Ex) Article Title, Author, Keywords
Ex) Article Title, Author, Keywords
Review Article 2019-12-31
2019-12-31
12
2611
444
Min Young Lee , Jae Kwon , Gang Woo Ryu , Ki Hoon Kim , Hyung Woo Nam , Kwang Pyo Kim
https://doi.org/10.14316/pmp.2019.30.4.75
Diagnostic reference level (DRL) is employed to optimize the radiation doses of patients. The objective of this study is to review the DRLs for interventional procedures in Korea and abroad. Literature review was performed to investigate radiation dose index and measurement methodology commonly used in DRL determination. Dose area product (DAP) and fluoroscopy time within each major procedure category were systematically abstracted and analyzed. A wide variation was found in the radiation dose. The DAP values and fluoroscopy times ranged 0.01–3,081 Gy·cm2 and 2–16,878 seconds for all the interventional procedures, 8.5–1,679 Gy·cm2 and 32–5,775 seconds for the transcatheter arterial chemoembolization (TACE), and 0.1–686 Gy·cm2 and 16–6,636 seconds for the transfemoral cerebral angiography (TFCA), respectively. The DRL values of the DAP and fluoroscopy time were 238 Gy·cm2 and 1,224 seconds for the TACE and 189 Gy·cm2 and 686 seconds for the TFCA, respectively. Generally, the DRLs of Korea were lower than those of other developed countries, except for the percutaneous transluminal angioplasty with stent in arteries of the lower extremity (LE PTA and stent), aneurysm coil embolization, and Hickman insertion procedures. The wide variation in the radiation doses of the different procedures suggests that more attention must be paid to reduce unnecessary radiation exposure from medical imaging. Furthermore, periodic nationwide survey of medical radiation exposures is necessary to optimize the patient dose for radiation protection, which will ultimately contribute to patient dose reduction and radiological safety.
Original Article 2019-12-31
2019-12-31
1
1116
285
Jeong Ho Kim1,2, Seongmoon Jung2, Jung-in Kim1,2,3
https://doi.org/10.14316/pmp.2019.30.4.89
This study aims to develop new markers based on silicone rubber and urethane rubber to enhance visibility in low magnetic field magnetic resonance (MR) imaging.
Four types of markers were fabricated using two different base materials. Two of the markers were composed of two different types of silicone rubber: DragonSkin™ 10 MEDIUM and BodyDouble™ SILK. The other two markers were composed of types of urethane rubber: PMC™ 780 DRY and VytaFlex™ 20. Silicone oil (KF-96 1000cs) was added to the fabricated markers. The allocated amount of oil was 20% of the weight (wt%) of each respective marker. The MR images of the markers, with and without the silicone oil, were acquired using MRIdian with a low magnetic field of 0.35 T. The signal intensities of each MR image for the markers were analyzed using ImageJ software and the visibility for each was compared.
The highest signal intensity was observed in VytaFlex ™ 20 (279.67±3.57). Large differences in the signal intensities (e.g., 627% in relative difference between BodyDouble™ SILK and VytaFlex™ 20) among the markers were observed. However, the maximum difference between the signal intensities of the markers with the silicone oil showed only a 62% relative difference between PMC™ 780 DRY and DragonSkin ™ 10 MEDIUM. An increase in the signal intensity of the markers with the silicone oil was observed in all markers.
New markers were successfully fabricated. Among the markers, DragonSkin™ 10 MEDIUM with silicone oil showed the highest MR signal intensity.
Original Article 2019-12-31
2019-12-31
3
1024
345
Chiyoung Jeong , Jae Won Park , Jungwon Kwak , Si Yeol Song , Byungchul Cho
https://doi.org/10.14316/pmp.2019.30.4.94
To evaluate the clinical feasibility of knowledge-based planning (KBP) for volumetric-modulated arc radiotherapy (VMAT) in spine stereotactic body radiotherapy (SBRT).
Forty-eight VMAT plans for spine SBRT was studied. Two planning target volumes (PTVs) were defined for simultaneous integrated boost: PTV for boost (PTV-B: 27 Gy/3fractions) and PTV elective (PTV-E: 24 Gy/3fractions). The expert VMAT plans were manually generated by experienced planners. Twenty-six plans were used to train the KBP model using Varian RapidPlan. With the trained KBP model each KBP plan was automatically generated by an individual with little experience and compared with the expert plan (closed-loop validation). Twenty-two plans that had not been used for KBP model training were also compared with the KBP results (open-loop validation).
Although the minimal dose of PTV-B and PTV-E was lower and the maximal dose was higher than those of the expert plan, the difference was no larger than 0.7 Gy. In the closed-loop validation, D1.2cc, D0.35cc, and Dmean of the spinal cord was decreased by 0.9 Gy, 0.6 Gy, and 0.9 Gy, respectively, in the KBP plans (
The dose coverage and uniformity for PTV was slightly worse in the KBP for spine SBRT while the dose to the spinal cord was reduced, but the differences were small. Thus, inexperienced planners could easily generate a clinically feasible plan for spine SBRT by using KBP.
