Teik Hin Tan - Academia.edu (original) (raw)

Papers by Teik Hin Tan

The Medical journal of Malaysia, 2019

BACKGROUND Lung cancer is one of the leading causes of cancer-related mortality worldwide. Pulmon... more BACKGROUND Lung cancer is one of the leading causes of cancer-related mortality worldwide. Pulmonary nodules are commonly encountered in clinical practice because of the recent implementation of low-dose CT lung screening programme, incidental finding on cardiac CT or CT for nonthoracic related disease. 18F-FDG PET-CT plays an important role in the management of pulmonary nodules. METHODS In this pictorial review, we present six different scenarios of using 18F-FDG PET-CT in the management of suspicious pulmonary nodule or mass. The advantages and limitations of 18F-FDG PET-CT and Herder model are discussed. RESULTS 18F-FDG PET-CT with risk assessment using Herder model provides added value in characterising indeterminate pulmonary nodules. Besides, 18F-FDG PET-CT is valuable to guide the site of biopsy and provide accurate staging of lung cancer. CONCLUSION To further improve its diagnostic accuracy, careful history taking, and CT morphological evaluation should be taken into consi...

Medical Physics, 2022

PURPOSE Voxel-based dosimetry is potentially accurate than organ-based dosimetry because it consi... more PURPOSE Voxel-based dosimetry is potentially accurate than organ-based dosimetry because it considers the anatomical variations in each individual and the heterogeneous radioactivity distribution in each organ. Here, voxel-based dosimetry for 177 Lu-DOTATATE therapy was performed using single and multiple voxel S-value (VSV) methods and compared with Monte Carlo simulations. To verify these methods, we adopted sequential 177 Lu-DOTATATE SPECT/CT dataset acquired from Sunway Medical Centre using the major vendor's SPECT/CT scanner (Siemens) METHODS: The administered activity of 177 Lu-DOTATATE was 7.99 ± 0.36 GBq. SPECT/CT images were acquired 0.5, 4, 24, and 48 h after injection in Sunway Medical Centre. For the multiple VSV method VSV kernels of 177 Lu in media with various densities were generated by GATE simulation first. The second step involved the convolution of the time-integrated activity map with each kernel to produce medium-specific dose maps. Third, each medium-specific dose map was masked using binary medium masks, which were generated from CT-based density maps. Finally, all masked dose maps were summed to generate the final dose map. VSV methods with four different VSV sets (1, 4, 10, and 20 VSVs) were compared. Voxel-wise density correction for the single VSV method was also performed. The absorbed doses in the kidneys, bone marrow, and tumors were analyzed, and the relative errors between the VSV and Monte Carlo simulation approaches were estimated. Organ-based dosimetry using OLINDA/EXM was also compared RESULTS: The accuracy of the multiple VSV approach increased with the number of dose kernels. The average dose estimation errors of a single VSV with density correction and 20 VSVs were less than 6% in most cases, although organ-based dosimetry using OLINDA/EXM yielded an error of up to 123%. The advantages of the single VSV method with density correction and the 20 VSVs over organ-based dosimetry were most evident in bone marrow and bone-metastatic tumors with heterogeneous medium properties. CONCLUSION The single VSV method with density correction and multiple VSV method with 20 dose kernels enabled fast and accurate radiation dose estimation. Accordingly, voxel-based dosimetry methods can be useful for managing administration activity and for investigating tumor dose responses to further increase the therapeutic efficacy of 177 Lu-DOTATATE. This article is protected by copyright. All rights reserved.

Nuclear Medicine and Molecular Imaging, 2022

Purpose To evaluate the clinical outcome of Q-SPECT/CT in pulmonary thromboembolic disease. Metho... more Purpose To evaluate the clinical outcome of Q-SPECT/CT in pulmonary thromboembolic disease. Methods From Jan 2020 to Jan 2021, 30 consecutive patients (M:F = 8:22; median age = 52 year (21-89)) suspected of having acute pulmonary embolism (PE) or chronic thromboembolic pulmonary hypertension (CTEPH) were referred for non-contrasted Q-SPECT/CT. All patients were COVID-19 PCR negative. MSKCC Q-SPECT/CT and/or PISAPED criteria were used to determine the presence of thromboembolic disease in Q-SPECT/CT. Final diagnosis was made based on composite reference standards that included at least 2-month clinical cardiorespiratory assessment and follow-up imaging. Results Q-SPECT/CT was positive in 19 patients: indeterminate in 1 and 10 were negative. Three false positive cases were observed during follow-up. Of the remaining 16 true positives, all patients' cardiorespiratory symptom were improved or stabilised after treatment with anticoagulants. The overall sensitivity, specificity, PPV, NPV and accuracy of Q-SPECT/CT were 100% (95% CI, 79.41-100%), 78.57% (95% CI, 49.20-95.34%), 84.21% (95% CI, 66.41-93.57%), 100% and 90.00% (95% CI, 73.47-97.89%) respectively. Conclusions In the current COVID-19 pandemic, Q-SPECT/CT can be an alternative modality to detect pulmonary thromboembolic disease. Normal Q-SPECT/CT excludes pulmonary thromboembolic disease with high degree of certainty. However, false positive has been observed.

