Nuclear medicine practice in Japan: a report of the eighth nationwide survey in 2017

Vision transformer to differentiate between benign and malignant slices in 18F-FDG PET/CT

Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) is widely used for the detection, diagnosis, and clinical decision-making in oncological diseases. However, in daily medical practice, it is often difficult to make clinical decisions because of physiological FDG uptake or cancers with poor FDG uptake. False negative clinical diagnoses of malignant lesions are critical issues that require attention. In this study, Vision Transformer (ViT) was used to automatically classify 18F-FDG PET/CT slices as benign or malignant. This retrospective study included 18F-FDG PET/CT data of 207 (143 malignant and 64 benign) patients from a medical institute to train and test our models. The ViT model achieved an area under the receiver operating characteristic curve (AUC) of 0.90 [95% CI 0.89, 0.91], which was superior to the baseline Convolutional Neural Network (CNN) models (EfficientNet, 0.87 [95% CI 0.86, 0.88], P < 0.001; DenseNet, 0.87 [95% CI 0.86, 0.88], P < 0.001). Even when FDG uptake was low, ViT produced an AUC of 0.81 [95% CI 0.77, 0.85], which was higher than that of the CNN (DenseNet, 0.65 [95% CI 0.59, 0.70], P < 0.001). We demonstrated the clinical value of ViT by showing its sensitive analysis of easy-to-miss cases of oncological diseases.

Nuclear medicine practice in Japan: a report of the ninth nationwide survey in 2022

Subcommittee on Survey of Nuclear Medicine Practice in Japan has performed a nationwide survey of nuclear medicine practice every 5 years since 1982 to survey contemporary nuclear medicine practice and its changes over the years. The subcommittee sent questionnaires, including the number and category of examinations as well as the kind of the radiopharmaceuticals during the 30 days of June 2022 to all nuclear medicine institutes in Japan. The total numbers of them for the year 2022 were estimated depends on the 1-month data. A total of 1095 institutes responded to the survey, including 364 positron emission tomography (PET) centers. The recovery rate was 90.6%. The number of gamma cameras installed was 1299 in total, with 2.5% decrease in 5 years. Dual-head cameras and hybrid SPECT/CT scanners accounted for 83.8% and 35.5%, respectively. The number of single-photon tracer studies in 2022 was 1.11 million which means increase in 2.7% in 5 years. Bone scintigraphy was a leading examination (31.0%), followed by myocardial scintigraphy (27.1%) and cerebral perfusion study (23.8%) in order. The percentage of SPECT studies showed an increase from 63.5% in previous survey to 66.8% in this survey. PET centers have also increased from 389 to 412, as compared with the previous one. One hundred and twenty-two PET centers have installed one or two in-house cyclotrons. Increasing trends of the PET studies were observed from 1992 to 2017, the trend changed and PET studies showed 1.5% decrease in 5 years. 18F-FDG accounted for 98.6% (610,497 examinations). PET examinations using 11C-methionine, 13N-NH3 and 11C-PIB have decreased, with 1624, 2146 and 525 examinations, respectively in 2022. The total number of nuclear medicine examination was eventually increased by 1.0%. Therapies for pheochromocytoma or paraganglioma (PPGL) with 131I-MIBG and for neuroendocrine tumor with 177Lu-DOTA-TATE were newly started, however, a total number of targeted radionuclide therapy was decreased by 17.7% because 131I-radioiodine and 223Ra targeted therapies were decreased and supply of some radioisotopes was discontinued. 131I-radioiodine targeted therapy showed a decrease in 5 years (- 15.9%), including 4099 patients for thyroid cancer. The number of out-patient thyroid bed ablation therapy with 1110 MBq of 131I was also decreased to 1015 per year. The number of admission rooms specialized for radionuclide targeted therapy increased from 157 to 160. The number of 223Ra targeted therapies for castration-resistant metastatic prostate cancer (mCRPC) was 1041 patients. This survey was performed during COVID-19 pandemic, however, total number of nuclear medicine examinations was almost same as previous survey (+ 1.0%). Radionuclide therapies with 131I-MIBG and 177Lu-DOTA-TATE were newly started, and new radionuclide therapy will be available in future, therefore, the development of radionuclide therapy will be continued. We are convinced that this survey report is useful in understanding the current status of the nuclear medicine practice in Japan, and in devising the new strategy to strengthen a role of nuclear medicine.

