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1
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Mobile phones and sleep - A review

100%
Supe S.
Polish Journal of Medical Physics And Engineering
|
2010
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vol. 16
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issue 1
1-10
EN
The increasing use of mobile phones has raised concerns regarding the potential health effects of exposure to the radiofrequency electromagnetic fields. An increasing amount research related to mobile phone use has focussed on the possible effects of mobile phone exposure on human brain activity and function. In particular, the use of sleep research has become a more widely used technique for assessing the possible effects of mobile phones on human health and wellbeing especially in the investigation of potential changes in sleep architecture resulting from mobile phone use. Acute exposure to a mobile phone prior to sleep significantly enhances electroencephalogram spectral power in the sleep spindle frequency range. This mobile phone-induced enhancement in spectral power is largely transitory and does not linger throughout the night. Furthermore, a reduction in rapid eye movement sleep latency following mobile phone exposure was also found, although interestingly, neither this change in rapid eye movement sleep latency or the enhancement in spectral power following mobile phone exposure, led to changes in the overall quality of sleep. In conclusion, a short exposure to the radiofrequency electromagnetic fields emitted by a mobile phone handset immediately prior to sleep is sufficient to induce changes in brain activity in the initial part of sleep. The consequences or functional significance of this effect are currently unknown and it would be premature to draw conclusions about possible health consequences.
2
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Mobile phones and hearing - A review

51%
Lakshmanagowda P., Supe S., Viswanath L., Kunjar S.
Polish Journal of Medical Physics And Engineering
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2009
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vol. 15
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issue 3
161-175
EN
Mobile phones are being widely used throughout the world. Although there is no clear evidence of harmful effects of radiofrequency (RF) radiation at the levels used by these devices, there is widespread public concern that there may be potential for harm. Of all anatomical structures, the ear is closest to the mobile phone, which may lead to relatively high energy deposition in the ear compared to other parts of the body. Till the year 2000 only a few studies had addressed potential adverse effects of EMFs on the hearing system. The potential adverse effects of mobile phone exposure on the hearing system should be investigated, because mobile phones are usually held close to the ear. Until now, most studies have assessed the influence of RF radiation on the central or peripheral auditory system. However, clear conclusions cannot be drawn from these studies regarding the presence or absence of effects because of the limitations in the audiological and/or dosimetric approaches and limited sample sizes. results. Although the presence of possible effects on hearing threshold levels cannot be dismissed entirely, the evidence available is not sufficiently strong to conclude that there are adverse effects. A replication study with a shift in hearing threshold levels at high frequencies as the a priori hypothesis is desirable to resolve this issue.
3
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External beam radiotherapy for palliation of painful bone metastases: pooled data bioeffect dose response analysis of dose fractionation

51%
Naveen T., Supe S., Ganesh K., Samuel J.
Polish Journal of Medical Physics And Engineering
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2009
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vol. 15
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issue 1
33-45
EN
Bone metastases develop in up to 70% of newly diagnosed cancer patients and result in immobility, anxiety, and depression, severely diminishing the patients quality of life. Radiotherapy is a frequently used modality for bone metastasis and has been shown to be effective in reducing metastatic bone pain and in some instances, causing tumor shrinkage or growth inhibition. There is controversy surrounding the optimal fractionation schedule and total dose of external beam radiotherapy, despite many randomized trials and overviews addressing the issue. This study was undertaken to apply BED to clinical fractionation data of radiotherapeutic management of bone metastases in order to arrive at optimum BED values for acceptable level of response rate.A computerised literature search was conducted to identify all prospective clinical studies that addressed the issue of fractionation for the treatment of bone metastasis. The results of these studies were pooled together to form the database for the analysis. A total of 4111 number of patients received radiation dose ranging from 4 to 40.5 Gy in 1 to 15 fractions with dose per fraction ranging from 2 to 10 Gy. Single fraction treatments were delivered in 2013 patients and the dose varied from 4 to 10 Gy. Multifraction treatments were delivered in 2098 patients and the dose varied from 15 to 40.5 Gy. The biological effective dose (BED) was evaluated for each fractionation schedule using the linear quadratic model and an α/β value of 10 Gy. Response rate increased significantly beyond a BED value of 14.4 Gy (p < 0.01). Based on our analysis and indications from the literature about higher retreatment and fracture rate of single fraction treatments, minimum BED value of 14.4 Gy is recommended.
4
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Comparision of beam data requirements for MLC commissioning on a TPS

