Asia Oceania Journal of Nuclear Medicine and Biology最新文献

Objectives: To develop the following three attenuation correction (AC) methods for brain ¹⁸F-fluorodeoxyglucose-positron emission tomography (PET), using deep learning, and to ascertain their precision levels: (i) indirect method; (ii) direct method; and (iii) direct and high-resolution correction (direct+HRC) method.

Methods: We included 53 patients who underwent cranial magnetic resonance imaging (MRI) and computed tomography (CT) and 27 patients who underwent cranial MRI, CT, and PET. After fusion of the magnetic resonance, CT, and PET images, resampling was performed to standardize the field of view and matrix size and prepare the data set. In the indirect method, synthetic CT (SCT) images were generated, whereas in the direct and direct+HRC methods, a U-net structure was used to generate AC images. In the indirect method, attenuation correction was performed using SCT images generated from MRI findings using U-net instead of CT images. In the direct and direct+HRC methods, AC images were generated directly from non-AC images using U-net, followed by image evaluation. The precision levels of AC images generated using the indirect and direct methods were compared based on the normalized mean squared error (NMSE) and structural similarity (SSIM).

Results: Visual inspection revealed no difference between the AC images prepared using CT-based attenuation correction and those prepared using the three methods. The NMSE increased in the order indirect, direct, and direct+HRC methods, with values of 0.281×10^-3, 4.62×10^-3, and 12.7×10^-3, respectively. Moreover, the SSIM of the direct+HRC method was 0.975.

Conclusion: The direct+HRC method enables accurate attenuation without CT exposure and high-resolution correction without dedicated correction programs.

Peritoneal carcinomatosis (PC), the spread of cancer cells in the peritoneum, is a significant concern in advanced gastrointestinal and gynecological cancers. This case series includes findings on the appearance and pattern of PC on ¹⁸F-fluorodeoxyglucose positron emission tomography/CT (¹⁸F-FDG PET/CT). The primary sources of peritoneal dissemination are direct invasion from abdominal or pelvic tumors and metastatic spread from distant tumors. The accurate preoperative diagnosis and quantification of PC play a vital role in determining the appropriate treatment approach, with a particular emphasis on surgical planning. Several imaging modalities have been employed in preoperative evaluation, such as computed tomography (CT), magnetic resonance imaging (MRI), and ¹⁸F-FDG PET/CT. Among these modalities, ¹⁸F-FDG PET/CT has demonstrated improved anatomical localization and accurate information about the nature of pathological findings. The case series showcases four cases that illustrate the imaging characteristics of PC on FDG PET/CT. FDG PET/CT plays a vital role in diagnosing and assessing PC, aiding in its detection, staging, and treatment planning. It surpasses conventional imaging techniques in identifying and characterizing lesions and detecting the primary tumor site in cases where its location is unknown. Furthermore, FDG PET/CT additionally assists in evaluating treatment response and monitoring disease progression, providing insights into treatment effectiveness and guiding patient management decisions.

Objectives: To address the problem of using large volumes of long-lived radionuclides in test phantoms to check calibration accuracy of PET and SPECT systems we have developed a test object which (a) contains less radioactivity, (b) has a low total volume, and (c) is easier to store than currently used phantoms, while still making use of readily-available "standardised" test objects.

Methods: We have designed a hollow acrylic cylindrical insert compatible with the NEMA/IEC PET Body Image Quality (IQ) phantom used in NU 2 performance testing of PET systems. The insert measures 90 mm internal diameter and 70 mm internal height and so is sufficiently large to not be subject to partial volume effects in PET or SPECT imaging. The volume of the insert is approximately 500 mL. It has been designed as a replacement for the standard long cylindrical "lung insert" in the IQ phantom without needing to remove the fillable hollow spheres of the phantom. The insert been tested with ¹⁸F, ⁶⁸Ga and ¹²⁴I PET/CT and ^99mTc, ¹³¹I and ¹⁷⁷Lu SPECT/CT on scanners that had previously been calibrated for these radionuclides.

Results: The scanners were found to produce accurate image reconstructions in the insert with  5% of the true value without any confounding uncertainty from partial volume effects when compared to NEMA NU 2-2018 Phantom measurement.

