Dinesh Singh

Publications (61)114.71 Total impact

• Article: Utility of intrastriatal ratios of FDOPA to differentiate idiopathic Parkinson's disease from atypical parkinsonian disorders.

  Abhinav Jaimini, Madhavi Tripathi, Maria M D'Souza, Puja Panwar, Rajnish Sharma, Saloni Mehta, Santosh Pandey, Sanjiv Saw, Dinesh Singh, Yachna Solanki, Anil K Mishra, Anupam Mondal
  [show abstract] [hide abstract]
  ABSTRACT: AIM: The striatal-to-occipital ratio (SOR) is commonly used as an analytical parameter in L-3,4-dihydroxy-6-F-fluorophenylalanine (FDOPA) PET studies. It has been shown to be useful in differentiating idiopathic Parkinson's disease (IPD) patients from healthy individuals. We assessed the performance of SORs and subregional ratio of striatal-to-occipital ratios (RSORs) in the clinical assessment of nigrostriatal dopaminergic function for differentiating typical IPD from atypical parkinsonian disorders (APD). MATERIALS AND METHODS: A total of 117 patients referred from movement disorder clinics in speciality neurology centres underwent an FDOPA PET study and were kept under follow-up for at least 2 years. Sixty-five patients (43 IPD and 22 APD) completed the 2-year follow-up and were included in the final analysis. Their PET images were spatially normalized to occipital counts and analysed with three striatal subregional regions of interest (caudate, anterior putamen and posterior putamen) and two occipital regions of interest. The RSORs of the caudate and posterior putamen, the caudate and anterior putamen, the caudate and whole putamen and the anterior putamen and posterior putamen were also calculated and compared between the IPD and APD groups using the t-test. RESULTS: The P values for these SORs were found to be insignificant between IPD and APD patients (caudate: 0.1325; anterior putamem: 0.5469; and posterior putamen: 0.9835). However, the RSORs of the caudate and posterior putamen showed significant differences between these two populations of patients. CONCLUSION: The SOR method is already known to be a good diagnostic tool to differentiate between IPD patients and the normal population. SOR, however, fails to distinguish IPD from APD patients, and hence the RSOR of the caudate and posterior putamen can be utilized to differentiate between them.
  Nuclear Medicine Communications 02/2013; · 1.40 Impact Factor
• Source

  Available from: Abhinav Jaimini

  Article: 18F-FDG PET/CT in the Diagnosis of Tumor Thrombus from Anaplastic Thyroid Carcinoma in a Young Boy

  Maria M D 'souza, Abhinav Jaimini, Rajnish Sharma, Madhavi Tripathi, Dinesh Singh, Santosh Pandey, Anupam Mondal
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  ABSTRACT: Anaplastic thyroid carcinoma is an uncommon, highly aggressive malignancy usually presenting in the elderly. An eighteen year old boy was recently diagnosed as anaplastic carcinoma of the thyroid. PET/CECT scan performed for staging, revealed a large FDG avid heterogeneously enhancing thyroid mass with bilateral jugular venous thrombosis, which also showed increased FDG uptake, thus pointing towards tumor thrombus. To our knowledge, this is the first case wherein the PET/CT diagnosis of tumor thrombosis from anaplastic thyroid carcinoma was made in a young patient.
  07/2012;
• Source

  Available from: ArXiv

  Article: Is there an observable limit to Lorentz invariance at the Compton wavelength scale?

  Dinesh Singh, Nader Mobed
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  ABSTRACT: The possibility of a frame-induced violation of Lorentz invariance due to non-inertial spin-1/2 particle motion is explored in detail for muon decay while in orbit near the event horizon of a microscopic Kerr black hole. It is explicitly shown that kinematic and curvature contributions to the muon’s decay spectrum—in the absence of any unforeseen processes due to quantum gravity—lead to its stabilization at the muon’s Compton wavelength scale. This example is emblematic of the search for unambiguous indicators to critically assess current and future approaches to quantum gravity research. KeywordsSpin-1/2 particles in curved space–time-Fermi normal co-ordinates-Muon decay-Casimir properties
  General Relativity and Gravitation 04/2012; 42(7):1707-1718. · 2.07 Impact Factor
• Article: Effects of addition of ketamine, fentanyl and saline with Propofol induction on hemodynamics and laryngeal mask airway insertion conditions in oral clonidine premedicated children.