51%
Solaiappan G., Singaravelu G., Prakasarao A., Supe S.
Polish Journal of Medical Physics And Engineering
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2008
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vol. 14
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issue 2
63-77
EN
The treatment planning system (TPS) has become a key element in the radiotherapy process with the introduction of computer tomography (CT) based 3D conformal treatment planning. Commissioning of a MLC on a TPS either for conformal radiotherapy or intensity modulated radiation therapy (IMRT) requires beam data to be generated on a linear accelerator. Most of the TPS require these beam data to be generated with routine collimator jaws. However some TPS demand the data to be provided for MLC shaped fields. This prompted us to investigate whether beam data with jaws differ than that with MLC and whether the jaw based beam data would suffice for the commissioning of a MLC on a TPS.Beam data like percentage depth dose (PDD), cross beam profiles and output factors was acquired for jaws and MLC defined square fields for 6, 10 and 23 MV photon beams. Percentage depth dose and cross beam profiles were acquired with a radiation field analyzer RFA-200, CC13-S ion chambers with active volume of 0.13 cm3 and OmniPro-Accept software from Scanditronix-Wellhofer. A Medtec-TG51 water tank with Max-4000 electrometer and 0.6 cc PTW ionization chamber and a mini phantom from Standard Imaging was utilized for output measurements for millennium-120 MLC (Varian Medical Systems) and SRS diode detector (Scanditronix-Wellhofer) of 0.6 mm diameter of active area and 0.3 mm of active volume thickness for micro-MLC (BrainLab).The difference in PDD in the build-up region for millennium MLC was ±1.0% for 6 MV photons. For 10 MV photons the PDD difference was within ±4.0%. The difference in PDD for 23 MV photons ranged from 0% to 40.0%. PDD difference from build-up depth to about 28 cm was within ±1.0%. Difference in PDD crossed ±1.0% at 30 cm depth for 6 MV photons. The difference in PDD in the build-up region for mMLC was ±8.0% for 6 MV photons. For the smallest field size studied with micro-MLC i.e. 0.6 × 0.6 cm2 difference in PDD was more than ±1.0% in the build-up region and beyond a depth of 8.0 cm. The profiles for jaws and MLC agreed within the umbra region. However in the penumbra region small differences in doses were observed. The collimator scatter factor (Sc), phantom scatter factor (Sp) and output factor values for MLC were different that those for jaws.The differences in beam characteristics could have implication for intensity modulated radiation therapy and stereotactic radiosurgery in terms of dose in the build up region, exit dose, dose to the planning target volume (PTV) and organ at risk (OAR). Impact of these dosimetric differences between jaw and MLC needs to be further studied in terms of dose volume histograms for PTV and OAR and its further impact on tumor control probability (TCP) and normal tissue complication probability (NTCP).
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Dosimetrical evaluation of Leksell Gamma Knife 4C radiosurgery unit

