I am well-versed not only with Internal Medicine and entire spectrum of Nuclear Medicine, I am equally comfortable with high level of computation including dosimetry, mathematical modeling & tracer kinetics, statistical analyses and various image processing softwares. Presently, I am involved in the interpretation and analysis of PET-CT scans, using various radiotracers, in patients with cancers and various brain disorders, and evaluation of brain white matter with diffusion tensor imaging (DTI), including tractography. I am also involved in several grant preparation and submission, including permissions from our institute's review board and am a co-investigator in an NIH-funded grant regarding evaluation of children with tuberous sclerosis using alpha-methyl tryptophan (PI: Dr Harry T Chugani, MD).

 My particular strength and expertise lies in brain PET, particularly pediatric brain PET using different PET tracers, such as ¹⁸F-FDG (for glucose metabolism), ¹¹C-flumazenil (for benzodiazepine receptors), ¹¹C-alpha-methyltryptophan (for serotonin and kinurenine metabolism), ¹¹C-Leucine (for protein synthesis), ¹¹C-PK11195 (for brain inflammation), etc. Our center is one of the leading pediatric PET centers in the world and people from all around the US and many different countries come to our center for these various PET scans. I have a special interest in the evaluation of neuroinflammation using ¹¹C-PK11195 PET in children with neurological disorders, such as epilepsy, autism, Nieman Pick disease type-C, leukodystrophy, PANDAS, etc, and ours is one of the few PET centers in the world where this kind of study is performed. My works regarding ¹¹C-PK11195 PET evaluation of neuroinflammation have been published in various peer-reviewed journals, including "Journal of Nuclear Medicine", ranked first in the world among imaging journals and "Pediatric Neurology", a leading pediatric neurology journal. I am also responsible for the analysis and interpretation of ¹¹C-alpha-methyltryptophan (AMT) PET scan in children with tuberous sclerosis and intractable epilepsy; a study unique in identifying the epileptic tuber and thus helping in epilepsy surgery planning, and being performed at only few centers in the world and patients, from as far as Australia, Norway and Argentina, routinely come to our center for this particular PET imaging. In a recent study, I also demonstrated that AMT PET scan can non-invasively identify cortical dysplasia (Taylor type IIB) in children with intractable epilepsy, thus greatly helping in treatment planning and prognostication. This work was published in "Epilepsia", the leading epilepsy journal. I also evaluated the role of voxel based analysis, such as statistical parametric mapping (SPM), of FDG PET images in the presurgical lateralization and localization of epileptic foci in children with intractable epilepsy using normal adult FDG images as controls. I demonstrated that such objective analysis is possible in children more than 6 years of age, even in the absence of age-matched controls, and can be a very useful complement to the visual analysis. This work has been published in the "Journal of Nuclear Medicine". I also conducted a study of memory localization in human brain with the help of ¹¹C-leucine brain PET scan, whose results were partially presented at the 9th Congress of Asia Oceania Federation of Nuclear Medicine & Biology 2008, in New Delhi, India.

I am also extensively using DTI-MRI to evaluate neuronal pathways or circuitries. Recently, I determined the origin and course of the cortico-spinal tracts using DTI tractography in a large number of healthy children and children with focal epilepsy to address the controversy surrounding century old traditional belief that corticospinal tract arises from pre-central gyrus and passes through the anterior half of the posterior limb of the internal capsule. We also validated the DTI Tractography outcomes using cortical stimulation in children with focal epilepsy. I found that the corticospinal tract most frequently originates from both pre-central and post-central gyri and the corticospinal tracts typically go through not the anterior but posterior portion of the posterior limb of internal capsules, bilaterally. In addition, I also quantitatively measured the ontogenic changes of DTI measures in a large number of healthy children. I believe that these results have increased our understanding of the anatomy of corticospinal tracts in relation to the primary motor cortex and will be of great interest and help to researchers and clinicians, particularly, epileptologists and epilepsy surgeons. This work has been published in "American Journal of Neuroradiology", a leading neuroimaging journal. In another study, I analyzed the frontal lobe association tracts and corpus callosum in patients with autism and had some very significant and interesting findings, which I think may help in understanding the neuroanatomic basis of autistic features. These findings were published in "Cerebral Cortex", a very prestigious and leading neuroscience journal. I have also evaluated neuronal connectivity using DTI-MRI in children with early deprivation to find the effect or orphanage on neuronal circuitry and its relationship with various neuro-cognitive outcomes. These are only some of the examples of my extensive work involving PET and DTI-MRI.

