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238 results on '"Khosla, D."'

31. A maximum-entropy method for MEG source imaging

Author

Khosla, D. and Singh, M.

Subjects
Magnetoencephalography -- Methods, Business, Electronics, Electronics and electrical industries
Abstract

Magnetoencephalographic imaging is the estimation of three-dimensional neuronal current sources on the cortical surface from the measured magnetoencephalogram (MEG). It is a highly under-determined inverse problem as there are many 'feasible' images which are consistent with the MEG. Previous approaches to this problem have concentrated on the use of weighted minimum-norm inverse methods. These methods often produce overly smoothed images and exhibit bias towards surface sources. In this work we explore the maximum-entropy approach to obtain better solutions to the problem. This estimation technique selects, from the possible set of feasible images, the image with the highest entropy permitted by the available information. In order to account for the presence of noise in the data, we have also incorporated a noise rejection term into the maximum-entropy method (MEM). This makes our approach mirror a Bayesian maximum a posteriori probability (MAP) formulation. Additional information from other modalities like functional magnetic resonance imaging (fMRI) can also be incorporated into the proposed method in the form of a prior bias function to improve solutions. We demonstrate the method with experimental phantom data from a clinical 122-channel MEG system.

Published
1997

32. Segmentation of functional MRI by K-means clustering

Author

Singh, M., Patel, P., Khosla, D., and Kim, T.

Subjects
Magnetic resonance imaging -- Research, K-theory -- Usage, Cluster analysis -- Usage, Business, Electronics, Electronics and electrical industries
Abstract

A preliminary study was conducted to segment 1.5T fMRIs into the microvasculature and relatively large blood vessels using the intensity, phase and temporal delay of activated pixels as three correlated parameters in gradient echo images. Images acquired during visual stimulation using a checkerboard flashing at 8Hz were investigated. Activated pixels were identified by correlating their time-course in the gradient echo images to a model of the stimulation 'on'-'off' sequence. The temporal delay of each activated pixel was estimated by fitting its time-course to a reference sinusoidal function. The mean signal intensity and phase difference of the activated pixels was computed by subtracting the average of the 'on' images from the average of the 'off' images. After mapping each pixel onto a three-dimensional feature space (intensity, phase shift and temporal delay), a clustering method based on a K-means algorithm was employed to classify pixels into two or three classes representing the relatively large blood vessels and the microvasculature. Good demarcation between large veins and activated gray matter was achieved with this method.

Published
1996

33. Estimation of T2* in functional spectroscopy during visual stimulation

Author

Singh, M., Patel, P., and Khosla, D.

Subjects
Proton magnetic resonance spectroscopy -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Changes in [T2.sup.*] of activated pixels were estimated using single voxel and 1D chemical shift imaging (CSI) proton spectroscopy during visual stimulation. A single voxel was angulated and positioned to enclose activated pixels as determined by a corresponding functional MRI study. Eddy currents in angulated voxel studies produced a bump in the water peak, which was removed by modeling a biexponential function with two frequencies to fit the time domain data. The results show approximately 1.8% [T2.sup.*] change when averaged over five subjects. Non-angulated voxels, which do not enclose the activated pixels as closely as the angulated voxels but are free from eddy current artifacts were also studied. It was possible to separate the contributions from brain tissue and cerebrospinal fluid (csf) in the non-angulated voxels through a two-compartment model. Changes in the [T2.sup.*] during stimulation were detected for the tissue compartment only. Fitting also determined the amplitude of the water signal which is directly related to any T1 or in-flow related changes. The results show negligible changes in the amplitude. The height of the water peak in frequency domain, which is directly related to [T2.sup.*], was found to increase during stimulation in a proportionate manner. The peak height was also used to localize activation in the visual cortex in 1D CSI experiments. It is concluded that [T2.sup.*] changes reflecting a blood oxygenation level dependent or BOLD effect are demonstrated in these studies.

Published
1996

34. Separation of veins from activated brain tissue in functional magnetic resonance images at 1.5T

Author

Singh, M., Kim, T., Kim, H., and Khosla, D.