51%
Sajeev T., Mustafa M., Supe S.
Polish Journal of Medical Physics And Engineering
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2011
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vol. 17
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issue 3
105-120
EN
A number of experiments was performed using standard protocols, in order to evaluate the dosimetric accuracy of Leksell Gamma Knife 4C unit. Verification of the beam alignment has been performed for all collimators using solid plastic head phantom and Gafchromic™ type MD-55 films. The study showed a good agreement of Leksell Gammaplan calculated dose profiles with experimentally determined profiles in all three axes. Isocentric accuracy is verified using a specially machined cylindrical aluminium film holder tool made with very narrow geometric tolerances aligned between trunnions of 4 mm collimator. Considering all uncertainties in all three dimensions, the estimated accuracy of the unit was 0.1 mm. Dose rate at the centre point of the unit has been determined according to the IAEA, TRS-398 protocol, using Unidose-E (PTW-Freiburg, Germany) with a 0.125 cc ion chamber, over a period of 6 years. The study showed that the Leksell Gamma Knife 4C unit is excellent radiosurgical equipment with high accuracy and precision, which makes it possible to deliver larger doses of radiation, within the limits defined by national and international guidelines, applicable for stereotactic radiosurgery procedures.
6
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Physical characteristics of photon beam from a CLINAC-DBX single energy accelerator

51%
Umbarkar R., Supe S., Pandey M., Ashok J.
Polish Journal of Medical Physics And Engineering
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2011
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vol. 17
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issue 3
143-151
EN
Commissioning beam data are treated as a reference and ultimately used by treatment planning systems, therefore, it is vitally important that the collected data are of the highest quality, in order to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. High-energy photon and electron beams from different accelerators of the same nominal energy may have different dosimetric characteristics due to differences in target and flattening filter materials, accelerator guide and collimator designs. In the present study, clinically pertinent data for the available photon energy were investigated. For making measurements in water, first time in India, a three dimensional radiation field analyzer RFA (CRS- Scan -O-Plan) was used. For absolute dosimetry and other measurements like relative output factors, wedge factors etc., a DOSE1 electrometer (Scanditronix Wellhofer) in a white polystyrene was employed. All the measured data were utilized as an input to the ECLIPSE treatment planning system for further clinical use.
7
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IMRT implementation and patient specific dose verification with film and ion chamber array detectors

45%
Saminathan S., Manickam R., Chandraraj V., Supe S., Keshava S.
Polish Journal of Medical Physics And Engineering
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2009
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vol. 15
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issue 2
87-102
EN
Implementation of Intensity Modulation Radiotherapy (IMRT) and patient dose verification was carried out with film and I'mariXX using linear accelerator with 120-leaf Millennium dynamic multileaf collimator (dMLC). The basic mechanical and electrical commissioning and quality assurance tests of linear accelerator were carried out. The leaf position accuracy and leaf position repeatability checks were performed for static MLC positions. Picket fence test and garden fence test were performed to check the stability of the dMLC and the reproducibility of the gap between leaves. The radiation checks were performed to verify the position accuracy of MLCs in the collimator system. The dMLC dosimetric checks like output stability, average leaf transmission and dosimetric leaf separation were also investigated. The variation of output with gravitation at different gantry angles was found to be within 0.9%. The measured average leaf transmission for 6 MV was 1.6% and 1.8% for 18 MV beam. The dosimetric leaf separation was found to be 2.2 mm and 2.3 mm for 6 MV and 18 MV beams. In order to check the consistency of the stability and the precision of the dMLC, it is necessary to carryout regular weekly and monthly checks. The dynalog files analysis for Garden fence, leaf gap width and step wedge test patterns carried out weekly were in good agreement. Pretreatment verification was performed for 50 patients with ion chamber and I'matiXX device. The variations of calculated absolute dose for all treatment fields with the ion chamber measurement were within the acceptable criterion. Treatment Planning System (TPS) calculated dose distribution pattern was comparable with the I'matriXX measured dose distribution pattern. Out of 50 patients for which the comparison was made, 36 patients were agreed with the gamma pixel match of > 95% and 14 patients were with the gamma pixel match of 90-95% with the criteria of 3% delta dose (DD) and 3 mm distance-to-agreement (DTA). Commissioning and quality assurance of dMLC for IMRT application requires considerable time and effort. Many dosimetric characteristics need to be assessed carefully failing which the delivered dose will be significantly different from the planned dose. In addition to the issues discussed above we feel that individual MU check is necessary before the treatment is delivered.
8
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Quality assurance and dosimetric analysis of intensity modulation radiotherapy using compensators for head and neck cancers

