Treatment planning study comparing proton therapy, RapidArc and IMRT for a synchronous bilateral lung cancer case

We present a case of synchronous bilateral inoperable lung cancer which required treatment with external beam radiotherapy to a radical dose. Intensity-modulated radiotherapy (IMRT) was used. More conformal dose distribution within the planning target volume was obtained using IMRT than the conventional technique. Dose-volume constraints defined for the lungs were met. Treatment was subsequently delivered using a seven-field IMRT plan. The patient remains alive and disease-free 48 months after the completion of radiotherapy. IMRT can be considered an effective treatment for synchronous bilateral lung cancer.

Dosimetric research on intensity-modulated arc radiotherapy planning for left breast cancer after breast-preservation surgery

<p><strong>Purpose: </strong>The purpose of this study is to analyze and compare the dosimetric parameters of three dimensional conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) in selected non-small cell lung cancer (NSCLC) cases. <strong></strong></p><p><strong>Methods: </strong>Ten patients with inoperable NSCLC were selected for this study. The 3DCRT and IMRT plans were generated for all patients following Radiation Therapy Oncology Group (RTOG) guidelines. Generated plans were then compared on the basis of planning target volume (PTV) coverage, dose delivered to organs at risk, homogeneity index (HI), and conformity index (CI) for the prescribed dose (PD) of 50 Gy in 25 fractions.</p><p><strong>Results: </strong>The mean D<sub>95 </sub>and D<sub>99 </sub>(dose to the 95% and 99% volume) for the PTV were found better in the 3DCRT plans compared to the ones in the IMRT plans. On an average, the volume receiving 20 Gy (V<sub>20</sub>) of contralateral lung was 2.91% and 3.03% in the 3DCRT and IMRT plans, respectively. The D<sub>mean</sub> of contralateral lung was 3.17 Gy (3DCRT) versus 4.2 Gy (IMRT), whereas the D<sub>mean</sub> of ipsilateral lung was 12.69 Gy (3DCRT) and 13.82 Gy (IMRT). The V<sub>20</sub> of ipsilateral lung was found to be slightly lower in the 3DCRT (25.67%) when compared to the IMRT (30.50%). The dose to the heart was comparable in the 3DCRT and IMRT plans (mean dose: 4.42 Gy versus 4.48 Gy; D<sub>33</sub>: 3.77 Gy versus and 4.02 Gy). For the spinal cord, the D<sub>max </sub>was found to be lower in the 3DCRT plans (18.40 Gy) when compared to the IMRT plans (25.49 Gy). The HI was 1.08 versus 1.41 in the 3DCRT and IMRT plans, respectively. The CI was identical (1.67) in both sets of plans.</p><p><strong>Conclusion: </strong>Based on the results of this study, the PTV coverage was found to be slightly better in the 3DCRT plans when compared to the one in the IMRT plans. On average, the dose to the organs at risk were found to be comparable.</p>

To prospectively compare volumetric intensity-modulated arc therapy (VMAT) and conventional intensity-modulated radiation therapy (IMRT) in coverage of planning target volumes and avoidance of multiple organs at risk (OARs) in patients undergoing definitive chemoradiotherapy for advanced (stage III or IV) squamous cell cancer of the head and neck. Computed tomography scans of 20 patients with advanced tumors of the larynx, naso-, oro- and hypopharynx were prospectively planned using IMRT (7 field) and VMAT using two arcs. Calculated doses to planning target volume (PTV) and OAR were compared between IMRT and VMAT plans. Dose-volume histograms (DVH) were utilized to obtain calculated doses to PTV and OAR, including parotids, cochlea, spinal cord, brainstem, anterior tongue, pituitary and brachial plexus. DVH's for all structures were compared between IMRT and VMAT plans. In addition the plans were compared for dose conformity and homogeneity. The final treatment plan was chosen by the treating radiation oncologist. VMAT was chosen as the ultimate plan in 18 of 20 patients (90%) because the plans were thought to be otherwise clinically equivalent. The IMRT plan was chosen in 2 of 20 patients because the VMAT plan produced concentric irradiation of the cord which was not overcome even with an avoidance structure. For all patients, VMAT plans had a lower number of average monitor units on average (MU = 542.85) than IMRT plans (MU = 1612.58) (P < 0.001). Using the conformity index (CI), defined as the 95% isodose volume divided by the PTV, the IMRT plan was more conformal with a lower conformity index (CI = 1.61) than the VMAT plan (CI = 2.00) (P = 0.003). Dose homogeneity, as measured by average standard deviation of dose distribution over the PTV, was not different with VMAT (1.45 Gy) or IMRT (1.73 Gy) (P = 0.069). There were no differences in sparing organs at risk. In this prospective study, VMAT plans were chosen over IMRT 90% of the time. Compared to IMRT, VMAT plans used only one third of the MUs, had shorter treatment times, and similar sparing of OAR. Overall, VMAT provided similar dose homogeneity but less conformity in PTV irradiation compared to IMRT. This difference in conformity was not clinically significant.

