فهرست مطالب

Medical Physics - Volume:17 Issue: 3, 2020
  • Volume:17 Issue: 3, 2020
  • تاریخ انتشار: 1399/02/12
  • تعداد عناوین: 12
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  • Sanaz Hariri Tabrizi *, Nematollah Heidarloo, Mina Tavallaie Pages 133-136
    Introduction

    The gamma index is a known parameter for radiotherapy dose verification. Many free and commercial programs have been written for the calculation of this index. However, the verification of the results has been overlooked in many of the programs. The present study tested the validity of three gamma index calculator programs.

    Material and Methods

    The gamma indices for three measured and calculated dose distribution pairs presented in Low et al., Medical Physics, (1998) were calculated using three programs to compare with the results of the published paper. They included an executable program working in Gnuplot software environment (i.e., Gamma_index.exe), simple implementation of the formulas by MATrix LABoratory (MATLAB) software (i.e., Simple m-file), and CalcGamma MATLAB-based program distributed at GitHub website (i.e., Geurts). The resulted gamma distributions were compared with the three figures of the study by Low et al.

    Results

    According to the results, it was observed that neither Gamma_index.exe nor Simple m-file calculated gamma indices was valid, with up to 31% difference in pass rates. On the other hand, Geurts showed fairly good agreement with the gamma indices presented in Low et al. paper.

    Conclusion

    Use of gamma index calculator programs, such as Gamma_index.exe should strongly be prohibited without verification. Furthermore, the implementation of the gamma index formulas without enough preprocessing of the data results in invalid values. Geurts is a reliable program that can be used in its current form or it can be changed to stand-alone executable software for the use in studies and clinics.

    Keywords: Gamma index, Radiotherapy, Dose Distribution Verification
  • Laith Najam *, Qusay AL-Dulamey, Yasir Al Jawwady Pages 137-141
    Introduction

    The study aimed to find the low dose effect gamma ray on some hematological parameters in male albino rats obtained from the Mosul University, IRAQ, and also studied the radioprotective effect of black seed oil on the hematological parameters.

    Material and Methods

    The system is made of 241Am as gamma source .The rats were exposed to gamma radiation for limit period .Hematological investigations in which the red blood cells (RBC) also white blood cells (WBC) were found by the result of Neubauer haemocytometer method hemoglobin(Hb) concentration obtained due to cyanomethaemoglobin test. The packed cell volume (PCV) was determined using the micro-centrifuge method. Platelets were achieved.

    Results

    All hematological parameters found significantly decreased in all groups receiving daily dose of 6 mGy/h for 7h/day for 25, and 50 days compared with those in the control group. However group 2. Treated with 400 mg/kg wt /day for 25 days, showed a significant increase in the mentioned parameters.  Groups 3 and 4 were exposed to gamma ray in two stages(at a daily dose 6 mGy/h for 7h /day for 25 and 50 days) .Group 4 showed a significant enhancement  in hematological parameter when  treated  with  black seed oil , compared with group3 which had a significant decrease in these parameters compared with the control group.

    Conclusion

    The present work showed the function of black seed oil considered as an advanced material in decreasing the oxidant stress on hematological parameters againstgamma ray with limited dose.

