Simplified Assessment of Radioiodine Biokinetics for Thyroid Cancer Patients: A Practical Approach Using Continuous External Radiation Monitoring.

INTRODUCTION: The biokinetics of radioiodine (RAI) in thyroid cancer patients are complex. This study aims to develop a practical approach for assessing RAI biokinetics to predict patient discharge time and estimate radiation exposure to caregivers. METHODS: We retrospectively reviewed data from patients with differentiated thyroid carcinoma undergoing RAI treatment. Serial radiation dose rates were dynamically collected during hospitalization and fitted to a biexponential model to assess the biokinetic features: RAI uptake fraction of thyroid tissue (Ft) and effective half-life of extra-thyroid tissue (Tet). Correlations with 99mTc thyroid uptake ratio (TcUR), radiation retention ratio (RR), renal function, and body mass index (BMI) were analyzed. RESULTS: Thirty-five patients were enrolled. The derived Ft was 0.08 ± 0.06 and Tet was 7.57 ± 1.45 h. Pearson's correlation analysis revealed a significant association between Ft and both TcUR and RR (p < 0.05), while Tet correlated with renal function and BMI (p < 0.05). CONCLUSION: This novel and practical method assessing RAI biokinetics demonstrates consistency with other parameters and related studies, enhancing the model reliability. It shows promise in predicting an appropriate discharge time and estimating radiation exposure to caregivers, allowing for modifications to radiation protection precautions to follow ALARA principle and minimize the potential risks from radiation exposure.

The Titrated Mannitol Improved Central [99mTc] Tc TRODAT-1 Uptake in an Animal Model-A Clinically Feasible Application.

[99mTc]Tc TRODAT-1 is a widely used single photon emission tomography (SPECT) radiopharmaceutical in Asian practice for early detection of central dopaminergic disorders. However, its imaging quality remains sub-optimal. To overcome this problem, mannitol, an osmotic agent was used to observe its effect on improving striatal [99mTc]Tc TRODAT-1 uptake in rat brain by titrated human dosages to investigate a clinically feasible way to improve human imaging quality. [99mTc]Tc TRODAT-1 synthesis and quality control were performed as described. Sprague-Dawley rats were used for this study. The animal in vivo nanoSPECT/CT and ex vivo autoradiography were employed to observe and verify the striatal [99mTc]Tc TRODAT-1 uptake in rat brains using clinically equivalent doses (i.e., 0, 1 and 2 mL groups, each n = 5) of mannitol (20% w/v, equivalent to 200 mg/mL) by an intravenous administration. Specific binding ratios (SBRs) were calculated to express the central striatal uptake in different experimental groups. In the NanoSPECT/CT imaging, the highest SBRs of striatal [99mTc]Tc TRODAT-1 were reached at 75-90 min post-injection. The averaged striatal SBRs were 0.85 ± 0.13 (2 mL normal saline, the control group), 0.94 ± 0.26 (1 mL mannitol group) and 1.36 ± 0.12 (2 mL mannitol group, p < 0.01 which were significantly different than the control as well as 1 mL mannitol groups (p < 0.05). The SBRs from ex vivo autoradiography also showed a comparable trend of the striatal [99mTc]Tc TRODAT-1 uptake in the 2 mL, 1 mL mannitol and the control groups (1.76 ± 0.52, 0.91 ± 0.29, and 0.21 ± 0.03, respectively, p < 0.05). No remarkable changes of vital signs were found in the mannitol groups and the controls. Pre-treated mannitol revealed a significant increase of the central striatal [99mTc]Tc TRODAT-1 uptake in a rat model which not only enabled us to perform pre-clinical studies of dopaminergic related disorders but also provided a potential way to further optimize image quality in clinical practice.

Very-Low-Dose Radiation and Clinical Molecular Nuclear Medicine.

Emerging molecular and precision medicine makes nuclear medicine a de facto choice of imaging, especially in the era of target-oriented medical care. Nuclear medicine is minimally invasive, four-dimensional (space and time or dynamic space), and functional imaging using radioactive biochemical tracers in evaluating human diseases on an anatomically configured image. Many radiopharmaceuticals are also used in therapies. However, there have been concerns over the emission of radiation from the radionuclides, resulting in wrongly neglecting the potential benefits against little or any risks at all of imaging to the patients. The sound concepts of radiation and radiation protection are critical for promoting the optimal use of radiopharmaceuticals to patients, and alleviating concerns from caregivers, nuclear medicine staff, medical colleagues, and the public alike.

Fully Automated Delineation of Gross Tumor Volume for Head and Neck Cancer on PET-CT Using Deep Learning: A Dual-Center Study.