  Tanmoy Ghatak, Dinesh Singh, Rajni Kapoor, Jaishree Bogra
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  ABSTRACT: The aim of this double-blind, prospective, randomized, controlled study was to compare the effect of addition of ketamine; fentanyl and saline with propofol anesthesia on hemodynamic profile and laryngeal mask airway (LMA) insertion conditions in oral clonidine premedicated children. 180 children (age 2 - 10 years) were at first given oral clonidine (4 μg/kg) 90 minutes before operation, and then were randomly allocated to receive either ketamine 0.5 mg/kg (n=60), fentanyl 1 μg/kg (n=60) or 0.9% normal saline (n=60) before induction with propofol 3.0 mg/kg. Insertion of LMA was performed within 1 minute of injection of propofol. Heart rate and mean blood pressure were noted 1 min before induction (baseline), immediately after induction, before and after insertion of LMA for up to 3 min. Following LMA insertion, 6 subjective end points were noted-mouth opening, coughing, swallowing, patient's movement, laryngospasm, and ease of an insertion. LMA insertion summed score was prepared depending upon these variables. LMA insertion summed score was nearly similar in ketamine and fentanyl group, which were significantly better than saline group (P<0.004). Mean blood pressure and heart rate were maintained in ketamine than with fentanyl or saline group. Incidence of prolonged apnea (>120 secs.) was higher in fentanyl group compared to ketamine and saline group. Even in oral clonidine premedicated children, addition of ketamine with propofol provides hemodynamic stability and comparable conditions for LMA insertion like fentanyl propofol with significantly less prolonged apnea.
  Saudi journal of anaesthesia. 04/2012; 6(2):140-4.
• Article: Spectrum of neurocognitive dysfunction in Indian population on FDG PET/CT imaging.

  Rajnish Sharma, Madhavi Tripathi, Maria M D'Souza, Abhinav Jaimini, Raunak Varshney, Puja Panwar, Aruna Kaushik, Sanjeev Saw, Romana Seher, Santosh Pandey, Dinesh Singh, Yachna Solanki, Anil K Mishra, Anupam Mondal, Rp Tripathi
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  ABSTRACT: A variety of neurodegenerative disorders produce significant abnormal brain function which can be detected using fluorodeoxyglucose positron emission tomography (FDG PET) scan even when structural changes are not detected on CT or MRI Scan. A study was undertaken at our institute to evaluate the FDG PET/CT findings in Indian population suffering from mild cognitive impairment (MCI), Alzheimer's disease (AD), fronto-temporal dementia (FTD), dementia with lewy body disease (DLBD) and other miscellaneous causes of dementia. 117 subjects having neurocognitive deficits and 36 normals were included in our study. All patients underwent a detailed history and clinical examination. This was followed by a mini mental state examination. Subsequently an FDG brain PET scan and an MRI were done. In the patient population included in our study group 36 were normal, 39 had MCI, 40 had AD, 14 had FTD, and 13 had DLBD and 11 dementia due to other miscellaneous causes. MCI patients showed primarily reduced tracer uptake in the mesio-temporal cortex. AD patients showed reduced tracer concentration in temporo-parietal lobes, while patients with advanced diseases showed frontal lobe disease additionally. In subjects of FTD, reduced radiotracer uptake in the fronto-temporal lobes was noted. In addition, FTD patients also showed basal ganglia defects. In contrast the DLBD patients showed globally reduced FDG uptake including severely affecting the occipital cortices. In the current study the F18-FDG PET scans have been shown to be highly useful in the diagnosis of various neurocognitive disorders of the brain. AD was found to be the most common dementia in the Indian population followed by MCI. Diffuse Lewy body disease, FTD and other miscellaneous categories of dementia had a near similar incidence.
  Indian Journal of Nuclear Medicine 04/2011; 26(2):67-77.
• Article: Spectrum of brain abnormalities detected on whole body F-18 FDG PET/CT in patients undergoing evaluation for non-CNS malignancies.