    Keywords: Gamma Ray, Hematological, Black Seed Oil (Nigella Sativa), Free radical
  • Azimeh Dehkordi * Pages 142-152
    Introduction
    Pharmacokinetic (PK) modeling of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is widely applied in tumor diagnosis and treatment evaluation. Precision analysis of the estimated PK parameters is essential when they are used as a measure for therapy evaluation or treatment planning. In this study, the accuracy of PK parameters in brain DCE-MRI studies was quantified in relation to two major sources of error(including pre-contrast longitudinal-relaxation time, T1,0 and flip angle, α).
    Material and Methods
    3470 dynamic contrast-enhanced-curves were simulated using a wide variation of the PK parameters. The bias of contrast concentration due to the systematic biases in α and T1,0 was calculated and added to both contrast concentration and AIF profiles. Thereafter, the PK parameters were estimated for each simulated curve in the presence of different percentages of relative biases in α and T1,0. The mean percentage error (MPE) of PK parameters was then calculated for all simulated curves.
    Results
    The results indicated that plasma volume(vp) was the most sensitive parameter to bias of contrast concentration, which may overestimate up to 700% in 10% coincidence relative bias in α and T1,0. The lowest MPE was related to the backward transfer constant (kep), which was ~2%-15% in 10% coincidence relative bias in each α and T1, 0.
    Conclusion
    Utilization of a nested model selection technique, along with an accurate estimator, such as maximum-likelihood estimation, created a unique approach for investigating the effect of the bias in the concentration measurement to the estimated PK parameters without the addition of any extra biases to the parameters during the estimation.
    Keywords: Dynamic Contrast-Enhanced Magnetic Resonance Imaging, Kinetic Analysis, Contrast Concentration Bias, MPE of PK Parameters
  • Leni Fitri *, Yuni Warty, Freddy Haryanto, Umar Fauzi, Fourier Latief Pages 153-160
    Introduction
    Micro-CT scanner with a resolution of about 5 micrometers is one of the modalities used to create three-dimensional/two-dimensional images of urinary stones. This study aimed to optimize imaging parameters in micro-computed tomography (CT) scanner based on the signal-to-noise ratio (SNR) of urinary stones for the analysis of stone composition.
    Material and Methods
    In this study,eight micro-CT scanning protocols were applied to five urinary stones taken from different patients. Each scanning protocol had different voltage, current, and exposure parameters. The reconstructed images were then analyzed based on image brightness and SNR. The optimized imaging parameters which were chosen were that having high SNR because the high-quality image has high SNR.
    Results
    The results showed that two groups of urinary stones had the same mean Hounsfield Units (HU) value in the third scanning protocols (i.e., 65 kV, 123 µA, and 850 ms). Mean HU values in group one (i.e., stones numbered 1, 3, and 4) were reported as 790, 760, and 720, respectively. The second group (i.e., stones numbered 2 and 5) had mean HU values of -514 and -343, respectively. The imaging parameters (i.e., 75 kV, 106 µA, and 600 ms) had high SNR (25-34) for the first group. The SNR (12.8-13.25) was for the second group at imaging parameters (i.e., 85 kV, 94 µA, and 500 ms).
    Conclusion
    Based on the SNR, the two optimal imaging parameters for the first and second groups were reported as 75 kV, 106 µA, and 600 ms, as well as 85 kV, 94 µA, and 500 ms, respectively.
    Keywords: Imaging parameters, Micro CT, optimization, SNR, Urinary stone
  • Aditya Hariyanto, Fachrina Mariyam, Levina Almira, Endarko Endarko *, Bambang S Pages 161-169
    Introduction
    This study aimed to evaluate the efficacy of a synthesized bolus in the reduction of damage to body tissues and the protection of the organ at risk (OAR) in radiotherapy application. Several properties of the synthesized bolus, including density, transmission factor, and effective mass attenuation coefficient, were investigated.
    Material and Methods
    The materials used comprising of propylene glycol (PG), silicone rubber (SR), and aluminum (Al). The dimension of the synthesized bolus was measured using an acrylic case with a size of 11×11 cm² and thickness sizes of 0.5, 1, and 1.5 cm. Furthermore, the boluses were irradiated by linear accelerator with the photon beam energies of 6 and 10 MV, using linier accelerator (LINAC) Varian 2300ix.
    Results
    In this research,the density of synthesized bolus was evaluated by mass per volume equation. The results showed that the density of bolus was similar to the density of tissue/water, fat, and air. .  Furthermore the bolus with the composition of PG 24%, SR 8%, and Al 1.5% of all energies, transmission factors of 0.978 and 0.984, thickness of 1.5 cm, and effective mass attenuation coefficients of 0.0144 and 0.0107 cm²/g had the closest properties to the body tissues in terms of dosimetry characterization.
