Objective(s): The Philippine Journal of Nuclear Medicine, the official publication and peer-reviewed journal of the Philippine Society of Nuclear Medicine, serves as a primary repository of research articles by Filipino nuclear medicine physicians. Despite rapid global developments in nuclear medicine, local research output remains underexplored. With 20 volumes and multiple articles published, the PJNM best reflects the situation of nuclear medicine research in the country. This study analyzed and described local research productivity through a bibliometric analysis of PJNM from 2002 to 2025.Methods:Full-text research articles were retrieved from both physical and online sources. Eligible articles were classified by study type. Bibliographic data such as authorship and institutional affiliation were extracted. Descriptive statistics and bibliometric mapping using VOSviewer were employed to evaluate publication trends, collaboration networks, and keyword occurrences.Results:A total of 134 full text articles were included. Publication output peaked during 2010-2012, followed by stable but modest productivity in subsequent years. Observational studies (53%) comprised the majority of publications, followed by case report/series (40%), and meta-analyses/systematic review (7%). No experimental studies were published. JM Obaldo was the most prolific author (n=24), while GFL Goco demonstrated the strongest collaborative links (37). St. Luke’s Medical Center-Quezon City produced the highest research output and linkages. Keyword mapping revealed seven thematic clusters, namely: bone imaging, cardiac and parathyroid scintigraphy, radioactive iodine therapy for thyroid cancer, pediatric scintigraphy, prostate cancer and theranostics, MPI SPECT image quality, and renal scintigraphy. The more recent articles focused on oncology, PET/CT, and theranostics.Conclusion:PJNM reflects the growth and evolving focus of nuclear medicine research in the Philippines. While research output is diverse and increasingly aligned with international trends, there is a need to strengthen experimental and translational studies, foster broader collaborations, and achieve international indexing to enhance visibility and global impact.
The planar whole body iodine scan (WBIS) has traditionally been used as the primary imaging technique for assessment of patients with thyroid cancer. This case report examines the imaging findings of a 61-year-old male with follicular thyroid carcinoma who underwent total thyroidectomy and received adjuvant radioactive iodine (RAI) treatment. A planar post-ablation WBIS revealed the commonly seen pattern of multiple foci of iodine uptake in the central neck region suggesting postsurgical thyroid remnant, thyroglossal duct remnant and central lymph node metastasis. However, single photon emission computed tomography (SPECT) / computed tomography (CT) imaging excluded lymph node metastasis and revealed iodine contamination over the mentum superimposed on the thyroid bed. This case report highlights the importance of utilizing SPECT /CT even for patients with apparently central neck uptake to prevent incorrect staging and treatment planning. In this report, we also present a review of the literature highlighting various pitfalls that can affect the interpretation of the WBIS and potentially result in false-positive findings in the neck region.
Chronic Recurrent Multifocal Osteomyelitis (CRMO) is a rare autoinflammatory bone disorder characterized by episodic bone pain, swelling, and radiologic evidence of sterile osteolytic lesions. We report the case of a 59-year-old woman (initial symptoms at age 51) with rheumatoid arthritis and remote triple-negative breast cancer who developed bilateral tibial lesions, observed serially over an eight-year follow-up period. The bone lesions appeared spontaneously, remained for variable durations, and regressed without specific treatment, paralleling pain severity. Laboratory data showed elevated inflammatory markers, while biopsy ruled out infection and malignancy. Bone scintigraphy and MRI confirmed multifocal active bone lesions, consistent with CRMO. The case highlights the diagnostic challenges of CRMO in adults, especially in the presence of other autoimmune conditions, and emphasizes the importance of long-term imaging follow-up. This case also illustrates that CRMO may mimic malignancy or infectious osteomyelitis, yet respond well to anti-inflammatory therapy alone. Early recognition can prevent unnecessary interventions.