  Madhavi Tripathi, Abhinav Jaimini, Maria M D'Souza, Rajnish Sharma, Jyotika Jain, Gunjan Garg, Dinesh Singh, Nitin Kumar, Anil K Mishra, Rajesh K Grover, Anupam Mondal
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  ABSTRACT: We present the pattern of metabolic brain abnormalities detected in patients undergoing whole body (WB) F-18 flurodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) examination for non-central nervous system (CNS) malignancies. Knowledge of the PET/CT appearance of various intracranial metabolic abnormalities enables correct interpretation of PET scans in oncological patients where differentiation of metastasis from benign intracranial pathologies is important and improves specificity of the PET study. A complete clinical history and correlation with CT and MRI greatly helps in arriving at a correct imaging diagnosis.
  Indian Journal of Nuclear Medicine 04/2011; 26(2):123-9.
• Article: A rare case of pemphigus vegetans mimicking malignancy on F-18 FDG PET/CT.

  Maria M D'souza, Paschal V D'souza, Abhinav Jaimini, Rajnish Sharma, Madhavi Tripathi, Dinesh Singh, Anupam Mondal
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  ABSTRACT: A 42-year-old man with a history of chronic smoking and alcoholism was suspected to harbor a malignancy involving the perioral region and the scalp. He underwent an F-18 FDG PET/CT scan which revealed abnormal F-18 FDG accumulation in the oral mucosa and lips, extending to the nose, scalp, and bilateral cervical lymph nodes. Further work-up ultimately revealed the lesions to be secondary to pemphigus vegetans. Pemphigus vegetans is a rare variant of pemphigus vulgaris, an autoimmune bullous cutaneous disorder and involves mainly the flexural regions of the body. Unlike pemphigus vulgaris, lesions of pemphigus vegetans present as heaped up, eroded, and ulcerative plaques in the intertriginous regions of the body. Occasional lesions may be present on scalp and elsewhere in the Hallopeau variant of the disease. The use of F-18 FDG PET in the field of oncology is rapidly evolving; however, it is not tumor specific. The integration of CT into PET has increased the specificity of this modality. Nevertheless, there are many physiologic and benign conditions that may result in high accumulation of FDG, and may mimic malignancy. Familiarity with F-18 FDG-avid nonmalignant lesions may extend the use of F-18 FDG PET imaging beyond the field of oncology. To the best of our knowledge, this is the first description of PET/CT findings in pemphigus vegetans.
  Clinical nuclear medicine 03/2011; 36(3):248-51. · 3.92 Impact Factor
• Source

  Available from: ArXiv

  Article: Local Space-Time Curvature Effects on Quantum Orbital Angular Momentum

  Dinesh Singh, Nader Mobed
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  ABSTRACT: This paper claims that local space-time curvature can non-trivially contribute to the properties of orbital angular momentum in quantum mechanics. Of key importance is the demonstration that an extended orbital angular momentum operator due to gravitation can identify the existence of orbital states with half-integer projection quantum numbers "m" along the axis of quantization, while still preserving integer-valued orbital quantum numbers "l" for a simply connected topology. The consequences of this possibility are explored in depth, noting that the half-integer "m" states vanish as required when the locally curved space-time reduces to flat space-time, fully recovering all established properties of orbital angular momentum in this limit. In particular, it is shown that a minimum orbital number of "l = 2" is necessary for the gravitational interaction to appear within this context, in perfect correspondence with the spin-2 nature of linearized general relativity.
  01/2011;
• Article: A comparative study of two different doses of epidural neostigmine coadministered with lignocaine for post operative analgesia and sedation.

