Nuclear Medicine and Molecular Imaging最新文献

Purpose: Since accurate lung cancer segmentation is required to determine the functional volume of a tumor in [¹⁸F]FDG PET/CT, we propose a two-stage U-Net architecture to enhance the performance of lung cancer segmentation using [¹⁸F]FDG PET/CT.

Methods: The whole-body [¹⁸F]FDG PET/CT scan data of 887 patients with lung cancer were retrospectively used for network training and evaluation. The ground-truth tumor volume of interest was drawn using the LifeX software. The dataset was randomly partitioned into training, validation, and test sets. Among the 887 PET/CT and VOI datasets, 730 were used to train the proposed models, 81 were used as the validation set, and the remaining 76 were used to evaluate the model. In Stage 1, the global U-net receives 3D PET/CT volume as input and extracts the preliminary tumor area, generating a 3D binary volume as output. In Stage 2, the regional U-net receives eight consecutive PET/CT slices around the slice selected by the Global U-net in Stage 1 and generates a 2D binary image as the output.

Results: The proposed two-stage U-Net architecture outperformed the conventional one-stage 3D U-Net in primary lung cancer segmentation. The two-stage U-Net model successfully predicted the detailed margin of the tumors, which was determined by manually drawing spherical VOIs and applying an adaptive threshold. Quantitative analysis using the Dice similarity coefficient confirmed the advantages of the two-stage U-Net.

Conclusion: The proposed method will be useful for reducing the time and effort required for accurate lung cancer segmentation in [¹⁸F]FDG PET/CT.

Purpose: In this study, we propose a deep learning (DL)-based voxel-based dosimetry method in which dose maps acquired using the multiple voxel S-value (VSV) approach were used for residual learning.

Methods: Twenty-two SPECT/CT datasets from seven patients who underwent ¹⁷⁷Lu-DOTATATE treatment were used in this study. The dose maps generated from Monte Carlo (MC) simulations were used as the reference approach and target images for network training. The multiple VSV approach was used for residual learning and compared with dose maps generated from deep learning. The conventional 3D U-Net network was modified for residual learning. The absorbed doses in the organs were calculated as the mass-weighted average of the volume of interest (VOI).

Results: The DL approach provided a slightly more accurate estimation than the multiple-VSV approach, but the results were not statistically significant. The single-VSV approach yielded a relatively inaccurate estimation. No significant difference was noted between the multiple VSV and DL approach on the dose maps. However, this difference was prominent in the error maps. The multiple VSV and DL approach showed a similar correlation. In contrast, the multiple VSV approach underestimated doses in the low-dose range, but it accounted for the underestimation when the DL approach was applied.

Conclusion: Dose estimation using the deep learning-based approach was approximately equal to that in the MC simulation. Accordingly, the proposed deep learning network is useful for accurate and fast dosimetry after radiation therapy using ¹⁷⁷Lu-labeled radiopharmaceuticals.

Introduction: Amyloid-beta (Aβ) imaging test plays an important role in the early diagnosis and research of biomarkers of Alzheimer's disease (AD) but a single test may produce Aβ-negative AD or Aβ-positive cognitively normal (CN). In this study, we aimed to distinguish AD from CN with dual-phase ¹⁸F-Florbetaben (FBB) via a deep learning-based attention method and evaluate the AD positivity scores compared to late-phase FBB which is currently adopted for AD diagnosis.

Materials and methods: A total of 264 patients (74 CN and 190 AD), who underwent FBB imaging test and neuropsychological tests, were retrospectively analyzed. Early- and delay-phase FBB images were spatially normalized with an in-house FBB template. The regional standard uptake value ratios were calculated with the cerebellar region as a reference region and used as independent variables that predict the diagnostic label assigned to the raw image.

Results: AD positivity scores estimated from dual-phase FBB showed better accuracy (ACC) and area under the receiver operating characteristic curve (AUROC) for AD detection (ACC: 0.858, AUROC: 0.831) than those from delay phase FBB imaging (ACC: 0.821, AUROC: 0.794). AD positivity score estimated by dual-phase FBB (R: -0.5412) shows a higher correlation with psychological test compared to only dFBB (R: -0.2975). In the relevance analysis, we observed that LSTM uses different time and regions of early-phase FBB for each disease group for AD detection.

Conclusions: These results show that the aggregated model with dual-phase FBB with long short-term memory and attention mechanism can be used to provide a more accurate AD positivity score, which shows a closer association with AD, than the prediction with only a single phase FBB.