Original Article 2019-12-31
2019-12-31
6
1043
328
Hyeongmin Jin , Dong-Yun Kim , Jong Min Park , Hyun-Cheol Kang , Eui Kyu Chie , Hyun Joon An
https://doi.org/10.14316/pmp.2019.30.4.104
Online magnetic resonance-guided adaptive radiotherapy (MRgART), an emerging technique, is used to address the change in anatomical structures, such as treatment target region, during the treatment period. However, the electron density map used for dose calculation differs from that for daily treatment, owing to the variation in organ location and, notably, air pockets. In this study, we evaluate the dosimetric effect of electron density override on air pockets during online ART for pancreatic cancer cases.
Five pancreatic cancer patients, who were treated with MRgART at the Seoul National University Hospital, were enrolled in the study. Intensity modulated radiation therapy plans were generated for each patient with 60Co beams on a ViewrayTM system, with a 45 Gy prescription dose for stereotactic body radiation therapy. During the treatment, the electron density map was modified based on the daily MR image. We recalculated the dose distribution on the plan, and the dosimetric parameters were obtained from the dose volume histograms of the planning target volume (PTV) and organs at risk.
The average dose difference in the PTV was 0.86Gy, and the observed difference at the maximum dose was up to 2.07 Gy. The variation in air pockets during treatment resulted in an under- or overdose in the PTV.
We recommend the re-contouring of the air pockets to deliver an accurate radiation dose to the target in MRgART, even though it is a time-consuming method.
Original Article 2019-12-31
2019-12-31
0
1662
619
Nuri Lee , Chankyu Kim , Mi Hee Song , Se Byeong Lee
https://doi.org/10.14316/pmp.2019.30.4.112
The advantages of ocular proton therapy are that it spares the optic nerve and delivers the minimal dose to normal surrounding tissues. In this study, it developed a solid eye phantom that enabled us to perform quality assurance (QA) to verify the dose and beam range for passive single scattering proton therapy using a single phantom. For this purpose, a new solid eye phantom with a polymethyl-methacrylate (PMMA) wedge was developed using film dosimetry and an ionization chamber.
The typical beam shape used for eye treatment is approximately 3 cm in diameter and the beam range is below 5 cm. Since proton therapy has a problem with beam range uncertainty due to differences in the stopping power of normal tissue, bone, air, etc, the beam range should be confirmed before treatment. A film can be placed on the slope of the phantom to evaluate the Spread-out Bragg Peak based on the water equivalent thickness value of PMMA on the film. In addition, an ionization chamber (Pin-point, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose.
The eye phantom was used for independent patient-specific QA. The differences in the output and beam range between the measurement and the planned treatment were less than 1.5% and 0.1 cm, respectively.
An eye phantom was developed and the performance was successfully validated. The phantom can be employed to verify the output and beam range for ocular proton therapy.
Original Article 2019-12-31
2019-12-31
4
1425
452
Chang Yeol Lee , Woo Chul Kim , Hun Jeong Kim , Jeongshim Lee , Hyun Do Huh
https://doi.org/10.14316/pmp.2019.30.4.120
This study was designed to evaluate the dosimetric performance of Mobius3D by comparison with an aSi-based electronic portal imaging device (EPID) and Octavius 4D, which are conventionally used for patient-specific prescription dose verification.
The study was conducted using nine patients who were treated by volumetric modulated arc therapy. To evaluate the feasibility of Mobius3D for prescription dose verification, we compared the QA results of Mobius3D to an aSi-based EPID and the Octavius 4D dose verification methods. The first was the comparison of the Mobius3D verification phantom dose, and the second was to gamma index analysis.
The percentage differences between the calculated point dose and measurements from a PTW31010 ion chamber were 1.6%±1.3%, 2.0%±0.8%, and 1.2%±1.2%, using collapsed cone convolution, an analytical anisotropic algorithm, and the AcurosXB algorithm respectively. The average difference was found to be 1.6%±0.3%. Additionally, in the case of using the PTW31014 ion chamber, the corresponding results were 2.0%±1.4%, 2.4%±2.1%, and 1.6%±2.5%, showing an average agreement within 2.0%±0.3%. Considering all the criteria, the Mobius3D result showed that the percentage dose difference from the EPID was within 0.46%±0.34% on average, and the percentage dose difference from Octavius 4D was within 3.14%±2.85% on average.
We conclude that Mobius3D can be used interchangeably with phantom-based dosimetry systems, which are commonly used as patient-specific prescription dose verification tools, especially under the conditions of 3%/3 mm and 95% pass rate.
Original Article 2019-12-31
2019-12-31
1
1158
315
Mohammad Mahfujur Rahman , Chan Hyeong Kim , Hyun Do Huh , Seonghoon Kim
https://doi.org/10.14316/pmp.2019.30.4.128
Segmental analysis of volumetric modulated arc therapy (VMAT) is not clinically used for compositional error source evaluation. Instead, dose verification is routinely used for plan-specific quality assurance (QA). While this approach identifies the resultant error, it does not specify which machine parameter was responsible for the error. In this research study, we adopted an approach for the segmental analysis of VMAT as a part of machine QA of linear accelerator (LINAC).