Potential for Dose-escalation in the Post-prostatectomy Setting with Intensity Modulated Radiation Therapy: A Dosimetric Study using EORTC Consensus Guidelines for Target Volume Contours

NTCP modeling analysis of acute hematologic toxicity in whole pelvic radiation therapy for gynecologic malignancies – A dosimetric comparison of IMRT and spot-scanning proton therapy (SSPT)

Estimation of secondary cancer risks following rectal cancer photon and proton therapy: A computational phantom study.

Purpose: Triple channel correction acquisition (TCCA) is a model‐based method for obtaining the characteristic curve of Gafchromic EBT2 film (EBT2). In this study the TCCA method was applied to EBT2 film dosimetry of intensity modulated radiation therapy (IMRT) and intensity modulated arc therapy (IMAT). Method and Materials:EBT2 films were calibrated by a field‐by‐field method in 13 steps. All films were scanned by using flat‐bed scanners at one day after the irradiation. Seven characteristic curves obtained by the TCCA method were compared with those of a single channel acquisition (SCA) method. For clinical applications, the planar dose distributions of IMRT and IMAT plans were compared with dose distributions measured with EBT2 films. The film analyses were performed by applying both TCCA and SCA. We chose two IMRT plans and two Varian IMAT (RapidArc) plans, which were created by the BrainLAB i‐plan and Eclipse Varian treatment planning systems for IMRT and RapidArc, respectively. Results: The constancy of the characteristic curves obtained by TCCA was better than that of SCA. The most significant difference between the characteristic curves of TCCA and SCA was observed in a low dose range between 25 cGy and 100 cGy. The results of clinical cases demonstrated that the dose difference between the measured and planned doses in high dose gradient regions was smaller with TCCA than that with SCA. Conclusions: We showed that characteristic curves obtained by the TCCA method have a good constancy compared with those of SCA. The potential advantage of TCCA was seen in high dose gradient regions in clinically relevant IMRT and IMAT cases. Hence, EBT2 film dosimetry with the TCCA method can be used for high precision patient specific QA.

A Treatment Planning System for Intensity-Modulated Small Animal Radiotherapy Realized Using an Existing Movable Rectangular Collimator

Radiotherapy of the posterior fossa for medulloblastoma treatment can induce ototoxicity, especially when combined with cisplatin chemotherapy. Sensorineural hearing loss can be severe enough to cause permanent disability, which may compromise cognitive development in paediatric patients. This study evaluates the sparing of the cochlea in conventional radiotherapy, three-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT). CT scans of three patients were used to plan posterior fossa radiotherapy using coplanar beam arrangements. The posterior fossa and the cochlea were contoured as well as other organs-at-risk (non-posterior fossa brain, lenses, optic nerves, pituitary and cervical spinal cord). Three treatment plans were compared: conventional two-dimensional treatment (parallel-opposed lateral pair); 3D-CRT (two wedged posterior oblique fields); and a four-field coplanar IMRT plan. 3D-CRT and IMRT reduced cochlear doses to less than 70% of the mean target dose. These plans also reduced dose to the non-posterior fossa brain and cervical spinal cord. IMRT showed no advantage over 3D-CRT in sparing the optic nerves and lenses, compared with 3D-CRT. Normal tissue doses were higher in both conformal techniques than in the IMRT plans. Conformal techniques reduced the dose to the cochlea, non-posterior fossa brain and cervical spinal cord. The small size and proximity to the planning target volume (PTV) of the cochlea limited the effectiveness of the IMRT plan. Coplanar 3D-CRT was judged superior to coplanar IMRT, particularly in children, because it achieved adequate sparing of the cochlea and anterior cranial structures, such as the lenses and optic nerves, without compromising the dose to the posterior fossa.

