Morphological and Metabolic Criteria of COVID-19 Vaccine Associated Axillary Nodes on 18-Fluorodeouxyglucose PET/CT Imaging in Breast Cancer Patients.

BACKGROUND:  In the current era vaccine-associated lymphadenopathy (VAL) is not an uncommon presentation on 18F-FDG PET/CT examinations in patients inoculated with Coronavirus disease 2019 (COVID-19) vaccination. In this study, we are presenting data of VAL on 18F-FDG PET/CT regarding its prevalence, temporal response to vaccination and imaging characteristics of VAL. METHODS: Seventy-eight (78) consecutive vaccinated breast cancer (BC) patients who had 18FDG PET/CT were retrospectively analyzed. All patients had COVID-19 vaccine shots in contralateral arms and none in breast cancer site axilla (BSA).  In 35 patients 18FDG avid nodes were found in vaccine site axilla (VSA). In 25 patients 18FDG avid nodes were found in BSA. Morphological criteria on CT images like size, presence of fatty hila and fat stranding of axillary nodes were analyzed. Metabolic criteria on PET images like SUVmax of nodes and liver as reference were also measured. RESULTS: Out of 78 patients, 35 had   positive nodes in VSA (45% prevalence) and 25/78 had BSA (33% prevalence). Mean duration of COVID-19 vaccination in each group was 8 ±04 week (non-significant p-value). On CT images, 18FDG avid nodes in VSA were significantly smaller (10 ± 03 mm) and with intact fatty hila without fat stranding than nodes in BSA with loss of fatty hila (25 ±10 mm; p <0.0001). Mean SUVmax of nodes in VSA was significantly lower (2.4 ±1.1) than nodes in BSA (10.2 ±5.5 - p-value <0.0001). Nodes in VSA showed a significant positive linear correlation between size and SUVmax (p-value 0.00001).  Similarly, nodes in VSA showed a significant negative linear correlation between duration and SUVmax (p-value 0.00003).  In VSA group, 03 patients having SUVmax >2 SD of Hepatic SUVmax were subjected to ultrasound guided fine needle aspiration (FNA) and turned out to be metastatic in nature. CONCLUSION: In COVID-19 vaccinated patients with BC, 18FDG avid nodes in VSA may pose diagnostic challenge. However, morphological (size < 10 mm short axis, intact fatty hila without fat stranding) and metabolic criteria (SUVmax <2.4 with negative correlation with time of inoculation) have higher diagnostic accuracy in resolving the dilemma. Nodes in VSA having SUVmax > 2 SD of hepatic SUVmax should be considered for FNA to rule out possible metastasis.

Intense Fluorodeoxyglucose Uptake in Aggressive Systemic Mastocytosis without Associated Hematological Neoplasm: Unusual Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Presentation.

Systemic mastocytosis (SM) is a relatively rare heterogeneous group of disorders characterized by uncontrolled proliferation and accumulation of clonal mast cells in one or more organs. Indolent SM is the most common variety. Less common variety is aggressive systemic mastocytosis (aSM) type with or without associated hematological neopalsm (AHN). Fludeoxyglucose (FDG) positron emission tomography/computed tomography has a limited role in aSM without AHN as these exhibit low FDG avidity. We are presenting a biopsy-proven case of aSM without AHN showing abnormally high FDG uptake in lesions involving skin, nodes, marrow, and muscles.

Hyperammonemic Encephalopathy Secondary to Urinary Tract Infection.

Hyperammonemic encephalopathy (HE) refers to a clinical condition characterized by abrupt alteration in mental status (AMS) with markedly elevated plasma ammonia levels and frequently results in intractable coma and death. While hepatic cirrhosis is by far the most common etiology for hyperammonemia together with drugs such as valproic acid as well as urea cycle disorders, non-hepatic causes of hyperammonemia are rare and pose a clinical challenge. In this report, we describe a case of HE caused by obstructive urinary tract infection due to urease-producing bacteria in a 69-year-old man with two episodes of obstructive uropathy associated with AMS resolving with treatment with antibiotics and lactulose with normalization of ammonia level. We also provide a review of the literature with emphasis on the recognition of this serious entity of HE in the setting of obstructive uropathy to avoid the possible complications that include intractable coma and high mortality from this potentially treatable disorder.