    Conclusion
    The results revealed that the synthesized bolus could increase the percentage surface dose, reduce skin-sparing effect, and protect OAR. The findings indicated that the synthesized bolus had a potential application in clinical therapy.
    Keywords: Bolus, Propylene Glycol, Transmission Factor, Dosimetry, Accelerator
  • Eslam Maamoun * Pages 170-174
    Introduction
    Recent studies of Computed Tomography (CT) conducted on patient dose reduction have recommended using an iterative reconstruction algorithm and mA (mili-Ampere) dose modulation. The current study aimed to evaluate Iterative Dose Reduction Algorithm (IDREAM) as an iterative reconstruction algorithm.
    Material and Methods
    Two CT protocols (i.e., A: 120 KV /150 mA, FBP; B: 120KV/ (20-150) mAs, IDREAM) to scan water and acrylic phantoms. A number of 40 patients were assigned to two CT protocols (C: n=20, 120KV/160 ±10 mAs, FBP and D: n=20, 120 KV/ (30-150 mAs, IDREAM), the two groups (C and D) were then referred to abdomen and pelvis CT scan (Sinovision, insitum 16) with contrast. Image quality parameters, dose calculations were measured for all groups (i.e., A, B, C, and D).
    Results
    Group B had a highly significant SNR with less significant noise (P<0.05), in comparison with group A. In addition, uniformity was markedly higher for group B (P<0.05) in water phantom and insignificantly different (P>0.05) in acrylic phantom, as compared to group A.  CTDIvol (A: 13.94 mGy ; B: 6.91 mGy , P<0.05  ) and   DLP (A:501.76 mGy.cm ; B :248.88 mGy.cm). Noise and SNR were significantly different (P<0.05) in group D against C. CTDIvol (C: 30.3±5.2 mGy ; D : 15.4 ±2.7 mGy, P<0.05 ) ,   DLP (C:544±100 mGy.cm; D :272.3±50.3 mGy.cm ,P<0.05) and the effective dose (C:8.1±1.5 mSv; D :4.08±0.75 mSv,P<0.05)
    Conclusion
    The results of the present study were indicative of the feasibility of IDREAMas an iterative reconstruction algorithm.
    Keywords: Computed Tomography, FBP, IDREAM, image noise, Image Quality, Iterative Algorithm SNR
  • Fawzia Mubarak *, Hesham Saleh Pages 175-182
    Introduction
    The present study investigated the relatively high concentrations of natural radionuclides in raw material that used in ceramic manufacturing, and estimated the occupational exposure due to these activity concentrations.
    Material and Methods
    A high-purity Germanium detector was used to determine naturally occurring radionuclides in raw materials that used in ceramic manufacturing. Activity concentrations of these materials lead to potential radiological hazards due to gamma and alpha radiation. These hazards were evaluated in the present study.
    Results
    Maximum activity concentrations was5844, 1065 and 41 Bq/kg for 226Ra, 232Th and 235U in powdered quartz; however, maximum activity concentration for 40K was 1868 Bq/kg in colors. These activities were observed to be exceeding the exemption limit. Pancreasreceived the lowest dose (i.e., 0.02 mSv/y), while skin received the highest dose (i.e., 0.044mSv/y). Internal hazard index (Hin) was reported as 53.74, which exceed the recommended value (Hin≤1). Alpha index was 42.4 which led to over exposure. Representative level index and excess lifetime cancer risk were 0.00062 and 0.641 respectively. The total annual external dose was 2.62 m Gy/y which led to 1.83 mSv/y effective dose. Radiological hazard due to radon inhalation was 1.53E-06 mSv/y.
    Conclusion
    Due to the high activity concentrations of raw materials (especially zirconium compounds) and consequently the associated high dose, specific regulations must be applied in the ceramic industry in Egypt.
    Keywords: occupational exposure, External Dose, Internal Dose, Ceramics
  • Mohamad Reza Rezaie Rayeni Nejad *, Reza Shahhedarypoor, Saeed Mohammadi, Parviz Parvaresh Pages 183-187
    Introduction
    Radiation therapy is regarded as the mainstay treatment for head or neck cancer patients. In this method, the backscattered radiation of dental composites can damage the surrounding tissue.
    Material and Methods
    The current study compared the effects of electron beam radiation on healthy teeth with the tooth filled with materials used in dentistry with FLUKA and MCNPX2.6 codes. The simulation was performed for a 512 mm3 cubic tooth composed of Amalgam and Ceramco materials.
    Results
    The simulation results indicated that patients with dental caries who inevitably filled their teeth with artificial restorationreceived a more effective dose, as compared to others. Moreover, it was revealed that Ceramco increases the radiation risk more than Amalgam does. Therefore, Amalgam is the right choice for dental filling.
    Conclusion
    Based on the obtained results, ceramic material poses patients to increased radiation risk more than Amalgam does; therefore, it is recommended that Amalgam be used to fill dental cavities.
    Keywords: Radiation Therapy, Electron, Monte Carlo Method, tooth, Restoration Material
  • Dinesh Saroj, Suresh Yadav *, Gopa Ghosh, Shuchishree Shukla, Gaurav Gupta, S. Choudhary Pages 188-196
    Introduction

