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ORIGINAL ARTICLE
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Dosimetric comparison of volumetric modulated arc therapy and dynamic conformal arc therapy techniques for radiosurgery of single brain metastasis


1 Department of Radiation Oncology, Yeni Yuzyil University Gaziosmanpasa Hospital; Department of Radiation Oncology, Nisantasi University, Istanbul, Turkey
2 Department of Radiation Oncology, Nisantasi University, Istanbul, Turkey
3 Department of Radiation Oncology, Bahcesehir University, Istanbul, Turkey
4 Department of Radiation Oncology, Baskent University Medical Faculty, Adana, Turkey

Date of Submission02-Jun-2020
Date of Decision20-Sep-2020
Date of Acceptance21-Dec-2020
Date of Web Publication17-Jul-2021

Correspondence Address:
Ismail Faruk Durmus,
Department of Radiation Oncology, Yeni Yuzyil University Gaziosmanpasa Hospital, Istanbul
Turkey
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcrt.JCRT_738_20

 > Abstract 


Background: Volumetric modulated arc therapy (VMAT) and/or dynamic conformal arc therapy (DCAT) techniques are commonly used for the radiosurgical management of the intracranial primary or metastatic tumors. Because the literature on the dosimetric comparison is scarce, we intended to dosimetrically compare the VMAT and DCAT techniques for radiosurgery of single brain metastasis.
Materials and Methods: The VMAT- and DCAT-based radiosurgical plans of 28 patients presenting with single brain metastasis were compared in terms of conformity index (CI), gradient index (GI), heterogeneity index (HI), Paddick CI (CIPaddick), high-dose spillage (HDS%), monitor units (MUs), and beam-on times. The dosimetric verification of the plans was measured with the new transmission detector Dolphin and assessed in the Compass software.
Results: For the whole study population, the CI (1.12 vs. 1.21; P = 0.011), GI (4.41 vs. 4.61; P < 0.001), and HDS% (6.83 vs. 13.06; P < 0.001) were all found to be significantly better with VMAT. Similar results were found between the two techniques in terms of HI (VMAT 1.46 vs. DCAT 1.44; P = 0.065) and CIPaddick (VMAT 1.07 vs. DCAT 1.12; P = 0.0103). On the other hand, the DCAT plans were found to offer 25.1% lower MU (3178 vs. 4242; P < 0.001) and 19.9% lower beam-on times (411 vs. 326 s; P < 0.001) compared to VMAT plans. For pretreatment plan verification, in gamma analyses, ≥90% pass was achieved for the criteria of 3% dose difference (DD)-3-mm distance to agreement (DTA), 2% DD-2-mm DTA, and 3% DD-1-mm DTA.
Conclusions: The results of our present dosimetric study implied that the VMAT was capable to offer significantly more conformal stereotactic radiosurgery plans with steeper dose falloff beyond the target volume for single brain metastasis than the DCAT, which attained at the cost of significantly higher MU and beam-on times.

Keywords: Brain metastasis, dynamic conformal arc therapy, plan quality indices, radiosurgery, volumetric modulated arc therapy



How to cite this URL:
Durmus IF, Okumus A, Pehlivan B, Topkan E. Dosimetric comparison of volumetric modulated arc therapy and dynamic conformal arc therapy techniques for radiosurgery of single brain metastasis. J Can Res Ther [Epub ahead of print] [cited 2021 Nov 29]. Available from: https://www.cancerjournal.net/preprintarticle.asp?id=321713




 > Introduction Top


The recent improvements in the radiological imaging tools, patient positioning, and treatment planning systems (TPSs) and the successful implementation of the noninvasive frameless cranial stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy (SRT) resulted in ample increments in the routine use of these sophisticated treatment techniques for the sustainable management of numerous primary and metastatic brain tumors.[1] The fundamental principles of SRS and SRT consolidate the precise delivery of the ablative doses to the intended target volume in a single or multi-fractionation manner (usually ≤5 fractions) by utilizing isocentric or nonisocentric noncoplanar beams with rapid and sharp dose falloff outside the target volume, with the resultant avoidance or minimization of the treatment-related toxicities in the neighboring healthy tissues.[1],[2],[3],[4],[5] These guiding principles and consequential clinical goals can be satisfactorily accomplished with either of the volumetric modulated arc therapy (VMAT) or dynamic conformal arc therapy (DCAT) techniques. Nowadays, the VMAT technique is one of the standard treatment practices in SRS/SRT to facilitate the sharp dose gradient outside the target volume. Moreover, the conformity index (CI) is better in VMAT as compared to the conventional static field.[6] In contrast to DCAT, VMAT is inverse planning and optimizes the multileaf collimator (MLC) shapes, gantry speed, and dose rate simultaneously, which leads to an increase in treatment plan complexity.

