limit value in all areas inside the cyclotron vault room. By these procedures, the decommissioning process of the cyclotron vault room was more efficiently performed.

Stereotactic body radiation therapy for primary lung cancers clinically diagnosed without pathological confirmation: a single-institution experience.

BACKGROUND: Pathological diagnosis of small lung lesions is sometimes difficult in medically inoperable patients. The purpose of this study was to evaluate the adverse events and the outcomes of stereotactic body radiation therapy (SBRT) for lung lesions which were clinically diagnosed as primary lung cancer without pathological confirmation. METHODS: Between April 2003 and April 2011, 88 patients with small lung lesions which were clinically diagnosed as primary lung cancer were treated with SBRT. The median tumor size was 19 mm (range 8-40 mm). The radiation dose was 48 Gy in four fractions in all patients. The median follow-up was 23 months (range 6-91 months). RESULTS: Recurrence was observed in 13 patients. The local control rate, progression-free survival rate, and overall survival rate at 3 years were 90, 67, and 80 %, respectively. Two patients (2.3 %) had Grade 2 radiation pneumonitis, and six patients (6.8 %) had Grade 2 rib fractures. There were no adverse events of Grade 3 or greater. CONCLUSIONS: SBRT appears to be a safe and effective treatment option for small lung lesions that are clinically diagnosed as primary lung cancer without pathological confirmation.

Esophagectomy-related thoracic duct injury detected by lymphoscintigraphy with 99mTc-diethylenetriamine pentaacetic acid-human serum albumin: report of a case.

Chylothorax is an uncommon but potentially life-threatening complication of esophagectomy. A 72-year-old man underwent thoracoscopy-assisted subtotal esophagectomy and reconstruction with a gastric tube, through a retrosternal route, after preoperative chemoradiotherapy. Chylothorax was detected after starting enteral feeding on postoperative day (POD) 7. Despite conservative therapy such as fasting, total parenteral nutrition, and octreotide administration, massive fluid drainage continued. On POD 19, lymphoscintigraphy with (99m)Tc-diethylenetriamine pentaacetic acid-human serum albumin (HSA-D) was performed and the site of leakage was detected at the level of the fourth thoracic vertebra. On POD 23, the thoracic duct was ligated, following which the volume of chylothorax decreased. Lymphoscintigraphy 12 days after the reoperation showed no leakage from the thoracic duct. We recommend lymphoscintigraphy with (99m)Tc-HSA-D for locating the chyle leakage site and helping decide about the operative indication.

[Targeted radionuclide therapy for castration-resistant prostate cancer].

Although patients with castration-resistant prostate cancer frequently have metastases to the bone, they have a relatively favorable prognosis. Therefore, it is important to keep or improve the level of patient's quality of life. The use of strontium-89 for the management of the pain from bone metastasis was approved in 2007 in Japan. A new bone-targeting radiopharmaceuticals using radium-223 is also promising, because a randomized trial showed an overall survival advantage of radium-223 in prostate patients with bone metastases. In this review, we summarize the role of targeted radionuclide therapy for castration-resistant prostate cancer, focusing on strontium-89 and radium-223.

Recent topics in fibroblast activation protein inhibitor-PET/CT: clinical and pharmacological aspects.

Recently, positron emission tomography (PET) with fibroblast activation protein inhibitor (FAPI) has gained significant attention as an advanced tumor diagnostic imaging tool. FAPI PET has a promising potential owing to its ability to accurately depict most malignant tumors. It has an accuracy that is comparable to or surpassing the diagnostic accuracy of PET using 18F-fluorodeoxyglucose (FDG). Moreover, FAPI PET can identify malignant lesions that may be inconclusive on FDG PET. Beyond its application in neoplastic disorders, there have been encouraging reports suggesting the utility of FAPI PET in non-neoplastic conditions such as respiratory or cardiac diseases. This article aimed to provide a comprehensive overview of the recently published articles investigating FAPI and discuss its clinical utility with an emphasis on its application in tumor diagnostics. Numerous radiopharmaceutical FAPIs, including 18F- and 68Ga-labeled compounds, have been developed, and they offer various advantages and applications. With the progress in the FAPI PET synthesis to enhance accumulation and retention in pathological lesions, future studies are expected to provide valuable data on its therapeutic efficacy.