    The present study evaluated the dosimetric comparison between 6MV flattened filter (FF) and flattening filter-free (FFF) photon beams in intensity-modulated radiation therapy (IMRT) technique for the treatment of glioblastoma (GBM) patients.

    Material and Methods

    The present study was conducted on 10 patients with GBM previously planned and treated with 6MV FF photon beam by IMRT technique. Additional IMRT plans were retrospectively created using 6MV FFF photon beam for each patient plan. The dose prescription, beam parameters, and planning objective were kept same in both plans. The plans were evaluated using cumulative dose-volume histogram (c-DVH). Both types of plans were compared on the basis of homogeneity index (HI), conformity index (CI), beam-on time (BOT), monitor unit (MU), and doses to organs at risk (OARs).

    Results

    Dose received by 95% (D95%) of planning target volume (PTV) coverage was observed significantly higher in 6MV_FF_IMRT plan than 6MV_FFF_IMRT plan (P<0.05). No significant dose differences were noticed for HI, CI, D98%, and D2% between both plans. Significantly lower Dmax for the brainstem, eyes, and eye lens was observed in 6MV_FFF_IMRT plan. For the brain, less than 2% mean dose was observed in 6MV_FFF_IMRT plan than 6MV_FF_IMRT plan (P=0.017). In 6MV_FFF_IMRT plan, mean BOT decreased by 39% in comparison to that in 6MV_FF_IMRT plans.

    Conclusion

    The 6MV FFF beam provides a desirable and clinically acceptable IMRT plan for the treatment of GBM than 6MV FF beam. In addition, 6MV FFF beam provides higher MUs, better OARs sparing, lower scattered dose, and lower beam delivery time.

