• Radiation Oncology Journal
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• 제36권1호
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• pp.1-10
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• 2018

Intensity-modulated radiation therapy (IMRT) has been considered the most successful development in radiation oncology since the introduction of computed tomography into treatment planning that enabled three-dimensional conformal radiotherapy in 1980s. More than three decades have passed since the concept of inverse planning was first introduced in 1982, and IMRT has become the most important and common modality in radiation therapy. This review will present developments in inverse IMRT treatment planning and IMRT delivery using multileaf collimators, along with the associated key concepts. Other relevant issues and future perspectives are also presented.

• Journal of Yeungnam Medical Science
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• 제25권2호
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• pp.85-91
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• 2008

Intensity-modulated radiation therapy (IMRT) is believed to be one of the best radiation treatment techniques. IMRT is able to deliver fatal doses of radiation to the tumor region with minimal exposure of critical organs. It is essential to have a comprehensive quality assurance program to assure precision and accuracy in treatment, due to the character of IMRT. We applied quality assurance technique to the Eclipse treatment planning system and sought to determine its effectiveness in patient treatment planning. An acrylic phantom, film, and an ionization chamber were used in this study.

• Radiation Oncology Journal
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• 제34권4호
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• pp.313-321
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• 2016

Purpose: Total scalp irradiation (TSI) is a rare but challenging indication. We previously reported that non-coplanar intensity-modulated radiotherapy (IMRT) was superior to coplanar IMRT in organ-at-risk (OAR) protection and target dose distribution. This consecutive treatment planning study compared IMRT with volumetric-modulated arc therapy (VMAT). Materials and Methods: A retrospective treatment plan databank search was performed and 5 patient cases were randomly selected. Cranial imaging was restored from the initial planning computed tomography (CT) and target volumes and OAR were redelineated. For each patients, three treatment plans were calculated (coplanar/non-coplanar IMRT, VMAT; prescribed dose 50 Gy, single dose 2 Gy). Conformity, homogeneity and dose volume histograms were used for plan. Results: VMAT featured the lowest monitor units and the sharpest dose gradient (1.6 Gy/mm). Planning target volume (PTV) coverage and homogeneity was better in VMAT (coverage, 0.95; homogeneity index [HI], 0.118) compared to IMRT (coverage, 0.94; HI, 0.119) but coplanar IMRT produced the most conformal plans (conformity index [CI], 0.43). Minimum PTV dose range was 66.8%-88.4% in coplanar, 77.5%-88.2% in non-coplanar IMRT and 82.8%-90.3% in VMAT. Mean dose to the brain, brain stem, optic system (maximum dose) and lenses were 18.6, 13.2, 9.1, and 5.2 Gy for VMAT, 21.9, 13.4, 14.5, and 6.3 Gy for non-coplanar and 22.8, 16.5, 11.5, and 5.9 Gy for coplanar IMRT. Maximum optic chiasm dose was 7.7, 8.4, and 11.1 Gy (non-coplanar IMRT, VMAT, and coplanar IMRT). Conclusion: Target coverage, homogeneity and OAR protection, was slightly superior in VMAT plans which also produced the sharpest dose gradient towards healthy tissue.

• Radiation Oncology Journal
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• 제36권1호
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• pp.63-70
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• 2018

Purpose: The objective of this study was to compare dosimetric characteristics of three-dimensional conformal radiotherapy (3D-CRT) and two types of intensity-modulated radiotherapy (IMRT) which are step-and-shoot intensity modulated radiotherapy (s-IMRT) and modulated arc therapy (mARC) for thoracic esophageal cancer and analyze whether IMRT could reduce organ-at-risk (OAR) dose. Materials and Methods: We performed 3D-CRT, s-IMRT, and mARC planning for ten patients with thoracic esophageal cancer. The dose-volume histogram for each plan was extracted and the mean dose and clinically significant parameters were analyzed. Results: Analysis of target coverage showed that the conformity index (CI) and conformation number (CN) in mARC were superior to the other two plans (CI, p = 0.050; CN, p = 0.042). For the comparison of OAR, lung V5 was lowest in s-IMRT, followed by 3D-CRT, and mARC (p = 0.033). s-IMRT and mARC had lower values than 3D-CRT for heart $V_{30}$ (p = 0.039), $V_{40}$ (p = 0.040), and $V_{50}$ (p = 0.032). Conclusion: Effective conservation of the lung and heart in thoracic esophageal cancer could be expected when using s-IMRT. The mARC was lower in lung $V_{10}$, $V_{20}$, and $V_{30}$ than in 3D-CRT, but could not be proven superior in lung $V_5$. In conclusion, low-dose exposure to the lung and heart were expected to be lower in s-IMRT, reducing complications such as radiation pneumonitis or heart-related toxicities.