Radiation Physics and Chemistry, 2021

Abstract Standard iterative Ordered Subset Expectation Maximisation (OSEM) reconstruction is well... more Abstract Standard iterative Ordered Subset Expectation Maximisation (OSEM) reconstruction is well established in SPECT/CT, but despite its wide applications in image processing it comes with limitations in image noise and quality. A novel algorithm, xQuant (developed by Siemens Healthcare), uses Ordered Subset Conjugate Gradient Maximisation (OSCGM) which enables image quantification assessment such as standardised uptake value (SUV) measurements for reliable disease detection and evaluation of therapy response. As such, xQuant allows for dosimetry measurements, staging and management of diseases, analogous to the PET/CT modality for staging cancers and chemotherapy management. This study compares the accuracy of xQuant algorithm and current OSEM, by analysing image noise, SUV quantification and varying image reconstruction parameters. Standard clinical phantoms are used for comparison of both reconstruction algorithms: xQuant SUV accuracy with various Tc99m activity and varying scan times are performed for analysis. Results indicate that SUV measurements from xQuant are similar to expected SUV, regardless of selected reconstruction parameters, varying radiation activity and delayed scan times. Image noise assessment has shown that xQuant has lesser value of coefficient of variation (CoV) compared to standard OSEM, indicating xQuant's superior noise suppression without compromising image quality. The quantifiable superiority of xQuant reconstruction algorithm supersedes the basic iterative 3D OSEM reconstruction. It shows higher resolution qualitative assessment and provides consistent quantitative analysis. The reliability and superiority of xQuant enables clinical SPECT/CT quantification to detect disease and improve therapy management.

Journal of Parenteral and Enteral Nutrition, 2020

Background: Muscle wasting, prevalent in hemodialysis (HD) patients diagnosed with protein energy... more Background: Muscle wasting, prevalent in hemodialysis (HD) patients diagnosed with protein energy wasting, represents an assessment challenge in the outpatient HD setting. Quadriceps muscle thickness (QMT) and cross-sectional area (CSA) assessment by ultrasound (US) is a potential surrogate measure for muscle wasting. We aimed to determine the validity of US to measure QMT and CSA against the gold standard, computed tomography (CT). Methods: Twenty-six HD patients underwent US and CT scans on the same day, post-dialysis session. QMT for rectus femoris (RF) and vastus intermedius (VI) muscles was taken at the midpoint and 2/3 of both thighs and CSA of the RF muscle (RF CSA), respectively. Correlation between US and CT measurements was determined by intraclass correlation coefficient (ICC) and Bland-Altman plot. Results: ICC (95% CI) computed between US and CT was 0.

Clinical Nuclear Medicine, 2020

Recent case reports and series have demonstrated the usefulness of 68 Ga/ 18 F-PSMA PET/CT in res... more Recent case reports and series have demonstrated the usefulness of 68 Ga/ 18 F-PSMA PET/CT in restaging recurrent renal cancer after nephrectomy. We presented a case of a patient with renal mass who had undergone both 18 F-FDG and 68 Ga-PSMA PET/CT for diagnosis and staging. Concordant tracer uptake in the primary tumor and metastatic lesions was demonstrated by both radiotracers. Final histopathological reports revealed clear cell renal cell carcinoma. Furthermore, unusual left metacarpal bone metastasis was also detected.

Nuclear medicine and molecular imaging, 2018

The National Cancer Institute is the only referral centre in Malaysia that provides Ga-DOTA-pepti... more The National Cancer Institute is the only referral centre in Malaysia that provides Ga-DOTA-peptide imaging. The purpose of this study is to determine the impact of Ga-DOTA-peptide PET/CT on the management of gastrointestinal neuroendocrine tumours (GI-NET). A cross-sectional study was performed to review the impact of Ga-DOTA-peptide (Ga-DOTATATE or Ga-DOTATOC) PET/CT on patients with biopsy-proven GI-NET between January 2011 and December 2015. Suspected NET was excluded. Demographic data, tumoral characteristics, change of disease stage, pre-PET intended management and post-PET management were evaluated. Over a 5-year period, 82 studies of Ga-DOTA-peptide PET/CT were performed on 44 GI-NET patients. The most common primary site was the rectum (50.0%) followed by the small bowel, stomach and colon. Using WHO 2010 grading, 40.9% of patients had low-grade (G1) tumour, 22.7% intermediate (G2) and 4.5% high (G3). Of ten patients scheduled for pre-operative staging, Ga-DOTA-peptide PET/...

Clinical Nuclear Medicine, 2017

A 47-year-old man with newly diagnosed nasopharyngeal carcinoma underwent staging 18 F-FDG PET/CT... more A 47-year-old man with newly diagnosed nasopharyngeal carcinoma underwent staging 18 F-FDG PET/CT. Apart from showing increased FDG uptake in the primary site and locoregional nodal and liver metastases, an unusual site of intense FDG focus was demonstrated in the left adrenal gland. He underwent CT-guided biopsy, and the histopathologic diagnosis was benign fibrous histiocytoma.