  Mamta Harjai, Girish Chandra, V K Bhatia, Dinesh Singh, Priyesh Bhaskar
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  ABSTRACT: Adjuvants have been used to prolong analgesic effects of epidural local anaesthetics. We studied two different doses of neostigmine. PATIENTS #ENTITYSTARTX00026; A randomized double blind study was conducted on ninety adult females scheduled for lower intra abdominal surgeries. The study was designed to compare two doses of epidural neostigmine co administered with lignocaine, with regard to its analgesic efficacy and its effect on sedation in postoperative period. Patients were divided into three groups of 30 each. Group I received lignocaine 1% (9ml) with normal saline (1ml), group II lignocaine1% (9ml) with neostigmine 100μg in saline (1ml) and group III received lignocaine 1% (9ml) with neostigmine 200μg in NS (1ml). Group I served as a control. In operating room, after putting epidural catheter, general anesthesia was administered with propofol (2mg kg(-1)), succinylcholine (2mg kg(-1)) and maintained with O2, N2O, relaxant technique. At the end of surgery, patients were reversed. Epidural analgesic medication was administered to after proper recovery from anesthesia. Intensity of pain relief on VAS, duration of analgesia, level of sensory block, motor blockade, sedation by sedation score and complications were assessed. The addition of neostigmine resulted in significant longer duration of analgesia (dose independent) and sedation (dose dependent). Sensory and motor blockade were identical in all three groups. There was no incidence of respiratory depression, pruritus, bradycardia or hypotension in any group. Two patients in control group and one, receiving neostigmine (200μg), developed nausea/vomiting. Co administration of epidural neostigmine and lignocaine appears to be a useful technique for postoperative analgesia as it increases the duration of analgesia and provides desirable sedation at the same time.
  Journal of Anaesthesiology Clinical Pharmacology 10/2010; 26(4):461-4.
• Article: Cervical and uterine metastasis from carcinoma of breast diagnosed by PET/CT: an unusual presentation.

  Maria M D'souza, Rajnish Sharma, Madhavi Tripathi, Sanjiv Kumar Saw, Anuja Anand, Dinesh Singh, Anupam Mondal
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  ABSTRACT: A 44-year-old apparently healthy woman presented with a 5-month history of intermittent vaginal bleeding. Clinical examination raised the suspicion of cervical neoplasia which was confirmed to be a metastatic adenocarcinoma on subsequent histopathological evaluation. An F-18 FDG PET/CT scan performed soon after revealed increased uptake in the cervix, extending upwards into the endometrial cavity. Additionally, small FDG avid spiculated soft tissue density masses were visualized in bilateral breast parenchyma, which proved to be lobular carcinoma on sonomammography followed by histopathology. Multiple lytic FDG avid skeletal metastases were also noted. Endometrial biopsy showed infiltrative malignant tumor with cytologic features similar to those observed in the breast biopsy specimen. The entire spectrum of findings pointed to a diagnosis of bilateral lobular carcinoma with uterine, cervical, and skeletal metastasis. Metastasis to the uterus and cervix from a breast primary is extremely rare. Most cases have been diagnosed in the follow-up of known cases of breast carcinoma. Our case is unique in that the patient, who had no prior history of breast carcinoma, was suspected to have a breast primary with cervical and uterine metastasis, based on the PET/CT findings.
  Clinical nuclear medicine 10/2010; 35(10):820-3. · 3.92 Impact Factor
• Source

  Available from: ArXiv

  Article: A New Perspective on Path Integral Quantum Mechanics in Curved Space-Time

  Dinesh Singh, Nader Mobed
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  ABSTRACT: A fundamentally different approach to path integral quantum mechanics in curved space-time is presented, as compared to the standard approaches currently available in the literature. Within the context of scalar particle propagation in a locally curved background, such as described by Fermi or Riemann normal co-ordinates, this approach requires use of a constructed operator to rotate the initial, intermediate, and final position ket vectors onto their respective local tangent spaces, defined at each local time step along some arbitrary classical reference worldline. Local time translation is described using a quantum mechanical representation of Lie transport, that while strictly non-unitary in operator form, nevertheless correctly recovers the free-particle Lagrangian in curved space-time, along with new contributions. This propagator yields the prediction that all probability violating terms due to curvature contribute to a quantum violation of the weak equivalence principle, while the remaining terms that conserve probability also correspondingly satisfy the weak equivalence principle, at least to leading-order in the particle's Compton wavelength. Furthermore, this propagator possesses an overall curvature-dependent and gauge-invariant phase factor that can be interpreted as the gravitational Aharonov-Bohm effect and Berry's phase.
  08/2010;
• Article: Evaluation of the effect of magnesium sulphate vs. clonidine as adjunct to epidural bupivacaine.