Esophageal cancers predominantly metastasize through direct invasion, lymphatic dissemination, or hematogenous spread. Frequent metastatic locations comprise the liver, lymph nodes, lungs, and bones. However, direct bronchial metastases are extremely rare. We report a case of a 50-year-old male diagnosed with esophageal squamous cell carcinoma who received neoadjuvant chemoradiotherapy and subsequent esophagectomy with gastric pull-up reconstruction. Two years after surgery, follow-up imaging indicated suspicious bronchial lesion. On 18F-FDG PET/CT, the bronchial lesion exhibited only mild 18F-FDG uptake, which may underestimate its malignancy. Histopathological assessment verified metastatic squamous cell carcinoma, congruent with the primary esophageal tumor. This case illustrates the diagnostic limitations of 18F-FDG PET/CT in specific situations and emphasizes the necessity of incorporating clinical, endoscopic, and pathological findings in intricate cases.
Oncocytic thyroid carcinoma (OTC) and tenosynovial giant cell tumor (TGCT) are rare neoplasms with distinct biological behavior, and their coexistence has not been previously well documented. We report a rare case of concurrent recurrent OTC and diffuse-type TGCT (TGCT-D) in a 45-year-old man who presented with a rapidly enlarging soft-tissue mass involving the left ankle and foot. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) demonstrated intensely FDG-avid lesions in the thyroid bed consistent with recurrent disease, as well as a hypermetabolic infiltrative musculoskeletal lesion in the left ankle and foot, initially suspected to represent metastatic spread. However, histopathological examination of the ankle lesion established the diagnosis of TGCT-D. This case illustrates an important diagnostic pitfall in oncology imaging: FDG-avid musculoskeletal lesions in patients with known malignancy do not necessarily represent metastases. Careful integration of clinical information, cross-sectional imaging, particularly MRI, and histopathological confirmation is essential to avoid misdiagnosis and to ensure appropriate management.
Objective(s): Diabetic patients are at high risk for developing diabetic cardiomyopathy, often initially presenting as left ventricular diastolic dysfunction (LVDD). While echocardiography is the standard for diagnosing LVDD, Gated SPECT (GSPECT) offers simultaneous assessment of perfusion and function. This study aimed to evaluate the diagnostic value of diastolic parameters derived from GSPECT for detecting LVDD in diabetic patients without known heart disease, using echocardiography as a reference. Methods: In this cross-sectional study, 60 diabetic patients without a history of cardiac disease underwent both GSPECT myocardial perfusion imaging and echocardiography within a two-week period. Diastolic function was assessed on GSPECT using peak filling rate (PFR) and time to peak filling rate (TTPFR). Echocardiography served as the gold standard for classifying diastolic function as normal, grade 1, or grade 2 dysfunction. Diagnostic accuracy, sensitivity, and specificity of GSPECT parameters were calculated. Results: Based on echocardiography, 51.7% of patients had LVDD (45% grade 1, 6.7% grade 2). The PFR derived from GSPECT demonstrated a sensitivity of 87% and a specificity of 48.2% for detecting LVDD, with an overall accuracy of 68.3%. TTPFR showed high sensitivity (90.3%) but low specificity (17.2%). A significant correlation was found between the ischemia pattern on GSPECT and the presence of diastolic dysfunction (p=0.01). Lower PFR values were significantly associated with male gender, age >60 years, and smoking. Conclusion: Gated SPECT, particularly the PFR parameter, shows high sensitivity for the detection of LVDD in asymptomatic diabetic patients. Incorporating diastolic function analysis into routine GSPECT reporting can provide valuable incremental information for the early diagnosis and risk stratification of diabetic cardiomyopathy.