Nuclear Medicine and Molecular Imaging, 2012

Ectopic thyroid or thyroid ectopia is a rare developmental anomaly with the prevalence of 1 per 1... more Ectopic thyroid or thyroid ectopia is a rare developmental anomaly with the prevalence of 1 per 100,000-300,000 population. Even rarer, such an anomaly manifests as dual thyroid ectopia. To our best knowledge, only one case has been reported on dual thyroid ectopia with Graves' disease in the English literature. We present here a case of dual thyroid ectopia complicated by Graves' disease, whereby the diagnosis was rendered through judicious use of various diagnostic modalities coupled with a close clinical follow-up. In this case, therapeutic consideration should be personalized with proper informed consent of the patient. Keywords Dual thyroid ectopia. Dual ectopic thyroid. Graves' disease. 99m Tc-pertechnetate thyroid scintigraphy T. H. Tan (*) : B. N. Lee : S.

World Journal of Nuclear Medicine

Positron emission tomography-computed tomography (PET-CT) has demonstrated its usefulness in eval... more Positron emission tomography-computed tomography (PET-CT) has demonstrated its usefulness in evaluating nonspecific abdominal and inflammatory symptoms. We report a case of young woman with chronic right upper quadrant abdominal pain. Fluorine-18 fluorodeoxyglucose PET-CT showed subhepatic hypermetabolism. Subsequent diagnostic laparoscopy confirmed the uncommon diagnosis of Fitz-Hugh-Curtis syndrome.

Nuclear Medicine and Molecular Imaging, 2021

Tumour-induced osteomalacia is a rare paraneoplastic syndrome that manifests as chronic hypophosp... more Tumour-induced osteomalacia is a rare paraneoplastic syndrome that manifests as chronic hypophosphataemia, non-specific bone pain and muscle weakness. It is generally caused by phosphaturic mesenchymal tumour (PMT), which is uncommonly associated with synchronous tumours. However, diagnosis is often delayed for several years due to the rarity, indolent growing nature and non-specific symptoms of the disease, often resulting in an overlook by clinicians during assessments. The patient initially presented with hypophosphataemia and generalised skeletal pain with multiple atraumatic fractures. Blood tests revealed serum calcium levels at the upper limit and extremely low inorganic phosphate levels. Herein, we report a case where two synchronous PMTs from two different sites were detected by ‘extended’ whole-body Ga-68 DOTATATE PET-CT, leading to remission of the disease after complete surgical removal. Early detection and diagnosis of PMT neoplasm is crucial, as complete surgical resection of this tumour is the only definitive treatment currently known. Upon excision, this curable disease will result in complete resolution of symptoms and blood parameters, leading to remission of the disease which significantly improves the patient’s quality of life. PMT often over-expresses somatostatin receptors (SSTR), predominantly subtype 2A, and Ga-68 DOTATATE PET-CT is a selective SSTR imaging that targets this characteristic over-expression in these tumours. The high diagnostic accuracy of Ga-68 DOTATATE PET-CT should be the primary imaging modality for full evaluation of this disease.

Radiation Physics and Chemistry

Asia Oceania journal of nuclear medicine & biology, 2016

The present study aimed to evaluate the role of pre-therapeutic (18)fluorine-fluorodeoxyglucose p... more The present study aimed to evaluate the role of pre-therapeutic (18)fluorine-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG PET-CT) and maximum standardized uptake value (SUVmax) in guiding the treatment strategy and predicting the prognosis of esophageal carcinoma, using the survival data of the patients. The present retrospective, cohort study was performed on 40 consecutive patients with esophageal carcinoma (confirmed by endoscopic biopsy), who underwent pre-operative (18)F-FDG PET-CT staging between January 2009 and June 2014. All the patients underwent contrast-enhanced CT and non-contrasted (18)F-FDG PET-CT evaluations. The patients were followed-up over 12 months to assess the changes in therapeutic strategies. Survival analysis was done considering the primary tumor SUVmax, using the Kaplan-Meier product-limit method. In a total of 40 patients, (18)F-FDG PET-CT scan led to changes in disease stage in 26 (65.0%) cases, with upstaging and downs...

Clinical nuclear medicine, Jan 30, 2016

Primary squamous cell carcinoma (SCC) of the trachea is rare. Here, we presented a rare case of p... more Primary squamous cell carcinoma (SCC) of the trachea is rare. Here, we presented a rare case of primary SCC of the trachea arising 4 years after radioiodine (RAI) treatment of papillary carcinoma of the thyroid. In this case, concomitant uptake of I-RAI and F-FDG was demonstrated in the thyroidal mass with tracheal invasion, which mimicked mixed well-differentiated and dedifferentiated thyroid carcinoma. The diagnosis of SCC of the trachea was made only after tracheal biopsy. This case illustrates that FDG-avid thyroid bed lesion, in the presence of thyroid carcinoma, may not necessarily be related to the thyroid pathology.

Introduction: In adolescent hyperthyroidism, rendering non-hyperthyroidism after first dose is us... more Introduction: In adolescent hyperthyroidism, rendering non-hyperthyroidism after first dose is usually desired to avoid prolonged hyperthyroid sequelae and multiple radiation exposure. Various methods have been suggested to deliver first optimal dose. This study is to assess clinical outcome of estimated-dose method in Hospital Kuala Lumpur. Methodology: 126 consecutive hyperthyroid adolescents (F:M=6, 10-19 year-old) receiving radioiodine between January 2000 and December 2012 were reviewed. Twelve were excluded. Thyroid volume was estimated by clinical assessment. Range of estimated radioiodine activity in non-palpable, small, moderate and large goitre was (5-10mCi), (7-15mCi), (10-25mCi) and (20-25mCi) respectively. Therapeutic response was defined as elimination of hyperthyroidism biochemically on subsequent follow-up. Results: Duration of medical therapy prior radioiodine was 0.2-10 years. No reported acute event. Overall success rate after 1st dose and 2nd dose was 53.0% and 8...