Conclusions: The "ARTnet Insert" is simple to use, inexpensive, compatible with current phantoms and is suitable for both PET and SPECT systems. It does not suffer from significant partial volume losses permitting its use even with the poor spatial resolution of high-energy imaging with ¹³¹I SPECT. Furthermore, it uses less radioactivity in a smaller volume than would be required to fill the entire phantom as is usually done. Long-term storage is practical while allowing radioactive decay of the insert contents.

Objectives: Despite significant progress in the field of nuclear medicine, basic nuclear medicine awareness and understanding among clinicians remains unsatisfactory, leading to under utilization of nuclear medicine modalities. To evaluate the awareness and knowledge regarding nuclear medicine and appropriate use of Nuclear medicine modalities, among medical students and faculty members.

Method: In this descriptive cross sectional study, a self timer limited objective questionnaire based on Google forms was distributed to the study population and scores obtained by the participants were analyzed.

Results: Percent scores range for intern, residency trainees, and senior resident/faculty groups for general awareness were 16-46%, 37-58% and 62-91% and for knowledge and appropriate use were 7-21%, 28-43%, and 35-85% respectively. Overall, 61% of the participants had poor awareness and knowledge regarding nuclear medicine modalities. None of the participants had received nuclear medicine exposure or education during their academics or training. Only 49% of the participants considered utilizing nuclear medicine modalities for their patient management.

Conclusion: Undergraduate interns and residency trainees had a poor to fair level of awareness and knowledge regarding nuclear medicine. Hence creating more awareness in early stages of their career by incorporating Nuclear medicine basic education in medical undergraduate curriculum is required. The senior residents/faculty members had a moderate to good level of awareness and knowledge but still improvement in their knowledge would lead to a more appropriate and better utilization of nuclear medicine modalities for optimum patient management in a variety of clinical settings.

Perforation of the bowel can be a life-threatening condition and is usually clinically diagnosed when a patient presents with such features as severe abdominal pain, tenderness, and tachycardia. Bowel perforation may be corroborated by various conventional imaging modalities, including X-ray, ultrasonography, computed tomography, and magnetic resonance imaging. Nuclear medicine imaging modalities seldom have a role to play in these settings. Rarely diagnosis of perforation may be missed if it is concealed and does not present with the usual signs. Mostly the perforation will eventually be diagnosed if they develop signs and symptoms and is taken up for an exploratory laparotomy. A delay in diagnosis can later lead to significant patient morbidity or even mortality. This report describes a case where possible intestinal perforation was suspected on a ^99mTc-DTPA renogram in a postoperative patient with significant urine leak, the presence of which was confirmed intraoperatively. To our knowledge, this was the first such case in the literature.

Pineal gland tumors are significant despite being rare (<1%) among all brain tumors. Germ cell tumors are the most common among the pineal gland tumors. Often affecting young adults, pineal gland germ cell tumors are hard to diagnose due to different symptoms and potential spread. But they rarely show leptomeningeal spread and extracranial metastases. Other differentials include primary tumors of the pineal region, Pineal gliomas, and metastases. The leptomeningeal spread of these tumors has not been studied so far. Conventional radiological imaging modalities are routinely used to diagnose and evaluate these tumors. We report a case here showing a pineal gland tumor with leptomeningeal spread detected by ¹⁸F-FDG PET/CT. Our case shows how pineal gland tumors can behave unusually and how ¹⁸F-FDG PET/CT can be crucial for accurately assessing the extent of the disease in the body to provide effective treatment. This case report illustrates the rare type of spread of pineal gland tumor and how ¹⁸F-FDG PET/CT helps detect this rare type of metastasis, thereby helping in prognostication and deciding further treatment of the patient.

Splenosis occurs as a result of autotransplantation of splenic tissue following splenic injury or splenectomy. A 56-year-old man with esophageal cancer underwent thoracoscopic-assisted subtotal esophagectomy accompanied by three-field lymph node dissection, and retrosternal gastric tube reconstruction. The spleen was injured during the surgery and was removed. A retrosternal nodule of 12 mm in diameter was detected near the reconstructed gastric tube on computed tomography (CT) performed 3 years and 6 months postoperatively. Retrospectively, the nodule was observed in the same area on early postoperative CT and gradually increased in size. No accessory spleen was identified on the preoperative CT. Splenosis was suspected, and ^99mTc-Sn-colloid single photon emission computed tomography (SPECT)/CT was performed. It revealed intense uptake in the retrosternal nodule, consistent with the diagnosis of thoracic splenosis. Subsequently, the patient has been under observation without treatment. ^99mTc-labeled colloid SPECT/CT allowed confident diagnosis of thoracic splenosis following esophageal cancer surgery. This examination is considered valuable for the evaluation of ectopic splenic tissue.