Subjects
Brain -- Magnetic resonance imaging, Magnetic resonance imaging -- Methods, Image processing -- Digital techniques, Business, Electronics, Electronics and electrical industries
Abstract

A feasibility study was conducted to segment 1.5T functional magnetic resonance images (fMRIs) into gray matter and veins using individual pixel intensity difference and temporal phase delay as two correlated parameters in 1.5T gradient echo images. The time-course of each pixel in gradient echo images acquired during visual stimulation with a checkerboard flashing at 8Hz was correlated to the stimulation 'on'-'off' sequence to identify activated pixels, and the temporal delay of each activated pixel was computed by fitting its time-course to a reference sinusoidal function. A histogram of the product of each pixel's intensity (in the activated image) and corresponding temporal delay could be fitted to a bimodal distribution, which was then used to segment the functional image into veins and activated brain tissue. The results show relatively good demarcation between large veins and activated gray matter using this method.

Published
1995

35. Effect of phase encoding steps on 1D chemical shift imaging of lactate during brain activation

Author

Singh, M., Khosla, D., Kim, H., and Kim, T.

Subjects
Lactic acid -- Research, Chemical reactions -- Research, Nuclear magnetic resonance -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Lactate is a unique indicator of brain activation and is detectable in vivo by proton magnetic resonance spectroscopy. Previous brain activation studies have been confined to single-voxel localization of lactate. To extend this work to 1D chemical shift imaging, computer simulation and test-object studies were conducted to examine tradeoffs among the number of phase encoding steps, signal-to-noise ratio (snr) and resolution. An iterative algorithm was developed to reduce truncation artifacts arising from a limited number of phase encoding steps. The results indicate that the resolution and snr attained with 8 phase encoding steps and 16 averages per step after applying the truncation reduction algorithm are approximately equal to those attained with 32 encoding steps and 4 averages per step. Thus, 32 steps would be preferred since contamination is minimized with increasing steps.

Published
1994

36. Functional MRI at 1.5T

Author

Singh, M., Kim, H., Kim, T., and Khosla, D.

Subjects
Magnetic resonance imaging -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Human studies were conducted to determine the feasibility of functional MRI during auditory stimulation using conventional hardware (i.e., without echo-planar imaging) in a Philips 1.5T Gyroscan system. A gradient-echo pulse sequence was optimized to minimize the effect of gradient sound. Simple tonal stimulation and linguistic stimuli designed to activate regions responsible for comprehension were investigated. Also, functional images in response to visual and somatosensory stimulation were generated, albeit with a different gradient-echo sequence to optimize contrast and temporal resolution. A registration technique was developed to reduce head motion artifacts. Cerebrospinal fluid pulsation artifacts however, were not removable even with flow compensating gradient pulses. A phase-shift imaging technique was investigated which has the potential to separate the relatively large blood vessels from the microvasculature. Results of functional imaging indicate a 2-9% increase in signal intensity localized to the corresponding auditory, visual or somatosensory brain regions during stimulation.

Published
1994

37. Dosimetric evaluation and clinical outcome in post-operative patients of carcinoma vulva treated with intensity-modulated radiotherapy

Author

Khosla, D., Patel, F., Shukla, A., Rai, B., Oinam, A., and Sharma, S.

Subjects
Varian Medical Systems Inc., TCP/IP (Network protocols), Cancer -- Patient outcomes -- Care and treatment, Medical equipment industry, Radiotherapy, Cancer patients -- Patient outcomes -- Care and treatment, Radiation (Physics), TCP/IP, Health
Abstract

Byline: D. Khosla, F. Patel, A. Shukla, B. Rai, A. Oinam, S. Sharma BACKGROUND: To compare dosimetric parameters of intensity-modulated radiation therapy (IMRT) with 3D conformal radiotherapy (3DCRT) in post-operative [...]

Published
2015

39. Long term survival after whole brain radiotherapy for brain metastasis in follicular dendritic cell sarcoma

Author

Dimri, K., Trehan, R., Pandey, A., and Khosla, D.

Subjects
Dendritic cells -- Physiological aspects, Brain cancer -- Diagnosis -- Care and treatment -- Case studies, Radiotherapy -- Health aspects, Health
Abstract

Byline: K. Dimri, R. Trehan, A. Pandey, D. Khosla Sir, We present a rare case of brain metastasis in a patient with follicular dendritic cell sarcoma (FDCS), who was treated [...]