Clinical Nuclear Medicine, 2015

A 17-year-old adolescent boy with biochemically raised 2-hour urinary metanephrine and normetanep... more A 17-year-old adolescent boy with biochemically raised 2-hour urinary metanephrine and normetanephrine as well as CT findings of retroperitoneal soft tissue mass and bony metastases was referred for further assessment. Apart from Ga DOTATATE PET/CT evaluation, pretargeted systemic radionuclide therapy assessment with I-MIBG scintigraphy showed unusual phenomenon of MIBG superscan. Postsurgically, restaging Tc-MDP bone scintigraphy showed typical bone superscan features. The MIBG superscan was better delineated on post-I-MIBG therapy images.

Nuclear Medicine and Molecular Imaging, 2015

To evaluate the diagnostic performance of (68)Ga-DOTATATE (18)F-fluorodeoxyglucose ((18)F-FDG) po... more To evaluate the diagnostic performance of (68)Ga-DOTATATE (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET)/computed tomography (CT), (18)F-FDG PET/CT and (131)I-MIBG scintigraphy in the mapping of metastatic pheochromocytoma and paraganglioma. Seventeen patients (male = 8, female = 9; age range, 13-68 years) with clinically proven or suspicious metastatic pheochromocytoma or paraganglioma were included in this prospective study. Twelve patients underwent all three modalities, whereas five patients underwent (68)Ga-DOTATATE and (131)I-MIBG without (18)F-FDG. A composite reference standard derived from anatomical and functional imaging findings, along with histopathological information, was used to validate the findings. Results were analysed on a per-patient and on per-lesion basis. Sensitivity and accuracy were assessed using McNemar's test. On a per-patient basis, 14/17 patients were detected in (68)Ga-DOTATATE, 7/17 patients in (131)I-MIBG, and 10/12 patients in (18)F-FDG. The sensitivity and accuracy of (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG were (93.3 %, 94.1 %), (46.7 %, 52.9 %) and (90.9 %, 91.7 %) respectively. On a per-lesion basis, an overall of 472 positive lesions were detected; of which 432/472 were identified by (68)Ga-DOTATATE, 74/472 by (131)I-MIBG, and 154/300 (patient, n = 12) by (18)F-FDG. The sensitivity and accuracy of (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG were (91.5 %, 92.6 % p < 0.0001), (15.7 %, 26.0 % p < 0.0001) and (51.3 %, 57.8 % p < 0.0001) respectively. Discordant lesions were demonstrated on (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG. Ga-DOTATATE PET/CT shows high diagnostic accuracy than (131)I-MIBG scintigraphy and (18)F-FDG PET/ CT in mapping metastatic pheochromocytoma and paraganglioma.

Nuclear Medicine and Molecular Imaging, 2015

We reported a rare finding of isolated pericardial uptake detected by SPECT/CT on posttherapeutic... more We reported a rare finding of isolated pericardial uptake detected by SPECT/CT on posttherapeutic radioiodine whole body scan. This case highlights the usefulness of hybrid SPECT/CT, with subsequent correlation with biochemical results, in ruling out metastatic pericardial effusion in the postsurgical radioiodine remnant ablation setting. The effusion was resolved after reinstituted thyroid replacement therapy. Recombinant thyrotropin is recommended to avoid such rare but life-threatening complication.

Nuclear medicine and molecular imaging, 2014

In neuroendocrine liver metastases of unknown primary, a multimodality approach is usually adopte... more In neuroendocrine liver metastases of unknown primary, a multimodality approach is usually adopted and consists of transabdominal ultrasound, endoscopic ultrasound (EUS), computed tomography (CT), magnetic resonance imaging (MRI), nuclear medicine techniques, endoscopy and exploratory surgery. The purpose of the study is to evaluate the diagnostic value of (68)Ga-DOTATATE positron emission tomography (PET)/CT as part of a multimodality approach in neuroendocrine liver metastases of unknown primary. Six patients (M:F = 5:1, age range 28-56 years) with immunohistochemically proven neuroendocrine liver metastases but inconclusive initial CT work-up were retrospectively analysed. Clinical finding, histopathology, comparative imaging and follow-up were used to validate the results when ethically justified. (68)Ga-DOTATATE PET/CT identified the primary tumour in five out of six (83.3 %) patients: pancreas (n = 4) and stomach (n = 1). Out of three patients with indeterminate primary on ini...

World journal of nuclear medicine, 2014

We described a case of 51-year-old female patient presented with a right calf necrotising fasciit... more We described a case of 51-year-old female patient presented with a right calf necrotising fasciitis (NF) where osteomyelitis (OM) was suspected. (99m)Tc-hydroxymethane diphosphonate three-phase bone scintigraphy and (99m)Tc-besilosomab scan failed to demonstrate classical features of OM. The final diagnosis was only made by isolating Acinetobacter sp. in both intra-operative bone and tissue cultures from below-knee amputation. As conclusions, the detection of lower limb OM by (99m)Tc-besilosomab scan is not easy when there is concurrence overlying NF. The unusual three-phase bone scan finding of pericortical accumulation of tracer as an early sign of OM is highlighted in this case.