Impact of Primary Tumor Size, SUVmax of Primary Tumor and the Most Avid Neck Node on Baseline 18 FDG PET/CT upon Disease Recurrence in Head and Neck Oropharyngeal SCC Using Standardized Imaging Protocol.

Objective The purpose fo this prospective study was to find the impact of primary tumor size (Ts), standardized uptake values (SUVmax) of primary tumor, and the most avid neck node on disease recurrence in patients with head and neck oropharyngeal squamous cell carcinoma (HNOP-SCC). Material and methods We included patients with HNOP-SCC (without distant metastasis-M0 disease) who had pre- and post-treatment F-18 fluorodeoxyglucose positron emission tomography/computed tomography ( 18 FDG PET/CT) using strict standardized imaging protocol from 2017 to 2019. Based on follow-up ( 18 FDG PET/CT) findings, patients were categorized as disease free (no or minimal 18 FDG uptake ≤ background over surgical bed and no distant metastasis) and disease recurrence ( 18 FDG uptake > background over surgical bed with or without nodal and/or distant metastasis). Ts and SUVmax of primary tumor and the most avid neck node were compared and impact of these was studied upon disease recurrence. Results Total 112 patients were included. No significant difference was seen in mean age (overall: 60 ± 14 years), gender distribution (overall M:F: 69:31%), body mass index (overall: 25.20 ± 5.82), and history of diabetes (overall: 19%) between disease-free and disease recurrence groups. Similarly, no significant difference was observed for fasting blood sugar (overall: 110 ± 28 mg%), 18 FDG dose (overall: 169 ± 37 MBq), and uptake period (overall: 70 ± 12 minutes) between two groups ensuring strict adherence to standardized imaging protocol. Significant difference ( p < 0.05) was observed between disease-free and disease recurrence for Ts (25 ± 10 vs. 33 ± 14 mm), SUVmax of primary tumor (6.2 ± 6.8 vs. 9.3 ± 7.2) and the most avid neck node (2.1 ± 3.3 vs. 4.7 ± 5.9) and median follow-up (13 ± 12 vs. 08 ± 13 months), respectively. Using receiver operating characteristic analysis, Ts greater than 29 mm, baseline tumor SUVmax greater than 4.6, and nodal SUVmax greater than 6.2 were found independent predictors for disease recurrence. Nodal SUVmax greater than 6.2 was found an independent predictor of shortest disease-free survival (DFS) than Ts and tumor SUVmax. Conclusion We conclude that in HNOP-SCC, primary Ts (> 29 mm), SUVmax of primary tumor (> 4.6), and the most avid neck node (> 6.2) in baseline 18 FDG PET/CT using standardized imaging protocol are the independent predictors of disease recurrence. Furthermore, SUVmax greater than 6.2 of the most avid node predicts the shortest DFS than primary Ts and SUVmax of primary tumor.

Neurolymphomatosis - Rare presentation in non-Hodgkin's lymphoma: The role of 18F-fluorodeoxyglucose positron-emission tomography and computerized tomography imaging.

Neurolymphomatosis (NLS) is infiltration of lymphoma cells into the peripheral or cranial nervous system and is a rare manifestation of non-Hodgkin lymphoma (NHL). Nerve biopsy is considered as the gold standard for diagnosis but not a preferred choice, and magnetic resonance imaging has lower reported sensitivity. 18F-Fluorodeoxyglucose (18FDG) positron-emission tomography and computerized tomography (PET/CT) has a higher sensitivity for diagnosing and assessing the neurological and nonneurological metabolic tumor volume and response evaluation to therapy. We present the case of a lady, known to have NHL in remission. She presented with a short history of severe pain and weakness of the right lower limb. Baseline and interim 18FDG PET/CT played a crucial role in diagnosing and assessing the extent of NLS and nonneurological disease burden and also in evaluation of response to treatment.

Progression Free Survival and Predictor of Recurrence in DLBCL patients with Negative Interim 18FDG PET/CT Using Standardized Imaging and Reporting Protocols.