Published
2014

40. Role of neoadjuvant concurrent chemoradiation in locally advanced unresectable pancreatic cancer: A feasibility study at tertiary care centre

Author

Kapoor, R., Khosla, D., Gupta, R., Bahl, A., Shukla, A., and Sharma, S.

Subjects
Chemotherapy -- Methods -- Patient outcomes, Cancer -- Chemotherapy, Radiotherapy -- Methods -- Patient outcomes, Pancreatic cancer -- Care and treatment, Health
Abstract

Byline: R. Kapoor, D. Khosla, R. Gupta, A. Bahl, A. Shukla, S. Sharma Background: Pancreatic cancer has an extremely poor prognosis and prolonged survival is achieved only by resection with [...]

Published
2014

44. CELL BIOLOGY AND SIGNALING

Author

Furnari, F., primary, Fenton, T., additional, Nathanson, D., additional, de Alberquerque, C. P., additional, Kuga, D., additional, Wanami, A., additional, Dang, J., additional, Yang, H., additional, Tanaka, K., additional, Gao, L., additional, Oba-Shinjo, S., additional, Uno, M., additional, Inda, M.-d.-M., additional, Bachoo, R., additional, James, C. D., additional, DePinho, R., additional, Vandenberg, S., additional, Zhou, H., additional, Marie, S., additional, Mischel, P., additional, Cavenee, W., additional, Szerlip, N., additional, Pedraza, A., additional, Huse, J., additional, Mikkelsen, T., additional, Brennan, C., additional, Castellani, R. J., additional, Ivanova, S., additional, Gerzanich, V. V., additional, Simard, J. M., additional, Ito, M., additional, See, W., additional, Mukherjee, J., additional, Ohba, S., additional, Tan, I.-L., additional, Pieper, R. O., additional, Lukiw, W. J., additional, Culicchia, F., additional, Pogue, A., additional, Bhattacharjee, S., additional, Zhao, Y., additional, Proescholdt, M. A., additional, Merrill, M., additional, Storr, E. M., additional, Lohmeier, A., additional, Brawanski, A., additional, Abraham, S., additional, Jensen, R., additional, Khatua, S., additional, Gopal, U., additional, Du, J., additional, He, F., additional, Golub, T., additional, Isaacs, J. S., additional, Dietrich, J., additional, Kalogirou-Valtis, Y., additional, Ly, I., additional, Scadden, D., additional, Proschel, C., additional, Mayer-Proschel, M., additional, Rempel, S. A., additional, Schultz, C. R., additional, Golembieski, W., additional, Brodie, C., additional, Mathew, L. K., additional, Skuli, N., additional, Mucaj, V., additional, Imtiyaz, H. Z., additional, Venneti, S., additional, Lal, P., additional, Zhang, Z., additional, Davuluri, R. V., additional, Koch, C., additional, Evans, S., additional, Simon, M. C., additional, Ranganathan, P., additional, Clark, P., additional, Salamat, S., additional, Kuo, J. S., additional, Kalejta, R. F., additional, Bhattacharjee, B., additional, Renzette, N., additional, Moser, R. P., additional, Kowalik, T. F., additional, McFarland, B. C., additional, Ma, J.-Y., additional, Langford, C. P., additional, Gillespie, G. Y., additional, Yu, H., additional, Zheng, Y., additional, Nozell, S. E., additional, Huszar, D., additional, Benveniste, E. N., additional, Lawrence, J. E., additional, Cook, N. J., additional, Rovin, R. A., additional, Winn, R. J., additional, Godlewski, J. A., additional, Ogawa, D., additional, Bronisz, A., additional, Lawler, S., additional, Chiocca, E. A., additional, Lee, S. X., additional, Wong, E. T., additional, Swanson, K. D., additional, Liu, K.-w., additional, Feng, H., additional, Kazlauskas, A., additional, Smith, E. M., additional, Symes, K., additional, Hamilton, R. L., additional, Nagane, M., additional, Nishikawa, R., additional, Hu, B., additional, Cheng, S.-Y., additional, Silber, J., additional, Jacobsen, A., additional, Ozawa, T., additional, Harinath, G., additional, Brennan, C. W., additional, Holland, E. C., additional, Sander, C., additional, Huse, J. T., additional, Sengupta, R., additional, Dubuc, A., additional, Ward, S., additional, Yang, L., additional, Northcott, P., additional, Kroll, K., additional, Taylor, M., additional, Wechsler-Reya, R., additional, Rubin, J., additional, Chu, W.-T., additional, Lee, H.-T., additional, Huang, F.-J., additional, Aldape, K., additional, Yao, J., additional, Steeg, P. S., additional, Lu, Z., additional, Xie, K., additional, Huang, S., additional, Sim, H., additional, Agudelo-Garcia, P. A., additional, Viapiano, M. S., additional, Saldivar, J., additional, Dolan, C., additional, Mora, M., additional, Nuovo, G., additional, Cole, S., additional, Stegh, A. H., additional, Ryu, M.-J., additional, Liu, Y., additional, Zhong, X., additional, Marwaha, S., additional, Li, H., additional, Wang, J., additional, Chang, Q., additional, Zhang, J., additional, Ng, H.