• Radiation Oncology Journal
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• 제31권2호
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• pp.104-110
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• 2013

Purpose: Intensity modulated arc therapy (IMAT) is a form of intensity modulated radiation therapy (IMRT) that delivers dose in single or multiple arcs. We compared IMRT plans versus single-arc field (1ARC) and multi-arc fields (3ARC) IMAT plans in high-risk prostate cancer. Materials and Methods: Sixteen patients were studied. Prostate ($PTV_P$), right pelvic ($PTV_{RtLN}$) and left pelvic lymph nodes ($PTV_{LtLN}$), and organs at risk were contoured. $PTV_P$, $PTV_{RtLN}$, and $PTV_{LtLN}$ received 50.40 Gy followed by a boost to $PTV_B$ of 28.80 Gy. Three plans were per patient generated: IMRT, 1ARC, and 3ARC. We recorded the dose to the PTV, the mean dose ($D_{MEAN}$) to the organs at risk, and volume covered by the 50% isodose. Efficiency was evaluated by monitor units (MU) and beam on time (BOT). Conformity index (CI), Paddick gradient index, and homogeneity index (HI) were also calculated. Results: Average Radiation Therapy Oncology Group CI was 1.17, 1.20, and 1.15 for IMRT, 1ARC, and 3ARC, respectively. The plans' HI were within 1% of each other. The $D_{MEAN}$ of bladder was within 2% of each other. The rectum $D_{MEAN}$ in IMRT plans was 10% lower dose than the arc plans (p < 0.0001). The GI of the 3ARC was superior to IMRT by 27.4% (p = 0.006). The average MU was highest in the IMRT plans (1686) versus 1ARC (575) versus 3ARC (1079). The average BOT was 6 minutes for IMRT compared to 1.3 and 2.9 for 1ARC and 3ARC IMAT (p < 0.05). Conclusion: For high-risk prostate cancer, IMAT may offer a favorable dose gradient profile, conformity, MU and BOT compared to IMRT.

• Radiation Oncology Journal
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• 제37권4호
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• pp.249-253
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• 2019

Purpose: We aimed to analyze the trend in intensity-modulated radiation therapy (IMRT) use in Korea from 2011 to 2018. Materials and Methods: We collected data from the Health and Insurance Review and Assessment Service (HIRA) big data based on the National Health Insurance Service claims and reimbursements records using primary treatment planning codes (HD 041) for IMRT from 2011 to 2018. We analyzed the changing patterns in clinical application to specific tumor sites and regional differences in IMRT utilization. Results: The use of IMRT has exhibited an 18-fold steep rise from 1,921 patients in 2011 to 34,759 in 2018. With regard to IMRT in 2018, 70% of patients (24,248/34,759) were treated in metropolitan areas (Seoul, Incheon, and Gyeonggi Province). IMRT was most commonly used to treat breast, lung, and prostate cancers in 2018. Among these, the use of IMRT for breast cancer shows the most remarkable increase from 2016 when the National Health Insurance began to cover IMRT for all solid tumors. Conclusion: The use of IMRT is steadily increasing to treat cancer and is concentrated in metropolitan areas.

• Radiation Oncology Journal
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• 제36권4호
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• pp.276-284
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• 2018

Purpose: Traditionally, three-dimensional conformal radiation therapy (3D-CRT) is used for neoadjuvant chemoradiation in locally advanced rectal cancer. Intensity-modulated radiation therapy (IMRT) was later developed for more conformal dose distribution, with the potential for reduced toxicity across many disease sites. We sought to use the National Cancer Database (NCDB) to examine trends and predictors for IMRT use in rectal cancer. Materials and Methods: We queried the NCDB from 2004 to 2015 for patients with rectal adenocarcinoma treated with neoadjuvant concurrent chemoradiation to standard doses followed by surgical resection. Odds ratios were used to determine predictors of IMRT use. Univariable and multivariable Cox regressions were used to determine potential predictors of overall survival (OS). Propensity matching was used to account for any indication bias. Results: Among 21,490 eligible patients, 3,131 were treated with IMRT. IMRT use increased from 1% in 2004 to 22% in 2014. Predictors for IMRT use included increased N stage, higher comorbidity score, more recent year, treatment at an academic facility, increased income, and higher educational level. On propensity-adjusted, multivariable analysis, male gender, increased distance to facility, higher comorbidity score, IMRT technique, government insurance, African-American race, and non-metro location were predictive of worse OS. Of note, the complete response rate at time of surgery was 28% with non-IMRT and 21% with IMRT. Conclusion: IMRT use has steadily increased in the treatment of rectal cancer, but still remains only a fraction of overall treatment technique, more often reserved for higher disease burden.