The Medical journal of Malaysia, 2019

BACKGROUND Lung cancer is one of the leading causes of cancer-related mortality worldwide. Pulmon... more BACKGROUND Lung cancer is one of the leading causes of cancer-related mortality worldwide. Pulmonary nodules are commonly encountered in clinical practice because of the recent implementation of low-dose CT lung screening programme, incidental finding on cardiac CT or CT for nonthoracic related disease. 18F-FDG PET-CT plays an important role in the management of pulmonary nodules. METHODS In this pictorial review, we present six different scenarios of using 18F-FDG PET-CT in the management of suspicious pulmonary nodule or mass. The advantages and limitations of 18F-FDG PET-CT and Herder model are discussed. RESULTS 18F-FDG PET-CT with risk assessment using Herder model provides added value in characterising indeterminate pulmonary nodules. Besides, 18F-FDG PET-CT is valuable to guide the site of biopsy and provide accurate staging of lung cancer. CONCLUSION To further improve its diagnostic accuracy, careful history taking, and CT morphological evaluation should be taken into consi...

Medical Physics, 2022

PURPOSE Voxel-based dosimetry is potentially accurate than organ-based dosimetry because it consi... more PURPOSE Voxel-based dosimetry is potentially accurate than organ-based dosimetry because it considers the anatomical variations in each individual and the heterogeneous radioactivity distribution in each organ. Here, voxel-based dosimetry for 177 Lu-DOTATATE therapy was performed using single and multiple voxel S-value (VSV) methods and compared with Monte Carlo simulations. To verify these methods, we adopted sequential 177 Lu-DOTATATE SPECT/CT dataset acquired from Sunway Medical Centre using the major vendor's SPECT/CT scanner (Siemens) METHODS: The administered activity of 177 Lu-DOTATATE was 7.99 ± 0.36 GBq. SPECT/CT images were acquired 0.5, 4, 24, and 48 h after injection in Sunway Medical Centre. For the multiple VSV method VSV kernels of 177 Lu in media with various densities were generated by GATE simulation first. The second step involved the convolution of the time-integrated activity map with each kernel to produce medium-specific dose maps. Third, each medium-specific dose map was masked using binary medium masks, which were generated from CT-based density maps. Finally, all masked dose maps were summed to generate the final dose map. VSV methods with four different VSV sets (1, 4, 10, and 20 VSVs) were compared. Voxel-wise density correction for the single VSV method was also performed. The absorbed doses in the kidneys, bone marrow, and tumors were analyzed, and the relative errors between the VSV and Monte Carlo simulation approaches were estimated. Organ-based dosimetry using OLINDA/EXM was also compared RESULTS: The accuracy of the multiple VSV approach increased with the number of dose kernels. The average dose estimation errors of a single VSV with density correction and 20 VSVs were less than 6% in most cases, although organ-based dosimetry using OLINDA/EXM yielded an error of up to 123%. The advantages of the single VSV method with density correction and the 20 VSVs over organ-based dosimetry were most evident in bone marrow and bone-metastatic tumors with heterogeneous medium properties. CONCLUSION The single VSV method with density correction and multiple VSV method with 20 dose kernels enabled fast and accurate radiation dose estimation. Accordingly, voxel-based dosimetry methods can be useful for managing administration activity and for investigating tumor dose responses to further increase the therapeutic efficacy of 177 Lu-DOTATATE. This article is protected by copyright. All rights reserved.

Nuclear Medicine and Molecular Imaging, 2022

Purpose To evaluate the clinical outcome of Q-SPECT/CT in pulmonary thromboembolic disease. Metho... more Purpose To evaluate the clinical outcome of Q-SPECT/CT in pulmonary thromboembolic disease. Methods From Jan 2020 to Jan 2021, 30 consecutive patients (M:F = 8:22; median age = 52 year (21-89)) suspected of having acute pulmonary embolism (PE) or chronic thromboembolic pulmonary hypertension (CTEPH) were referred for non-contrasted Q-SPECT/CT. All patients were COVID-19 PCR negative. MSKCC Q-SPECT/CT and/or PISAPED criteria were used to determine the presence of thromboembolic disease in Q-SPECT/CT. Final diagnosis was made based on composite reference standards that included at least 2-month clinical cardiorespiratory assessment and follow-up imaging. Results Q-SPECT/CT was positive in 19 patients: indeterminate in 1 and 10 were negative. Three false positive cases were observed during follow-up. Of the remaining 16 true positives, all patients' cardiorespiratory symptom were improved or stabilised after treatment with anticoagulants. The overall sensitivity, specificity, PPV, NPV and accuracy of Q-SPECT/CT were 100% (95% CI, 79.41-100%), 78.57% (95% CI, 49.20-95.34%), 84.21% (95% CI, 66.41-93.57%), 100% and 90.00% (95% CI, 73.47-97.89%) respectively. Conclusions In the current COVID-19 pandemic, Q-SPECT/CT can be an alternative modality to detect pulmonary thromboembolic disease. Normal Q-SPECT/CT excludes pulmonary thromboembolic disease with high degree of certainty. However, false positive has been observed.