During my stay at the department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India, I participated in all the diagnostic and therapeutic activities of the department and was actively involved in numerous clinical trials such as, optimization of radioiodine dose for remnant thyroid ablation in differentiated thyroid cancer, role of lithium and ipanoic acid in the radioiodine treatment of hyperthyroidism, role of 99m-Tc-DMSA in the evaluation of renal scar in diabetic patients, role of 99m-Tc-MDP bone scan/SPECT along with MRI in the evaluation of low back ache, clinical evaluation of 99m-Tc-LLEC (a glomerular agent) renal scan as a single modality to assess renal function and morphology simultaneously, role of gastroesophageal study and gastric emptying study in gastric motility disorders and post-gastric surgery, evaluation of post-traumatic bone healing with 99m-Tc-MDP bone scan/SPECT, role of 99m-Tc-DTPA GFR studies in the evaluation of patients with chronic renal failure and anaemia, etc., the results of which have been published in various peer-reviewed international scientific journals. I was also actively involved in red blood cell mass estimation and red blood cell survival studies in patients with various haematological disorders such as Thalassemia, Polycythemia, etc.; studies done only in that department in whole of India,.

The department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India, conducts the largest number of nuclear neuro-imaging studies in India. These include brain imaging in patients with intractable epilepsy using ictal and interictal Tc99m ECD/HMPAO SPECT with use of MATLAB and SPM for SISCOM/SISCOS. During my residency there, I was actively involved in a multicentric study, conducted by International Atomic Energy Agency, on comparative evaluation of Ictal brain SPECT, EEG, MRI and CT scan in the management of patients with refractory seizures in India. Besides, I also actively participated in clinical trials evaluating the role of 99m-Tc-HMPAO/ECD brain SPECT in children with attention deficit hyperactivity disorder, patients with hypertension, hyperlipidaemia, and the role of 99m-Tc-ECD, GHA & TF in differentiating remnant/recurrent tumor vs necrotic/fibrotic tissue after surgery/radiotherapy/chemotherapy in patients with brain tumor.

