water phantom
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2022 ◽  
Vol 17 (01) ◽  
pp. T01002
Author(s):  
S. Sajedi ◽  
L. Bläckberg ◽  
S. Majewski ◽  
H. Sabet

Abstract The intraoperative gamma probe (IPG) based on single gamma-ray detection remains the current gold standard modality for sentinel lymph node identification and tumor removal in cancer patients. However, IPGs do not meet the <5% false negative rate (FNR) requirement, a key metric suggested by the American Society of Clinical Oncology (ASCO). We aim to reduce FNR by using time of flight (TOF) PET detector technology in limited angle geometry system by using only two detector panels in coincidence. For proof of concept, we used two Hamamatsu TOF PET detector modules (C13500-4075YC-12) featuring 12× 12 arrays of 4.14× 4.14× 20 mm3 LFS crystal pixels with 4.2 mm pitch and coupled one-one to silicon photomultiplier (SiPM) pixels. The measured detector coincidence timing resolution (CTR) was 271 ps FWHM for the whole detector. We 3D printed lesion phantom containing spheres 2–10 mm in diameter, representing lymph nodes, and placed it inside a 10-liter warm background water phantom. Experimental results showed that with subminute data acquisition, 6 mm diameter spheres could be identified in the image when a lesion phantom with a 10:1 activity ratio to background was used. The simulation results were in good agreement with the experimental data by resolving 6 mm diameter spherical lesions with a 60 second acquisition time in a 25 cm deep background water phantom with a 10:1 activity ratio. As expected, the image quality improved as the CTR improved in the simulation and with decreasing background water phantom depth or increasing lesion-to-background activity ratio in the experiment. With the results presented here, we concluded that using a limited angle TOF PET detector system is a major step forward for intraoperative applications in that lesion detectability is beyond what conventional gamma- and NIR-based probes could achieve.


Cancers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 26
Author(s):  
Marco Cavallone ◽  
Yolanda Prezado ◽  
Ludovic De Marzi

Proton MiniBeam Radiation Therapy (pMBRT) is a novel strategy that combines the benefits of minibeam radiation therapy with the more precise ballistics of protons to further optimize the dose distribution and reduce radiation side effects. The aim of this study is to investigate possible strategies to couple pMBRT with dipole magnetic fields to generate a converging minibeam pattern and increase the center-to-center distance between minibeams. Magnetic field optimization was performed so as to obtain the same transverse dose profile at the Bragg peak position as in a reference configuration with no magnetic field. Monte Carlo simulations reproducing realistic pencil beam scanning settings were used to compute the dose in a water phantom. We analyzed different minibeam generation techniques, such as the use of a static multislit collimator or a dynamic aperture, and different magnetic field positions, i.e., before or within the water phantom. The best results were obtained using a dynamic aperture coupled with a magnetic field within the water phantom. For a center-to-center distance increase from 4 mm to 6 mm, we obtained an increase of peak-to-valley dose ratio and decrease of valley dose above 50%. The results indicate that magnetic fields can be effectively used to improve the spatial modulation at shallow depth for enhanced healthy tissue sparing.


2021 ◽  
pp. 162-166
Author(s):  
Ioannis Vlachos ◽  
Ioannis Kandarakis ◽  
Giorgos Panayiotakis

Radiation protection for personnel working with X-rays is of vital importance. Several studies have been published regarding the secondary radiation and the shielding requirements to areas that are adjacent to the X-ray units. In this work, secondary radiation in a conventional radiographic room, in terms of dose rate (mSv/hr), as a function of different radiographic exposure factors has been studied. The measurements were performed with a 451P Fluke Biomedical survey meter on a Philips Medio 65 CP-H X-ray generator with a cylindrical water phantom. It was found that the dose rate from the scatter radiation decreases with distance. An added filtration of 2.0 mmAl at 100 kVp reduced the secondary dose rate further by 21.4%. The results of this study may be of value during exposure of personnel that are not protected by shielding materials. Highlights Ÿ It was found that the dose rate from the scatter radiation decreases with distance. An added filtration of 2.0 mmAl at 100 kVp reduced the secondary dose rate further by 21.4%. Ÿ The mean secondary X-ray energies for 60, 80, 100 and 100 kV with 2 mmAl added, were calculated as 34.41, 51.12, 69.03 and 71.29 keV respectively. Ÿ The results of this study are of value during exposure of people such as radiographers, and patients during the use of mobile X-ray units.


2021 ◽  
Vol 16 (10) ◽  
pp. P10016
Author(s):  
T.A. Bykov ◽  
D.A. Kasatov ◽  
A.M. Koshkarev ◽  
A.N. Makarov ◽  
V.V. Leonov ◽  
...  
Keyword(s):  

2021 ◽  
Author(s):  
Yoshinori Tanabe ◽  
Toshie Iseri ◽  
Ryouta Onizuka ◽  
Takayuki Ishida ◽  
Hidetoshi Eto ◽  
...  