Radiation Physics and Chemistry, 2021

Abstract Standard iterative Ordered Subset Expectation Maximisation (OSEM) reconstruction is well... more Abstract Standard iterative Ordered Subset Expectation Maximisation (OSEM) reconstruction is well established in SPECT/CT, but despite its wide applications in image processing it comes with limitations in image noise and quality. A novel algorithm, xQuant (developed by Siemens Healthcare), uses Ordered Subset Conjugate Gradient Maximisation (OSCGM) which enables image quantification assessment such as standardised uptake value (SUV) measurements for reliable disease detection and evaluation of therapy response. As such, xQuant allows for dosimetry measurements, staging and management of diseases, analogous to the PET/CT modality for staging cancers and chemotherapy management. This study compares the accuracy of xQuant algorithm and current OSEM, by analysing image noise, SUV quantification and varying image reconstruction parameters. Standard clinical phantoms are used for comparison of both reconstruction algorithms: xQuant SUV accuracy with various Tc99m activity and varying scan times are performed for analysis. Results indicate that SUV measurements from xQuant are similar to expected SUV, regardless of selected reconstruction parameters, varying radiation activity and delayed scan times. Image noise assessment has shown that xQuant has lesser value of coefficient of variation (CoV) compared to standard OSEM, indicating xQuant's superior noise suppression without compromising image quality. The quantifiable superiority of xQuant reconstruction algorithm supersedes the basic iterative 3D OSEM reconstruction. It shows higher resolution qualitative assessment and provides consistent quantitative analysis. The reliability and superiority of xQuant enables clinical SPECT/CT quantification to detect disease and improve therapy management.

Journal of Parenteral and Enteral Nutrition, 2020

Background: Muscle wasting, prevalent in hemodialysis (HD) patients diagnosed with protein energy... more Background: Muscle wasting, prevalent in hemodialysis (HD) patients diagnosed with protein energy wasting, represents an assessment challenge in the outpatient HD setting. Quadriceps muscle thickness (QMT) and cross-sectional area (CSA) assessment by ultrasound (US) is a potential surrogate measure for muscle wasting. We aimed to determine the validity of US to measure QMT and CSA against the gold standard, computed tomography (CT). Methods: Twenty-six HD patients underwent US and CT scans on the same day, post-dialysis session. QMT for rectus femoris (RF) and vastus intermedius (VI) muscles was taken at the midpoint and 2/3 of both thighs and CSA of the RF muscle (RF CSA), respectively. Correlation between US and CT measurements was determined by intraclass correlation coefficient (ICC) and Bland-Altman plot. Results: ICC (95% CI) computed between US and CT was 0.

Clinical Nuclear Medicine, 2020

Recent case reports and series have demonstrated the usefulness of 68 Ga/ 18 F-PSMA PET/CT in res... more Recent case reports and series have demonstrated the usefulness of 68 Ga/ 18 F-PSMA PET/CT in restaging recurrent renal cancer after nephrectomy. We presented a case of a patient with renal mass who had undergone both 18 F-FDG and 68 Ga-PSMA PET/CT for diagnosis and staging. Concordant tracer uptake in the primary tumor and metastatic lesions was demonstrated by both radiotracers. Final histopathological reports revealed clear cell renal cell carcinoma. Furthermore, unusual left metacarpal bone metastasis was also detected.

Nuclear medicine and molecular imaging, 2018

The National Cancer Institute is the only referral centre in Malaysia that provides Ga-DOTA-pepti... more The National Cancer Institute is the only referral centre in Malaysia that provides Ga-DOTA-peptide imaging. The purpose of this study is to determine the impact of Ga-DOTA-peptide PET/CT on the management of gastrointestinal neuroendocrine tumours (GI-NET). A cross-sectional study was performed to review the impact of Ga-DOTA-peptide (Ga-DOTATATE or Ga-DOTATOC) PET/CT on patients with biopsy-proven GI-NET between January 2011 and December 2015. Suspected NET was excluded. Demographic data, tumoral characteristics, change of disease stage, pre-PET intended management and post-PET management were evaluated. Over a 5-year period, 82 studies of Ga-DOTA-peptide PET/CT were performed on 44 GI-NET patients. The most common primary site was the rectum (50.0%) followed by the small bowel, stomach and colon. Using WHO 2010 grading, 40.9% of patients had low-grade (G1) tumour, 22.7% intermediate (G2) and 4.5% high (G3). Of ten patients scheduled for pre-operative staging, Ga-DOTA-peptide PET/...

Clinical Nuclear Medicine, 2017

A 47-year-old man with newly diagnosed nasopharyngeal carcinoma underwent staging 18 F-FDG PET/CT... more A 47-year-old man with newly diagnosed nasopharyngeal carcinoma underwent staging 18 F-FDG PET/CT. Apart from showing increased FDG uptake in the primary site and locoregional nodal and liver metastases, an unusual site of intense FDG focus was demonstrated in the left adrenal gland. He underwent CT-guided biopsy, and the histopathologic diagnosis was benign fibrous histiocytoma.

Nuclear Medicine and Molecular Imaging, 2012

Ectopic thyroid or thyroid ectopia is a rare developmental anomaly with the prevalence of 1 per 1... more Ectopic thyroid or thyroid ectopia is a rare developmental anomaly with the prevalence of 1 per 100,000-300,000 population. Even rarer, such an anomaly manifests as dual thyroid ectopia. To our best knowledge, only one case has been reported on dual thyroid ectopia with Graves' disease in the English literature. We present here a case of dual thyroid ectopia complicated by Graves' disease, whereby the diagnosis was rendered through judicious use of various diagnostic modalities coupled with a close clinical follow-up. In this case, therapeutic consideration should be personalized with proper informed consent of the patient. Keywords Dual thyroid ectopia. Dual ectopic thyroid. Graves' disease. 99m Tc-pertechnetate thyroid scintigraphy T. H. Tan (*) : B. N. Lee : S.

