Asia Oceania Journal of Nuclear Medicine and Biology最新文献

Objectives: The spatial resolution of emission tomographic imaging systems can lead to a significant underestimation in the apparent radioactivity concentration in objects of size comparable to the resolution volume of the system. The aim of this study was to investigate the impact of the partial volume effect (PVE) on clinical imaging in PET and SPECT with current state-of-the-art instrumentation and the implications that this has for radionuclide dosimetry estimates.

Methods: Using the IEC Image Quality Phantom we have measured the underestimation in observed uptake in objects of various sizes for both PET and SPECT imaging conditions. Both single pixel measures (i.e., SUV_max) and region of interest mean values were examined over a range of object sizes. We have further examined the impact of the PVE on dosimetry estimates in OLINDA in ¹⁷⁷Lu SPECT imaging based on a subject with multiple somatostatin receptor positive paragangliomas in the head and neck.

Results: In PET, single pixel estimates of uptake are affected for objects less than approximately 18 mm in minor axis with existing systems. In SPECT imaging with medium energy collimators (e.g., for ¹⁷⁷Lu imaging), however, the underestimates are far greater, where single pixel estimates in objects less than 2-3×the resolution volume are significantly impacted. In SPECT, region of interest mean values are underestimated in objects less than 10 cm in diameter. In the clinical case example, the dosimetry measured with SPECT ranged from more than 60% underestimate in the largest lesion (28×22 mm in maximal cross-section; 10.2 cc volume) to >99% underestimate in the smallest lesion (4×5 mm; 0.06 cc).

Conclusion: The partial volume effect remains a significant factor when estimating radionuclide uptake in vivo, especially in small volumes. Accurate estimates of absorbed dose from radionuclide therapy will be particularly challenging until robust solutions to correct for the PVE are found.

Objectives: We evaluated the relationship between regional accumulations of the tau positron emission tomography (PET) tracer THK5351 and cognitive dysfunction in the Alzheimer's disease (AD) continuum.

Methods: The cases of 18 patients with AD or mild cognitive impairment (MCI) due to AD who underwent three-dimensional MRI, fluoro-2-deoxyglucose (FDG)-(PET), Pittsburgh compound B (PiB)-amyloid PET, and THK5351-tau PET were analyzed. Their mean age was 70.6±11.3, their mean Mini-Mental State Examination (MMSE) score was 22.3±6.8, and their mean Alzheimer Disease Assessment Scale-Cognitive Subtest (ADAS) score was 12.5±7.3. To determine the correlation between each patient's four imaging results and their MMSE and ADAS scores, we performed a voxel-wise statistical analysis with statistical parametric mapping (SPM).

Results: The SPM analysis showed that the bilateral parietotemporal FDG accumulations and MMSE scores were positively correlated, and the bilateral parietotemporal FDG accumulations were negatively correlated with ADAS scores. There were significant correlations between bilateral parietotemporal and left posterior cingulate/precuneus THK5351 accumulations and MMSE/ADAS scores.

Conclusion: In the AD brain, THK5351 correlates with neuropsychological test scores as well as or more additional than FDG due to its affinity for both tau and monoamine oxidase-B (MAO-B), and measurements of THK5351 may thus be useful in estimating the progression of AD.

This series lists a pictorial quiz pertaining to identification of normal and abnormal anatomical structures and landmarks at a given level on computed tomography (CT). Readers are expected to identify and appreciate the changes from normal anatomy and variations of a given pathology. The main structures assessed in this quiz are the pons, ventricular system of the brain, and the basal cisterns. Particular emphasis is placed on the presentations of intra-cranial haemorrhages, particularly sub-arachnoid and epidural haemorrhages, and masses around the region of the pons, midbrain and cerebellum. There is also a question pertaining to increased intracranial pressure. Differential diagnoses are also given where necessary to guide clinical practice and further learning. A Points to remember section details key clinical pearls. Furthermore, key resources have been cited as recommendations for further reading. It is anticipated that this series will enhance the understanding of sectional anatomy of the brain to aid in brain CT interpretation.

Objectives: In the treatment of castration-resistant prostate cancer (CRPC) with bone metastases, radium-223 dichloride (Ra-223) is the only bone-targeted drug that shows survival benefits. Completing six courses of Ra-223 treatment is thought to be associated with better patient survival, but this treatment has a relatively high rate of acute adverse events.

Methods: This retrospective study included 85 patients from 12 institutions in Japan to investigate the clinical significance of the completion of Ra-223 treatment and acute adverse events in CRPC patients.

Results: Six courses of Ra-223 treatment were completed in 65.9% of the patients. Grade 3 or higher acute adverse events were observed in 27.1% of patients. The prostate specific antigen and alkaline phosphatase declined at 26.9% and 87.9%, respectively. The overall survival rates at 12 and 24 months were 80.7% and 63.2%, respectively. Both completion of six courses of Ra-223 treatment and absence of grade 3 or higher acute adverse events were associated with longer overall survival. In univariate analysis, factors related to the history of treatment (five or more hormone therapy agents and cytotoxic chemotherapy) and hematological parameters (Prostate specific antigen (PSA) doubling time, alkaline phosphatase, hemoglobin, albumin, and serum calcium) were associated with completing six courses of Ra-223 treatment without experiencing grade 3 or higher acute adverse events. Multivariate analysis showed that a history of chemotherapy, PSA doubling time, hemoglobin, and serum calcium showed statistical significance. We built a predictive score by these four factors. Patients with lower scores showed higher rates of treatment success (p<0.001) and longer overall survival (p<0.001) with statistical significance.