39%
Tyagi A., Nangia S., Chufal K., Mishra M., Ghosh D., Supe S., Singh M.
Polish Journal of Medical Physics And Engineering
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2009
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vol. 15
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issue 4
193-208
EN
In this study we describe our experience in implementing compensator based intensity modulated radiotherapy (cIMRT) for head and neck cancer with regard to pre treatment quality assurance (QA), dosimetric parameters and other technical detail.This study represents the analysis of initial 48 patients who underwent cIMRT for head and neck cancers. All patients were treated with pre treatment QA in terms of point dose with ion chamber and spatial dose comparison with film dosimetry.In our study for all 48 patients, compensators revealed a deviation in central axis dose of 2% ± 1.8% in terms of cumulative calculated versus measured dose. Target coverage for high dose volume (70 Gy) was adequate in terms of volume receiving 93% and 95% of the prescription dose, which was 98.5% and 97.5% respectively. Parotid and other critical organs were spared adequately. Contralateral parotid (CLP) was spared. V30 Gy and V35 Gy was 55.9% and 36.8% for CLP and average dose was 31.7 Gy. Median variation in cumulative measured dose versus cumulative calculated dose was 1.8% (SD + 1.8) and mean variation was 2.5% (95%CI 1.5, 2.6). Range was 0 to 7%.cIMRT is practically feasible. Our QA tests revealed high degree of concordance between cumulative measured doses versus cumulative calculated doses. All dosimetric parameters were within acceptable limits. The manufacturing of compensator is cumbersome but it is a one time job followed by easy treatment delivery and simple QA procedure, high monitor unit (MU) efficiency and less treatment time. cIMRT is easy to implement and now can be applied to larger number of patients with different type of tumor.
9
Content available remote

Electron beam characteristics at extended source to surface distance for a Clinac-DHX linear accelerator

39%
Arunkumar T., Supe S., Ravikumar M., Sathiyan S., Ganesh K., Varatharaj C.
Polish Journal of Medical Physics And Engineering
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2009
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vol. 15
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issue 3
121-133
EN
A uniform dose to the target site is required with a knowledge of delivered dose, central axis depth dose and beam flatness for successful electron treatment at an extended source to surface distance (SSD). In an extended SSD treatment under dosage of the lateral tissue may occur due to reduced beam flatness. To study the changes in beam characteristics, the depth dose curves, beam flatness and isodose distributions were measured at different SSDs from 100 to 120 cm for clinically used field sizes from (4×4) to (25×25) cm2 and beam energies ranging from 6 MeV to 20 MeV. Our results suggest that the change in depth dose is minimal except in the buildup region for most energy. In general surface dose is decreased as the SSD increased moderately. It was observed that the loss in beam flatness is significant for smaller fields, higher isodose lines, and lower energies. The penumbra enlarged and the uniformity index reduced with increasing SSD.
10
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Dosimetric investigation of dual energy photon beams with assymmetric collimator jaws

39%
Varatharaj C., Ravikumar M., Supe S., Sathiyan S., Ganesh K., Arunkumar T.
Polish Journal of Medical Physics And Engineering
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2008
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vol. 14
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issue 1
33-46
EN
Many modern linear accelerators are equipped with asymmetric collimators or jaws that can be moved independently. Asymmetric jaws have got many clinical applications in radiation therapy. In the present study, the dosimetric characteristics of asymmetric collimators from our linear accelerator with 6 and 18 MV X-rays were carried out. The field size factors (FSF) and half value layer (HVL) were measured in a water phantom using 0.6 cc Farmer chamber for symmetric and asymmetric fields for both 6 and 18 MV X-rays. Measurements of beam penumbra, percentage depth dose (PDD), cross beam profiles and calculated isodose curves were measured by RFA 300 for both asymmetric and symmetric fields. The FSF were found to agree with in 3% for symmetric and asymmetric fields. The HVL in water was found to be 15.8 cm and 14.4 cm for 6 MV photons and 26 cm and 22.9 cm for 18 MV photons at the central axis and at 20 cm off the central axis. At 30 cm depth the percentage depth dose for symmetric and asymmetric fields were found to differ as high as 6% for 6 MV and 4% for 18 MV fields. No observable difference in penumbra was noticed for symmetric and asymmetric fields of same dimensions. The constrictions of isodose curves at the edge nearer to central axis were noticed for asymmetrically placed fields. The observed differences could be due to the passage of primary beam through differential thickness of the flattening filter which alters the beam quality.
11
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A novel technique to evaluate the geometrical accuracy of CT-MR image fusion in Gamma Knife radiosurgery procedures