  Tanmoy Ghatak, Girish Chandra, Anita Malik, Dinesh Singh, Vinod Kumar Bhatia
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  ABSTRACT: For treatment of intra and postoperative pain, no drug has yet been identified that specifically inhibits nociception without associated side effects. Magnesium has antinociceptive effects in animal and human models of pain. The current prospective randomised double-blind study was undertaken to establish the effect of addition of magnesium or clonidine, as adjuvant, to epidural bupivacaine in lower abdominal and lower limb surgeries. A total of 90 American Society of Anesthesiology (ASA) grade I and II patients undergoing lower abdominal and lower limb surgeries were enrolled to receive either magnesium sulphate (Group B) or clonidine (Group C) along with epidural bupivacaine for surgical anaesthesia. All patients received 19 ml of epidural bupivacaine 0.5% along with 50 mg magnesium in group B, 150 mcg clonidine in Group C, whereas in control group (Group A), patients received same volume of normal saline. Onset time, heart rate, blood pressure, duration of analgesia, pain assessment by visual analogue score (VAS) and adverse effects were recorded. Onset of anaesthesia was rapid in magnesium group (Group B). In group C there was prolongation of duration of anaesthesia and sedation with lower VAS score, but the incidence of shivering was higher. The groups were similar with respect to haemodynamic variables, nausea and vomiting. The current study establishes magnesium sulphate as a predictable and safe adjunct to epidural bupivacaine for rapid onset of anaesthesia and clonidine for prolonged duration of anaesthesia with sedation.
  Indian journal of anaesthesia 07/2010; 54(4):308-13.
• Article: Prospective evaluation of solitary thyroid nodule on 18F-FDG PET/CT and high-resolution ultrasonography.

  Maria Mathew D'Souza, Raman Kumar Marwaha, Rajnish Sharma, Abhinav Jaimini, Shaji Thomas, Dinesh Singh, Manjula Jain, Param Jit Singh Bhalla, Madhavi Tripathi, Anjani Tiwari, Anil Mishra, Anupam Mondal, Rajendra Prashad Tripathi
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  ABSTRACT: The utility of 18F-FDG PET/CT in the assessment of thyroid nodules is unclear as there are several conflicting reports on the usefulness of SUV as an indicator to distinguish benign from malignant thyroid lesions. This study incorporated an additional parameter, namely dual time point imaging, to determine the diagnostic accuracy of PET/CT imaging. The performance of 18F-FDG PET/CT was compared to that of high-resolution ultrasound which is routinely used for the evaluation of thyroid nodules. Two hundred patients with incidentally detected solitary thyroid nodules were included in the study. Each patient underwent ultrasound and PET/CT evaluation within 7 days of each other, reported by an experienced radiologist and nuclear medicine specialist, respectively, in a blinded manner. The PET/CT criteria employed were maximum SUV (SUV(max)) at 60 min and change in SUV(max) at delayed (120 min) imaging. Final diagnosis was based on pathological evaluation and follow-up. Of the 200 patients, 26 had malignant and 174 had benign nodules. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of ultrasound were 80.8, 81.6, 39.6, 96.6 and 81.5%, respectively. Using SUV(max) at 60 min as the diagnostic criterion, the above indices were 80.8, 84.5, 43.8, 96.7 and 84%, respectively, for PET/CT. The SUV(max) of malignant thyroid lesions was significantly higher than benign lesions (16.2 +/- 10.6 vs. 4.5 +/- 3.1, respectively; p = 0.0001). Incorporation of percentage change in SUV(max) at delayed imaging as the diagnostic criterion yielded a slightly improved sensitivity, specificity, PPV, NPV and accuracy of 84.6, 85.6, 46.8, 97.4 and 85.5%, respectively. There was a significant difference in percentage change in SUV(max) between malignant and benign thyroid lesions (14.9 +/- 11.4 vs. -1.6 +/- 13.7, respectively; p = 0.0001). However, there was no statistically significant difference (95% confidence interval) between the diagnostic performance of PET/CT and ultrasound. Routine use of 18F-FDG PET/CT with SUV(max) at 60 min as the sole diagnostic criterion does not appear to have a significant advantage over high-resolution ultrasound in the evaluation of thyroid nodules. Incorporation of dual time point imaging enhances image interpretation, and yields a higher diagnostic performance, yet it is not statistically significant. Bearing in mind the cost, limited availability and radiation exposure, routine use of 18F-FDG PET/CT for distinguishing benign from malignant thyroid nodules cannot be recommended.
  Annals of Nuclear Medicine 04/2010; 24(5):345-55. · 1.50 Impact Factor
• Article: Antitubercular drug poisoning in a pregnant woman