Evaluation of attenuation correction method for head holder in brain perfusion single-photon emission computed tomography

Head holder attenuation affects brain perfusion single-photon emission computed tomography (SPECT) image quality. Here, we proposed a head holder-attenuation correction (AC) method using attenuation coefficient maps calculated by Chang's method from CT images. Then, we evaluated the effectiveness of the head holder-AC method by numerical phantom and clinical cerebral perfusion SPECT studies. In the numerical phantom, the posterior counts were 10.7% lower than the anterior counts without head holder-AC method. However, by performing head holder-AC, the posterior count recovered by approximately 6.8%, approaching the true value. In the clinical study, the normalized count ratio was significantly increased by performing the head holder-AC method in the posterior-middle cerebral artery, posterior cerebral artery and cerebellum regions. There were no significant increases in other regions. The head holder-AC method can correct the counts attenuated by the head holder.

Detectability of cold tumors by xSPECT bone technology compared with hot tumors: a supine phantom study

Detecting cold as well as hot tumors is vital for interpreting bone tumors on single-photon emission computed tomography (SPECT) images. This study aimed to visually and quantitatively demonstrate the detectability of cold tumors using xSPECT technology compared with that of hot tumors in the phantom study. Five tumors of different sizes and normal bone contained a mixture of 99mTc and K2HPO4 in a spine phantom. We acquired SPECT data using an xSPECT protocol and transverse images were reconstructed using xSPECT Bone (xB) and xSPECT Quant (xQ). Mean standardized uptake values (SUVmean) in volumes of interest (VOI) were calculated. Recovery coefficients (RCs) for each tumor site were calculated with reference to radioactive concentrations. The SUVmeans of the whole vertebral body for hot tumor bone image in cortical bone phantom reconstructed by with xB and xQ were 5.77 and 4.86 respectively. The SUVmean of xB was similar to the true value. The SUVmeans for xB and xQ reconstructed images of cold tumors were both approximately 0.16. The RC of the cold tumor on xQ images increased as the tumor diameter decreased, whereas that of xB remained almost constant regardless of the tumor diameter. In conclusion, the quantitative accuracy of detecting hot and cold tumors was higher in the xB image than in the xQ image. Moreover, the visual detectability of cold tumors was also excellent in xB images.

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.

Convolutional neural network-based program to predict lymph node metastasis of non-small cell lung cancer using 18F-FDG PET

PURPOSE

To develop a convolutional neural network (CNN)-based program to analyze maximum intensity projection (MIP) images of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) positron emission tomography (PET) scans, aimed at predicting lymph node metastasis of non-small cell lung cancer (NSCLC), and to evaluate its effectiveness in providing diagnostic assistance to radiologists.

METHODS

We obtained PET images of NSCLC from public datasets, including those of 435 patients with available N-stage information, which were divided into a training set (n = 304) and a test set (n = 131). We generated 36 maximum intensity projection (MIP) images for each patient. A residual network (ResNet-50)-based CNN was trained using the MIP images of the training set to predict lymph node metastasis. Lymph node metastasis in the test set was predicted by the trained CNN as well as by seven radiologists twice: first without and second with CNN assistance. Diagnostic performance metrics, including accuracy and prediction error (the difference between the truth and the predictions), were calculated, and reading times were recorded.

RESULTS

In the test set, 67 (51%) patients exhibited lymph node metastases and the CNN yielded 0.748 predictive accuracy. With the assistance of the CNN, the prediction error was significantly reduced for six of the seven radiologists although the accuracy did not change significantly. The prediction time was significantly reduced for five of the seven radiologists with the median reduction ratio 38.0%.

CONCLUSION

The CNN-based program could potentially assist radiologists in predicting lymph node metastasis by increasing diagnostic confidence and reducing reading time without affecting diagnostic accuracy, at least in the limited situations using MIP images.

Performance Characteristics of a New-Generation Digital Bismuth Germanium Oxide PET/CT System, Omni Legend 32, According to NEMA NU 2-2018 Standards

