Asia Oceania Journal of Nuclear Medicine and Biology最新文献

Objectives: This study aimed to examine the influence of changes in CT values on PET images, specifically focusing on errors in CT-based attenuation correction and scatter coincidence correction (CTAC/SC) caused by gastrointestinal gas. Furthermore, it aimed to demonstrate the effectiveness of time-of-flight (TOF) PET in reducing CTAC/SC errors.

Methods: PET images were reconstructed using multiple CT images with varying CT values. The study then compared the fluctuations in pixel values of the PET images corresponding to the different CT values utilized for CTAC/SC between non-TOF and TOF acquisitions.

Results: PET pixel values fluctuated with changes in CT values. In the phantom study, TOF showed a significantly smaller change in PET pixel value of 1.00±0.27 kBq/mL compared to 3.72±1.33 kBq/mL in the non-TOF at sites with a CT change of +1000 HU. In the patient study, a linear regression analysis was performed to determine the effect of changes in CT values due to gastrointestinal gas migration on standard uptake value (SUV).The results showed that the TOF group had a lower ratio of change in SUV to change in CT values compared to the non-TOF group. These findings revealed that PET pixel values exhibited fluctuations in response to changes in CT values, and TOF-PET effectively mitigated CTAC/SC errors arising from gastrointestinal gas.

Conclusions: TOF-PET has the potential to reduce the occurrence of suspicious accumulation.

Malignant peripheral nerve sheath tumors (MPNST) are rare, aggressive soft tissue sarcomas that arise from peripheral nerves and often present a diagnostic and therapeutic challenge. They can occur sporadically or in association with neurofibromatosis type 1 (NF1), a genetic disorder caused by mutations in the NF1 gene. This report presents the unique case of a 33-year-old male with progressive dry cough, hoarseness, and neck swelling who underwent a total thyroidectomy, revealing a high-grade malignant peripheral nerve sheath tumor invading the thyroid. FDG PET/CT led to the additional diagnosis of NF1. This case stands out due to the rarity of finding an MPNST within the thyroid and the simultaneous identification of NF1. It underscores the importance of screening MPNST patients for NF1 and vice versa, spotlighting the expanding role of FDG PET/CT in comprehensive evaluations. To our knowledge, this report presents the first case of NF1-associated MPNST with thyroid involvement worldwide.

Objectives: In systemic radionuclide therapy such as radioiodine (I-131) for differentiated thyroid cancer, post-therapy dosimetry is essential to verify pre-therapy predictions, which in turn informs the next treatment. However, post-therapy multi-time point dosimetry is resource intensive and unfeasible in many institutions. We devised a schema of rapid predictive dosimetry by circumventing post-First Strike multi-time point dosimetry with carefully assigned gestalt values of predicted kinetics to personalise the Second Strike prescription.

Methods: Verification is performed after the First Strike. Patient-specific time-activity curve is plotted from serial measurements of whole body exposure rates to obtain its decay constant; its inverse is the whole body Time Integrated Activity Coefficient (TIAC). The percentage of whole body TIAC attributed to blood is carefully assigned by gestalt based on population kinetics tabulated in Part 1, adjusted by any metastasis on I-131 whole body scintigraphy. Marrow absorbed dose is calculated by EANM formularism. Lung safety threshold at 48h post-therapy is linearly scaled by height, where the patient's risk of lung radiotoxicity is revealed from the whole body time-activity curve value at 48h. Predictive prescription for the second I-131 fraction (Second Strike) is by careful gestalt assessment based on predicted kinetics, remaining marrow and lung tolerance, marrow dose rate constraint per fraction (0.265 Gy/h), local regulatory and facility requirements in relation to radiation protection. Tumour dosimetry is obviated under the assumption of severe tumour absorbed dose heterogeneity. The final prescription for the Second Strike is usually the lowest I-131 activity amongst all clinical, dosimetric and regulatory constraints.

Results: This schema is incorporated into a Predictive Calculator spreadsheet for rapid predictive dosimetry, and is freely available. Calculations may be completed within minutes to generate personalised predictive prescriptions, making it feasible for routine clinical implementation.

Conclusion: Our innovative schema of rapid verification and predictive dosimetry bridges the technological gap between empiric vs theranostic prescription to help institutions modernise. Its expeditious design makes this schema feasible to be integrated into the routine clinical workflow. Its predictive estimates provide invaluable dosimetric insight to inform the next I-131 fraction, allowing every prescription to be scientifically rationalised and personalised according to individual circumstances.