I underwent training in radioiodine therapy of thyroid carcinoma and hyperthyroidism during my residency. During this period I was responsible for clinical evaluation of these patients, administration of therapeutic radio-iodine and in their post-therapy follow-up. Till 2006 more than 2800 thyroid cancer patients and 3200 hyperthyroid patients had undergone therapy and were on regular follow-up at thyroid clinic, All India Institute of Medical Sciences, New Delhi, India; the largest center in India for this purpose. I was actively associated with a randomized control trial to determine the lowest possible dose of radioiodine (¹³¹I) required for remnant ablation in patients with differentiated thyroid cancer, whose results have been published in the April 2004 issue of JCEM and have led to the world wide downward change in the administered radioiodine activity for this purpose. In another clinical trial, where I was actively associated, we demonstrated that radioiodine ablation of intact thyroid lobe is possible in thyroid cancer patients having undergone hemithyroidectomy and lobar ablation can be an attractive alternative to surgery for those who refuse to undergo completion thyroidectomy or had complication during initial surgery (published in Feb 2003 in Nucl Med Comm). Similarly, in a subsequent study, we showed that remnant thyroid ablation with radioiodine is possible after subtotal thyroidectomy also, thus reducing the chance of future recurrences and metastasis. Therefore, patient undergoing subtotal thyroidectomy can also benefit from the radioiodine therapy, which was not given to them till now. The results were published in Aug 2006 issue of Acta Oncologica. I also participated in the assessment of Tc99m-tetrofosmin and sestaMIBI as an alternative to radioiodine whole body scan in the follow-up of patients with thyroid carcinoma after radioiodine-ablation. In another study, we evaluated the fertility and genetic risk to the offspring from the exposure of high dose radioiodine, by assessing the pregnancy outcomes and health status of the children of female patients with DTC who had received therapeutic doses of radioiodine. We found that radioiodine treatment of differentiated thyroid cancer doesn't affect the female fertility and doesn't appear to be associated with any genetic risk to the offspring, thus allaying the apprehensions of female patients who would want to have children after radioiodine treatment of thyroid cancer. The results have been published in October 2005 issue of Int J Radiat Oncol Biol Phys, the number one journal in radiotherapy and have been extensively quoted in scientific and general literature. I also extensively studied the clinical features and characteristics of differentiated thyroid carcinoma in children and adolescents and tried to define the disease. Most of the patients in our study belonged to mild to moderate endemic iodine deficiency sub-Himalayan endemia, therefore I also tried to see, how iodine deficiency affects the development and clinical course of the disease and what implication it has on radioiodine neck uptake and radioiodine therapy. This was the only study of this type to be done from India and its findings shed important light on various aspects of the disease and helped in formulating an appropriate treatment strategy. I found that the incidence of differentiated thyroid carcinoma, particularly follicular variant is relatively higher in children and adolescents from endemic iodine deficient area. Younger the age (<10 years), more aggressive and widespread is the disease with male preponderance and high mortality (25%). In older children (>10 years), clinical course and prognosis appears to be same as in children from iodine sufficient area. The Post-surgical radioiodine ablation/therapy seems important and effective adjuvant in the management of differentiated thyroid cancer in children and adolescents. Part of this work was accepted for presentation in 7th congress of Asia-Oceania Federation of nuclear medicine & biology, held at Istanbul, Turkey from 1-5th Oct 2000 and I was awarded Young Scientist/Travel grant award for it. My findings, subsequently, got published in August 2001 issue of Nucl Med Communications. Subsequently, we critically reviewed the clinical characteristics, pattern of disease at presentation, histopathological subtype, treatment, course & outcome of differentiated thyroid cancer in children and adolescents presenting with pulmonary metastasis and compared radioiodine WBS with x-ray and CT chest in the diagnosis/evaluation of pulmonary metastasis. We found that a large number of children and adolescents with differentiated thyroid cancer present with pulmonary metastasis and majority of them could be missed on routine chest x-rays and even on CT scans. However, they can be detected by radioiodine whole body scan, as these metastases avidly concentrate radioiodine. We also found that these metastases usually respond very well to the radioiodine treatment. Therefore, we recommended a routine post-surgical evaluation with radioiodine WBS in all children so that any pulmonary metastases can be detected at the earliest and be dealt with promptly, thus reducing long term morbidity and mortality. Our findings were published in March 2004 issue of 'Thyroid' and have led to considerable change in approach and management of children with thyroid cancer.

I was also involved in a randomized control trial to evaluate the role of lithium as an adjuvant in the radioiodine treatment of hyperthyroidism. We found that the role of lithium as an adjuvant was insignificant and it should not be used, thus sparing the patient with possible serious side effects of lithium. In another randomized controlled trial, we assessed the effect of Iopanoic Acid (Telepaque) on radioiodine therapy of hyperthyroidism and its long-term outcome. We found that Telepaque can be used for rapid control of hyperthyroidism without any significant adverse effects or jeopardizing the subsequent radioiodine therapy and the long-term outcome of radioiodine therapy in this subset of patients was no way different compared to those prepared by conventional methods (published in Dec 2005 issue of JCEM). It paved the way for use of ipanoic acid in making severely hyperthyroid patient euthyroid quickly, thus relieving them of their symptoms as well as rendering them suitable for subsequent radioiodine therapy, a permanent cure of this condition. It is worthwhile to note that no other alternative is available, as of today, which can as quickly alleviate the symptoms of severe hyperthyroidism. I have also independently administered P-32/Sr-89/Sm-153 therapy for skeletal metastases and intra-articular Y-90/Re-188 for radiosynevectomy in cases of arthritis.