The Omni Legend 32 PET/CT system features silicon photomultiplier (SiPM)-based detectors with bismuth germanium oxide crystals and a 32-cm axial field of view (FOV). The present study aimed to determine the performance characteristics of the Omni Legend 32 PET/CT system according to National Electrical Manufacturers Association (NEMA) NU 2-2018 standards. Methods: The PET component of this system comprises 22 detector modules; each module contains 24 detector blocks with 72 bismuth germanium oxide crystals with a volume of 4.1 × 4.1 × 30 mm coupled to 18 SiPM devices with a 6 × 6 mm area, resulting in an axial FOV of 32 cm. The spatial resolution, sensitivity, count rate performance, and image quality delivered by PET were evaluated using the NEMA NU 2-2018 standard. PET images of 2 patients were evaluated to get a visual first impression of the Omni Legend 32 PET/CT system together with Precision DL. Results: The average spatial resolution at 1, 10, and 20 cm from the central axis was 4.3, 5.3, and 6.2 mm, respectively, for filtered backprojection and 3.7, 4.3, and 5.1 mm, respectively, for ordered-subset expectation maximization. The NEMA sensitivity was 47.30 and 47.05 cps/kBq at the axial center of the FOV and at a 10-cm radial offset, respectively. The scatter fraction, count rate accuracy, and peak noise-equivalent count rates were 35.4%, 1.7%, and 501.7 kcps, respectively, at 15.7 kBq/mL. Contrast recovery for the NEMA body phantom from the smallest to the largest sphere ranged from 61.3% to 93.0%, with a background variability of 5.4%-11.7% and a lung error of 5.1% for Q.Clear (β-value, 50). Good patient image quality was obtained with the Omni Legend 32. Conclusion: The Omni Legend 32 has class-leading sensitivity and count rates within the category of whole-body PET systems while maintaining spatial resolution broadly comparable to that of other current SiPM-based PET/CT systems. This combination of properties results in a very good image quality.

From FDG and beyond: the evolving potential of nuclear medicine

The radiopharmaceutical 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) has been dominantly used in positron emission tomography (PET) scans for over 20 years, and due to its vast utility its applications have expanded and are continuing to expand into oncology, neurology, cardiology, and infectious/inflammatory diseases. More recently, the addition of artificial intelligence (AI) has enhanced nuclear medicine diagnosis and imaging with FDG-PET, and new radiopharmaceuticals such as prostate-specific membrane antigen (PSMA) and fibroblast activation protein inhibitor (FAPI) have emerged. Nuclear medicine therapy using agents such as [177Lu]-dotatate surpasses conventional treatments in terms of efficacy and side effects. This article reviews recently established evidence of FDG and non-FDG drugs and anticipates the future trajectory of nuclear medicine.

Impact of γ factor in the penalty function of Bayesian penalized likelihood reconstruction (Q.Clear) to achieve high-resolution PET images

BACKGROUND

The Bayesian penalized likelihood PET reconstruction (BPL) algorithm, Q.Clear (GE Healthcare), has recently been clinically applied to clinical image reconstruction. The BPL includes a relative difference penalty (RDP) as a penalty function. The β value that controls the behavior of RDP determines the global strength of noise suppression, whereas the γ factor in RDP controls the degree of edge preservation. The present study aimed to assess the effects of various γ factors in RDP on the ability to detect sub-centimeter lesions.

METHODS

All PET data were acquired for 10 min using a Discovery MI PET/CT system (GE Healthcare). We used a NEMA IEC body phantom containing spheres with inner diameters of 10, 13, 17, 22, 28 and 37 mm and 4.0, 5.0, 6.2, 7.9, 10 and 13 mm. The target-to-background ratio of the phantom was 4:1, and the background activity concentration was 5.3 kBq/mL. We also evaluated cold spheres containing only non-radioactive water with the same background activity concentration. All images were reconstructed using BPL + time of flight (TOF). The ranges of β values and γ factors in BPL were 50-600 and 2-20, respectively. We reconstructed PET images using the Duetto toolbox for MATLAB software. We calculated the % hot contrast recovery coefficient (CRC_hot) of each hot sphere, the cold CRC (CRC_cold) of each cold sphere, the background variability (BV) and residual lung error (LE). We measured the full width at half maximum (FWHM) of the micro hollow hot spheres ≤ 13 mm to assess spatial resolution on the reconstructed PET images.

RESULTS

The CRC_hot and CRC_cold for different β values and γ factors depended on the size of the small spheres. The CRC_hot, CRC_cold and BV increased along with the γ factor. A 6.2-mm hot sphere was obvious in BPL as lower β values and higher γ factors, whereas γ factors ≥ 10 resulted in images with increased background noise. The FWHM became smaller when the γ factor increased.

CONCLUSION

High and low γ factors, respectively, preserved the edges of reconstructed PET images and promoted image smoothing. The BPL with a γ factor above the default value in Q.Clear (γ factor = 2) generated high-resolution PET images, although image noise slightly diverged. Optimizing the β value and the γ factor in BPL enabled the detection of lesions ≤ 6.2 mm.