    Keywords: Intensity-Modulated Radiotherapy, Photon beam, Glioblastoma
  • Vajiheh Vejdani Noghreiyan, Shahrokh Naseri *, Mehdi Momennezhad Pages 197-204
    Introduction
    Radiation therapy involves a multistep procedure; therefore, the error in patient set up is an inherent part of the treatment. Main purpose of this study was to determine the clinical target volume (CTV) to planning target volume (PTV) in head and neck cancer patients.
    Material and Methods
    A total of 15 patients who had daily portal images during the treatment courses were randomly selected in the present study. Systematic (Σ) and random (σ) errors were evaluated in three directions. The Isogray treatment planning system and Elekta linear accelerator were used in this study. Moreover, we had used MOSIAQ software as arecord and Verify system. Setup margins were calculated using three published margin recipes, including the International Commission on Radiation Units and Measurements (ICRU) report 62, as well as Stroom’s and van Herk’s formulae.
    Results
    Average magnitude of the translational errors was reported between 0.7 and 10 mm. The systematic and random errors for head and neck cancer patients were 3.55 (2.58-4.52) and 1.83 (1.56-2.10) mm, respectively. According to the ICRU report 62, as well as Stoorm’s and van Herk’s formulas, the required margins to cover the target were obtained within the ranges of 3.1-4.9, 6.4-10.5, and 7.7-12.7 mm, respectively.
    Conclusion
    According to the results of the present study, 6.5-10.5 mm extension in CTV to PTV margin can ensure that 90% of the head and neck cancer patients will receive a minimum cumulative CTV dose higher than or equal to 95% of the prescribed dose.
    Keywords: Image Guided, systematic errors, random errors, Cancer of head, neck, CTV To PTV Margin
  • Khatibeh Verdipoor, Asghar Mesbahi * Pages 205-212
    Introduction
    The present study aimed to evaluate the impact of PbO nano and micro-sized fillers on ordinary and heavy concretes for different photon energies.
    Material and Methods
    The MCNPX Monte Carlo code (version 2.6.0) was used for all simulations in the present study. A model of narrow-beam geometry was validated and utilized to calculate the linear attenuation of samples. Three concentrations of PbO, including the weight of 23%, 37.5%, and 50% were simulated. The nano- and microparticle-loaded concretes were simulated using the Lattice and Universe properties of MCNPX code. Finally, the mass attenuation coefficients of studied concretes were analyzed and compared in this study.
    Results
    Among all the studied concretes, the highest increase of 11% in attenuation coefficient was seen for concretes doped with PbO nanoparticles. The particle size effect was not observed for 18 MeV photon beam, and maximum difference between nano-fillers and micro-fillers was observed for photon energies around 1 MeV.
    Conclusion
    The difference between nano-fillers and micro-fillers was not significant for heavy concretes in comparison to that for ordinary concrete. It is recommended to apply PbO nanoparticles as effective filler in the ordinary concrete composition for providing higher shielding performance.
    Keywords: Attenuation Coefficient Concrete, Nanoparticle, Radiation
  • Mansour Zabihzadeh *, Mahbube Fadaei, Seyed Mohammad Hoseini, Sholeh Arvandi, Mohamad Tahmasebi Pages 213-219
    Introduction
    Physical wedge by modify photon beam shape and intensity has been utilized in radiotherapy to obtain uniformly dose distribution in tumor site with reduced hot spots. Calculation of dosimetric parameters for both symmetric and asymmetric wedged fields is proved necessary during linear accelerator (Linac) commissioning. The present study aimed to achieve output factors and dose profiles for symmetric and asymmetric wedged fields of 6 MV beams.
    Material and Methods
    The Siemens PRIMUS Linac head for 6 MV beam was simulated by BEAMnrc and all dose calculations were performed by DOSXYZnrc code. Percentage depth dose (PDD) and profiles for open and wedged (15° and 45°) fields were compared with corresponding measurements. Wedge factors for 10 x 10 cm2 field were obtained as a function of lateral distance as well for half beam wedged fields.
    Results
    Based on the results of the present study, the calculated doses were in agreement with the measured data. The output factors on the central axis of symmetric wedged beams decreased to 0.693 and 0.307 for 15˚, and 45˚ wedges. The total photon fluence of 15˚ and 45˚ physical wedged fields reduced to 71.6% and 27.7% of open field, respectively.
    Conclusion
    The output factor for asymmetric wedged fields was found to be lower than corresponding symmetric open and wedged fields, particularly at field edges. Lack of scattering photons near the half beam edges resulted in dose fall-off in these regions possible to be overestimated by treatment planning system and consequently caused cold spots at target volume.
    Keywords: Asymmetric Wedged Field Output Factor, Radiotherapy, Wedge Factor