To increase the efficacy of DCAT, the Monaco TPS allows modification in DCAT, where segment shape optimization (SSO) (Elekta CMS, Maryland Heights, MO, USA) and variable dose rate (VDR) are integrated with DCAT. The modified DCAT is an inverse planning-based delivery technique in which MLC conforms to the target projection and allows the optimization of gantry speed, dose rate, and segment shape to confirm the target. There is no sufficient literature available for the dosimetric comparison of modified DCAT versus VMAT for SRS/SRT. Besides, the modified DCAT also allows a partial blockage of a target which overlaps with organs at risk (OARs), if OARs are assigned with higher priority or as avoidance structure.[7]

Patient-specific quality assurance (QA) is a critical step for the evaluation of the stereotactic treatments that can be typically performed by one of the one-dimensional (1D), 2D, and 3D systems. While the individual 1D and 2D systems perform point dose (absolute dose) and dose fluence-map verifications, the 3D systems either evaluate the 3D dose maps or recalculate the dose distribution by relying upon the measured doses those transferred to the computed tomographic (CT) images. The calculated and measured dose distributions are objectively assessed by the gamma index and dose–volume histogram (DVH) analysis.[8] The gamma index method was first proposed by Low et al. in 1998[9] and later updated by Low and Dempsey in 2003,[10] which is still regularly utilized as a computerized verification tool for intensity-modulated radiation therapy (IMRT) plans. Briefly, the gamma index methodology is a calculation technique that directly depends on the dose difference (DD) and distance to agreement (DTA), where DD and DTA comprise the complementary parameters for asserting the dose distributions.[9],[10]

Although the VMAT and DCAT are the two commonly used SRS/SRT methods, the literature on their objective comparison in terms of the plan quality indices is scarce. Hence, we herein intended to dosimetrically compare these two SRS/SRT modalities to add to the limited literature on this particular subject, which may prove useful in precise determination of the best-fit SRS/SRT method for patients presenting with single brain metastasis.


 > Materials and Methods Top


Imaging, volume contouring, and treatment planning

Before planning the treatment, 28 patients were scanned with 1 mm slice thickness CT with Biograph mCT (Siemens Medical Solutions, Erlangen, Germany) and T1-weighted and contrast-enhanced magnetic resonance imaging (MRI) with the Magnetom Essenza (Siemens Medical Solutions, Erlangen, Germany). The images were then transferred to the Prosoma 4.1 (MedCom, Darmstadt, Germany) contouring tool, and a radiation oncologist experienced on cranial SRS/SRT contoured the gross tumor volumes (GTVs) and the OAR using the co-registered CT and MRI scans, trailed by the creation of the planning target volume (PTV) by adding a 2-mm margin to the GTV at all dimensions. Treatment planning conditions such as the location of the tumor, PTV (cc), prescription dose (Gy), groups by tumor volume (TV), and the number of fractions for all cases are defined in [Table 1].
Table 1: Treatment planning conditions such as the location of the tumor, volume of planning target volume (cc), prescription dose/fraction (Gy), groups by tumor volume, and the choice of treatment technique for all cases are defined in the table below

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For each patient, the SRS/SRT plans were created by utilizing the Monaco 5.11 TPS (Elekta, Crawley, England) and Agility head Elekta Versa HD with 5-mm MLF thickness (Elekta, Crawley, England) linear accelerator (LINAC). Treatment plans were created by using noncoplanar rotational fields with 6 MV-FFF (1400 MU/min) energy. Depending on the target localization, 4–6 half or full rotational fields were used as per patient basis, and the planning and optimization parameters were kept identical for both techniques. The planning parameters used were: target margin: 0–1 mm; beamlet width: 2.5 mm, fluence smoothing: high; minimum segment width: 5 mm; and grid size: 1.5 mm. Monte Carlo (MC) dose calculation algorithm was used for dose calculations with a statistical uncertainty range of 1% in the dose to medium mode. For DCAT plans, SSO and VDR were additionally utilized for planning purposes. For comparison purposes, both kinds of treatment plans were rescaled, so at least 95% of PTV received 100% of the prescription dose.

Plan quality indices

The following indices were calculated for plan quality assessment and comparisons.

The GI was defined as the dose falloff outside the target and calculated as the ratio of the 50% of the prescribed isodose volume (PIV50%) to the volume of the prescribed isodose (PIV):[11]

GI = PIV50%/PIV (1)

The CI was defined as the ratio of the PIV to the TV:[10]

CI = PIV/TV (2)

The more comprehensive Paddick CI (CIPaddick) was calculated according to the following formula:[12],[13]

CIPaddick = (TVPIV)2/TV × PIV (3)

where TVPIV: Target volume covered by the reference isodose, TV: Target volume, and PIV: Prescription isodose volume.