Unexpected radioactive iodine accumulation on whole-body scan after I-131 ablation therapy for differentiated thyroid cancer

We retrospectively evaluated the frequency of unexpected accumulation of radioactive iodine on the post-therapy whole-body scan (Rx-WBS) after radioactive iodine (RAI) ablation therapy in patients with differentiated thyroid cancer (DTC). We searched our institutional database for Rx-WBSs of DTC patients who underwent RAI ablation or adjuvant therapy between 2012 and 2019. Patients with distant metastasis diagnosed by CT or PET/CT before therapy, and those had previously received RAI therapy were excluded. In total, 293 patients (201 female and 92 male, median age 54 years) were selected. Two nuclear medicine physicians interpreted the Rx-WBS images by determining the visual intensity of radioiodine uptake by the thyroid bed, cervical and mediastinal lymph nodes, lungs, and bone. Clinical features of the patients with and without the metastatic accumulation were compared by chi-square test and median test. Logistic regression analyses were performed to compare the association between the presence of metastatic accumulation and these clinical factors. Eighty-four of 293 patients (28.7%) showed metastatic accumulation. Patients with metastatic RAI accumulation showed a significantly higher frequency of pathological N1 (pN1) and serum thyroglobulin (Tg) > 1.5 ng/ml under TSH stimulation (p = 0.035 and p = 0.031, respectively). Logistic regression analysis indicated that a serum Tg > 1.5 ng/ml was significantly correlated with the presence of metastatic accumulation (odds ratio = 1.985; p = 0.033). In conclusion, Patients with Tg > 1.5 ng/ml were more likely to show metastatic accumulation. In addition, the presence of lymph node metastasis at the initial thyroid surgery was also associated with this unexpected metastatic accumulation.

A Preliminary Study to Use SUVmax of FDG PET-CT as an Identifier of Lesion for Artificial Intelligence

Background: Diagnostic reports contribute not only to the particular patient, but also to constructing massive training dataset in the era of artificial intelligence (AI). The maximum standardized uptake value (SUVmax) is often described in daily diagnostic reports of [¹⁸F] fluorodeoxyglucose (FDG) positron emission tomography (PET) - computed tomography (CT). If SUVmax can be used as an identifier of lesion, that would greatly help AI interpret diagnostic reports. We aimed to clarify whether the lesion can be localized using SUVmax strings. Methods: The institutional review board approved this retrospective study. We investigated a total of 112 lesions from 30 FDG PET-CT images acquired with 3 different scanners. SUVmax was calculated from DICOM files based on the latest Quantitative Imaging Biomarkers Alliance (QIBA) publication. The voxels showing the given SUVmax were exhaustively searched in the whole-body images and counted. SUVmax was provided with 5 different degrees of precision: integer (e.g., 3), 1st decimal places (DP) (3.1), 2nd DP (3.14), 3rd DP (3.142), and 4th DP (3.1416). For instance, when SUVmax = 3.14 was given, the voxels with 3.135 ≤ SUVmax < 3.145 were extracted. We also evaluated whether local maximum restriction could improve the identifying performance, where only the voxels showing the highest intensity within some neighborhood were considered. We defined that "identical detection" was achieved when only single voxel satisfied the criterion. Results: A total of 112 lesions from 30 FDG PET-CT images were investigated. SUVmax ranged from 1.3 to 49.1 (median = 5.6). Generally, when larger and more precise SUVmax values were given, fewer voxels satisfied the criterion. The local maximum restriction was very effective. When SUVmax was determined to 4 decimal places (e.g., 3.1416) and the local maximum restriction was applied, identical detection was achieved in 33.3% (lesions with SUVmax < 2), 79.5% (2 ≤ SUVmax < 5), and 97.8% (5 ≤ SUVmax) of lesions. Conclusion: In this preliminary study, SUVmax of FDG PET-CT could be used as an identifier to localize the lesion if precise SUVmax is provided and local maximum restriction was applied, although the lesions showing SUVmax < 2 were difficult to identify. The proposed method may have potential to make use of diagnostic reports retrospectively for constructing training datasets for AI.