BACKGROUND: To determine progression free survival (PFS) and predictor of recurrence in patients with diffuse large B-cell lymphoma (DLBCL) with negative interim 18FDG PET/CT (iPET) using standardized imaging and reporting protocols. MATERIALS AND METHODS: This prospective study was conducted at PET/CT Section of a JCIA accredited healthcare facility from December 2015 till February 2020. Patients with DLBCL having complete metabolic response (CMR; Deauville score: 1-3) on iPET were selected and followed for a median period of 11 months (4-144 months).  End point response on follow-up PET/CT (either end of treatment or surveillance) was categorized as sustained CMR (sCMR) and disease recurrence. Kaplan Meier survival curve was used to measure PFS and receiver operating characteristics (ROC) was plotted for age, largest lesion size, highest standardized uptake value (SUVmax), disease stage and body mass index (BMI) on baseline scan to find their impact on recurrence. RESULTS: Total 185 patients with DLBCL who had achieved CMR on iPET with a median age 55 years (19 - 88 yr.) with male predominance (63% male) were selected. On follow-up, 123 (66%) had sCMR while recurrence was found in 34% (p <0.05). No significant difference in demographics was found between two groups. Median PFS time was 34 months (22.8 - 45.1 months). On ROC analysis, only baseline highest SUVmax was found as a significant independent predictor of disease recurrence at a cut off >22.6 (highest area under curve: 0.595; SE 0.046; p <0.05). CONCLUSION: We conclude that recurrence is found in 34% of DLBCL patients with a negative interim 18FDG PET/CT using standardized imaging and reporting protocols. Despite of early response, these patients need continued intensive follow-up especially those with a baseline SUVmax > 22.6.

Detection efficiency of 18F-flourodeoxyglucose positron emission tomography/computed tomography for primary tumors in patients with carcinoma of unknown primary.

Carcinoma of unknown primary (CUP) is defined as biopsy proven tumor metastases that remains unidentified after a thorough diagnostic evaluation. The purpose of this study was to find the detection efficiency of 18F-flourodeoxyglucose positron emission tomography/computed tomography (18FDG PET/CT) in patients with CUP. This prospective study was conducted at PET/CT Section of Department of Radiology, Aga Khan University Hospital Karachi, Pakistan from August 2017 to January 2018. Patients with a history of CUP referred for 18FDG PET/CT scan for detection of primary sites during the study were recruited. 18FDG PET/CT scan was acquired using standardized protocol, and patients with suspected primary sites underwent biopsies. Scan findings and biopsy results were analyzed to find the detection rate, sensitivity, area under curve (AUC), and positive predictive value (PPV). As no biopsy was performed in negative scan, true negative, and specificity could not be calculated. During the study, 46 consecutive patients with CUP were included. Mean age of cohort was 58 ± 17 years (63% male and 37% female) having a mean body mass index of 24.70 ± 4.97 kg/m2. Thirty-four patients (34/46) found to have a hypermetabolic focus suggestive of the primary tumor with known metastatic sites and subjected to biopsy which turned out to be positive in 26/34 patients (true positive). The primary tumor was detected in gastrointestinal and hepatobiliary in 8 (17%), head and neck in 6 (13%), genitourinary 4 (09%), lung 3 (06%), and miscellaneous sites in 5 (11%) patients. Detection rate, sensitivity and PPV of 18FDG PET/CT were 57%, 68%, and 76%, respectively. Remaining 12/46 patients with negative 18FDG PET/CT for primary focus did not have biopsy. Receiver operating character curve revealed fair diagnostic strength of 18FDG PET/CT for detecting unknown primary (AUC 0.667; P = 0.054; standard error = 0.083; confidence interval: 0.504-0.830). We conclude that 18FDG PET/CT is an effective tool for detecting primary tumor in patients with CUP and its upfront use could preclude the use of many futile diagnostic procedures. Furthermore, higher resolution scanners and acquiring delayed images in patients with negative study could reduce false-negative results in patients with CUP.

Staging and Response Evaluation to Neo-Adjuvant Chemoradiation in Esophageal Cancers Using 18FDG PET/ CT with Standardized Protocol.