World Journal of Nuclear Medicine

Positron emission tomography-computed tomography (PET-CT) has demonstrated its usefulness in eval... more Positron emission tomography-computed tomography (PET-CT) has demonstrated its usefulness in evaluating nonspecific abdominal and inflammatory symptoms. We report a case of young woman with chronic right upper quadrant abdominal pain. Fluorine-18 fluorodeoxyglucose PET-CT showed subhepatic hypermetabolism. Subsequent diagnostic laparoscopy confirmed the uncommon diagnosis of Fitz-Hugh-Curtis syndrome.

Nuclear Medicine and Molecular Imaging, 2021

Tumour-induced osteomalacia is a rare paraneoplastic syndrome that manifests as chronic hypophosp... more Tumour-induced osteomalacia is a rare paraneoplastic syndrome that manifests as chronic hypophosphataemia, non-specific bone pain and muscle weakness. It is generally caused by phosphaturic mesenchymal tumour (PMT), which is uncommonly associated with synchronous tumours. However, diagnosis is often delayed for several years due to the rarity, indolent growing nature and non-specific symptoms of the disease, often resulting in an overlook by clinicians during assessments. The patient initially presented with hypophosphataemia and generalised skeletal pain with multiple atraumatic fractures. Blood tests revealed serum calcium levels at the upper limit and extremely low inorganic phosphate levels. Herein, we report a case where two synchronous PMTs from two different sites were detected by ‘extended’ whole-body Ga-68 DOTATATE PET-CT, leading to remission of the disease after complete surgical removal. Early detection and diagnosis of PMT neoplasm is crucial, as complete surgical resection of this tumour is the only definitive treatment currently known. Upon excision, this curable disease will result in complete resolution of symptoms and blood parameters, leading to remission of the disease which significantly improves the patient’s quality of life. PMT often over-expresses somatostatin receptors (SSTR), predominantly subtype 2A, and Ga-68 DOTATATE PET-CT is a selective SSTR imaging that targets this characteristic over-expression in these tumours. The high diagnostic accuracy of Ga-68 DOTATATE PET-CT should be the primary imaging modality for full evaluation of this disease.

Radiation Physics and Chemistry

Asia Oceania journal of nuclear medicine & biology, 2016

The present study aimed to evaluate the role of pre-therapeutic (18)fluorine-fluorodeoxyglucose p... more The present study aimed to evaluate the role of pre-therapeutic (18)fluorine-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG PET-CT) and maximum standardized uptake value (SUVmax) in guiding the treatment strategy and predicting the prognosis of esophageal carcinoma, using the survival data of the patients. The present retrospective, cohort study was performed on 40 consecutive patients with esophageal carcinoma (confirmed by endoscopic biopsy), who underwent pre-operative (18)F-FDG PET-CT staging between January 2009 and June 2014. All the patients underwent contrast-enhanced CT and non-contrasted (18)F-FDG PET-CT evaluations. The patients were followed-up over 12 months to assess the changes in therapeutic strategies. Survival analysis was done considering the primary tumor SUVmax, using the Kaplan-Meier product-limit method. In a total of 40 patients, (18)F-FDG PET-CT scan led to changes in disease stage in 26 (65.0%) cases, with upstaging and downs...

Clinical nuclear medicine, Jan 30, 2016

Primary squamous cell carcinoma (SCC) of the trachea is rare. Here, we presented a rare case of p... more Primary squamous cell carcinoma (SCC) of the trachea is rare. Here, we presented a rare case of primary SCC of the trachea arising 4 years after radioiodine (RAI) treatment of papillary carcinoma of the thyroid. In this case, concomitant uptake of I-RAI and F-FDG was demonstrated in the thyroidal mass with tracheal invasion, which mimicked mixed well-differentiated and dedifferentiated thyroid carcinoma. The diagnosis of SCC of the trachea was made only after tracheal biopsy. This case illustrates that FDG-avid thyroid bed lesion, in the presence of thyroid carcinoma, may not necessarily be related to the thyroid pathology.

Introduction: In adolescent hyperthyroidism, rendering non-hyperthyroidism after first dose is us... more Introduction: In adolescent hyperthyroidism, rendering non-hyperthyroidism after first dose is usually desired to avoid prolonged hyperthyroid sequelae and multiple radiation exposure. Various methods have been suggested to deliver first optimal dose. This study is to assess clinical outcome of estimated-dose method in Hospital Kuala Lumpur. Methodology: 126 consecutive hyperthyroid adolescents (F:M=6, 10-19 year-old) receiving radioiodine between January 2000 and December 2012 were reviewed. Twelve were excluded. Thyroid volume was estimated by clinical assessment. Range of estimated radioiodine activity in non-palpable, small, moderate and large goitre was (5-10mCi), (7-15mCi), (10-25mCi) and (20-25mCi) respectively. Therapeutic response was defined as elimination of hyperthyroidism biochemically on subsequent follow-up. Results: Duration of medical therapy prior radioiodine was 0.2-10 years. No reported acute event. Overall success rate after 1st dose and 2nd dose was 53.0% and 8...