-K., additional, Poon, W. S., additional, Zhou, L., additional, Pang, J. C., additional, Chan, A., additional, Didier, S., additional, Kwiatkowska, A., additional, Ennis, M., additional, Fortin, S., additional, Rushing, E., additional, Eschbacher, J., additional, Tran, N., additional, Symons, M., additional, Roldan, G., additional, McIntyre, J. B., additional, Easaw, J., additional, Magliocco, A., additional, Wykosky, J., additional, Furnari, F., additional, Lu, D., additional, Mreich, E., additional, Chung, S., additional, Teo, C., additional, Wheeler, H., additional, McDonald, K. L., additional, Lawn, S., additional, Forsyth, P., additional, Sonabend, A. M., additional, Lei, L., additional, Kennedy, B., additional, Soderquist, C., additional, Guarnieri, P., additional, Leung, R., additional, Yun, J., additional, Sisti, J., additional, Castelli, M., additional, Bruce, S., additional, Bruce, R., additional, Ludwig, T., additional, Rosenfeld, S., additional, Bruce, J. N., additional, Canoll, P., additional, Lamszus, K., additional, Schulte, A., additional, Gunther, H. S., additional, Riethdorf, S., additional, Phillips, H. S., additional, Westphal, M., additional, Siegal, T., additional, Zrihan, D., additional, Granit, A., additional, Lavon, I., additional, Singh, M., additional, Chandra, J., additional, Nakashima, H., additional, Godlewski, J., additional, Chiocca, A. E., additional, Kapoor, G. S., additional, Poptani, H., additional, Ittyerah, R., additional, O'Rourke, D. M., additional, Sadraei, N. H., additional, Burgett, M., additional, Ahluwalia, M., additional, Tipps, R., additional, Khosla, D., additional, Weil, R., additional, Nowacki, A., additional, Prayson, R., additional, Shi, T., additional, Gladson, C., additional, Moeckel, S., additional, Meyer, K., additional, Bosserhoff, A., additional, Spang, R., additional, Leukel, P., additional, Vollmann, A., additional, Jachnick, B., additional, Stangl, C., additional, Proescholdt, M., additional, Bogdahn, U., additional, Hau, P., additional, Kaur, G., additional, Sun, M., additional, Kaur, R., additional, Bloch, O., additional, Jian, B., additional, Parsa, A. T., additional, Hossain, A., additional, Shinojima, N., additional, Gumin, J., additional, Feng, G., additional, Lang, F. F., additional, Li, L., additional, Yang, C.-R., additional, Chakraborty, S., additional, Hatanpaa, K., additional, Chauncey, S., additional, Jiwani, A., additional, Habib, A., additional, Nguyen, T., additional, Munson, J., additional, Machaidze, R., additional, Kaluzova, M., additional, Bellamkonda, R., additional, Hadjipanayis, C. G., additional, Zhang, Y., additional, McFarland, B., additional, Bredel, M., additional, Lee, S.-H., additional, Zerrouqi, A., additional, Khwaja, F., additional, Devi, N. S., additional, Van Meir, E. G., additional, Haseley, A., additional, Boone, S., additional, Wojton, J., additional, Yu, L., additional, Kaur, B., additional, Wojton, J. A., additional, Naduparambil, J., additional, Denton, N., additional, Chakravarti, A., additional, Conrad, C. A., additional, Wang, X., additional, Sheng, X., additional, Nilsson, C., additional, Marshall, A. G., additional, Emmett, M. R., additional, Hu, Y., additional, Mark, L., additional, Zhou, Y.-H. Z., additional, Dhruv, H., additional, McDonough, W., additional, Armstrong, B., additional, Tuncali, S., additional, Kislin, K., additional, Berens, M., additional, Plas, D., additional, Gallo, C., additional, Stringer, K., additional, Kendler, A., additional, McPherson, C., additional, Castelli, M. A., additional, Ellis, J. A., additional, Assanah, M., additional, Ogden, A., additional, Liang, J., additional, Piao, Y., additional, deGroot, J. F., additional, Gordon, N., additional, Patel, D., additional, Palanichamy, K., additional, Hervey-Jumper, S., additional, Wang, A., additional, He, X., additional, Zhu, T., additional, Heth, J., additional, Muraszko, K., additional, Fan, X., additional, Liu, W. M., additional, Huang, P., additional, Rani, S., additional, Stettner, M. R., additional, Jerry, S., additional, Dai, Q., additional, Kappes, J., additional, Gladson, C. L., additional, Chakravarty, D., additional, Koul, D., additional, Alfred Yung, W. K., additional, Jensen, S. A., additional, Luciano, J., additional, Calvert, A., additional, Nagpal, V., additional, Stegh, A., additional, Kang, S.-H., additional, Yu, M. O., additional, Lee, M.-G., additional, Chi, S.-G., additional, Chung, Y.-G., additional, Cooper, M. K., additional, Valadez, J. G., additional, Grover, V. K., additional, Kouri, F. M., additional, Chin, L., additional, Ahluwalia, M. S., additional, Weil, R. J., additional, McGraw, M., additional, Barnett, G. H., additional, Kang, C., additional, Zou, J., additional, Lan, F., additional, Yue, X., additional, Shi, Z., additional, Zhang, K., additional, Han, L., additional, Pu, P., additional, Seaman, B. F., additional, Tran, N. D., additional, Battiste, J. D., additional, Sirasanagandla, S., additional, Maher, E. A., additional, Sugiarto, S., additional, Persson, A., additional, Munoz, E. G., additional, Waldhuber, M., additional, Stallcup, W., additional, Philips, J., additional, Berger, M. S., additional, Bergers, G., additional, Weiss, W. A., additional, and Petritsch, C., additional