I did my PhD on "Dosimetric and Therapeutic Evaluation of Trans-Arterial Rhenium-188 in Cases of Inoperable Hepatocellular Carcinoma (HCC)", a multicentric trial conducted by IAEA, which was first of its kind in that part of the world. I was personally involved in the clinical work-up, radiolabelling (of Re-188 with lipiodol), dosimetry, transarterial therapy and follow-up of liver cancer patients. I was involved in the radiological evaluation of the patients with triple phase CT scan using various reconstruction techniques such as multiplanar image reconstruction (MPR) and maximum intensity projection (MIP) and DSA guided injection of Re-188-lipiodol into the tumor after hepatic artery catheterisation. During the course of this work, I modified and simplified the dosimetric and labeling techniques, which was discussed and accepted in a IAEA research co-ordination meeting held in Dec 2003 in New Delhi, published in April 2004 issue of World Journal of Nuclear Medicine and now being followed by other participating countries. The results of my study were encouraging and promising and it appeared that besides having better and favorable physical characteristics, Re-188 also has good tumoricidal effect which was associated with increased survival. With our study, we demonstrated that with individual dosimetry, one can safely administer the maximum possible amount of Re-188-HDD-lipiodol to the tumor without jeopardizing other organs and in patients where dosimetry is not possible, empirically around 5.5 GBq (150 mCi) of activity can be safely administered as it will deliver adequate radiation dose to the tumor in most of the patients. We demonstrated that Re-188-HDD-lipiodol therapy in HCC is safe, effective and promising therapeutic option in patients with inoperable large and/or multifocal HCC, thus opening a new vista and giving hope to millions of such patients who had hitherto not much therapeutic options. We also found that besides using trans-arterial Rhenium-188-lipiodol therapy for palliative treatment of large tumors, it may be used to manage portal vein thrombosis (published in Nov 2005 issue of European Journal of Radiology Extra) and sometimes with curative intent for multiple but small and inoperable tumors (published in Feb 2006 issue of Eur J Gastroenterol Hepatol). Part of my work was accepted for platform presentation in the 51st annual meeting of Society of Nuclear Medicine (SNM), the most prestigious body of Nuclear Medicine, held in June 2004 at Philadelphia, USA and was selected for the highlight session. It has been published in May 2007 issue of "Radiology", one of the best and most esteemed journals with very high impact factor and again as part of the whole multicenter trial in Dec 2007 issue of Int J Radiat Oncol Biol Phys and March 2008 issue of Seminars in Nuclear Medicine, the most respected journal in Nuclear Medicine. I was awarded first prize of "young Professional Award" for my PhD work by the Society of Nuclear Medicine in 2006. I am the first scholar from India to be honored with this award.

Throughout my residency, PhD and thereafter, I orally presented numerous seminars covering the entire spectrum of nuclear medicine and have actively participated in various other teaching programs. I have numerous high quality scientific & widely acclaimed publications, including review articles in reputed national and international journals. I have also written many chapters in textbooks for Nuclear Medicine, Biochemistry, Pediatrics, Neurology and Surgery, which are read by medical students and professionals. Recently, I wrote a chapter about PET imaging in seizure analysis, in "Encyclopedia of Basic Epilepsy Research" by Elsevier Ltd, Oxford, UK, which will work as a reference and guide for people working with epilepsy worldwide. I have received several young scientist/investigator awards from various professional bodies such as International thyroid Congress, Indo-American Society of Nuclear Medicine, Asia Oceania Federation of Nuclear Medicine and Biology, International Atomic Energy Agency (IAEA), Society of Nuclear Medicine, Radiological Society of North America, National Institute of Health, US, etc, including "Young Investigator Travel Award", for my work on evaluation of neuroinflammation using C-11-[R]-PK11195 PET scan in children with Niemann Pick disease type-C, from society of Nuclear Medicine, in a molecular imaging symposium at NIH, Bethesda, USA and "Molecular Imaging travel award" for my work "Uptake pattern, Tracer Kinetics and Receptor Binding of C-11-[R]-PK11195 in the Brain of Children and Adults" from Radiological Society of North America, in Chicago, IL, in year 2010. Same year, my work "Evaluation of cerebellar serotonin synthesis capacity using AMT PET scan in children with autism spectrum disorder" was selected for 'Brain Imaging Council Young Investigator Award Symposium' in the 57^thannual meeting of the Society of Nuclear Medicine, in Salt Lake City, Utah, from 5-9 June, 2010. I have presented my works in several international conferences and congresses and was invited as a speaker to deliver a lecture on radionuclide management of inoperable hepatocellular carcinoma at an international workshop organized by IAEA in 2003 in New Delhi and by World Radiopharmaceutical therapy council to deliver a plenary lecture in the International symposium on radiopharmaceutical therapy-2008 in Goa, India. Recently, I was invited to deliver a lecture for NINDS autism-epilepsy workshop at National Institute of Health, Bethesda, USA. My work regarding neuroinflammation in children with NPC has been also highlighted and covered by online press:

View my resume with list of publications.