Transthyretin cardiac amyloidosis (ATTR-CA) is increasingly recognized as a cause of heart failure in elderly patients. Noninvasive diagnosis with technetium-99m pyrophosphate (99mTc-PYP) scintigraphy has become established, but quantitative approaches for therapy monitoring remain under investigation. We present a case of wild-type ATTR-CA in an 82-year-old man treated with tafamidis. Baseline echocardiography showed concentric left ventricular hypertrophy with preserved ejection fraction, impaired global longitudinal strain, and elevated B-type natriuretic peptide (BNP). Planar and SPECT/CT imaging with 99mTc-PYP demonstrated diffuse myocardial uptake (grade 3, H/CL 1.97). Quantitative analysis with GI-BONE software yielded SUVmax 4.2, amyloid deposition volume (AmyDV) 122 cm³, and total amyloid uptake (TAU) 313. Endomyocardial biopsy confirmed wild-type ATTR. After 18 months of tafamidis therapy, symptoms persisted with further GLS impairment and BNP elevation, while echocardiographic wall thickness remained increased. In contrast, repeat PYP imaging showed reduced uptake (grade 2, H/CL 1.64) with markedly decreased quantitative indices (SUVmax 2.3, AmyDV 2 cm³, TAU 4). This case demonstrates that volumetric indices can capture substantial therapy-related changes, although discordance with functional and biomarker findings highlights the need for integrated assessment. Quantitative 99mTc-PYP SPECT/CT may serve as a promising tool for therapy monitoring in ATTR-CA.
Objective(s): Currently, the treatment of prostate and neuroendocrine tumors with radiopharmaceuticals derived from lutetium-177 is the focus of many radionuclide therapy centers. One of the reasons for turning to lutetium radiopharmaceuticals is their favorable dosimetry and stability. Directly excreting the urine of patients treated with these radiopharmaceuticals into the hospital's waste water and consequently into the city's waste water and finally into agricultural fields causes indirect radiation exposure. This study aims to calculate the radiation exposure of people in Tehran due to the presence of this radioactive material in the wastewater of urban areas. Methods: First, the activity concentration in wastewater was estimated, and then, the dose received by people was estimated via a mathematical model. Results: The amount of public dose of lutetium in wastewater from nuclear medicine centers in Tehran is 8712.9 nSv/year. Conclusion: The direct release of patients' urine into the wastewater of nuclear medicine centers in Tehran does not have a significant effect on the radiation exposure of people, and septic tanks are not necessary for these radiopharmaceuticals.
Cardiac metastases are uncommon, particularly in the left ventricle, where lesions often remain asymptomatic and can be easily overlooked on conventional imaging. Lung cancer, a leading cause of global cancer-related morbidity and mortality, accounts for approximately one-third of all cases of cardiac metastases among various malignancies. We present a 62-year-old male with stage IV squamous cell carcinoma of the lung, who exhibited widespread systemic metastases. Staging Fluorine-18 Fluorodeoxyglucose (¹⁸F-FDG) Positron Emission Tomography/Computed Tomography (PET/CT) revealed a hypermetabolic cavitary left upper lobe mass with a metastatic process involving multiple nodal, adrenal, hepatic, osseous, and cerebral deposits, along with an incidental focal FDG-avid lesion in the left ventricle that was not detected on initial CT. Echocardiography confirmed preserved cardiac function with a normal ejection fraction. Given uncommon nature of left ventricular involvement by squamous cell carcinoma and the limited number of similar reported cases, our findings contribute to the growing evidence supporting the critical role of ¹⁸F-FDG PET/CT in detecting clinically silent occult cardiac metastasis.