The treatment planning in radiation therapy (RT) can be arranged to combine benefits of computed tomography (CT) and magnetic resonance imaging (MRI) together to maintain dose calculation accuracy and improved target delineation. Our aim is study the dosimetric impact of uniform relative electron density assignment on IMRT treatment planning with additional consideration given to the effect of a 1.5 T transverse magnetic field (TMF) in MR-Linac.A series of intensity modulated RT (IMRT) plans were generated for two representative tumor sites, pancreas and prostate, using CT and MRI datasets. Representative CT-based IMRT plans were generated to assess the impact of different electron density (ED) assignment on plan quality using CT without the presence of a 1.5 T TMF. The relative ED (rED) values used were taken from the ICRU report 46. Four types of rED assignment in the organs at risk (OARs), the planning target volumes (PTV) and in the non-specified tissue (NST) were considered. Dose was recalculated (no optimization) using a Monaco 5.09.07a research planning system employing Monte Carlo calculations with an option to include TMF. To investigate the dosimetric effect of different rED assignment, the dose-volume parameters (DVPs) obtained from these specific rED plans were compared to those obtained from the original plans based on CT.Overall, we found that uniform rED assignment results in differences in DVPs within 3% for the PTV and 5% for OAR. The presence of 1.5 T TMF on IMRT DVPs resulted in differences that were generally within 3% of the Gold St for both the pancreas and prostate. The combination of uniform rED assignment and TMF produced differences in DVPs that were within 4–5% of the Gold St. Larger differences in DVPs were observed for OARs on T2-based plans.The effects of using different rED assignments and the presence of 1.5 T TMF for pancreas and prostate IMRT plans are generally within 3% and 5% of PTV and OAR Gold St values. There are noticeable dosimetric differences between the CT- and MRI-based IMRT plans caused by a combination of anatomical changes between the two image acquisition times, uniform rED assignment and 1.5 T TMF.

Planning comparison of intensity modulated radiation therapy delivered with 2 tangential fields versus 3-dimensional conformal radiotherapy for cardiac sparing in women with left-sided breast cancer

Inverse and forward optimization of one- and two-dimensional intensity-modulated radiation therapy-based treatment of concave-shaped planning target volumes: the case of prostate cancer.

Objective To compare the treatment effects,dosimetry,and toxicities to organs at risk of intensity-modulated radiation therapy (IMRT) and 3-dimentional conformal radiotherapy (3DCRT) plans for cervical carcinoma patients with recurrence and metastasis. Methods 62 cervical carcinoma patients with recurrence and metastasis were analyzed retrospectively, and divided into two groups including intensitymodulated radiation therapy group (n=29) and 3-dimentional conformal radiotherapy group (n=32).Patients were performed with 6 MV-X ray.The regimen was 1.8-2.2 Gy/f,1 f/d,18-33 times in total.Prescribed dose was 40-60 Gy and median dose was 52.8 Gy. At the same time for the IMRT group 29 cases were performed with 3DCRT, which was designed using the same prescribed dose to compare radiation dose distributed in organs at risk (OAR).Results The maximum dose of the two plans showed that bladder and small intestine in IMRT plans were lower than that in 3DCRT (P＜0.05), showing the IMRT's protective advantage. The maximum dose of PTV in IMRT plans were significantly higher than 3DCRT (P＜0.05). In the group of IMRT plans, the overall 1-,2-,and 3-year survival rates were 65.5 ％(19/29), 42.1％(8/19), and 25.0 ％(2/8),respectively,the median survival time was 19 months,of 28 deaths,21 patients died of tumor progression,7 patients died of distant metastases.In the group of 3DCRT plans,the overall 1-,2-,and 3-year survival rates were 60.6 ％(20/33),35.0 ％(7/20),and 14.3 ％(1/7),respectively,the median survival time was 17 months,of 32 deaths, 24 patients died of tumor progression, 8 patients died of distant metastasis. There were no significant differences in overall 1-, 2-, and 3-year survival rates between the two groups (P＞0.05). The incidence rate of toxicity in the IMRT plans was significantly lower than that in the 3DCRT plans, especially for patients with Ⅰ level and Ⅱ level.Conclusion The treatment effects of the IMRT plans are better than the 3DCRT plans for cervical carcinoma patients with recurrence and metastasis. IMRT plans can improve radiation dose in tumors and reduce the dose distributed in normal issue and reduce the incidence of the side effect. Key words: Uterine cervical neoplasms; Recurrence; Neoplasm metastasis; Radiotherapy,intensity-modulated; Radiotherapy, conformal

Dosimetric Impact of Using the Acuros XB Algorithm for Intensity Modulated Radiation Therapy and RapidArc Planning in Nasopharyngeal Carcinomas