Background: Precise staging of esophageal cancer (EC) is important for selection of optimal treatment option and prognostication. Aim of this study was to assess the role of 18FDG PET/CT in staging and response evaluation to neoadjuvant chemoradiation (nCR) in EC patients using standardized imaging protocol. Material and methods: This prospective study was conducted at PET/CT Section of Department of Radiology, Aga Khan University Hospital Karachi, Pakistan from July 2017 till February 2018. We included 34 biopsy proven EC patients who had 18FDG PET/CT and CT of neck, chest and abdomen as part of initial staging. Eleven patients had post-nCR 18FDG PET/CT using standardized imaging protocol as per EANM guidelines. CT and PET/CT based staging was compared. Based on PERCIST criteria, response evaluation was assessed using change in highest SUVmax (%ΔSUVmax) in baseline and follow-up scans (primary lesion, node or extra-nodal metastases). Results: Mean age of cohort was 57 ± 14 years (23 males and 11 females) having adenocarcinoma (AC) in 23 and squamous cell cancer (SCC) in 11 patients. Mean 18FDG dose, uptake time and hepatic SUVmean for baseline scans were 169 ±54 MBq, 65 ±10 minute and 1.91 ± 0.49 which were within ± 10%, ± 15% and ± 20% for follow-up scans in 11 patients respectively. Mean size (craniocaudal dimension in mm) and SUVmax of primary tumor was 56 ±27 mm and 13.4 ± 4.7. Based on 18FDG PET/CT findings, patients were categorized into N0 (10/34), N1 (09/34), N2 (11/34) and N3 (04/34) while 11/32 had stage IV disease. No significant difference was seen in AC and SCC groups. CT found stage IV disease in 3/34 (09%) while PET/CT found in 11/34 (32%; p value: 0.019) cases. PET/CT showed concordance with CT in 41% while discordance (all with upstaging) seen in 59%. On follow-up PET/CT, complete metabolic response was seen in 5/11 (45%) and partial metabolic response was noted in 6/11 (55% - p value non-significant) patients. Median %ΔSUVmax over primary lesions was 49.84% (-32.69 -100%) while over nodal sites it was 41.18% (-82.60 -100%). Conclusion: We conclude that 18FDG PET/CT was found a sensitive tool in initial staging of EC. Compared with CT, it had higher diagnostic accuracy for distant nodal and extra-nodal metastasis. %ΔSUVmax between baseline and post-nCR studies acquired with standardized protocol had changed management in more than half of our patients. For response evaluation in EC more studies with standardized 18FDG PET/CT imaging protocols are warranted.

Pure Uterine Lipoma on 18FDG PET/CT: Rare But Easy to Diagnose.

Tumors of the uterus are extremely uncommon. Pure lipomas of the uterus are very rare, and only a few cases have been reported. We are presenting a case of a post-menopausal lady, a survivor of right breast cancer who had an 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (18FDG PET/CT) for evaluation of a suspected right lung nodule. The scan was negative for hypermetabolic abnormality. However, a hypodense and non-metabolic lesion was seen in the fundus of the uterus. On subsequent hysterectomy, it was found to be a pure lipoma.

Predictors of metabolic response in propensity-matched lymphoma patients on interim 18F-fluorodeoxyglucose positron-emission tomography/computed tomography using standardized imaging and reporting protocol: Do we really have one?

The purpose of this prospective study was to determine metabolic response predictor(s) in propensity-matched patients having lymphomas who had baseline and interim 18fluorodeoxyglucose (FDG) positron-emission tomography/computed tomography (PET/CT) using strict standardized imaging and reporting protocols. This prospective study was conducted at PET/CT section of a JCI-accredited healthcare facility from April 2017 to February 2018. Patients with baseline and interim 18FDG PET/CT scans using standardized protocol were selected. Interim scans were performed not earlier than 2nd or later than 4th chemotherapy. During the study period, 97 of 112 consecutive patients with lymphomas (Hodgkin-HL: 32/97 and Non-Hodgkin-NHL: 65/97) were included in the study. Mean age of cohort was 45 ± 19 years (71% male and 29% female) having a mean body mass index (BMI) of 25.57 ± 5.54 Kg/m2 having Stage I (21%), Stage II (18%), Stage III (16%), and Stage IV (45%) disease. Bulky disease was found in 14% and 18FDG-avid marrow deposits in 33%. Standardized PET/CT imaging protocol as per EANM guidelines was strictly adopted for baseline and interim studies. %Δ changes in fasting blood sugar, 18FDG dose, uptake time, and liver SUV mean were 3.96%, 2.83%, 2.49%, and 12.15%, respectively. Based on Deauville's scoring, cohort was divided into responders having Score 1-3 (49/97) and nonresponders having Score 4-5 (48/97). The demographic analysis found no significant difference between responders and nonresponders for age, gender, BMI, staging, bulky disease or marrow involvement, and study protocol. No significant coefficient or odd ratios were found on multivariate analysis for age, gender, maximum standardized uptake value (SUVmax), size, BMI, NHL, and advance disease (Stage III and IV) in both groups (χ2: 5.12; receiver operating characteristic [95% confidence interval]: 0.616 [0.51-0.713]; P =0.528). Among responders, baseline SUVmax and tumor size had a direct correlation with a metabolic response on iPET, more pronounced in NHL than HL groups (SUVmax: 13.4 vs. 19.5 and size: 52 vs. 87 mm; P < 0.0001). We conclude that no significant predictor was found for response in propensity-matched patients with lymphomas (both HL and NHL) who had baseline and interim PET/CTs acquired with a standardized protocol. However, NHL responders were found to have higher baseline median SUVmax and larger lesion size as compared to HL responders. Although, these data are not in concordance with published findings but need to be validated with larger studies using standardized imaging and reporting protocols in propensity-matched patients with lymphomas.

