Browsing by Author "Subhash Chand Kheruka"

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A new method to correct the attenuation map in simultaneous transmission/emission tomography using 153Gd/ 67Ga radioisotopes
(2012) Subhash Chand Kheruka; Brian F. Hutton; Umesh Chand Naithani; Lalit Mohan Aggarwal; Nirmal Kumar Painuly; Anil Kumar Maurya; Sanjay Gambhir
Reconstruction of the tomographic images without attenuation correction can cause erroneously high count densities and reduced image contrast in low attenuation regions. In order to solve the problem of photon attenuation, one needs to know the attenuation coefficient for the individual patient being studied. Therefore, we made an attempt to correct the attenuation map in simultaneous transmission/emission tomography with 153Gd/ 67Ga using maximum likelihood method using the expectation maximization (ML-EM) algorithm to correct the transmission window for both the spillover and downscatter. Spillover fraction, scatter fraction and parameters for the scatter function (A, b and c) were determined experimentally and optimized using the optimization program written in IDL based on simplex theory. All measurements were performed on a Vertex gamma camera using the anthropomorphic thorax phantom for validation of data obtained by the proposed method. It was observed that without spillover and downscatter correction, the mean counts were 19.29 in liver and 26.90 in lung, whereas after after applying the corrections, the mean counts were reduced to 3.80 and 15.10 in liver and lung, respectively, which were close to true mean counts (liver 2.15 and lung 14.89). In this proposed method, we introduced the set of F t (spillover) and K t (downscatter) to account for the variations in projection pixels (f t and k t) with the density and thickness. The F t and K t were determined using the transmission data by an iterative process. The quantitative error was reduced by 98.0% for lung and 90.0% for liver when the corrected transmission images were obtained after the subtraction of spillover and downscatter fraction.
An investigation of a sinogram discontinuity artifact on myocardial perfusion imaging
(2012) Subhash Chand Kheruka; Umesh Chand Naithani; Lalit Mohan Aggarwal; Nirmal Kumar Painuly; Anil Kumar Maurya; Sanjay Gambhir
Our purpose was to find out the cause of an unusual distinct break seen on a patient's sinogram despite within-tolerance results on all quality assurance tests during myocardial perfusion imaging (MPI) and corrective measures. Methods: SPECT quality control is a prerequisite to obtaining high-quality diagnostic images. Daily uniformity and energy-peaking tests and weekly center-of-rotation (COR) tests are run to check the performance of the SPECT system. A distinct break in the sinogram of an MPI study was noticed for 1 patient, despite routine quality control tests that showed the system to be well within tolerance limits. Critical inspection of the g-camera revealed that the 2 detector heads did not make complete contact with each other at a 90° position and that a gap of as much as 10.0 mm was left between the 2 edges of the detectors even though COR testing showed the system to be within tolerance limits. After this gap had been minimized (210-mm position), the MPI study of this patient was repeated. Results: Reduction of the gap between detectors corrected the sinogram discontinuity. On the MPI study, the break in the sinogram existed because the 2 detectors were not acquiring the data at the same position in their useful fields of view. When one of the detectors was tilted to exactly 45°, the gap was reduced and the data were acquired at the same useful field of view for both detectors. Conclusion: The sinogram artifact may arise even after perfect COR calibration, and in the reported case, the discontinuity in the sinogram was rectified by correcting the angle of the detectors. Meticulous investigation for artifacts must be performed to minimize the probability of false results. © 2012 by the Society of Nuclear Medicine, Inc.