Published
2011
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48. Dosimetric evaluation and clinical outcome in post-operative patients of carcinoma vulva treated with intensity-modulated radiotherapy.

Author

D., Khosla, F. D., Patel, A. K., Shukla, B., Rai, A. S., Oinam, S. C., Sharma, Khosla, D, Patel, F D, Shukla, A K, Rai, B, Oinam, A S, and Sharma, S C

Subjects
VULVAR cancer, CANCER radiotherapy, CANCER treatment, RADIATION dosimetry, CANCER patient care
Abstract

Background: To compare dosimetric parameters of intensity-modulated radiation therapy (IMRT) with 3D conformal radiotherapy (3DCRT) in post-operative patients of vulvar cancer and to assess clinical outcome and toxicity with IMRT.Materials and Methods: A total of 8 post-operative patients of vulvar cancer were treated with IMRT. All patients were also planned by 3DCRT for comparison with IMRT. The two plans were compared in terms of conformity index, homogeneity index, tumor control probability (TCP) and normal tissue complication probability (NTCP) for the planning target volume and organs at risk (OAR).Results: IMRT resulted in significantly lesser doses to rectum, bladder, bowel and femoral head as compared with 3DCRT plans. Mean conformity and homogeneity indices were better and within range with IMRT. The TCP was comparable between the two treatment plans and NTCP for rectum, bladder, bowel and femoral head was significantly less with IMRT as compared with 3DCRT. Treatment was well-tolerated and none of the patients developed Grade 3 or higher toxicity.Conclusion: IMRT yielded superior plans with respect to target coverage, homogeneity and conformality while lowering dose to adjacent OAR as compared with 3DCRT. Thus, IMRT offers a reduction in NTCP while maintaining TCP. [ABSTRACT FROM AUTHOR]

Published
2015
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