Purpose: In this study, we proposed an automated deep learning (DL) method for head and neck cancer (HNC) gross tumor volume (GTV) contouring on positron emission tomography-computed tomography (PET-CT) images. Materials and Methods: PET-CT images were collected from 22 newly diagnosed HNC patients, of whom 17 (Database 1) and 5 (Database 2) were from two centers, respectively. An oncologist and a radiologist decided the gold standard of GTV manually by consensus. We developed a deep convolutional neural network (DCNN) and trained the network based on the two-dimensional PET-CT images and the gold standard of GTV in the training dataset. We did two experiments: Experiment 1, with Database 1 only, and Experiment 2, with both Databases 1 and 2. In both Experiment 1 and Experiment 2, we evaluated the proposed method using a leave-one-out cross-validation strategy. We compared the median results in Experiment 2 (GTVa) with the performance of other methods in the literature and with the gold standard (GTVm). Results: A tumor segmentation task for a patient on coregistered PET-CT images took less than one minute. The dice similarity coefficient (DSC) of the proposed method in Experiment 1 and Experiment 2 was 0.481∼0.872 and 0.482∼0.868, respectively. The DSC of GTVa was better than that in previous studies. A high correlation was found between GTVa and GTVm (R = 0.99, P < 0.001). The median volume difference (%) between GTVm and GTVa was 10.9%. The median values of DSC, sensitivity, and precision of GTVa were 0.785, 0.764, and 0.789, respectively. Conclusion: A fully automatic GTV contouring method for HNC based on DCNN and PET-CT from dual centers has been successfully proposed with high accuracy and efficiency. Our proposed method is of help to the clinicians in HNC management.

Percutaneous Cryoablation vs Partial Nephrectomy: Cost Comparison of T1a Tumors.

PURPOSE: To compare cost of percutaneous cryoablation vs open and robot-assisted partial nephrectomy of T1a renal masses from the hospital perspective. MATERIALS AND METHODS: We retrospectively compared cost, clinical and tumor data of 37 percutaneous cryoablations to 26 open and 102 robot-assisted partial nephrectomies. Total cost was the sum of direct and indirect cost of procedural and periprocedural variables. Clinical data included demographics, Charlson Comorbidity Index (CCI), hospitalization time, complication rate, ICU admission rate, and 30-day readmission rates. Tumor data included size, RENAL nephrometry score, and malignancy rate. Student's t-test was used for continuous variables and Fisher's exact or chi-square tests for categorical data. RESULTS: Mean total cost was lower for percutaneous cryoablation than open or robot-assisted partial nephrectomy: $6067 vs $11392 or $11830 (p<0.0001) with lower cost of procedure room: $1516 vs $3272 or $3254 (p<0.0001), room and board: $95 vs $1907 or $1106 (p<0.0001), anesthesia: $684 vs $1223 or $1468 (p<0.0001), and laboratory/pathology fees: $205 vs $804 or $720 (p<0.0001). Supply and device cost was higher than open: $2596 vs $1352 (p<0.0001), but lower than robot-assisted partial nephrectomy: $3207 (p=0.002). Mean hospitalization times were lower for percutaneous cryoablation (p<0.0001), while age and CCI were higher (p<0.0001). No differences in tumor size, nephrometry score, malignancy rate complication, ICU, or 30-day readmission rates were observed. CONCLUSION: Percutaneous cryoablation can be performed at significantly lower cost than open and robotic partial nephrectomies for similar masses.

Primary tumour standardised uptake value is prognostic in nonsmall cell lung cancer: a multivariate pooled analysis of individual data.

(18)F-fluoro-2-deoxy-d-glucose positron emission tomography (PET) complements conventional imaging for diagnosing and staging lung cancer. Two literature-based meta-analyses suggest that maximum standardised uptake value (SUVmax) on PET has univariate prognostic value in nonsmall cell lung cancer (NSCLC). We analysed individual data pooled from 12 studies to assess the independent prognostic value of binary SUVmax for overall survival.After searching the published literature and identifying unpublished data, study coordinators were contacted and requested to provide data on individual patients. Cox regression models stratified for study were used.Data were collected for 1526 patients (median age 64 years, 60% male, 34% squamous cell carcinoma, 47% adenocarcinoma, 58% stage I-II). The combined univariate hazard ratio for SUVmax was 1.43 (95% CI 1.22-1.66) and nearly identical if the SUV threshold was calculated stratifying for histology. Multivariate analysis of patients with stage I-III disease identified age, stage, tumour size and receipt of surgery as independent prognostic factors; adding SUV (HR 1.58, 95% CI 1.27-1.96) improved the model significantly. The only detected interaction was between SUV and stage IV disease.SUV seems to have independent prognostic value in stage I-III NSCLC, for squamous cell carcinoma and for adenocarcinoma.