Higher event rate in patients with high-risk Duke Treadmill Score despite normal exercise-gated myocardial perfusion imaging.

This prospective study was carried out to find the negative predictive value of various Duke Treadmill Scores (DTSs) in patients with normal myocardial perfusion imaging (MPI). This study was conducted from August 2012 to July 2015, and 603 patients having normal exercise MPIs were included. Patients were followed for 2 years for fatal myocardial infarction (FMI) and nonfatal myocardial infarction (NFMI). Follow-up was not available in 23 patients, leaving a cohort of 583 participants. DTS was low risk (≥5) in 286, intermediate risk (between 4 and - 10) in 211, and high risk (≤-11) in 86 patients. Patients with high- and intermediate-risk DTS were significantly elder than low-risk DTS cohort. Patients with high-risk DTS had significantly higher body mass index with male preponderance compared to other groups. No significant difference was found among three groups regarding modifiable or nonmodifiable risk factors and left ventricular ejection fraction. On follow-up, single FMI was observed in high-risk DTS group (log-rank test value = 5.779, P = 0.056). Five NFMI events were observed in high-risk DTS (94.2% survival; log-rank test value = 19.398, P = 0.0001; significant) as compared to two events each in low- and intermediate-risk DTS (nonsignificant). We conclude that patients with normal exercise MPI and low-to-intermediate risk DTS have significantly low NFMI. High-risk DTS despite normal exercise MPI had high NFMI. Further, validation studies to find the predictive value of symptomatic and asymptomatic ST deviation resulting in high-risk DTS in patients with normal exercise MPI are warranted.

Massive Tumor Thrombus in Left Renal Vein and Inferior Vena Cava in Renal Cell Carcinoma on 18-fluorodeoxyglucose Positron Emission Tomography/computerized Tomography: "Suspension Bridge Sign".

Tumor thrombosis is a relatively uncommon complication of renal cell carcinoma (RCC), and its diagnosis has therapeutic and prognostic implication. Computerized tomography (CT) is the primary imaging modality for staging RCC, but it has low sensitivity to differentiate between tumor thrombus and bland or benign thrombus. 18-fluorodeoxyglucose positron emission tomography/CT (PET/CT) has a limited role in diagnosis and staging of RCC, but its diagnostic accuracy is considerably high for detection of metabolically active tumor thrombus. We are presenting a case of metastatic left-sided RCC with massive hypermetabolic tumor thrombus extending from left kidney to left renal vein and inferior vena cava giving an interesting "Suspension Bridge" appearance on PET/CT images.

Diagnostic Challenges in Prostate Cancer and 68Ga-PSMA PET Imaging: A Game Changer?

Prostate cancer (PC) is the most frequent solid tumor in men and the third most common cause of cancer mortality among men in developed countries. Current imaging modalities like ultrasound (US), computerized tomography (CT), magnetic resonance imaging (MRI) and choline based positron emission (PET) tracing have disappointing sensitivity for detection of nodal metastasis and small tumor recurrence. This poses a diagnostic challenge in staging of intermediate to high risk PC and restaging of patients with biochemical recurrence (PSA >0.2 ng/ml). Gallium-68 labeled prostate specific membrane antigen (68Ga-PSMA) PET imaging has now emerged with a higher diagnostic yield. 68Ga-PSMA PET/CT or PET/MRI can be expected to offer a one-stop-shop for staging and restaging of PC. PSMA ligands labeled with alpha and beta emitters have also shown promising therapeutic efficacy for nodal, bone and visceral metastasis. Therefore a PSMA based theranostics approach for detection, staging, treatment, and follow-up of PC would appear to be highly valuable to achieve personalized PC treatment.