Conclusions: Accomplishing six courses of Ra-223 treatment without grade 3 or higher acute adverse events was a prognostic factor in patients with mCRPC treated with Ra-223. We built a predictive score of treatment success and need future external validation.

Objectives: The prevalence of coronary artery disease (CAD) is high in patients with epilepsy using antiepileptic drugs (AED). Epilepsy, AED, or the type and duration of AED use , may contribute to higher CAD risk.In this study, myocardial perfusion imaging (MPI) was compared between patients using carbamazepine and valproate.

Method: Out of 73 patients receiving carbamazepine or valproate monotherapy for more than 2 years, visited at a tertiary referral clinic, 32 patients participated in a 2-day stress and rest phases MPI. For each phase, 15-25 mCi 99mTc-MIBI was injected, at peak exercise or by pharmacologic stimulation for the stress phase. SPECT with cardiac gating was done by a dual-head gamma camera and processed and quantified. Scans with at least one definite reversible hypo-perfusion segment were considered abnormal.

Results: Seventeen patients received carbamazepine monotherapy and 15 valproates. Age and duration of AED use were similar between the groups. Two scans were abnormal (6.3%) both in valproate group (13.3%). Duration of AED use was higher in patients with abnormal scans. In patients receiving monotherapy >2 years, the frequency of abnormal MPI was similar between groups (P-value=0.12). In patients receiving monotherapy > 5 years, prevalence of abnormal MPI was higher in the valproate group (28.6% vs. 0.0%; P-value=0.042). Considering valproate subgroup, ischemic patients had higher duration of AED use, comparing with the normal patients (17.0±4.2 vs. 6.4±4.8, P-value=0.014).

Conclusion: MPIs were abnormal in patients receiving valproate after 5 years compared to patients receiving carbamazepine. Long-term valproate use may increase the risk of CAD.

¹⁸F-fluorodeoxyglucose Positron emission tomography (¹⁸F-FDG PET/CT ) is now being used as a single modality for metastatic workup and response evaluation in breast cancer. An increase in metabolic activity indicates disease progression; however, metabolic flare should be kept in mind. Metabolic flare is a well-documented phenomenon reported in metastatic breast and prostate cancer. Despite a favorable response to therapy, there is a paradoxical increase in radiopharmaceutical uptake. The flare phenomenon with various chemotherapeutic and hormonal agents is well acknowledged in bone scintigraphy. However, very few cases have been documented on PET/CT. Increased uptake may be noted after treatment is instituted. The increased osteoblastic activity is associated with the healing response of bone tumors. We report a case of treated breast cancer. She presented with metastatic recurrence after four years of initial management. The patient was started on paclitaxel chemotherapy. Serial ¹⁸F- FDG PET/CT demonstrated metabolic flare and complete metabolic response.

Graves' disease (GD) is the commonest cause of hyperthyroidism, accounted for 70-80% in iodine sufficient countries and up to 50% in iodine deficient countries. Combination of genetic predisposition and environmental factors influences the development of GD. Graves' orbitopathy (GO) represents the most common extra-thyroidal manifestation of GD with substantial impact on morbidity and quality of life. Expression of thyroid stimulating hormone receptor (TSHR) mRNA and protein in orbital tissues infiltrated by the activated lymphocytes produced by thyroid cells (Thyroid Receptor Antibody) results in the secretion of inflammatory cytokines that leads to the development of histological and clinical characteristics of GO. A subdivision of TRAb, thyroid stimulating antibody (TSAb), was found to have a close relationship with the activity and severity of GO, and suggested to be considered as a direct parameter of GO. Here, we present a 75-year-old female with a history of GD that has successfully been treated with radioiodine treatment, who developed GO 13 months after therapy while being hypothyroid with high TRAb level. The patient was given a second dose of radioiodine ablation to maintain GO with successful result.

Objectives: While increased uptake at the bone fractural site gradually decreases over time on bone scans, the rate of change has not been quantitatively evaluated. The purpose of this study was to quantify the extent of bone metabolic changes in fractural lesions on bone SPECT/CT.

Methods: We reviewed bone scans acquired by dedicated SPECT/CT and chose those scans in which quantitative SPECT/CT of the same range was acquired twice or more. We set the region of interest on lesions of bone fracture and degeneration, and measured the maximum standardized uptake value (SUV_max). From the SUV_max of lesions and the interval between scans, a value for 30-day change in SUV_max was calculated as ∆SUV_max30d. The relationship between preSUV_max, SUV_max for the first scan of the comparison, and ∆SUV_max30d was evaluated utilizing a linear least-squares method. Furthermore, we assessed the ability to differentiate between fracture and degeneration using receiver operating characteristics (ROC) analysis and the Mann-Whitney U test. All cases were then categorized into five groups according to preSUV_max. Values of p <0.05 were considered statistically significant.