Prognostic Value of (18)F-FDG PET-CT in Nasopharyngeal Carcinoma: Is Dynamic Scanning Helpful?

OBJECTIVES: To evaluate the differences in prognostic values of static and dynamic PET-CT in nasopharyngeal carcinoma (NPC). MATERIAL AND METHODS: Forty-five patients who had static scan were recruited. Sixteen had dynamic scan. The primary lesions were delineated from standardized uptake value (SUV) maps from static scan and K i maps from dynamic scan. The average follow-up lasted for 34 months. The patients who died or those with recurrence/residual disease were considered "poor outcome"; otherwise they were considered "good outcome." Fisher's exact test and ROC analysis were used to evaluate the prognostic value of various factors. RESULTS: Tumor volume thresholded by 40% of maximal SUV (VOLSUV40) significantly predicted treatment outcome (p = 0.024) in the whole cohort. In 16 patients with dynamic scan, all parameters by dynamic scan were insignificant in predicting the outcome. The combination of maximal SUV, maximal K i , VOLSUV40, and VOL K i 37 (the tumor volume thresholded by 37% maximal K i ) achieved the highest predicting accuracy for treatment outcome with sensitivity, specificity, and accuracy of 100% in these 16 patients; however this improvement compared to VOLSUV40 was insignificant. CONCLUSION: Tumor volume from static scan is useful in NPC prognosis. However, the role of dynamic scanning was not justified in this small cohort.

Systemic mastocytosis: a rare cause of single vertebral body uptake on bone scan.

Systemic Mastocytosis is a rare condition characterized by the abnormal proliferation of Mast Cells. Presentation as a solitary vertebral body lesion is extremely uncommon and may be confused with more ominous conditions such as metastasis. Familiarity with the condition can heighten clinical suspicion, direct tissue diagnosis, guide management and indicate appropriate follow up. We present a case of a 64-year-old woman undergoing staging for recently diagnosed breast cancer who was found to have Systemic Mastocytosis of a single vertebral body.

The appearance of congenitally corrected transposition of the great arteries on myocardial perfusion imaging.

We present a case of incidentally discovered congenitally corrected transposition of the great arteries (ccTGA), initially seen on stress-rest myocardial perfusion imaging (MPI). ccTGA has a characteristic appearance on MPI, which reflects the functional alterations associated with this condition.

18F-FDG PET assessment of Lewy body dementia with cerebellar diaschisis.

Alzheimer disease and Lewy body dementia are the 2 most common causes of dementia. Each disease has distinctive regional metabolic reduction patterns on (18)F-FDG PET. In this report, we present a rare case of an elderly man with dementia whereby (18)F-FDG PET clearly showed Lewy body disease with crossed cerebellar diaschisis.

The use of 99mTc-MDP bone scanning to assess facial bone growth.

Bone scanning is an important technique to detect mandibular growth, and its quantitation aids in deciding the optimal timing for surgery. Here, we will discuss a case of abnormal mandibular growth and use of bone scanning to evaluate the facial bone growth.

Implications of Ambient Glucose Variation on the Target-to-Background Ratio of Hepatic Tumors By (18)FDG-PET Imaging.

OBJECTIVES: To investigate the effects of ambient glucose on quantitative analysis of hepatic tumors on 2-deoxy-2-((18)F)-fluoro-D-glucose ((18)FDG) positron emission tomography (PET) and to establish a method for glucose correction. PATIENTS AND METHODS: Eighty-six patients with hepatic lesions identified on (18)FDG PET/computed tomography (CT) were analyzed. The serum glucose level (Glc) was recorded prior to imaging, and the maximum standardized uptake value (SUV) in the hepatic tumors and the average SUV in normal liver were determined. The inverse relationship of SUV to glucose can be defined as d (SUV)/d (Glc) = g*SUV/(Glc), where g is the glucose sensitivity. Simulations using glucose level from 70 to 250 mg/dl were performed to evaluate the effects of Glc on the maximum SUV of malignant hepatic lesions and normal liver. RESULTS: By logarithmic transformation and linear regression, g for metastasis was significantly higher than that for normal liver (-0.636 ± 0.144 vs. -0.0536 ± 0.0583; P = 0.00092). Simulation studies showed that the SUV in malignant lesions will decrease rapidly when Glc level is >120 mg/dl, while background liver remains relatively constant up to 250 mg/dl. CONCLUSION: The tumor FDG uptake is much more sensitive to ambient glucose level variation than the background liver. Therefore, correction by the glucose sensitivity factor will result in more accurate SUV measurements and make semi-quantitative analysis of (18)FDG PET scans more reliable.