  Rahul Dutta, Surya Dube, Dinesh Singh
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  ABSTRACT: A 20-year-old female in her third month of pregnancy, presented with generalised tonic clonic seizures, metabolic acidosis and coma following suicidal ingestion of antitubercular medication. We successfully managed the case with pyridoxine, sodium bicarbonate and mechanical ventilation.
  Indian Journal of Anaesthesia. 01/2010;
• Article: Evaluation of the effect of magnesium sulphate vs. clonidine as adjunct to epidural bupivacaine

  Tanmoy Ghatak, Girish Chandra, Anita Malik, Dinesh Singh, Vinod Bhatia
  [show abstract] [hide abstract]
  ABSTRACT: For treatment of intra and postoperative pain, no drug has yet been identified that specifically inhibits nociception without associated side effects. Magnesium has antinociceptive effects in animal and human models of pain. The current prospective randomised double-blind study was undertaken to establish the effect of addition of magnesium or clonidine, as adjuvant, to epidural bupivacaine in lower abdominal and lower limb surgeries. A total of 90 American Society of Anesthesiology (ASA) grade I and II patients undergoing lower abdominal and lower limb surgeries were enrolled to receive either magnesium sulphate (Group B) or clonidine (Group C) along with epidural bupivacaine for surgical anaesthesia. All patients received 19 ml of epidural bupivacaine 0.5% along with 50 mg magnesium in group B, 150 mcg clonidine in Group C, whereas in control group (Group A), patients received same volume of normal saline. Onset time, heart rate, blood pressure, duration of analgesia, pain assessment by visual analogue score (VAS) and adverse effects were recorded. Onset of anaesthesia was rapid in magnesium group (Group B). In group C there was prolongation of duration of anaesthesia and sedation with lower VAS score, but the incidence of shivering was higher. The groups were similar with respect to haemodynamic variables, nausea and vomiting. The current study establishes magnesium sulphate as a predictable and safe adjunct to epidural bupivacaine for rapid onset of anaesthesia and clonidine for prolonged duration of anaesthesia with sedation.
  Indian Journal of Anaesthesia. 01/2010;
• Source

  Available from: Henry Sunpath

  Article: Normative scores for a brief neuropsychological battery for the detection of HIV-associated neurocognitive disorder (HAND) among South Africans.