Current and future perspectives on functional molecular imaging in nephro-urology: theranostics on the horizon

In recent years, a paradigm shift from single-photon-emitting radionuclide radiotracers toward positron-emission tomography (PET) radiotracers has occurred in nuclear oncology. Although PET-based molecular imaging of the kidneys is still in its infancy, such a trend has emerged in the field of functional renal radionuclide imaging. Potentially allowing for precise and thorough evaluation of renal radiotracer urodynamics, PET radionuclide imaging has numerous advantages including precise anatomical co-registration with CT images and dynamic three-dimensional imaging capability. In addition, relative to scintigraphic approaches, PET can allow for significantly reduced scan time enabling high-throughput in a busy PET practice and further reduces radiation exposure, which may have a clinical impact in pediatric populations. In recent years, multiple renal PET radiotracers labeled with 11C, 68Ga, and 18F have been utilized in clinical studies. Beyond providing a precise non-invasive read-out of renal function, such radiotracers may also be used to assess renal inflammation. This manuscript will provide an overview of renal molecular PET imaging and will highlight the transformation of conventional scintigraphy of the kidneys toward novel, high-resolution PET imaging for assessing renal function. In addition, future applications will be introduced, e.g. by transferring the concept of molecular image-guided diagnostics and therapy (theranostics) to the field of nephrology.

Patient arm position during quantitative bone single-photon emission computed tomography/computed tomography acquisition can affect image quality and quantitative accuracy: a phantom study

PURPOSE

The present study used a phantom to determine the effects of various arm positions on bone SPECT/computed tomography (CT) images and the optimal arm position to acquire good-quality and quantitatively accurate images.

MATERIALS AND METHODS

We designed a phantom study of five simulated arm positions that are assumed during SPECT image acquisition. All SPECT data were acquired during a total of 120 projections of 10 and 100 s/view over 360° in a non-circular mode and reconstructed using Flash 3D (Siemens Healthineers). We evaluated contrast (QH,17 mm), image noise (NB,17 mm), contrast-to-noise ratios (QNRs), and visual scores according to the guidelines for bone SPECT acquisition protocols published by the Japanese Society of Nuclear Medicine Technology. The SUVmean, SUVmax, and SUVpeak were calculated and quantitative errors were evaluated using the recovery coefficient (RC) and the root means square error (RMSE).

RESULTS

The spatial resolution of SPECT images was better when the arms were down than raised with simulated shoulder disorders. Raised arms with shoulder disorders significantly increased the NB,17 mm and decreased the QH,17 mm, and the QNR in each image differed over a range from 2.2 to 5.2. The visual score was >1.5 with the arms down, raised normally, and raised with moderate shoulder disorders. The SUVmax and SUVpeak were overestimated compared with 100-min data for all images, whereas SUVmean was underestimated. Raised arms with a shoulder disorder decreased RCmax, and RCmean and RCpeak suppressed differences among arm positions. In addition, RMSE with the arms down and raised normally were close to that for 100-min data.

CONCLUSION

Bone SPECT images with good quality and quantitative accuracy can be acquired with patients holding their arms down by their sides. This will help patients with shoulder pain who have difficulties raising their arms.

The usefulness of SwiftScan technology for bone scintigraphy using a novel anthropomorphic phantom

The aim of this study was to demonstrate the usefulness of SwiftScan with a low-energy high-resolution and sensitivity (LEHRS) collimator for bone scintigraphy using a novel bone phantom simulating the human body. SwiftScan planar image of lateral view was acquired in clinical condition; thereafter, each planar image of different blend ratio (0–80%) of Crality 2D processing were created. SwiftScan planar images with reduced acquisition time by 25–75% were created by Poisson’s resampling processing. SwiftScan single photon emission computed tomography (SPECT) was acquired with step-and-shoot and continuous mode, and SPECT images were reconstructed using a three-dimensional ordered subset expectation maximization incorporating attenuation, scatter and spatial resolution corrections. SwiftScan planar image showed a high contrast to noise ratio (CNR) and low percent of the coefficient of variance (%CV) compared with conventional planar image. The CNR of the tumor parts in SwiftScan SPECT was higher than that of the conventional SPECT image of step and shoot acquisition, while the %CV showed the lowest value in all systems. In conclusion, SwiftScan planar and SPECT images were able to reduce the image noise compared with planar and SPECT image with a low-energy high-resolution collimator, so that SwiftScan planar and SPECT images could be obtained a high CNR. Furthermore, the SwiftScan planar image was able to reduce the acquisition time by 25% when the blend ratio of Clarity 2D processing set to more than 40%.