Atypical Presentation of Sarcoidosis on ¹8F-FDG PET/CT.

On (18)F-FDG PET, inflammatory processes can be one of the most confounding factors for interpretation, particularly when the presentation of the process is atypical, as it was in the case of sarcoidosis reported here. Clinicians should be aware that sarcoidosis may mimic lung malignancies and lymphomas, regardless of typical or atypical appearance on (18)F-FDG PET.

Revisiting morphine-augmented hepatobiliary imaging for diagnosing acute cholecystitis: the potential pitfall of high false positive rate.

PURPOSE: The aim of this retrospective study was to investigate the efficacy of morphine-augmented hepatobiliary imaging (MAHBI) for diagnosing acute cholecystitis (AC). METHODS: Sixty-eight patients (Male:Female = 36:32, age = 54 ± 17 years) referred for diagnosis of AC by 30-min post-morphine MAHBI after the standard 1-h imaging were recruited. Non-visualization of gallbladder on 30-min post-morphine images by visual analysis was considered positive. Final diagnosis of pathological examination for all patients was used as the gold standard. RESULTS: There was significant correlation of AC and MAHBI (p < 0.05). There were 45 true positive (TP), 19 false positive (FP), 4 true negative (TN), and no false negative (FN) cases using gallbladder visualization by 30-min post-morphine as the criteria, with a high false positive rate of 83%. The sensitivity, specificity, accuracy, positive and negative predictive values of MAHBI in detecting AC were 100%, 17%, 72%, 70%, and 100%, respectively. CONCLUSIONS: MAHBI is sensitive but may not specific for diagnosing AC due to the potential pitfall of high false positive rate. Correlation with other clinical findings is recommended for optimal patient management.

Neurocysticercosis on 18F-FDG PET/MRI: co-registered Images.

This is a case of a 32-year-old female patient who presented with new onset partial complex seizures. MRI of the brain demonstrated a suspicious ring-enhancing lesion in the right temporal lobe. This finding was felt to be a primary brain malignancy or less likely an infectious process. (18)F-FDG PET of the brain was able to exclude malignancy and provided evidence to support neurocysticercosis in the mesial temporal lobe as the cause for the patient's seizures. Neurocysticercosis is a neurologic infection caused by Taenia solium. It is rare in the United States and difficult to diagnose.

Detailed characterization of the early response of head-neck cancer xenografts to irradiation using (18)F-FDG-PET imaging.

PURPOSE: To investigate the metabolic information provided by (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) during the early response of head-and-neck squamous cell carcinoma (HNSCC) xenografts to radiotherapy (RT). METHODS AND MATERIALS: Low-passage HNSCC cells (UT14) were injected into the rear flanks of female nu/nu mice to generate xenografts. After tumors grew to 400-500 mm(3), they were treated with either 15 Gy in one fraction (n = 18) or sham RT (n = 12). At various time points after treatment, tumors were assessed with 2-h dynamic FDG-PET and immediately harvested for direct histological correlation. Different analytical parameters were used to process the dynamic PET data: kinetic index (Ki), standard uptake value (SUV), sensitivity factor (SF), and retention index (RI). Tumor growth was assessed using the specific growth rate (SGR) and correlated with PET parameters using the Pearson correlation coefficient (r). Receiver operating characteristic (ROC) and the area under the ROC curve (AUC) were used to test PET parameters for their ability to predict for radiation necrosis and radiation change. RESULTS: Tumor growth was arrested for the first 20 days after RT and recovered thereafter. Histologically, radiation change was observed in the peripheral regions of tumors between days 7 and 23 after RT, and radiation necrosis were observed in the central regions of tumors between days 7 and 40. Ki provided the best correlation with SGR (r = 0.51) and was the optimal parameter to predict for early radiation necrosis (AUC = 0.804, p = 0.07). SUV(30 min) was the strongest predictor for late radiation necrosis (AUC = 0.959, p = 0.004). Both RI(30-60 min) and SF(12-70 min) were very accurate in predicting for radiation change (AUC = 0.891 and 0.875, p = 0.009 and 0.01, respectively). CONCLUSIONS: Dynamic FDG-PET analysis (such as Ki or SF) may provide informative assessment of early radiation necrosis or radiation change of HNSCC xenografts after RT.

Dynamic PET-CT studies for characterizing nasopharyngeal carcinoma metabolism: comparison of analytical methods.