A 50-year-old woman was diagnosed with iron deficiency anemia on general medical examination. Further, contrast-enhanced abdominal CT and magnetic resonance imaging revealed a large hypervascular mass with internal degeneration and necrosis in the retroperitoneal space. She was referred to our hospital for further evaluation and treatment. Because the paraganglioma was most likely as the imaging diagnosis, ¹²³I-MIBG scintigraphy was performed. It revealed the marked abnormal accumulation in the retroperitoneal lesion indicating the paraganglioma and no other abnormal accumulation was noted. Several plasma catecholamines and their urinary metabolites were normal. On the subsequent ¹⁸F-FDG PET/CT, high FDG uptake was found in the retroperitoneal lesion (SUV_max=38). FDG uptake was also found in a small nodule at the base of the lower lobe of the right lung (SUV_max= 9.8). Contrast-enhanced imaging revealed a hypervascular nodule at the base of the right lung, suggesting pulmonary metastasis of a paraganglioma. The abdominal lesion and right lung nodule were excised, and retroperitoneal paraganglioma and pulmonary metastasis were diagnosed based on the pathology findings. In this case, ¹⁸F-FDG PET/CT was useful in the search for paraganglioma metastasis. We report a relationship between ¹²³I-MIBG accumulation and ¹⁸F-FDG uptake in paraganglioma and review the relevant literature.

Movement disorders are chronic neurological syndromes with both treatable and non-treatable causes. The top causes of movement disorders are Parkinson's disease and related disorders. Functional imaging investigations with Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) images play vital roles in diagnosis and differential diagnosis to guide disease management. Since there have been new advanced imaging technologies and radiopharmaceuticals development, there is a need for up-to-date consensus guidelines. Thus, the Nuclear Medicine Society of Thailand, the Neurological Society of Thailand, and the Thai Medical Physicist Society collaborated to establish the guideline for Nuclear Medicine investigations in movement disorder for practical use in patient care. We have extensively reviewed the current practice guidelines from other related societies and good quality papers as well as our own experience in Nuclear Medicine practice in movement disorders. We also adjust for the most suitability for application in Thailand and other developing countries.

Tenosynovial giant cell tumors represent a group of typically non-malignant tumors found within the joints and soft tissues. The occurrence of tenosynovial giant cell tumor alongside hematologic malignancies is an infrequent finding. Herein, we report a patient who presented with coinciding Hodgkin Lymphoma (HL) and tenosynovial giant cell tumor before chemotherapy initiation. The case was discovered during initial assessment using [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography/computed tomography (PET/CT) imaging for HL staging. An unrelated hypermetabolic mass within the left knee joint led to the discovery of this unusual case, which led to a CT-guided biopsy and tenosynovial giant cell tumor discovery. This was clearly demonstrated in interim and end-of-therapy PET/CT studies when all lymphomatous lesions had resolved but the tenosynovial giant cell tumor remained. This case serves as a reminder of the intricate nature of oncological pathology and emphasizes the need for thorough and vigilant diagnostic evaluation for optimal management plan.

Objectives: Breast carcinoma is the most common type of cancer in females. This study aims to compare fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) uptake pattern and apparent diffusion coefficient (ADC) value for the detection of the primary tumour and axillary metastases of invasive ductal breast carcinoma.

Methods: This study included 40 breast carcinoma lesions taken from 39 patients. After staging by positron emission tomography-computed tomography (PET/CT) and diffusion-weighted magnetic resonance imaging (MRI), breast surgery with axillary lymph node dissection or sentinel lymph node biopsy was performed.

Results: Primary lesion detection rate for PET/CT and diffusion-weighted MRI was high with 39 of 40 lesions (97.5%). The sensitivity and specificity for the detection of metastatic lymph nodes in axilla were 40.9%, 88.9%, with ¹⁸F-FDG PET/CT scans and 40.9%, 83.3%, for dw-MRI, respectively. No significant correlation was detected between ADC and SUV_max or SUV_max ratios. Estrogen receptor (p=0.007) and progesterone receptor (p=0.036) positive patients had lower ADC values. Tumour SUV_max was lower in T1 than T2 tumour size (p=0.027) and progesterone receptor-positive patients (p=0.029). Tumour/background SUV_max was lower in progesterone receptor-positive patients (p=0.004). Tumour/liver SUV_max was higher in grade III patients (p=0.035) and progesterone receptor negative status (p=0.043).

Conclusions: This study confirmed the high detection rate of breast carcinoma in both modalities. They have same sensitivity for the detection of axillary lymph node metastases, whereas the PET/CT scan had higher specificity. Furthermore, ADC, SUV_max and SUV_max ratios showed some statistical significance among the patient groups according to different pathological parameters.

Economics of today's busy clinical practice demand both time and cost-efficient methods of predictive dosimetry for liver radioembolisation. A rapid predictive schema adapted from the Medical Internal Radiation Dose (MIRD) method i.e., Partition Model, has been devised that can be completed within minutes. This rapid schema may guide institutions that do not have access to software capable of comprehensive auto-segmentation of lung, tumour and non-tumorous liver, or where rigorous artery-specific tomographic predictive dosimetry is unfeasible for the routine clinical workflow. This rapid schema is applicable to any beta-emitting radiomicrosphere, although absorbed dose-response thresholds will differ according to device. Sampling errors in lung, tumour and non-tumorous liver will compound and propagate throughout this schema. This rapid schema achieves efficiency in lieu of accuracy. The user must be mindful of potentially large sampling errors and assumes all responsibility. Any suspicion of significant error requires the user to revert back to standard-of-care methods.

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.