Objectives: Physiological myocardial ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake in oncologic positron emission tomography (PET)/computed tomography (CT) is commonly observed with multiple variations under clinical fasting conditions. The purpose of the present study was to evaluate physiological myocardial ¹⁸F-FDG uptake pattern by comparing with the results in cardiac sarcoidosis.

Methods: A total of 174 examinations in 174 patients without cardiac disease and 27 examinations in 17 patients with cardiac sarcoidosis were performed. The polar map images generated from ¹⁸F-FDG PET/CT data were visually assessed as "basal-ring," "focal," and "focal on diffuse" patterns. Semi-quantitative analysis was also performed using the regional relative ¹⁸F-FDG uptake (% uptake).

Results: On visual analysis, the "focal on diffuse" pattern was the most common in both examinations (43% and 59%, respectively). The physiological % uptake in the lateral and basal septal walls tended to be higher. Subgroup analysis showed significantly higher uptake in the mid-wall and left circumflex territory. In cardiac sarcoidosis patients, there was a significant difference only between segments 2 and 15 (p=0.04). No significant differences were observed between the base-mid-apical territory and coronary artery branch territory.

Conclusion: High ¹⁸F-FDG uptake in the basal septal walls is likely to be observed as both physiological uptake in patients without cardiac disease and pathological uptake in patients with cardiac sarcoidosis.

Objectives: Clinical interest in metabolic imaging of cancer has been growing in recent years. The increase in protein metabolism of cancer cells is interesting target for metabolic tumor imaging, for which radiolabeled amino acids can be applied. The aim of this study was to evaluate a newly developed radiolabeled amino acid as an imaging protein metabolism in melanoma tumor.

Methods: The radiolabeled tyrosine ([^99mTc][Tc-HYNIC/EDDA]-Tyr) was prepared and its biological properties was evaluated in B16F10 melanoma tumor. Moreover organs uptake and tumor accumulation were measured in mouse bearing B16F10 melanoma tumor.

Results: Radiolabeled tyrosine was attached in B16F10 melanoma cells and showed the cell binding capacity of 13.82±0.73%. In animal study, the accumulation of radiolabeled tyrosine was observed in B16F10 melanoma tumor (2.15±0.09 %ID/g) after 30 min post injection, so that the uptake ratio of tumor to muscle was about 5.11. Through scintigraphy process the melanoma tumor clearly visualized in mice at 30 min post injection.

Conclusion: These data suggest that the novel radiotracer ([^99mTc][Tc-HYNIC/EDDA]-Tyr) as an protein metabolism imaging agent, is able to transfer into melanoma cells and show great expectation for the clinical application in the imaging of melanoma tumors.

¹⁸F-Flurodeoxyglucose (FDG) PET/CT has been considered the modality of choice in detecting, staging, restaging and following-up with lymphoma patients. However, it has an uncertain role in differentiating hepatic lymphomatous relapse from other granulomatous diseases such as in candidiasis or sarcoidosis. Therefore, it is important to correlate the imaging findings with other modalities such as ultrasound, CT scan, MRI, and histology to direct the diagnosis and treatment. We present a case of a 33-year-old woman with large B-cell lymphoma in complete remission following treatment presenting with neutropenic fever following her final cycle of chemotherapy. Ultrasound of the abdomen and enhanced CT scan of the abdomen and pelvis were negative. The FDG PET/CT scan showed multiple FDG-avid hypodense hepatic lesions that were suggestive either of lymphoproliferative involvement or nonmalignant process. However, MRI of the abdomen performed four days later was suggestive of an infectious process, rather than a lymphoproliferative disorder. A subsequent CT-guided biopsy of a hepatic lesion showed granulomatous inflammation, with no evidence of malignancy or Tuberculosis. The patient was started on Caspofungin followed by Fluconazole. After 5 weeks, the clinical condition resolved, and the subsequent FDG PET/CT showed complete resolution of the FDG-avid multiple hepatic lesions.