  Dinesh Singh, John A Joska, Karl Goodkin, Enrique Lopez, Landon Myer, Robert H Paul, Sally John, Henry Sunpath
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  ABSTRACT: There is an urgent need to more accurately diagnose HIV-associated neurocognitive disorder (HAND) in Africa. Rapid screening tests for HIV-associated dementia are of limited utility due to variable sensitivity and specificity. The use of selected neuropsychological tests is more appropriate, but norms for HIV seronegative people are not readily available for sub-Saharan African populations. We sought to derive normative scores for two commonly used neuropsychological tests that generate four test scores -- namely the Trail-Making Test (Parts A and B) and the Digit Span Test [Forward (DSF) and Backward (DSB)]. To assess memory and recall, we used the memory item of the International HIV Dementia Scale (IHDS). One hundred and ten HIV seronegative participants were assessed at McCord Hospital, Durban, South Africa between March 3rd and October 31st, 2008. We excluded people with major depressive disorder, substance use abuse and dependence and head injuries (with or without loss of consciousness). All the participants in this study were African and predominantly female with an average age of 28.5 years and 10 years of education. Age and gender influenced neuropsychological functioning, with older people performing worse. The effect of gender was not uniform across all the tests. These two neuropsychological tests can be administered with the IHDS in busy antiretroviral clinics. Their performance can be measured against these norms to more accurately diagnose the spectrum and progression of HAND.
  BMC Research Notes 01/2010; 3:28.
• Article: Comparative evaluation of F-18 FDOPA, F-18 FDG, and F-18 FLT-PET/CT for metabolic imaging of low grade gliomas.

  Madhavi Tripathi, Rajnish Sharma, Maria D'Souza, Abhinav Jaimini, Puja Panwar, Raunak Varshney, Anupama Datta, Nitin Kumar, Gunjan Garg, Dinesh Singh, Rajesh K Grover, Anil K Mishra, Anupam Mondal
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  ABSTRACT: We undertook this prospective study to compare amino acid metabolism, glucose metabolism, and proliferation in primary and recurrent low grade gliomas using positron emission tomography (PET)/computed tomography with F-18 FDOPA, F-18 FDG, and F-18 FLT. Fifteen patients with newly diagnosed or previously treated low grade gliomas (WHO grade I or II) were subjected to F-18-FDOPA, F-18 FDG, and F-18 FLT PET/computed tomography studies on consecutive days. This included 2 patients in remission as control subjects. Uptake of all the 3 tracers were analyzed visually and quantified using standardized uptake values and tumor to normal (T/N) ratios. The accuracy of all the 3 PET tracers in the detection of newly diagnosed and recurrent low grade gliomas was compared. F-18 FDOPA was positive in all cases of primary and recurrent low grade gliomas and negative in the patients in remission. Tumor was visualized on F-18 FDG in 7 of 13 cases, F-18-FLT was positive in 4 of 13 cases. Average tumor standardized uptake values max for F-18 FDOPA (5.75 +/- 4.9) and F-18 FLT (1.8 +/- 0.91) was lower than that of F-18 FDG (8.5 +/- 4.4). T/N ratios for F-18-FDOPA (2.3 +/- 0.51) and F-18 FLT (1.8 +/- 0.91) were higher than F-18 FDG (1.03 +/- 0.64) providing good image contrast for tumor detection in positive cases. F-18 FDOPA scan is superior to both F-18 FLT and F-18 FDG for visualization of primary and recurrent low grade gliomas. F-18-FLT should not be considered for evaluation of recurrent low grade gliomas.
  Clinical nuclear medicine 12/2009; 34(12):878-83. · 3.92 Impact Factor
• Article: Effects of spacetime curvature on spin-1/2 particle zitterbewegung

  Dinesh Singh, Nader Mobed
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  ABSTRACT: This paper investigates the properties of spin-1/2 particle zitterbewegung in the presence of a general curved spacetime background described in terms of Fermi normal coordinates, where the spatial part is expressed using general curvilinear coordinates. Adopting the approach first introduced by Barut and Bracken for zitterbewegung in the local rest frame of the particle, it is shown that non-trivial gravitational contributions to the relative position and momentum operators appear due to the coupling of zitterbewegung frequency terms with the Ricci curvature tensor in the Fermi frame, indicating a formal violation of the weak equivalence principle. Explicit expressions for these contributions are shown for the case of quasi-circular orbital motion of a spin-1/2 particle in a Vaidya background. Formal expressions also appear for the time derivative of the Pauli–Lubanski vector due to spacetime curvature effects coupled to the zitterbewegung frequency. Also, the choice of curvilinear coordinates results in non-inertial contributions in the time evolution of the canonical momentum for the spin-1/2 particle, where zitterbewegung effects lead to stability considerations for its propagation, based on the Floquet theory of differential equations.
  Classical and Quantum Gravity 09/2009; 26(18):185007. · 3.32 Impact Factor
• Article: Clinical studies for improving radiotherapy with 2-deoxy-D-glucose: present status and future prospects.