Experimental evaluation of the GE NM/CT 870 CZT clinical SPECT system equipped with WEHR and MEHRS collimator

Purpose

A high‐energy‐resolution whole‐body SPECT‐CT device (NM/CT 870 CZT; C‐SPECT) equipped with a CZT detector has been developed and is being used clinically. A MEHRS collimator has also been developed recently, with an expected improvement in imaging accuracy using medium‐energy radionuclides. The objective of this study was to compare and analyze the accuracies of the following devices: a WEHR collimator and the MEHRS collimator installed on a C‐SPECT, and a NaI scintillation detector‐equipped Anger‐type SPECT (A‐SPECT) scanner, with a LEHR and LMEGP.

Methods

A line phantom was used to measure the energy resolutions including collimator characteristics in the planar acquisition of each device using ^99mTc and ¹²³I. We also measured the system's sensitivity and high‐contrast resolution using a lead bar phantom. We evaluated SPECT spatial resolution, high‐contrast resolution, radioactivity concentration linearity, and homogeneity, using a basic performance evaluation phantom. In addition, the effect of scatter correction was evaluated by varying the sub window (SW) employed for scattering correction.

Results

The energy resolution with ^99mTc was 5.6% in C‐SPECT with WEHR and 9.9% in A‐SPECT with LEHR. Using 123I, the results were 9.1% in C‐SPECT with WEHR, 5.5% in C‐SPECT with MEHRS, and 10.4% in A‐SPECT with LMEGP. The planar spatial resolution was similar under all conditions, but C‐SPECT performed better in SPECT acquisition. High‐contrast resolution was improved in C‐SPECT under planar condition and SPECT. The sensitivity and homogeneity were improved by setting the SW for scattering correction to 3% of the main peak in C‐SPECT.

Conclusion

C‐SPECT demonstrates excellent energy resolution and improved high‐contrast resolution for each radionuclide. In addition, when using 123I, careful attention should be paid to SW for scatter correction. By setting the appropriate SW, C‐SPECT with MEHRS has an excellent scattered ray removal effect, and highly homogenous imaging is possible while maintaining the high‐contrast resolution.

Gallium citrate-67 single-photon emission computed tomography/computed tomography for localizing the foci of classic fever and inflammation of unknown origin: A retrospective study of diagnostic yield

OBJECTIVES

Only few studies have assessed the use of gallium citrate-67 single-photon emission computed tomography/computed tomography (67Ga-SPECT/CT) for localizing the foci of classic fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Hence, the current study aimed to assess the diagnostic contribution of 67Ga-SPECT/CT in a tertiary referral setting where nuclear imaging tests are performed after an unsuccessful comprehensive primary diagnostic workup.

METHODS

We retrospectively assessed the medical records of 27 adult patients with FUO/IUO who had an unsuccessful diagnostic workup and who underwent 67Ga-SPECT/CT for the localization of FUO/IUO foci in our university hospital between 2013 and 2019. The primary outcome was diagnostic yield. The secondary outcomes were overall clinical efficacy and spontaneous remission of FUO/IUO symptoms in patients with a negative 67Ga-SPECT/CT finding.

RESULTS

Almost all patients completed the recommended diagnostic workup, except for urine culture and abdominal ultrasonography. Moreover, prior to 67Ga-SPECT/CT, all patients underwent thoraco-abdominopelvic CT scan, which was a non-diagnostic procedure. After a median follow-up of 843 days, the cause was identified in 16 (59%) patients. 67Ga-SPECT/CT successfully localized the FUO/IUO foci in eight patients (diagnostic yield = 30%; 95% confidence interval [CI]: 14%-50%). However, the causes remained unknown during follow-up in 11 (41%) patients. Among them, five experienced spontaneous regression of symptoms. 67Ga-SPECT/CT was negative in four of the five patients with spontaneous regression in symptoms without a definite cause. Considering this an important event, the overall clinical efficacy of 67Ga-SPECT/CT increased to 44% (95% CI: 25%-65%).

CONCLUSION

67Ga-SPECT/CT had an acceptable diagnostic yield for the localization of FUO/IUO foci, which are challenging to diagnose, in a contemporary tertiary referral care setting. In patients who experienced spontaneous regression in symptoms with an unexplained cause, the absence of abnormal uptake might indicate prospective spontaneous remission. Thus, 67Ga-SPECT/CT could be an active first-line nuclear imaging modality in settings where fluorine-18-fluorodeoxy glucose positron emission tomography and computed tomography is not available for the assessment of FUO/IUO causes.