Comparison of Hemodynamic Effects and Negative Predictive Value of Normal Adenosine Gated Myocardial Perfusion Scan With or Without Caffeine Abstinence.

For vasodilator stress, myocardial perfusion imaging (MPI) with at least 12-h caffeine abstinence is recommended, as it attenuates cardiovascular hyperemic response of adenosine and dipyridamole. However, many published conflicting results have shown no significant effect upon perfusion abnormalities in MPI performed without caffeine abstinence. The aim of this study was to compare the hemodynamic changes and negative predictive value (NPV) of normal MPIs with adenosine stress performed with or without caffeine abstinence. This was a prospective study that accrued 50 patients from May 2013 till September 2013 and followed till November 2014. These patients had a normal adenosine-gated MPI (GMPI) with technetium-99m methoxy isobutyl isonitrile ((99m)Tc-MIBI) after 12-h caffeine abstinence (no-caffeine). Next day, all patients had a repeat adenosine stress within 60 min after ingestion of a cup of coffee (about 80 mg of caffeine) followed by no MPI in 30 patients due to concern about radiation dose (prior-caffeine adenosine-no MPI; group A). Twenty patients opted for a repeat MPI (prior-caffeine adenosine-MPI; group B). Adenosine-induced hemodynamic response and NPV of the normal MPI with no-caffeine and prior-caffeine protocols were compared. The mean age of the study cohort was 57 ± 9 years with a male-to-female ratio of 76:24% and mean body mass index (BMI) of 26.915 ± 4.121 kg/m(2). Prevalence of hypertension, diabetes, dyslipidemia, and positive family history were 76%, 20%, 22%, and 17%, respectively. Comparison of group A with group B revealed no significant difference in demographic parameters, hemodynamic or electrocardiography (ECG) parameters, or left ventricular (LV) function parameters during adenosine intervention with prior-caffeine and no-caffeine protocols. During the follow-up, no fatal myocardial infarction (MI) was reported but 6 nonfatal MIs were reported based upon the history of short hospitalization for chest pain but without biochemical or ECG criteria for infarction (3/30 in group A and 3/20 group B). Event-free survival (EFS) for fatal MI was 100% for both the groups while EFS for nonfatal MI was 90% for group A and 85% for group B (nonsignificant P values). Kaplan-Meier survival plot also depicted nonsignificant EFS for nonfatal MI. This study did not find any significant attenuation effect upon adenosine-induced hemodynamic response and similar NPV of a normal GMPI in patients with or without caffeine abstinence. We assume that better designed prospective studies are required to validate findings of our study and provide justification for revision of guidelines about caffeine abstinence.

Significantly Low Effective Dose from 18FDG PET/CT Scans Using Dose Reducing Strategies: "Lesser is Better".

BACKGROUND: Fluorodeoxyglucose (18FDG) PET/CT imaging has become an important component of the management paradigm in oncology. However, the significant imparted radiation exposure is a matter of growing concern especially in younger populations who have better odds of survival. The aim of this study was to estimate the effective dose received by patients having whole body 18FFDG PET/CT scanning as per recent dose reducing guidelines at a tertiary care hospital. MATERIALS AND METHODS: This prospective study covered 63 patients with different cancers who were referred for PET/CT study for various indications. Patients were prepared as per departmental protocol and 18FDG was injected at 3 MBq/Kg and a low dose, nonenhanced CT protocol (LD NECT) was used. Diagnostic CT studies of specific regions were subsequently performed if required. Effective dose imparted by 18FDG (internal exposure) was calculated by using multiplying injected dose in MBq with coefficient 1.9?102 mSv/MBq according to ICRP publication 106. Effective dose imparted by CT was calculated by multiplying DLP (mGy.cm) with ICRP conversion coefficient "k" 0.015 [mSv / (mG. cm)]. RESULTS: Mean age of patients was 49 ±18 years with a male to female ratio of 35:28 (56%:44%). Median dose of 18FDG given was 194 MBq (range: 139293). Median CTDIvol was 3.25 (2.46.2) and median DLP was 334.95 (246.70 576.70). Estimated median effective dose imparted by 18FDG was 3.69 mSv (range: 2.855.57). Similarly the estimated median effective dose by low dose (nondiagnostic) CT examination was 4.93 mSv (range: 2.14 10.49). Median total effective dose by whole body 18FDG PET plus low dose nondiagnostic CT study was 8.85 mSv (range: 5.5613.00). CONCLUSIONS: We conclude that the median effective dose from a whole body 18FDG PET/CT in our patients was significantly low. We suggest adhering to recently published dose reducing strategies, use of ToF scanner with CT dose reducing option to achieve the lower if not the lowest effective dose. This would certainly reduce the risk of second primary malignancy in younger patients with higher odds of cure from first primary cancer.