Evaluation of single-photon emission computed tomography images obtained with and without copper filter by segmentation
(Medknow Publications, 2016) Subhash Chand Kheruka; Lalit Mohan Aggarwal; Neeraj Sharma; Umesh Chand Naithani; Anil Kumar Maurya; Sanjay Gambhir
Background: Measurement of accurate attenuation of photon flux in tissue is important to obtain reconstructed images using single-photon emission computed tomography (SPECT). Computed tomography (CT) scanner provides attenuation correction data for SPECT as well as anatomic information for diagnostic purposes. Segmentation is a process of dividing an image into regions having similar properties such as gray level, color, texture, brightness, and contrast. Image segmentation is an important tool for evaluation of medical images. X-ray beam used in CT scan is poly-energetic; therefore, we have used a copper filter to remove the low energy X-rays for obtaining correct attenuation factor. Images obtained with and without filters were quantitatively evaluated by segmentation method to avoid human error. Materials and Methods: Axial images of AAPM CT phantom were acquired with 3 mm copper filter (low intensity) and without copper filter (high intensity) using low-dose CT (140 kvp and 2.5 mA) of SPECT/CT system (Hawkeye, GE Healthcare). For segmentation Simulated Annealing Based Fuzzy c-means, algorithm is applied. Quantitative measurement of quality is done based on universal image quality index. Further, for the validation of attenuation correction map of filtered CT images, Jaszczak SPECT phantom was filled with 500 MBq of 99m Tc and SPECT study was acquired. Low dose CT images were acquired for attenuation correction to be used for reconstruction of SPECT images. Another set of CT images were acquired after applying additional 3 mm copper filter. Two sets of axial SPECT images were reconstructed using attenuation map from both the CT images obtained without and with a filter. Results and Conclusions: When we applied Simulated Annealing Based Fuzzy c-means segmentation on both the CT images, the CT images with filter shows remarkable improvement and all the six section of the spheres in the Jaszczak SPECT phantom were clearly visualized.
Negatively charged liposomes of sertraline hydrochloride: Formulation, characterization and pharmacokinetic studies
(Editions de Sante, 2020) Tejpratap Chauhan; Varsha Rani; Bhupendra Sahu; Adity Sharma; Subhash Chand Kheruka; Sanjay Gambhir; Veeresh Dube; Lalit M. Aggarwal; Ruchi Chawla
The present study was carried out with an objective to study the extent of delivery of negatively charged liposomes of sertraline hydrochloride to brain via intravenous route for treatment of depressive –like symptoms. Liposomes of sertraline hydrochloride were formulated by film hydration technique using cholesterol, hydrogenated soya phosphatidylcholine-L-α-phosphatidylcholine, and distearoyl phosphatidyl glycerol sodium. Uniform sized vesicles with porous surface morphology with vesicle size of 151.59 nm were prepared. Radioactive imaging performed using 99mTcO4 showed ~5% of uptake of labelled liposomes in brain within 2 h of administration. On administration of liposomes and free drug suspension, approximately, 205.06 ng/ml and 87.18 ng/ml of sertraline were estimated in brain at 36 h. The liposomes can be transported by transcelluar transport which includes phagocytosis and the use of phosphatidylcholine enhances macrophage internalization and delivery to brain. The study indicated significantly higher concentration of sertraline in brain after 36 h, on administration of liposomes as compared to free sertraline suspension. © 2020 Elsevier B.V.
Polylactide-co-glycolide nanoparticles of antitubercular drugs: Formulation, characterization and biodistribution studies
(Future Science Ltd, 2014) Ruchi Chawla; Harshendra S. Solanki; Subhash Chand Kheruka; Sanjay Gambhir; Veeresh Dube; Lalit M. Aggarwal; Brahmeshwar Mishra
Background: The present study was designed to prepare and characterize poly lactide-co-glycolide nanoparticles of antitubercular drugs (ATDs) for delivery through oral route to alveolar macrophages. Methods: Nanoparticles were prepared by double emulsification solvent evaporation method. Ex vivo and in vivo drug accumulation studies were performed in alveolar macrophages, harvested by broncheoalveolar lavaging. Internalization of nanoparticles was studied by confocal laser scanning microscopy. γ-scintigraphy imaging using technetium-99m was done to study the biodistribution pattern of nanoparticles. Results: High intracellular concentrations of ATDs were observed in macrophages within 30 min of administration of nanoparticles. Intense radioactivity recorded in liver, spleen and lungs revealed uptake of nanoparticles in macrophages, abundantly present in mononuclear phagocyte system present in these organs. Conclusion: Targeted delivery of ATDs will help reduce dose and associated side effects including hepatotoxicity of ATDs. Further studies are required to assess the potential therapeutic advantages for treatment of TB. © 2014 Future Science Ltd.