OBJECTIVES: To investigate the optimal PET protocol and analytical method to characterize the glucose metabolism in nasopharyngeal carcinoma (NPC). METHODS: Newly diagnosed NPC patients were recruited and a dynamic PET-CT scan was performed. The optimized threshold to derive the arterial input function (AIF) was studied. Two-tissue compartmental kinetic modeling using three, four, and five parameters, Patlak graphical analysis, and time sensitivity (S-factor) analysis were performed. The best compartmental model was determined in terms of goodness of fit, and correlated with Ki from Patlak graphical analysis and the S-factor. The methods with R>0.9 and P<0.05 were considered acceptable. The protocols using two static scans with its retention index (RI=(SUV(2)/SUV(1)-1)×100%, where SUV is the standardized uptake value) were also studied and compared with S-factor analysis. RESULTS: The best threshold of 0.6 was determined and used to derive AIF. The kinetic model with five parameters yields the best statistical results, but the model with k4=0 was used as the gold standard. All Ki values and some S-factors from data between various intervals (10-30, 10-45, 15-30, 15-45, 20-30, and 20-45 min) fulfilled the criteria. The RIs calculated from the S-factor were highly correlated to RI derived from simple two-point static scans at 10 and 30 min (R=0.9, P<0.0001). CONCLUSION: The Patlak graphical analyses and even a 20-min-interval S-factor analysis or simple two-point static scans were shown to be sufficient to characterize NPC metabolism, confirming the clinical feasibility of applying a short dynamic with image-derived AIF or simple two-point static PET scans for studying NPC.

Revisiting the Marrow Metabolic Changes after Chemotherapy in Lymphoma: A Step towards Personalized Care.

Purpose. The aims were to correlate individual marrow metabolic changes after chemotherapy with bone marrow biopsy (BMBx) for its potential value of personalized care in lymphoma. Methods. 26 patients (mean age, 58 ± 15 y; 13 female, 13 male) with follicular lymphoma or diffuse large B-cell lymphoma, referred to FDG-PET/CT imaging, who had BMBx from unilateral or bilateral iliac crest(s) before chemotherapy, were studied retrospectively. The maximal standardized uptake value (SUV) was measured from BMBx site over the same area on both initial staging and first available restaging FDG-PET/CT scan. Results. 35 BMBx sites in 26 patients were evaluated. 12 of 35 sites were BMBx positive with interval decrease in SUV in 11 of 12 sites (92%). The remaining 23 of 35 sites were BMBx negative with interval increase in SUV in 21 of 23 sites (91%). The correlation between SUV change over the BMBx site before and after chemotherapy and BMBx result was significant (P < 0.0001). Conclusions. This preliminary result demonstrates a strong correlation between marrow metabolic changes (as determined by FDG PET) after chemotherapy and bone marrow involvement proven by biopsy. This may provide a retrospective means of personalized management of marrow involvement in deciding whether to deliver more extended therapy or closer followup of lymphoma patients.

Radiographic and metabolic response rates following image-guided stereotactic radiotherapy for lung tumors.

PURPOSE: To evaluate radiographic and metabolic response after stereotactic body radiotherapy (SBRT) for early lung tumors. MATERIALS AND METHODS: Thirty-nine tumors were treated prospectively with SBRT (dose=48-60 Gy, 4-5 Fx). Thirty-six cases were primary NSCLC (T1N0=67%; T2N0=25%); three cases were solitary metastases. Patients were followed using CT and PET at 6, 16, and 52 weeks post-SBRT, with CT follow-up thereafter. RECIST and EORTC criteria were used to evaluate CT and PET responses. RESULTS: At median follow-up of 9 months (0.4-26), RECIST complete response (CR), partial response (PR), and stable disease (SD) rates were 3%, 43%, 54% at 6 weeks; 15%, 38%, 46% at 16 weeks; 27%, 64%, 9% at 52 weeks. Mean baseline tumor volume was reduced by 46%, 70%, 87%, and 96%, respectively at 6, 16, 52, and 72 weeks. Mean baseline maximum standardized uptake value (SUV) was 8.3 (1.1-20.3) and reduced to 3.4, 3.0, and 3.7 at 6, 16, and 52 weeks after SBRT. EORTC metabolic CR/PR, SD, and progressive disease rates were 67%, 22%, 11% at 6 weeks; 86%, 10%, 3% at 16 weeks; 95%, 5%, 0% at 52 weeks. CONCLUSIONS: SBRT yields excellent RECIST and EORTC based response. Metabolic response is rapid however radiographic response occurs even after 1-year post treatment.