Radioactive iodine treatment of papillary thyroid carcinoma in Japan

We have a unique history of using radioactive iodine (RAI) therapy and surgical treatment for thyroid cancer in Japan. Less than total thyroidectomy without RAI therapy was the most common management of papillary thyroid carcinoma (PTC) in the past. Limited availability of dedicated facilities for the RAI administration due to the strict regulations and insufficient coverage of the expenses were the major reasons that impacted on the management decisions. Following the publication of the Japanese clinical practice guidelines for thyroid tumors in 2010, the risk-adapted approach has become a standard where the high-risk and selected intermediate-risk PTC patients undergo total thyroidectomy followed by RAI therapy and thyrotropin suppression therapy. We are on the shoulders of pioneers who made every effort to bring the interventions closer to an ideal environment for patients. Armed with the revised clinical practice guidelines 2018 and devised inpatient/outpatient RAI therapy, Japanese physicians are ready to proceed to more rational management that would improve patients' outcomes. Directions for the future include further advancement of relevant clinical research to fill the gaps between current evidence and recommendations in the guidelines, and obtaining approval for high-dose RAI therapy on an outpatient basis to improve its effectiveness in both adjuvant and treatment settings.

Trends in the utilization of nuclear medicine technology in Jamaica: Audit of a private facility

This study sought to evaluate the types and frequencies of nuclear medicine studies that were carried out at a privately-run nuclear medicine facility in Kingston, Jamaica. Previous studies of this nature have not been done among this population, therefore the researchers sought to gather data which may prove to be useful for the growth of nuclear medicine practice in Jamaica. The study was a nonexperimental, retrospective study which involved an assessment of the records of all nuclear medicine patients who received a radiopharmaceutical during January 01, 2017, to December 31, 2018. The data extracted included age, gender, radiopharmaceutical administered, indication for study, and impression from scan. The total number of nuclear medicine scans that were carried out at the facility for the 2-year period was 3756. Of this number, 1889 (50.3%) were male and 1866 (49.7%) were female, with the age ranging from 3 months to 100 years. The types and frequencies of the most frequently occurring studies conducted were bone (2116, 56.3%), renal (867, 23.1%), thyroid (307, 8.2%), and lung (254, 6.8%). Patients aged 60 years and over accounted for the majority of the bone scans (1353/2116). The age group 26-59 years accounted for most of the scans of the lung (123/254), thyroid (209/307), parathyroid (34/65), and whole body (26/34). Patients under 12 years of age accounted for the majority of the renal (596/867), gastrointestinal (22/26), and hepatobiliary (16/28) scans. The audit of this private facility reflects the documented demand on the International Atomic Energy Agency database for Latin America and the Caribbean, and demonstrates the need for continuity of this specialized service in our population.

Impact of the COVID-19 pandemic in nuclear medicine departments: preliminary report of the first international survey

PURPOSE

Coronavirus disease-19 (COVID-19) pandemic is challenging the availability of hospital resources worldwide. The Young Group of the Italian Association of Nuclear Medicine (AIMN) developed the first international survey to evaluate the impact of COVID-19 in nuclear medicine (NM). The aim of this study was to perform a preliminary report of the ongoing survey.

METHODS

A questionnaire of thirty questions was prepared for all NM professionals addressing three main issues: (1) new scheduling praxes for NM diagnostic and therapeutic procedures, (2) assistance of patients with diagnosed or suspected COVID-19, and (3) prevention of COVID-19 spreading in the departments. An invitation to the survey was sent to the corresponding authors of NM scientific papers indexed in SCOPUS in 2019. Personal data were analysed per individual responder. Organisation data were evaluated per single department.

RESULTS

Two-hundred and ninety-six individual responders from 220 departments were evaluated. Most of the responders were from Europe (199/296, 67%). Approximately, all departments already changed their scheduling praxes due to the pandemic (213/220, 97%). In most departments, scheduled diagnostic and therapeutic procedures were allowed but quantitatively reduced (112/220, 51%). A significant reduction of diagnostic and therapeutic procedures (more than 20%) affected 198/220 (90%) and 158/220 (72%) departments, respectively. Incidental COVID-19 signs in NM exams occurred in 106/220 departments (48%). Few departments were closed or shifted to assist patients with COVID-19 (36/220, 16%). Most of the responders thought that pandemic would not permanently change the work of NM departments in the future (189/296, 64%).

CONCLUSIONS

According to this preliminary report of the first international survey, COVID-19 heavily impacted NM departments and professionals. New praxes for NM procedures, assistance, and prevention of COVID-19 have been applied during the pandemic.