Comparable Ablation Efficiency of 30 and 100 mCi of I-131 for Low to Intermediate Risk Thyroid Cancers Using Triple Negative Criteria.

BACKGROUND: There is controversy about ablation efficacy of low or high doses of radioiodine-131 (RAI) in patients with differentiated thyroid cancers (DTC). The purpose of this prospective study was to determine efficacy of 30 mCi and 100 mCi of RAI to achieve successful ablation in patients with low to intermediate risk DTC. MATERIALS AND METHODS: This prospective cross sectional study was conducted from April 2013 to November 2015. Inclusion criteria were patients of either gender, 18 years or older, having low to intermediate risk papillary and follicular thyroid cancers with T1-3, N0/N1/Nx but no evidence of distant metastasis.Thirty-nine patients were administered 30 mCi of RAI while 61 patients were given 100 mCi. Informed consent was acquired from all patients and counseling was done by nuclear physicians regarding benefits and possible side effects of RAI. After an average of 6 months (range 6-16 months; 2-3 weeks after thyroxin withdrawal), these patients were followed up for stimulated TSH, thyroglobulin (sTg) and thyroglobulin antibodies, ultrasound neck (U/S) and a diagnostic whole body iodine scan (WBIS) for ablation outcome. Successful ablation was concluded with stimulated Tg< 2ng/ml with negative antibodies, negative U/S and a negative diagnostic WBIS (triple negative criteria). ROC curve analysis was used to find diagnostic strength of baseline sTg to predict successful ablation. RESULTS: Successful ablation based upon triple negative criteria was 56% in the low dose and 57% in the high dose group (non-significant difference). Based on a single criterion (follow-up sTg<2 ng/ml), values were 82% and 77% (again non-significant). The ROC curve revealed that a baseline sTg level ≤ 7.4 ng/ml had the highest diagnostic strength to predict successful ablation in all patients. CONCLUSIONS: We conclude that 30 mCi of RAI has similar ablation success to 100 mCi dose in patients with low to intermediate risk DTC. A baseline sTg ≤ 7.4 ng/ml is a strong predictor of successful ablation in all patients. Low dose RAI is safer, more cost effective and more convenient for patients and healthcare providers.

Factors Predicting Early Release of Thyroid Cancer Patients from the Isolation Room after Radioiodine-131 Treatment.

BACKGROUND: Patients with differentiated thyroid cancers (DTC) who receive radioactive iodine-131 (RAI) are released from isolation when their dose rate is below the regulatory requirements. The purpose of this study was establish predicting factors for early release from the isolation facility after RAI administration in patients with DTC. MATERIALS AND METHODS: This was a prospective study which included 96 (58 females and 38 males) patients with DTC who had received RAI from April 2013 till August 2015. The study was duly approved by the ethical committee of the institute. Patients who had complete information of primary tumor size (PTS), serum TSH, stimulated thyroglobulin level [sTg] with antibodies (IU/ml) at the time of RAI treatment were included. All had a normal serum creatinine level. To attain lower effective half-life good hydration and administration of soft laxative were ensured. Dose rate was measured (immediately, 24 h and 36 h) at 1 meter distance from anterior mid trunk and a dose rate <50 µSv/h was considered as the releasing criterion. At 24 h 50 patients were released while the remaining 46 patients were released at 36 h. A post-ablative whole body scan (PA-WBIS) was performed 5-8 days after RAI ablation in all patients. RESULTS: Patients released after 24 h were significantly younger, had smaller lesions with higher proportion of papillary cancer, lower sTg, lower sTg/TSH ratio and had received a lower dose of RAI as comapred to those who were discharged after 36 h. Serum TSH and gender were not found to have any significant correlation between two cohorts. ROC and multivariate analysis have shown age ≤37 years, PTS ≤ 3.8 cm, RAI ≤ 150 mCi, sTg ≤ 145 ng/ml and sTg/TSH ≤ 1.085 as strong indepedent predictors for early release. CONCLUSIONS: We conclude that younger age (≤37 years), smaller tumor size (≤3.8 cm), lower RAI dose (≤150 mCi), lower sTg (≤145 ng/ml) and a lower sTg/TSH ratio (≤ 1.085) are significant independent predictors for release at 24 h after RAI treatment in DTC patients. Effective utilization of these factors could help the treating physicians to use limited number of internment facilities with higher throughput, lower cost and lower psychological stress to patients.