Clinical Nuclear Medicine, 2015

A 17-year-old adolescent boy with biochemically raised 2-hour urinary metanephrine and normetanep... more A 17-year-old adolescent boy with biochemically raised 2-hour urinary metanephrine and normetanephrine as well as CT findings of retroperitoneal soft tissue mass and bony metastases was referred for further assessment. Apart from Ga DOTATATE PET/CT evaluation, pretargeted systemic radionuclide therapy assessment with I-MIBG scintigraphy showed unusual phenomenon of MIBG superscan. Postsurgically, restaging Tc-MDP bone scintigraphy showed typical bone superscan features. The MIBG superscan was better delineated on post-I-MIBG therapy images.

Nuclear Medicine and Molecular Imaging, 2015

To evaluate the diagnostic performance of (68)Ga-DOTATATE (18)F-fluorodeoxyglucose ((18)F-FDG) po... more To evaluate the diagnostic performance of (68)Ga-DOTATATE (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET)/computed tomography (CT), (18)F-FDG PET/CT and (131)I-MIBG scintigraphy in the mapping of metastatic pheochromocytoma and paraganglioma. Seventeen patients (male = 8, female = 9; age range, 13-68 years) with clinically proven or suspicious metastatic pheochromocytoma or paraganglioma were included in this prospective study. Twelve patients underwent all three modalities, whereas five patients underwent (68)Ga-DOTATATE and (131)I-MIBG without (18)F-FDG. A composite reference standard derived from anatomical and functional imaging findings, along with histopathological information, was used to validate the findings. Results were analysed on a per-patient and on per-lesion basis. Sensitivity and accuracy were assessed using McNemar's test. On a per-patient basis, 14/17 patients were detected in (68)Ga-DOTATATE, 7/17 patients in (131)I-MIBG, and 10/12 patients in (18)F-FDG. The sensitivity and accuracy of (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG were (93.3 %, 94.1 %), (46.7 %, 52.9 %) and (90.9 %, 91.7 %) respectively. On a per-lesion basis, an overall of 472 positive lesions were detected; of which 432/472 were identified by (68)Ga-DOTATATE, 74/472 by (131)I-MIBG, and 154/300 (patient, n = 12) by (18)F-FDG. The sensitivity and accuracy of (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG were (91.5 %, 92.6 % p < 0.0001), (15.7 %, 26.0 % p < 0.0001) and (51.3 %, 57.8 % p < 0.0001) respectively. Discordant lesions were demonstrated on (68)Ga-DOTATATE, (131)I-MIBG and (18)F-FDG. Ga-DOTATATE PET/CT shows high diagnostic accuracy than (131)I-MIBG scintigraphy and (18)F-FDG PET/ CT in mapping metastatic pheochromocytoma and paraganglioma.

Nuclear Medicine and Molecular Imaging, 2015

We reported a rare finding of isolated pericardial uptake detected by SPECT/CT on posttherapeutic... more We reported a rare finding of isolated pericardial uptake detected by SPECT/CT on posttherapeutic radioiodine whole body scan. This case highlights the usefulness of hybrid SPECT/CT, with subsequent correlation with biochemical results, in ruling out metastatic pericardial effusion in the postsurgical radioiodine remnant ablation setting. The effusion was resolved after reinstituted thyroid replacement therapy. Recombinant thyrotropin is recommended to avoid such rare but life-threatening complication.

Nuclear medicine and molecular imaging, 2014

In neuroendocrine liver metastases of unknown primary, a multimodality approach is usually adopte... more In neuroendocrine liver metastases of unknown primary, a multimodality approach is usually adopted and consists of transabdominal ultrasound, endoscopic ultrasound (EUS), computed tomography (CT), magnetic resonance imaging (MRI), nuclear medicine techniques, endoscopy and exploratory surgery. The purpose of the study is to evaluate the diagnostic value of (68)Ga-DOTATATE positron emission tomography (PET)/CT as part of a multimodality approach in neuroendocrine liver metastases of unknown primary. Six patients (M:F = 5:1, age range 28-56 years) with immunohistochemically proven neuroendocrine liver metastases but inconclusive initial CT work-up were retrospectively analysed. Clinical finding, histopathology, comparative imaging and follow-up were used to validate the results when ethically justified. (68)Ga-DOTATATE PET/CT identified the primary tumour in five out of six (83.3 %) patients: pancreas (n = 4) and stomach (n = 1). Out of three patients with indeterminate primary on ini...

World journal of nuclear medicine, 2014

We described a case of 51-year-old female patient presented with a right calf necrotising fasciit... more We described a case of 51-year-old female patient presented with a right calf necrotising fasciitis (NF) where osteomyelitis (OM) was suspected. (99m)Tc-hydroxymethane diphosphonate three-phase bone scintigraphy and (99m)Tc-besilosomab scan failed to demonstrate classical features of OM. The final diagnosis was only made by isolating Acinetobacter sp. in both intra-operative bone and tissue cultures from below-knee amputation. As conclusions, the detection of lower limb OM by (99m)Tc-besilosomab scan is not easy when there is concurrence overlying NF. The unusual three-phase bone scan finding of pericortical accumulation of tracer as an early sign of OM is highlighted in this case.