Hyperfunctioning parathyroid glands may be rarely located in the thyroidal parenchyma and not identified by imaging or during surgical procedures. We present three patients with primary hyperparathyroidism related to hyperfunctioning intrathyroidal parathyroid retrospectively selected among 732 cases from own Institutional parathyroid PET/CT registry from 2018 to 2022. Intrathyroidal parathyroids showed intense ¹⁸F-fluorocholine uptake but a variable echographic pattern, inconstant ^99mTc-MIBI uptake, and atypic iodine-contrast enhancement. Although rare, the possibility of an intrathyroidal parathyroid should be considered when no hyperfunctioning gland is found on preoperative imaging and thorough bilateral neck exploration.

Early diagnosis of rheumatoid arthritis with the initiation of disease-modifying antirheumatic drugs is important to prevent future disability. Seronegative rheumatoid arthritis lacks the classical immunological markers, thus imposing clinical diagnostic difficulty. In this case, we reported ⁶⁸ Ga-FAPI PET/CT findings of seronegative rheumatoid arthritis in a 60-year-old lady. This case illustrates how ⁶⁸ Ga-FAPI PET/CT aids in the diagnosis of seronegative rheumatoid arthritis.

Metastasis from unknown primary is always a challenge because finding the true primary tumor significantly affects subsequent management. We present a case of malignant abdominal wall nodule initially diagnosed as metastasis from hepatocellular carcinoma through excisional biopsy and immunohistochemical (IHC) staining. Dual-tracer positron emission tomography/computed tomography (PET/CT) with ¹¹C-acetate and ¹⁸F-FDG, however, showed metabolic findings in favor of metastasis from lung origin, which was finally confirmed by ensuing a lung biopsy with additional IHC stains. This case illustrates the complementary molecular role of PET to pathology, particularly when dual-tracer or multi-tracer PET is used in conjunction with pathology methods for cross referencing and confirmation.

Purpose: We evaluated the kinetics of the hypoxia PET radiotracers, [18F]fluoromisonidazole ([18F]FMISO) and [18F]fluoroazomycin-arabinoside ([18F]FAZA), for tumor hypoxia detection and to assess the correlation of hypoxic kinetic parameters with static imaging measures in canine spontaneous tumors.

Methods: Sixteen dogs with spontaneous tumors underwent a 150-min dynamic PET scan using either [18F]FMISO or [18F]FAZA. The maximum tumor-to-muscle ratio (TMR_max) > 1.4 on the last image frame was used as the standard threshold to determine tumor hypoxia. The tumor time-activity curves were analyzed using irreversible and reversible two-tissue compartment models and graphical methods. TMR_max was compared with radiotracer trapping rate (k ₃), influx rate (K _i), and distribution volume (V _T).

Results: Tumor hypoxia was detected in 7/8 tumors in the [18F]FMISO group and 4/8 tumors in the [18F]FAZA group. All hypoxic tumors were detected at > 120 min with [18F]FMISO and at > 60 min with [18F]FAZA. [18F]FAZA showed better fit with the reversible model. TMR_max was strongly correlated with the irreversible parameters (k ₃ and K _i) for [18F]FMISO at > 90 min and with the reversible parameter (V _T) for [18F]FAZA at > 120 min.

Conclusions: Our results showed that [18F]FAZA provided a promising alternative radiotracer to [18F]FMISO with detecting the presence of tumor hypoxia at an earlier time (60 min), consistent with its favorable faster kinetics. The strong correlation between TMR_max over the 90-150 min and 120-150 min timeframes with [18F]FMISO and [18F]FAZA, respectively, with kinetic parameters associated with tumor hypoxia for each radiotracer, suggests that a static scan measurement (TMR_max) is a good alternative to quantify tumor hypoxia.

Supplementary information: The online version contains supplementary material available at 10.1007/s13139-022-00780-4.

Purpose: Available clinical data have revealed that coronavirus disease 2019 (COVID-19) is associated with a risk of pulmonary microthrombosis and small airway disease. These patients present with varying degrees of perfusion abnormalities. The purpose of this study was to evaluate the use of a ventilation/perfusion single-photon emission computed tomography/computed tomography (VQ SPECT/CT) in the detection and follow-up of persistent lung perfusion abnormalities that were suspected to be due to pulmonary microthrombosis, small airway disease, or both.