  B S Dwarakanath, Dinesh Singh, Ajit K Banerji, Rajiv Sarin, N K Venkataramana, R Jalali, P N Vishwanath, B K Mohanti, R P Tripathi, V K Kalia, Viney Jain
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  ABSTRACT: Higher rates of glucose usage generally correlate with poor prognosis in several types of malignant tumours. Experimental studies (both in vitro and in vivo) have shown that 2-deoxy-D-glucose (2-DG), a glucose analog and glycolytic inhibitor, enhances radiation-induced damage selectively in tumor cells while protecting normal cells, thereby suggesting that 2-DG can be used as a differential radiomodifier to improve the efficacy of radiotherapy. Clinical trials undertaken to study the feasibility, safety, and validity of this suggested approach will be described. Based on 2-DG-induced radiosensitization observed in primary organ cultures of cerebral glioma tissues, clinical trials were designed taking into consideration the radiobiology of gliomas and pharmacokinetics of 2-DG. Phase I/II clinical trials have unequivocally demonstrated that a combination of 2-DG (200-300 mg 2-DG per kg body weight orally administered after overnight fasting, 20 min before irradiation) with large weekly fractions (5 Gy/fraction) of low-LET radiotherapy is well tolerated without any acute toxicity or late radiation damage to the normal brain tissue. Nonserious transient side effects similar to hypoglycemia induced disturbances like restlessness, nausea, and vomiting were observed at the 2-DG doses used. Data from these trials involving more than 100 patients have clearly indicated a moderate increase in the survival, with a significant improvement in the quality of life with clinicopathological evidence of protection of normal brain tissue. A phase III multicentric trial to evaluate the efficacy of the combined treatment is in progress. Directions for future studies are discussed.
  Journal of cancer research and therapeutics 09/2009; 5 Suppl 1:S21-6. · 0.83 Impact Factor
• Article: F-18 flurodeoxyglucose negative, F-18 fluoride accumulating in a brain metastasis in a treated case of carcinoma of the breast.

  Madhavi Tripathi, Abhinav Jaimini, Namita Singh, Nikunj Jain, Maria D'Souza, Prabhjot Kaur, Dinesh Singh, Rajnish Sharma, Anupam Mondal
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  ABSTRACT: A 52-year-old woman undergoing treatment for carcinoma of the left breast with brain and bone metastases was referred for F-18 fluoride positron emission tomography-computed tomography (PET/CT) bone scan (FBS) to evaluate the status of a bone metastasis. Review of the plain fluoride-PET images section-wise revealed an intracranial focus of abnormal fluoride accumulation, which was localized to the right medial temporal lobe on the fused fluoride-PET/CT image, with no evidence of calcification corresponding to this lesion on CT. The pretreatment F-18 flurodeoxyglucose (FDG)-PET/CT study showed this lesion to correspond to the site of FDG accumulating in a brain metastasis. The patient had undergone radiation therapy (RT) for her brain metastasis. Brain FDG-PET/CT was then done, which failed to reveal FDG accumulation in the lesion. Magnetic resonance imaging and magnetic resonance spectroscopy of this lesion revealed features suggestive of radiation damage. The probable mechanism of fluoride accumulation in the metastatic brain lesion was related to cell membrane damage and protein denaturation post-RT. Thus, while reporting FBS the possibility of extraosseous accumulation in an intracranial metastasis must be kept in mind.
  Clinical nuclear medicine 06/2009; 34(5):287-9. · 3.92 Impact Factor