Nuclear Cardiology in Asia

Nuclear cardiology for patients with ischemic heart disease and cardiac failure is expanding in Asia, although quite heterogeneously. In Asia, Israel showed the highest utilization with more than 1000 scans/100,000 inhabitants a year followed by Korea, Japan, UAE, Turkey, Australia (250-999 scans/100,000). Saudi Arabia, Kuwait, Jordan, Lebanon, Iran, and Pakistan practiced 60-99 scans/100,000. Most of South East Asian countries, China, India, and Bangladesh practiced 1-50 scans/100,000 per year. Countries in Central Asia, Mongolia, Vietnam, Cambodia, Lao, Myanmar, Nepal, and Bhutan showed limited use or no nuclear cardiology practice. Myocardial perfusion imaging (MPI) in Asia was characterized by more frequent use of ²⁰¹Tl, less use of weight-based ^99mTc dosing, and a trend toward a lower rate of stress-only imaging. Accordingly, the effective dose in nuclear cardiology practices was higher than those of the rest of the world. ⁹⁹Mo-^99mTc generators are available in most countries, relying mainly on the global supply chain because there is little supply chain beyond countries within the region. In practice, the threshold values of left ventricular ejection fraction, end-systolic volume, and end-diastolic volume between normal and pathologic states were set based on the regional normal database in China and Japan because these values were dependent on age, gender, and body weight. The purpose of the MPI SPECT study was to evaluate myocardial ischemia in symptomatic patients with chest pain, effects of percutaneous coronary intervention and coronary artery bypass-graft, and cardiac function in patients with chronic heart failure. The ability of ^99mTc-based MPI for predicting hard cardiac events was confirmed in Asian inhabitants with low risk of ischemic heart disease. Human resource development of nuclear medicine professional and public awareness of nuclear medicine is key issues to promote nuclear cardiology in Asia. International organizations such as the International Atomic Energy Agency and academic organizations in the region such as Asia Oceania Federation of Nuclear Medicine and Biology, Asia Regional Cooperative Council for Nuclear Medicine, East Asia Nuclear Medicine Association, and Arab Society of Nuclear Medicine have an important role in addition to national Societies of Nuclear Medicine in each country and region.

A convolutional neural network-based system to classify patients using FDG PET/CT examinations

BACKGROUND

As the number of PET/CT scanners increases and FDG PET/CT becomes a common imaging modality for oncology, the demands for automated detection systems on artificial intelligence (AI) to prevent human oversight and misdiagnosis are rapidly growing. We aimed to develop a convolutional neural network (CNN)-based system that can classify whole-body FDG PET as 1) benign, 2) malignant or 3) equivocal.

METHODS

This retrospective study investigated 3485 sequential patients with malignant or suspected malignant disease, who underwent whole-body FDG PET/CT at our institute. All the cases were classified into the 3 categories by a nuclear medicine physician. A residual network (ResNet)-based CNN architecture was built for classifying patients into the 3 categories. In addition, we performed a region-based analysis of CNN (head-and-neck, chest, abdomen, and pelvic region).

RESULTS

There were 1280 (37%), 1450 (42%), and 755 (22%) patients classified as benign, malignant and equivocal, respectively. In the patient-based analysis, CNN predicted benign, malignant and equivocal images with 99.4, 99.4, and 87.5% accuracy, respectively. In region-based analysis, the prediction was correct with the probability of 97.3% (head-and-neck), 96.6% (chest), 92.8% (abdomen) and 99.6% (pelvic region), respectively.

CONCLUSION

The CNN-based system reliably classified FDG PET images into 3 categories, indicating that it could be helpful for physicians as a double-checking system to prevent oversight and misdiagnosis.

Nuclear oncology as seen by me in Japan: a historical review and future perspective

Since 1964 the author has seen and experienced the progress of nuclear medicine in Japan. The purpose of this review article is to trace the application of radiopharmaceuticals and instruments for the diagnosis of tumors and treatment of cancers in the past 55 years. The application of various radiopharmaceuticals for the detection of tumors and therapy of cancers are historically reviewed based on the author's personal clinical experience and research work. Nuclear medicine has been advanced by coordinated developments of instruments and radiopharmaceuticals like two wheels of a vehicle. The journey of nuclear medicine in the past was not necessarily a smooth one having met with periodic difficulties that changed its direction. The ways by which nuclear oncology has progressed by having overcome episodic problems are described. Future perspectives focusing on the recent trend of theranostics are described with the emphasis on efforts being made by the leadership of JSNM to contribute to the progress of nuclear medicine worldwide. The author believes that the multi-and trans-disciplinary collaboration of related specialists as well as other concerned parties will be necessary for the further progress of nuclear oncology in the future.