Objective(s): Gastric carcinoma is a major cause of cancer related mortality worldwide. Accurate staging, including detection of nodal and distant metastases, is essential for treatment planning. Conventional 18F-FDG PET/CT has important limitations in gastric cancer, especially in diffuse and mucinous histologic subtypes. Fibroblast activation protein inhibitor (FAPI) PET/CT targets cancer-associated fibroblasts and may improve lesion conspicuity.To systematically review and meta-analyse the diagnostic performance of 68Ga-FAPI PET/CT for staging of gastric carcinoma and, in studies with head-to-head data, to compare it with 18F-FDG PET/CT.Methods: This review followed PRISMA 2020 recommendations. The protocol was prospectively registered in PROSPERO (CRD420251056976). PubMed, EMBASE, Web of Science and Cochrane libraries were searched from January 2016 to December 2023 for clinical studies evaluating 68Ga-FAPI PET/CT in histologically confirmed gastric carcinoma. Two reviewers independently screened records, extracted data, and assessed risk of bias using QUADAS-2. For 68Ga-FAPI PET/CT, per patient 2×2 tables were constructed for detection of primary tumors and metastatic sites. Pooled sensitivity, specificity, positive and negative predictive values and accuracy were estimated using random effects models. Summary ROC (SROC) and hierarchical SROC (HSROC) curves were generated. Comparative analyses with 18F-FDG PET/CT were restricted to studies with head to head data in the same patient cohort, and areas under the curve (AUCs) were compared with DeLong’s test.Results: Fourteen studies (661 patients) were included; nine provided head to head comparisons with 18F-FDG PET/CT. For detection of primary gastric carcinoma with 68Ga-FAPI PET/CT, pooled sensitivity and specificity were 95-96% and 93% respectively, with an AUC of 0.96 (95% CI ~ 0.89-1.00). For metastatic disease, pooled accuracy for lymph node, omental, visceral and skeletal metastases ranged from ~89% to 97%. In head to head studies, 68Ga-FAPI PET/CT showed higher AUCs than 18F-FDG PET/CT for primary tumors (0.96 vs 0.76; p=0.001) and omental metastases (0.97 vs 0.78; p=2.6×10⁻⁵). Heterogeneity was moderate for most outcomes. Funnel plots and trim and fill analyses suggested possible small study effects, but adjusted pooled diagnostic odds ratios remained high.Conclusions: 68Ga-FAPI PET/CT demonstrates high diagnostic accuracy for staging of gastric carcinoma and appears to outperform 18F-FDG PET/CT in many settings, particularly for omental and some visceral metastases and for histologic subtypes with low FDG avidity. These findings support the use of 68Ga-FAPI PET/CT as a promising complementary imaging modality for staging and restaging, but not as a stand-alone diagnostic test. Larger, prospective multicentre studies with standardized protocols are required before routine guideline incorporation.
Primary leiomyosarcoma of the ovary is extremely rare, accounting for only 1% of ovarian tumors. Myxoid leiomyosarcoma (MLMS) is one of the subtypes. As far as we know, only few cases have been reported, and there is no imaging report of ovarian MLMS. This paper reports a case of primary MLMS of the ovary with multiple complex predominantly cystic masses and mild metabolism on PET/CT, and reviews the literature. A 70-year-old woman was admitted to the hospital due to intermittent abdominal distension accompanied by edema of lower limbs for 3 months. Abdominal CT showed multiple irregular complex predominantly cystic masses in the abdominal and pelvic cavity, with unclear lesion boundaries, and patchy mild to moderate enhancement. PET/CT showed inhomogeneous low uptake of FDG, SUVmax: 2.2；In the cystic area, there are multiple flocculent flotations with no FDG uptake. The patient underwent tumor debulking and omentectomy. Intraoperative exploration revealed that the tumors were complex, predominantly cystic masses accompanied by multiple solid septa, which originated in the right ovary. Finally, ovarian MLMS was histologically confirmed. Due to extensive myxoid degeneration, MLMS of the ovary is mostly manifested as large complex predominantly cystic masses on imaging, with uneven and mild uptake of glucose. In this paper, enhanced CT and FDG PET/CT findings of ovarian MLMS were reported, which made up the gap in the imaging of this disease.
Adrenal histoplasmosis is an uncommon manifestation of Histoplasma capsulatum infection and may closely mimic malignancy or granulomatous diseases on imaging. We describe an immunocompetent 51 year old man with 5 months of constitutional symptoms who underwent 18F-FDG PET/CT for evaluation of occult disease. The scan revealed intensely FDG avid bilateral adrenal masses with necrotic components, with no other abnormal sites. Biochemical testing confirmed primary adrenal insufficiency. CT guided adrenal biopsy, targeted to the most FDG-avid viable component, demonstrated necrotizing granulomatous inflammation with intracellular yeast forms consistent with Histoplasma capsulatum. Antifungal therapy with itraconazole plus glucocorticoid replacement led to clinical improvement and interval regression of adrenal lesions on follow-up. This case highlights the value of 18F-FDG PET/CT for detecting unsuspected adrenal histoplasmosis, localizing optimal biopsy targets, and facilitating timely treatment even in immunocompetent patients presenting with nonspecific symptoms.