Relationship between impaired cardiac sympathetic activity and spatial dyssynchrony in patients with non-ischemic heart failure: assessment by MIBG scintigraphy and tagged MRI.

BACKGROUND: Impairment of cardiac sympathetic activity has various detrimental effects on cardiac function. The purpose was to investigate the relationship between left ventricular (LV) dyssynchrony and cardiac sympathetic activity in non-ischemic heart failure (HF). METHODS: Twenty-seven patients with non-ischemic HF were enrolled. Cardiac sympathetic activity was assessed by heart-to-mediastinum ratio (H/M ratio) on (123)I-Metaiodobenzylguanidine scintigraphy. LV dyssynchrony was assessed by cross-correlation analysis of time curves of myocardial circumferential strains delivered from cine-tagging MR images. Temporal dyssynchrony was defined as contraction delay between septal and lateral segments >110 milliseconds. Spatial dyssynchrony was defined as the negative value of the maximum correlation for the two strain time curves. RESULTS: H/M ratio was significantly lower for patients with spatial dyssynchrony compared to patients without (1.8 ± 0.3 vs 2.1 ± 0.3, P < .05). There was no difference between patients with and without temporal dyssynchrony (2.0 ± 0.2 vs 2.0 ± 0.3). The incidence of spatial dyssynchrony was significantly higher in patients with H/M ratio <2.0 than those whose ratios were ≥2.0 (75% vs 20%, P = .001). There was no difference in the incidence of temporal dyssynchrony between the two groups (17% vs 20%). CONCLUSION: Impairment of cardiac sympathetic activity was found to be associated with spatial dyssynchrony in patients with non-ischemic HF.

Monte Carlo simulation study to explore optimum conditions for Astatine-211 SPECT.

211At is a promising nuclide for targeted radioisotope therapy. Direct imaging of this nuclide is important for in vivo evaluation of its distribution. We investigated suitable conditions for single-photon emission computed tomography (SPECT) imaging of 211At and assessed their feasibility using a homemade Monte Carlo simulation code, MCEP-SPECT. Radioactivity concentrations of 5, 10, or 20 kBq/mL were distributed in six spheres in a National Electrical Manufactures Association (NEMA) body phantom with a background of 1 kBq/mL. The energy window, projection number, and acquisition time were 71-88 keV, 60, and 60 s, respectively, per projection. A medium-energy collimator and three low-energy collimators were tested. SPECT images were reconstructed using the ordered subset expectation maximization (OSEM) method with attenuation correction (Chang method) and scatter correction (triple-energy-windows method). Image quality was evaluated using the contrast-to-noise ratio (CNR) for detectability and the contrast recovery coefficient (CRC) for quantitavity. The low-energy, high-sensitivity collimator exhibited the best detectability among the four types of collimators, with a maximum CNR value of 43. In contrast, the low-energy, high-resolution collimator exhibited excellent quantitavity, with a maximum CRC value of 102%. Scatter correction improved the image quality. In particular, the CRC value almost doubled after scatter correction. The detection of spheres smaller than 20 mm in diameter was difficult. In summary, low-energy collimators were suitable for the SPECT imaging of 211At. In addition, scatter correction was extremely effective in improving the image quality. The feasibility of 211At SPECT was demonstrated for lesions larger than 20 mm.

A review of harmonization strategies for quantitative PET.

PET can reveal in vivo biological processes at the molecular level. PET-derived quantitative values have been used as a surrogate marker for clinical decision-making in numerous clinical studies and trials. However, quantitative values in PET are variable depending on technical, biological, and physical factors. The variability may have a significant impact on a study outcome. Appropriate scanner calibration and quality control, standardization of imaging protocols, and any necessary harmonization strategies are essential to make use of PET as a biomarker with low bias and variability. This review summarizes benefits, limitations, and remaining challenges for harmonization of quantitative PET, including whole-body PET in oncology, brain PET in neurology, PET/MR, and non-18F PET imaging. This review is expected to facilitate harmonization of quantitative PET and to promote the contribution of PET-derived biomarkers to research and development in medicine.