• 한국의학물리학회지:의학물리
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• 제32권3호
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• pp.70-81
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• 2021

Purpose: This study was designed to investigate the dosimetric difference between intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) in head and neck cancer (HNC). The study primarily focuses on low-dose spillage evaluation between these two techniques. Methods: This retrospective study involved 45 patients with HNC. The treatment plans were generated using the IMRT and VMAT techniques for all patients. Dosimetric comparisons were performed in terms of target coverage, organ-at-risk (OAR) sparing, and various parameters, including conformity index, uniformity index, homogeneity index, conformation number, low-dose volumes, and normal tissue integral dose (NTID). Results: No significant (P>0.05) difference in planning target volume coverage (D_95%) was observed between IMRT and VMAT plans for supraglottic larynx, hard palate, and tongue cancers. A decrease in dose volumes ranging from 1 Gy to 30 Gy was observed for VMAT plans compared with those for IMRT plans, except for V_1Gy and V_30Gy for supraglottic larynx cancer and V_1Gy for tongue cancer. Moreover, decreases (P<0.05) in NTID were observed for VMAT plans compared with that for IMRT plans in supraglottic larynx (4.50%), hard palate (12.80%), and tongue (7.76%) cancers. In contrast, a slight increase in monitor units for VMAT compared with those for IMRT in supraglottic larynx (0.46%), hard palate (2.54%), and tongue (7.56%) cancers. Conclusions: For advanced-stage HNC, both IMRT and VMAT offer satisfactory clinical plans. VMAT offers a conformal and homogeneous dose distribution with comparable OAR sparing and higher dose falloff outside the target volume than IMRT, which provides an edge to reduce the risk of secondary malignancies for HNC over IMRT.

• 대한방사선치료학회지
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• 제29권1호
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• pp.57-68
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• 2017

목 적: 본 연구는 모양이 불규칙하고 손상위험장기(Organ At Risk, OAR)에 매우 인접한 타겟(Target)의 방사선 치료 시, 비동일평면상(Non-coplanar)의 빔(Beam)을 이용한 Fixed-field 세기변조 방사선치료(Intensity Modulated Radiation Therapy, IMRT)와 용적변조회전 방사선치료(Volumetric Modulated Arc Therapy, VMAT) 치료계획의 유용성을 평가 및 비교해 보고자 하였다. 대상 및 방법: 본원에서 True Beam STX(Varian Medical Systems, USA)를 이용하여 전체 두피(Whole Scalp), 부분적 두피(Partial Scalp), 그리고 전체 뇌실(Whole Ventricle)에 방사선 치료를 받은 환자 중 각 부위별로 2명 씩, 총 6명을 대상으로 하였다. VMAT 치료계획 시, Beamlet에 포함되는 OAR의 용적을 최소화하기 위해 Coplanar 또는 Non-coplanar 빔을 이용하였고, Fixed-field IMRT는 6명 모두 2개 이상의 카우치(Couch) 각도를 이용한 Non-coplanar IMRT(이하 ncIMRT)로 치료계획 하였다. 결 과: 양측 수정체, 양측 시신경, 시신경 교차, 그리고 뇌 줄기의 최대선량과 양측 안구와 해마의 평균선량을 측정하였고, 6명 모두 9개의 OAR 중 6개 이상에서 VMAT 치료계획이 ncIMRT보다 1.1배에서 8.2배가량 높은 선량 값을 나타내었다. 전체 두피와 부분적 두피의 치료 시, 20 Gy가 조사되는 뇌의 용적은 VMAT이 ncIMRT의 2배 이상이었고, 전체 뇌실의 치료 시에는 두 치료계획이 큰 차이를 보이지 않았다. 타겟 Coverage는 두 치료계획 모두 $PTV_{100%}=95%$를 만족시켰고, 타겟 내 최대선량과 치료 시 필요한 총 Monitor Unit(MU)은 ncIMRT가 VMAT보다 높았으며 두 치료계획 모두 임상적용을 위한 Gamma test 시행 결과, 2 mm/2 % 조건을 통과하였다. 결 론: 본 연구 결과, ncIMRT는 VMAT에 비해 치료 시 필요한 MU가 높아 치료시간과 장비의 로딩(Loading)을 증가시키므로 치료의 효율성은 다소 떨어지지만, VMAT과 비슷한 타겟 Coverage를 유지하면서, OAR의 선량은 훨씬 감소시키는 것을 알 수 있었다. 따라서 모양이 불규칙하고 OAR에 매우 인접해 있는 타겟의 방사선 치료 시에는 ncIMRT 치료계획을 고려해 볼 필요가 있다고 사료된다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권8호
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• pp.3365-3370
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• 2015

Radiotherapy has an important role in the treatment of prostate cancer. Three-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques are all applied for this purpose. However, the risk of secondary radiation-induced bladder cancer is significantly elevated in irradiated patients compared surgery-only or watchful waiting groups. There are also reports of risk of secondary cancer with low doses to normal tissues. This study was designed to compare received volumes of low doses among 3D-CRT, IMRT and VMAT techniques for prostate patients. Ten prostate cancer patients were selected retrospectively for this planning study. Treatment plans were generated using 3D-CRT, IMRT and VMAT techniques. Conformity index (CI), homogenity index (HI), receiving 5 Gy of the volume (V5%), receiving 2 Gy of the volume (V2%), receiving 1 Gy of the volume (V1%) and monitor units (MUs) were compared. This study confirms that VMAT has slightly better CI while thev olume of low doses was higher. VMAT had lower MUs than IMRT. 3D-CRT had the lowest MU, CI and HI. If target coverage and normal tissue sparing are comparable between different treatment techniques, the risk of second malignancy should be a important factor in the selection of treatment.