Secondary and tertiary hyperparathyroidism (HPT) are common complications in patients with end-stage renal disease (ESRD) and may result in renal osteodystrophy. While [18F]-FDG PET/CT is primarily used to evaluate malignancy, it may occasionally reveal metabolic or endocrine abnormalities. A 45-year-old male with ESRD on hemodialysis presented with generalized bone pain and radiologic suspicion of malignancy. [18F]-FDG PET/CT demonstrated diffusely increased skeletal uptake and multifocal lytic bone lesions, consistent with metabolic bone disease secondary to renal osteodystrophy. Incidental findings of soft tissue nodules in both tracheoesophageal grooves suggested parathyroid pathology. Subsequent [99mTc]-Tc-sestamibi SPECT/CT confirmed parathyroid adenomas/ hyperplasia. Laboratory tests revealed elevated calcium (10.8 mg/dL), phosphorus (7.2 mg/dL), and markedly increased parathyroid hormone (3120 pg/mL) levels.This case highlights that diffuse skeletal [18F]-FDG uptake in ESRD may mimic malignancy but actually represent metabolic bone disease due to secondary or tertiary HPT. The [18F]-FDG PET/CT findings of parathyroid lesions were incidental, while [99mTc]-Tc-sestamibi SPECT/CT accurately localized the hyperfunctioning glands. FDG PET/CT can incidentally demonstrate metabolic bone disease and parathyroid-[18F] abnormalities in ESRD, but [99mTc]-Tc-sestamibi SPECT/CT remains the preferred modality for parathyroid localization. Awareness of this potential finding may prevent misinterpretation and guide appropriate management.
Hyper-IgE Syndrome (HIES) is a rare immunodeficiency predisposing patients to infections, inflammation, and occasional neoplasia. We report a 17-year-old boy with HIES who presented with severe right thigh pain. FDG-PET/CT demonstrated a right adrenal mass (SUVmax=5.4), multiple pulmonary nodules, and a lytic-sclerotic femoral lesion (SUVmax=4.6), initially suggesting disseminated malignancy. Biopsy confirmed acute osteomyelitis and a benign spindle cell tumor of the adrenal gland. Two months later, persistent fever and elevated ESR prompted re-evaluation, revealing intense FDG uptake in the thoracic aorta (SUVmax=20.5) consistent with large vessel vasculitis, later confirmed by angiography. The combination of infection, benign tumor, and vasculitis illustrates the broad FDG uptake spectrum in HIES and the risk of misdiagnosis as malignancy. Integration of clinical, imaging, and histopathologic data was critical for accurate diagnosis. This case highlights FDG-PET/CT’s value in detecting inflammatory vascular disease and monitoring therapy, while reinforcing the importance of biopsy for definitive diagnosis. In immunodeficient patients, a multimodal diagnostic approach is essential to distinguish between malignant and benign FDG-avid lesions.