Methods: A retrospective study was conducted at the department of nuclear medicine of Universitas Academic Hospital in Bloemfontein, South Africa. We reviewed the studies of 78 non-hospitalized patients with COVID-19 infection referred to our department from July 2020 to June 2021 for a perfusion only SPECT/CT study or a VQ SPECT/CT study. Pulmonary embolism was suspected in all 78 cases.

Results: Seventy-eight patients were studied. The median (interquartile range) age was 45 (41-58) years, and the majority (n = 69; 88.5%) were females. Twenty-two (28.2%) of these patients had matching VQ defects with mosaic attenuation on CT. All nine of the patients who had follow-up studies had these abnormalities persistently, even after 1 year.

Conclusion: We confirm that the VQ scan is a safe and effective tool to identify and follow-up recovered COVID-19 patients with persistent ventilation and perfusion abnormalities suspicious of small airway disease and pulmonary microthrombosis.

Purpose: To evaluate the clinical outcome of Q-SPECT/CT in pulmonary thromboembolic disease.

Methods: From Jan 2020 to Jan 2021, 30 consecutive patients (M:F = 8:22; median age = 52 year (21-89)) suspected of having acute pulmonary embolism (PE) or chronic thromboembolic pulmonary hypertension (CTEPH) were referred for non-contrasted Q-SPECT/CT. All patients were COVID-19 PCR negative. MSKCC Q-SPECT/CT and/or PISAPED criteria were used to determine the presence of thromboembolic disease in Q-SPECT/CT. Final diagnosis was made based on composite reference standards that included at least 2-month clinical cardiorespiratory assessment and follow-up imaging.

Results: Q-SPECT/CT was positive in 19 patients: indeterminate in 1 and 10 were negative. Three false positive cases were observed during follow-up. Of the remaining 16 true positives, all patients' cardiorespiratory symptom were improved or stabilised after treatment with anticoagulants. The overall sensitivity, specificity, PPV, NPV and accuracy of Q-SPECT/CT were 100% (95% CI, 79.41-100%), 78.57% (95% CI, 49.20-95.34%), 84.21% (95% CI, 66.41-93.57%), 100% and 90.00% (95% CI, 73.47-97.89%) respectively.

Conclusions: In the current COVID-19 pandemic, Q-SPECT/CT can be an alternative modality to detect pulmonary thromboembolic disease. Normal Q-SPECT/CT excludes pulmonary thromboembolic disease with high degree of certainty. However, false positive has been observed.

Purpose: We investigated the prognostic value of maximum tumor dissemination (Dmax), the distance between malignant lesions that were farthest apart, as assessed by fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), and other clinical factors in patients with diffuse large B-cell lymphoma (DLBCL).We investigated the prognostic value of maximum tumor dissemination (Dmax), the distance between malignant lesions that were farthest apart, as assessed by fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), and other clinical factors in patients with diffuse large B-cell lymphoma (DLBCL).

Methods: Patients who underwent FDG PET/CT for initial staging and treatment response evaluation of DLBCL were reviewed retrospectively. Baseline Dmax, maximum standardized uptake value, total summation of all metabolic tumor volumes (tMTV), and total summation of all total lesion glycolysis (tTLG) were measured. The treatment response was evaluated at the interim and end of first-line treatment (EOT) using the Deauville score (DS). FDG PET/CT parameters and other clinical factors including sex, age, serum lactate dehydrogenase (LDH) level, stage, performance status, and the International Prognostic Index (IPI) were analyzed to identify factors prognostic of the time to progression (TTP) and disease-specific survival (DSS).

Results: A total of 63 patients were included. Univariate survival analysis identified Dmax (> 275 mm), tMTV (> 180 mL), tTLG (> 1300), interim DS (≥ 4), and EOT DS (≥ 4) as significant predictors of poor TTP. Serum LDH level (> 640 IU/L), IPI (≥ 4), tMTV (> 180 mL), tTLG (> 1300), interim DS (≥ 4), and EOT DS (≥ 4) were significant predictors of DSS. After multivariate survival analysis, Dmax (P = 0.008) and EOT DS (P = 0.005) were independent predictors of TTP. EOT DS was an independent predictor of DSS (P = 0.029).

Conclusions: Dmax at the time of diagnosis and the EOT response assessed by FDG PET/CT provide useful prognostic information additive to the IPI in patients with DLBCL.