Results: We investigated 175 scans from 60 patients and analyzed scan combinations for 157 fractural lesions and 266 degenerative lesions. The relationship between preSUV_max of fractural lesions and ∆SUV_max30d was approximated as ∆SUV_max30d =-0.15×preSUV_max +1.35 (R ²=0.60, p<0.0001). Area under the curves for all cases, 30≤ preSUV_max, 20≤ preSUV_max <30, 15≤ preSUV_max <20, 10≤ preSUV_max <15, and preSUV_max <10 were 0.73, 0.89, 0.86, 0.80, 0.91, and 0.59, respectively. Median ∆SUV_max30d was significantly lower at fractural lesions than at degenerative lesions (-0.62 vs -0.04; p <0.0001). As for analyses of groups divided by preSUV_max, all median ∆SUV_max30d for fractural lesions were significantly lower than those of degenerative lesions except for the group with preSUV_max <10.

Conclusion: The increased uptake at the fractural bone lesion observed in the quantitative bone SPECT/CT gradually decreased at the rate of SUV 0.15 per month, which showed a different trend with degenerative change.

Objectives: This study aimed to create a deep learning (DL)-based denoising model using a residual neural network (Res-Net) trained to reduce noise in ring-type dedicated breast positron emission tomography (dbPET) images acquired in about half the emission time, and to evaluate the feasibility and the effectiveness of the model in terms of its noise reduction performance and preservation of quantitative values compared to conventional post-image filtering techniques.

Methods: Low-count (LC) and full-count (FC) PET images with acquisition durations of 3 and 7 minutes, respectively, were reconstructed. A Res-Net was trained to create a noise reduction model using fifteen patients' data. The inputs to the network were LC images and its outputs were denoised PET (LC + DL) images, which should resemble FC images. To evaluate the LC + DL images, Gaussian and non-local mean (NLM) filters were applied to the LC images (LC + Gaussian and LC + NLM, respectively). To create reference images, a Gaussian filter was applied to the FC images (FC + Gaussian). The usefulness of our denoising model was objectively and visually evaluated using test data set of thirteen patients. The coefficient of variation (CV) of background fibroglandular tissue or fat tissue were measured to evaluate the performance of the noise reduction. The SUV_max and SUV_peak of lesions were also measured. The agreement of the SUV measurements was evaluated by Bland-Altman plots.

Results: The CV of background fibroglandular tissue in the LC + DL images was significantly lower (9.10$\pm$2.76) than the CVs in the LC (13.60$\pm$ 3.66) and LC + Gaussian images (11.51$\pm$ 3.56). No significant difference was observed in both SUV_max and SUV_peak of lesions between LC + DL and reference images. For the visual assessment, the smoothness rating for the LC + DL images was significantly better than that for the other images except for the reference images.

Conclusion: Our model reduced the noise in dbPET images acquired in about half the emission time while preserving quantitative values of lesions. This study demonstrates that machine learning is feasible and potentially performs better than conventional post-image filtering in dbPET denoising.

Objectives: The aim of this study was to investigate the effect on standardized uptake value (SUV) measurement variability of the positional relationship between objects of different sizes and the pixel of a positron emission tomography (PET) image.

Methods: We used a NEMA IEC body phantom comprising six spheres with diameters of 10, 13, 17, 22, 28, and 37 mm. The phantom was filled with ¹⁸F solution and contained target-to-background ratios (TBRs) of 2, 4, and 8. The PET data were acquired for 30 min using a SIGNA PET/MR scanner. The PET images were reconstructed with the ordered subsets expectation maximization (OSEM) algorithm with and without point-spread function (PSF) correction (OSEM + PSF + Filter and OSEM + Filter, respectively). A Gaussian filter of 4 mm full width at half maximum was applied in all reconstructions, except for one model (OSEM + PSF + no Filter). The matrix sizes were 128×128, 192×192, 256×256 and 384×384. Reconstruction was performed by shifting the reconstruction center position by 1 mm in the range 0 to 3 mm in the upward or rightward direction for each parameter. For all reconstructed images, the SUV_max of each hot sphere was measured. To investigate the resulting variation in the SUV_max, the coefficient of variation (CV) of each SUV_max was calculated.

Results: The CV of the SUV_max increased as the matrix size and the diameter of the hot sphere decreased in all reconstruction settings. With PSF correction, the CV of SUV_max increased as the TBR increased except when the TBR was 2. The CV of the SUV_max measured in the OSEM + PSF + no Filter images were larger than those measured in the OSEM + PSF + Filter images. The amount of this increase was higher for smaller spheres and larger matrix sizes and was independent of TBR.

Conclusions: Shifting the reconstruction center position of the PET image causes variability in SUV_max measurements. To reduce the variability of SUV measurements, it is necessary to use sufficient matrix sizes to satisfy sampling criterion and appropriate filters.