Objectives:This study aimed to systematically evaluate the diagnostic accuracy of hepatobiliary scintigraphy (HBS) for detecting bile leaks in post-traumatic and postoperative settings, given the increasing incidence of such complications following hepatobiliary surgeries and abdominal trauma. Methods:A systematic review and meta-analysis were conducted in accordance with the PRISMA guidelines. Literature searches of PubMed, Embase, and Scopus databases were performed through June 19, 2025. Studies were included if they assessed patients with suspected bile leak using HBS and reported sufficient data to construct diagnostic contingency tables. The quality of included studies was assessed using the QUADAS-2 tool. Pooled sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall diagnostic accuracy were calculated. Subgroup analyses evaluated diagnostic performance across clinical contexts such as post-trauma, liver transplant/resection, and cholecystectomy. Results:Sixteen studies with 673 patients were included. The pooled sensitivity and specificity of HBS were 0.882 (95% CI: 0.81-0.93) and 0.93 (95% CI: 0.83-0.97), respectively. The pooled PPV was 0.874 and NPV was 0.965, with an area under the SROC curve of 0.94, indicating excellent diagnostic performance. Subgroup analyses showed the highest accuracy in trauma patients, while specificity varied more in postoperative settings, particularly after liver transplant or resection. Conclusion:HBS is a highly sensitive and reliable imaging modality for ruling out bile leaks. While variability in specificity warrants cautious interpretation in complex surgical cases, HBS should be considered a valuable first-line, non-invasive diagnostic tool in evaluating suspected bile leaks.
Obgective(s): Reduced bone mineral density is often observed in breast cancer patients. Routine PET/CT scans can be used for detection of low bone mineral density. To evaluate prevalence of osteopenia, osteoporosis and fracture risk in pre and post-therapy breast carcinoma patients undergoing 18F-FDG PET/CT scans.Methods: In this retrospective study L1-L4 vertebral and femoral neck CT mean Hounsfield unit attenuation and their corresponding SUVmax values from initial staging and end of treatment FDG PET/CT scans performed in breast carcinoma patients were compared. Post chemo ± hormonal therapy FDG PET/CT HU values were also compared to DXA scan T- scores.Results: Significant increase in prevalence of post chemo ± hormonal therapy osteopenia, osteoporosis and fractures (62%, 18% and 16% vs baseline of 35%, 4% and 9% respectively). CECT mean attenuation values of ≤174.6 HU and ≤117.2 HU for detection of osteopenia and osteoporosis with sensitivity of 100% and specificity of 94.2 % for L1-L4 vertebrae, and ≤176.8 HU and ≤117.8 HU for osteopenia and osteoporosis with sensitivity of 100% and specificity 96.4% at femoral necks respectively were suggested. Furthermore, mean attenuation values of ≤125.9 HU with sensitivity and specificity of ~100% and 79% and ≤124.8 HU with sensitivity of 100% and specificity ~79.8% were suggested for increased L1-L4 vertebral and femoral neck fractures prevalence/ risk respectively. An associated post chemo ± hormonal therapy decline in vertebral and femoral neck mean SUVmax values in range of 14% was also observed.Conclusions: Baseline and post chemo ± hormonal therapy follow up FDG PET/CT scans allow opportunistic evaluation and can identify a significant number of patients with osteopenia, osteoporosis and patients at increased fracture risk with a high sensitivity and good specificity. They have potential to reduce need for DXA referrals, and also enable early initiation of prophylasix and therapy.
Objectivess:To report methodology that has been developed to provide real-time monitoring of radiation emissions from subjects treated with radionuclide therapies and summarise the radioiodine retention profiles of 250 subjects treated for differentiated thyroid cancer with 131I. Methods:A small ceiling-mounted radiation detector for continuously monitoring the exposure rate in the radiation isolation rooms has been developed. Measurements were made every minute after administration of 1-6 GBq of 131I over the one to three days typical inpatient admission. The data are saved in text format and have been fitted with a mono-exponential curve to measure retention half time. Results:The average effective retention half time (t½ (Eff)) for all subjects was 11.9±3.2 hrs (range: 5.0-23.1 hrs; n=250). Over 90% of the subjects had their serum TSH levels increased by injection of recombinant human TSH prior to treatment. Average retention half-time was found to be less in subjects lower than 55 year of age (t½ (Eff)=11.5 hrs) compared to those 55 or older (t½ (Eff)=14.4 hrs) (P=0.0007). Conclusions:Despite the subjects, being free to move around the isolation room during admission and thus changing the source-detector geometry markedly, the system has been able to characterise their retention profiles after radioiodine treatment. These real-time measurements have applications in planning therapy and monitoring the subjects during their admission to the hospital and can be used for "live" updates for all staff as well as providing insights into the fate of radioiodine in the body.