39%
Thomas S., Sampath S., IndiraDevi B., Bhanumathy G., Supe S., Musthafa M.
Polish Journal of Medical Physics And Engineering
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2010
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vol. 16
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issue 2
55-66
EN
In order to optimize the accuracy of imaging in Gamma Knife radiosurgery using the image fusion options available in the Leksell gamma plan. Phantom images from 1.5 Tesla MRI Scan (Magnetom vision - Siemens) and Computed Tomography images from Philips Brilliance 16 CT scanner were used for image fusion in Gammaplan treatment planning system. The images were fused using co-registration technique using multiview and imagemerge modules. Stereotactic coordinates were then calculated for known targets. Vector distances from the centre of the Leksell coordinate system to five known targets were measured in CT, MR and CT-MR fused images and compared with geometrical measurements. The mean values of maximum absolute errors were 0.34 mm, 0.41 mm.0.38 mm (along x-axis), 0.43 mm, 1.53 mm, 0.62 mm (along y-axis) and 0.75 mm 2.02 mm, 0.93 mm (along z-axis) for CT, MR and CT-MR fused image data respectively. The mean error in calculating the vector distances from the center of the Leksell coordinate system (100, 100, 100) to the known target volumes are 0.22 mm, 0.8 mm and 0.43 mm for CT, MR and CT-MR fused images, respectively. Image fusion functions available in gamma plan are useful for combining the features of CT and MR imaging modalities. These methods are highly useful in clinical situations where the error associated with Magnetic Resonance Imaging is beyond acceptable levels.
12
Content available remote

Measurement of Transit Time of a Gammamed-Plus Remote Afterloading High Dose Rate Brachytherapy Source

33%
Supe S., Shwetha B., Bijina T., Varatharaj C., Sathiyan S., Ganesh K., Arunkumar T., Ravikumar M.
Polish Journal of Medical Physics And Engineering
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2007
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vol. 13
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issue 2
55-63
EN
Accurate measurement of transit time of the HDR brachytherapy source of a remote after-loading unit is necessary to calculate the total radiation dose given to the treatment volume. Presently, most of the HDR brachytherapy treatment planning systems neglect the transit time in the computation of dose. The aim of this investigation is to use a well type ionization chamber to measure the transit time during the source movement between two dwell positions. As well type ionization chamber and a precision electrometer (manufacturer CD instruments, Bangalore) were used to measure the charge generated during the movement of the Ir-192 source of a Gammamed HDR brachytherapy unit with an interstitial needle. Effective transit time and effective speed were determined on the basis of methodology described by Sahoo [2]. Corrections were done on the basis of relative sensitivity values for varaious dwell position in the ionization chamber. In the present study the variation of effective speed with interdwell distance was minimal as compared with that of Sahoo [2]. The effective transit times were 0.129, 0.182, 0.301, 0.402, 0.701, and 0.993 seconds for 1, 2, 4, 6, 8 and 10 cm interdwell separations respectively. The effective transit times in the present study were higher than those of Sahoo [2]. Software modification accounting for the dynamic dose should be incorporated into all HDR planning systems. Such an improvement would enhance the safety and accuracy of HDR brachytherapy.
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