Abstract Accurate dose assessment during animal radiotherapy is beneficial for veterinary medicine and medical education. We evaluated the dose distributions of kilovoltage X-ray orthovoltage radiotherapy and created a dog skull water phantom for animal-specific radiotherapy. EGSnrc-based BEAMnrc and DOSXYZnrc codes were used to simulate orthovoltage dose distributions. At 10, 20, 30, 40, 50 and 80 mm in a water phantom, depth dose was measured with waterproof Farmer dosimetry chambers and the diagonal off-axis ratio was measured with Gafchromic EBT3 film to simulate orthovoltage dose distributions. Energy differences between orthovoltage and linear accelerated radiotherapy were assessed with a heterogeneous bone and tissue virtual phantom. The animal-specific phantom for radiotherapy quality assurance was created from CT scans of a dog and printed with a three-dimensional printer using polyamide 12 nylon, with insertion points for dosimetry chambers and Gafchromic EBT3 film. Monte Carlo simulated and measured dose distributions differed by no more than 2.0% along the central axis up to a depth of 80 mm. The anode heel effect occurred in shallow areas. The orthovoltage radiotherapy percentage depth dose in bone was >40%. Build-up was >40%, with build-down after bone exit, whereas linear accelerator radiotherapy absorption changed little in the bone. A highly water-impermeable, animal-specific dog skull water phantom could be created to evaluate dose distribution.Animal-specific water phantoms and Monte Carlo simulated pre-treatment radiotherapy is useful quality assurance for orthovoltage radiotherapy and yields a visually familiar phantom that will be useful for veterinary medical education.


2021 ◽  
Vol 1 (1) ◽  
pp. 22-25
Author(s):  
Heryani Heryani ◽  
Nurul Firdausi Nuzula ◽  
Ari Dwi Reskianto ◽  
Ryan Wahyu Widhianto

Analysis of Distributed Radiation Exposure in The Covid-19 Isolation Room in Kraton Re¬gional Hospital, Pekalongan Regency. Since Covid-19 was declared a world pandemic by WHO, isolation rooms have become a place that is often used to deal with pandemics. Radiological examinations or X-rays are used as a supporting examination in the diagnosis of Covid-19. So it is necessary to adjust the Covid protocol in the examination so that there is no transmission of the virus and the effects of unnecessary radiation. Isolation rooms used for radiological examinations of Covid-19 patients need to be reviewed for safety to comply with procedures. The purpose of this paper is to analyze the scattering radiation exposure in the Seruni isolation room of RSUD Kraton, Pekalongan Regency. The data in this paper were taken by measuring the amount of scatter radiation exposure in room B of the isolation room Seruni RSUD Kraton Pekalongan Regency, on February 16, 2021. This measurement was carried out with a water phantom as object with the highest exposure factor for thorax examination, namely 70 kV and 16 mAs and carried out at several points around the water phantom object with a distance of 2 meters from the source. The measurement results of scattered radiation exposure are then compared with the Dose Limit Value (NBD) for the general public of 1 mSv in one year. Analysis of the measure¬ment of scatter radiation exposure in the Seruni isolation room at Kraton Hospital, Pekalongan Regency, still experienced leaks and the exposure value exceeded tolerance. The measurement results in the hallway of the Seruni room are 676 Sv/h, in addition to the radiographer (2 meters on the left side of the phantom) it is 627.12 Sv/h, at a distance of 2 meters the right side of the phantom is 287.04 Sv/h, and a distance of 2 meters in front of the hall phantom of 676 Sv/h. The follow-up that needs to be done to optimize radiation protection is to install at least 3 scattering radiation shields.


2021 ◽  
Vol 1 (1) ◽  
pp. 18-21
Author(s):  
Josepa ND Simanjuntak ◽  
◽  
Martua Damanik ◽  
Elvita Rahmi Daulay

Optimization is an effort to ensure patient radiation safety and is the main action in overcoming concerns about CT-Scan radiation exposure. This led to the emergence of various measures to reduce the dose. This study aims to obtain a minimal dose with a high-quality image. Optimization efforts were carried out by the radiology team at Adam Malik Hospital Medan using a 16 slice GE CT-Scan and a water phantom with a diameter of 16 and 32 cm and an image quality questionnaire form. Collected data by observing the head, chest, and abdomen CT-Scan in adult patients (≥15 years). The data taken is the value of CTDI vol and DLP for a year. Then a water phantom scan was carried out with the head protocol using pitch parameters 0.562 and 0.938. The chest and abdomen use pitches of 1.375 and 1.75. The results obtained were evaluated and applied to patients, then filled in the image quality questionnaire scores. The results of CTDI_vol and DLP values with 16 and 32 cm water phantom scans showed a decrease in the dose value; for pitch 0.938, it was 1.6% lower than pitch 0.562, and pitch 1.75 was 1.2% lower, compared to pitch 1.375. For CT head examination using a pitch of 0.963, the CTDI_vol value was 1.5%, and DLP was 2%. For chest using a pitch of 1.75, CTDI_vol values were 1.3% and DLP 2%, while abdominal examination with a pitch of 1.75 obtained CTDI_vol values 1.8% and DLP 1.4%. From these three results, the CTDI_vol and DLP values were higher than the national DRL values. The value obtained is higher than the national DRL due to differences in the phantom test protocol with clinical implementation and the lack of accuracy in using other parameters. Changes in scan parameters are not comprehensive. Obtained a score of 3 in the questionnaire form stating that the radiology doctor can still interpret the image. This study concluded that it could make optimization efforts by changing the pitch parameter by paying attention to other parameters without reducing the quality of the image interpreted by the radiologist.


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