Objectives:This study aimed to evaluate the role of radioiodine uptake patterns and pulmonary nodule size in predicting progression- free survival (PFS) and overall survival (OS) in DTC patients with lung metastases only. Methods:A retrospective study was conducted on 189 DTC patients with pulmonary metastasis alone who were treated and monitored at the Department of Nuclear Medicine, Hospital 108, Vietnam from January 2004 to December 2018. They were categorized based on radioiodine uptake patterns on post-therapy whole-body scans (WBS) and CT-based pulmonary nodule sizes. Prognostic factors were identified by Kaplan-Meier survival and Cox regression. Results:The 5-year and 10-year OS rates were 96.83 % and 94.71 %. DTC-LM patients with diffuse radioiodine uptake and miliary metastases demonstrated significantly higher survival rates, with 5-year and 10-year PFS rates of 100% and 98.8%, respectively. In contrast, patients with nonavid metastases exhibited a markedly lower prognosis, with 5-year and 10-year PFS rates of 58.8% and 25.2%, respectively (p<0.001). Patients with nodules <5 mm had 5-year and 10-year PFS rates of 88.8% and 73.8%, respectively, while those with nodules 5-10 mm had rates of 79.8% and 52.7%. Patients with nodules ≥10 mm experienced the worst outcomes, with 5-year and 10-year PFS rates of 70.6% and 29.3% (p<0.001). Multivariate analysis confirmed that non-avid metastases, nodule size ≥10 mm, and age ≥55 were independent predictors of poor prognosis (HR:24.99, 5.96, and 6.58; p<0.001). Conclusions:Patterns of radioiodine uptake and pulmonary nodule sizes on CT imaging are crucial predictors of long-term clinical outcomes in DTC-LM. Diffuse iodine uptake and military pulmonary metastases are associated with favorable outcomes, while non-avid lung nodules and larger nodule sizes predict poorer survival.
Objective(s): To evaluate whether radiomic features extracted from 18F-NaF PET/CT scans, analyzed using machine learning (ML) methods, can improve the differentiation between true metastatic bone lesions (TP) and false-positive benign uptake (FP), thereby enhancing the diagnostic utility of 18F-NaF PET/CT.Methods: This retrospective study included 62 patients with known primary malignancies who underwent 18F-NaF PET/CT. Lesions were classified as TP or FP based on consensus interpretation including follow-up. Patients were randomly split into training (n=41) and validation (n=21) groups. Radiomic features were extracted from PET images using LIFEx software. Feature selection (ANOVA, RFE) and ML model training (SVM, Random Forest, XGBoost) were performed. Model performance was evaluated using accuracy, specificity, sensitivity, and AUC, initially with a train/validation split and subsequently with 5-fold cross-validation incorporating feature engineering and hyperparameter tuning. Feature importance was assessed using SHAP.Results: Significant differences in SUVmax (p=0.006) and SUVmean (p=0.034) were observed between TP and FP lesions. Initial validation showed XGBoost performed best (AUC=0.78). After optimization and 5-fold cross-validation on the combined dataset (n=62), the tuned XGBoost model achieved the highest performance (Mean Accuracy: 85.7% ±2.9%, Mean AUC: 0.86), outperforming Random Forest (AUC: 0.79) and SVM (AUC: 0.74). SHAP analysis identified SUVmax, SUVmean, Voxel Volume Num, GLRLM RLNU, and Skew.Conclusion: Radiomics-based machine learning classifiers, particularly XGBoost, demonstrated strong performance in distinguishing true metastatic from false-positive benign lesions on 18F-NaF PET/CT. Integrating radiomics and ML can potentially improve the diagnostic accuracy and robustness of 18F-NaF PET/CT for assessing bone metastases. Further validation in larger cohorts is warranted.