Predictive value of pyramidal lobe, percentage thyroid uptake and age for ablation outcome after 15 mCi fixed dose of radioiodine-131 in Graves' disease.

PURPOSE: The purpose was to find out the efficacy of fixed 15 mCi radioactive iodine-131 (RAI) dose and predictive values of various factors for inducing hypothyroidism in Graves' disease (GD). MATERIALS AND METHODS: Retrospective study conducted from January 2012 till August 2014. Patients with GD who had a technetium-99m thyroid scan, thyroid antibodies, received fixed 15 mCi RAI and did follow endocrine clinics for at least 6 months were selected. RAI was considered successful if within 6 months of RAI therapy patients developed hypothyroidism. RESULTS: Of the 370 patients with GD who had RAI during study period, 210 (57%) qualified study criteria. Mean age of patients was 48 ± 15 years with female: male ratio of 69:31, positive thyroid antibodies in 61%, means thyroid uptake of 15.09 ± 11.23%, and presence of pyramidal lobe in 40% of total population. Hypothyroidism was achieved in 161 (77%) patients while 49 (23%) patients failed to achieve it (remained either hyperthyroid or euthyroid on antithyroid medication). Patients who became hypothyroid were significantly younger with higher proportion of presence of thyroid antibodies and pyramidal lobe and lower percentage thyroid uptake than those who failed. Multiple logistic regression analysis revealed that age (odds ratio; OR = 2.074), pyramidal lobe (OR = 3.317), thyroid antibodies (OR = 8.198), and percentage thyroid uptake (OR = 3.043) were found to be significant prognostic risk factors for post-RAI hypothyroidism. Gender was found to have nonsignificant association with the development of hypothyroidism. Receiver operating characteristic analysis revealed age <42 years and thyroid uptake <15% as threshold values for the development of post-RAI hypothyroidism. CONCLUSION: We conclude that fixed (15 mCi) RAI dose is highly effective in rendering hypothyroidism in patients with GD. Age (≤42 years), thyroid uptake (≤15%) and presence of pyramidal lobe are strong predictors of hypothyroidism and must be considered for selecting optimal RAI dose.

Hybrid Imaging in Oncology.

In oncology various imaging modalities play a crucial role in diagnosis, staging, restaging, treatment monitoring and follow up of various cancers. Stand-alone morphological imaging like computerized tomography (CT) and magnetic resonance imaging (MRI) provide a high magnitude of anatomical details about the tumor but are relatively dumb about tumor physiology. Stand-alone functional imaging like positron emission tomography (PET) and single photon emission tomography (SPECT) are rich in functional information but provide little insight into tumor morphology. Introduction of first hybrid modality PET/CT is the one of the most successful stories of current century which has revolutionized patient care in oncology due to its high diagnostic accuracy. Spurred on by this success, more hybrid imaging modalities like SPECT/CT and PET/MR were introduced. It is the time to explore the potential applications of the existing hybrid modalities, developing and implementing standardized imaging protocols and train users in nuclear medicine and radiology. In this review we discuss three existing hybrid modalities with emphasis on their technical aspects and clinical applications in oncology.

"Pseudo-thyroid lobe": A diagnostic conundrum caused by ossified anterior longitudinal ligament on bone scan.

Radionuclide bone imaging is one of the most commonly performed nuclear medicine procedure around the world and characterized by its high sensitivity and relatively low specificity. False positive findings on a bone scan are very common; however, dense uptake over unilateral ossified anterior longitudinal ligament appearing as single thyroid lobe on a bone scan has not been described in the literature.