Two portal dose QA plans were generated for VMAT QA: a) for full arc and b) for the arc, which was segmented in 12 subsegments. We investigated the multileaf collimator (MLC) position and dosimetric accuracy in the full and segmented arc delivery schemes. A MATLAB program was used to calculate the MLC position error from the data in the dynalog file. The Gamma passing rate (GPR) and the measured to planned dose difference (DD) in each pixel of the electronic portal imaging device was the measurement for dosimetric accuracy. The eclipse treatment planning system and a MATLAB program were used to calculate the dosimetric accuracy.
The maximum root-mean-square error of the MLC positions were <1 mm. The GPR was within the range of 98%一99.7% and was similar in both types of VMAT delivery. In general, the DD was <5 calibration units in both full arcs. A similar DD distribution was found for continuous arc and segmented arcs sums. Exceedingly high DD were not observed in any of the arc segment delivery schemes. The LINAC performance was acceptable regarding the execution of the VMAT QA plan.
The segmental analysis proposed in this study is expected to be useful for the prediction of the delivery of the VMAT in relation to the gantry angle. We thus recommend the use of segmental analysis of VMAT as part of the regular QA.
Original Article 2019-12-31
2019-12-31
1
749
257
Soonchan Park , Joon Jang , Jang-Hoon Oh , Chang-Woo Ryu , Geon-Ho Jahng
https://doi.org/10.14316/pmp.2019.30.4.139
With neurodegeneration, the signal intensity of the cerebrospinal fluid (CSF) in the brain increases. The objective of this study was to evaluate chemical exchange saturation transfer (CEST) signals with and without the contribution of CSF signals in elderly human brains using two different 3T magnetic resonance imaging (MRI) sequences
Full CEST signals were acquired in ten subjects (Group I) with a three-dimensional (3D)-segmented gradient-echo echo-planar imaging (EPI) sequence and in ten other subjects (Group II) with a 3D gradient and spin-echo (GRASE) sequence using two different 3T MRI systems. The segmented tissue compartments of gray and white matter were used to mask the CSF signals in the full CEST images. Two sets of magnetization transfer ratio asymmetry (MTRasym) maps were obtained for each offset frequency in each subject with and without masking the CSF signals (masked and unmasked conditions, respectively) and later compared using paired t-tests.
The region-of-interest (ROI)-based analyses showed that the MTRasym values for both the 3D-segmented gradient-echo EPI and 3D GRASE sequences were altered under the masked condition compared with the unmasked condition at several ROIs and offset frequencies.
Depending on the imaging sequence, the MTRasym values can be overestimated for some areas of the elderly human brain when CSF signals are unmasked. Therefore, it is necessary to develop a method to minimize this overestimation in the case of elderly patients.
Technical Note 2019-12-31
2019-12-31
1
444
288
Jiwon Sung , Jaeman Son , Jong Min Park , Jung-in Kim , Chang Heon Choi
https://doi.org/10.14316/pmp.2019.30.4.150
The objective of this study is to monitor the radiation doses delivered to a cardiac implantable electronic device (CIED) by comparing the absorbed doses calculated by a commercial treatment planning system (TPS) to those measured by an in vivo dosimeter. Accurate monitoring of the radiation absorbed by a CIED during radiotherapy is necessary to prevent damage to the device. We conducted this study on three patients, who had the CIED inserted and were to be treated with radiotherapy. Treatment plans were generated using the Eclipse system, with a progressive resolution photon optimizer algorithm and the Acuros XB dose calculation algorithm. Measurements were performed on the patients using optically stimulated luminescence detectors placed on the skin, near the CIED. The results showed that the calculated doses from the TPS were up to 5 times lower than the measured doses. Therefore, it is recommended that in vivo dosimetry be conducted during radiotherapy for CIED patients to prevent damage to the CIED.
Technical Note 2019-12-31
2019-12-31
10
1812
345
So-Yeon Park , Noorie Choi , Byeong Geol Choi , Dong Myung Lee , Na Young Jang
https://doi.org/10.14316/pmp.2019.30.4.155
Radiological properties of newly introduced and existing 3-dimensional (3D) printing materials were evaluated by measuring their Hounsfield units (HUs) at varying infill densities. The six materials for 3D printing which consisted of acrylonitrile butadiene styrene (ABS), a unique ABS plastic blend manufactured by Zortrax (ULTRAT), high impact polystyrene (HIPS), polyethylene terephthalate glycol (PETG), polylactic acid (PLA), and a thermoplastic polyester elastomer manufactured by Zortrax (FLEX) were used. We used computed tomography (CT) imaging to determine the HU values of each material, and thus assess its suitability for various applications in radiation oncology. We found that several material and infill density combinations resembled the HU values of fat, soft tissues, and lungs; however, none of the tested materials exhibited HU values similar to that of bone. These results will help researchers and clinicians develop more appropriate instruments for improving the quality of radiation therapy. Using optimized infill densities will help improve the quality of radiation therapy by producing customized instruments for each field of radiation therapy.
pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829
Frequency: Quarterly
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