The HI which is defined as an indicator of the dose homogeneity within the target volume was calculated as the ratio of the maximum dose (Dmax) within the target volume to the dose of 95% in the target volume (D95):[14]

HI = Dmax/D95% (4)

The Radiation Therapy Oncology Group researchers created the HDS% index for the lung SBRT using the data of 0813 and 0915 Reports,[15],[16] where 105% of the prescription dose received by the volume outside the target (V105) was restricted to volumetrically not exceed the 15% of the PTV. As the HDS% index aids in detection of the high dose points beyond the target, we intended to use HDS% formula also for cranial SRS/SRT in our study:

HDS%= [(V105 − PTV)/PTV] × 100 (5)

Plan quality assurance

Plan QA measurements were performed using the Iba Dolphin (Iba Dosimetry, Germany) detector for the Elekta Versa HD LINAC-based SRS/SRT plans. The results were evaluated using the gamma index method in the DVH-based Iba Compass 4.0.27 software (Iba Dosimetry, Germany). The Dolphin detector is a transmission detector with a 2D ionization chamber array that can be used for pretreatment plan verifications as one of the measurement devices for Compass. The Dolphin detector consists of 1514 sensors (1513 parallel plate ionization chambers + 1 diode at the side) arranged in a grid. The effective volume and the diameter of the ionization chamber are 16 mm3 and 3.2 mm, respectively. The Dolphin detector's ion chambers have high resolution of 5 mm from center to center with an interior area of 15 cm × 15 cm. The active area (24 cm × 24 cm) is about 93% transparent for photon beams of 6 MV. The Compass system utilized in our study has consisted of the Dolphin detector and an integrated software solution comprising a superposition algorithm that models the LINAC head.[17] The 3D dose distributions were calculated from 2D measured fluence and the scatter kernel (collapsed cone) using the superposition formula. The 3D dose verification system compass is capable of reconstructing 3D dose distributions on the patient anatomy based on the fluence measured using a new transmission detector during treatment.[18] Thus, QA of each target and critical organ doses can be made in 3D dose distribution. In our study, we performed analyses of PTVD1, PTVD99, and PTVmean doses with DVH-based QA. We also performed DVH-based plan QA analyses incorporating the mean brain dose, 6 Gy absorbed dose percentage volume (V6), and 12 Gy absorbed dose percentage volume (V12). Gamma index analysis is performed according to the criteria of DD and DTA. The DTA is the distance between a dose point in the calculated distribution and the nearest point in the measured distribution containing the same dose value. The DD is the difference between a measured dose and a calculated dose at any point. The results were evaluated in transverse, sagittal and coronal planes based on the parameters of 3% DD-3 mm DTA, 2% DD-2 mm DTA, 1% DD-1 mm DTA, and 3% DD-1 mm DTA and 3D results were acquired. In addition, global gamma analysis approach and 5% threshold value were used in the assessment.

Statistics

To analyze the differences between the VMAT and DCAT plans for each of the previously described metrics, a Wilcoxon signed-rank test was used. The level of statistical significance was considered P < 0.05 for all calculations.[19]


 > Results Top


The present dosimetric investigation involved 28 patients with single brain metastasis who were planned to undergo cranial SRS/SRT. The mean target volume was 6.66 cc (range: 0.164–35.01 cc) for all patients. Patients were stratified into three target volume groups for comparative analyses: small target volume: ≤1.00 cc (n = 8); medium target volume: 1.01–5.00 cc (n = 9); and large target volume: >5.00 cc (n = 11). The VMAT and DCAT plans were compared according to the quality index values, HDS%, beam-on time, and MU values for the overall study population. In addition, the potential relationship between the target volumes and plan quality values was also investigated.

As shown in [Table 2], although no significant difference was observed between the VMAT and DCAT plans in terms of CIPaddick and HI values, yet the GI and CI values significantly favored the VMAT over the DCAT plans for the overall study population. Target volume-based analyses revealed that the CI was getting better with increments in the target volumes in both plans, yet the VMAT technique offered more conformal plans than the DCAT matches in all groups. For GI, the difference between the two techniques was only significant in the large target volume group in subgroup comparisons, which again favored the VMAT over the DCAT plans.
Table 2: Plan quality index values in volumetric modulated arc therapy and dynamic conformal arc therapy plans

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Considering the HDS%, the VMAT technique appeared to offer significantly better plans than the DCAT plans in all but the large target volume group, in which a P = 0.068 was very close to the significance level [Table 3]. However, conversely, the DCAT plans offered significantly smaller MUs and beam-on times than the VMAT plans [Table 2]. When all 28 patients were considered, the DCAT technique offered plans with 25.1% (P < 0.001) lower MU and 19.9% (P < 0.001) lower beam-on times than the VMAT technique. More importantly, we observed that the difference between the two techniques was becoming more prominent with increments in target volumes: the MU and beam-on time difference increased to 42.7% and 28.6% in the large target volume groups, respectively.
Table 3: High-dose spillage (%), monitor units, beam-on time results in dynamic conformal arc therapy and volumetric modulated arc therapy plans

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The results of the 3D gamma analysis of VMAT and DCAT plans obtained with the DVH-based Compass software are as shown in [Table 4]. The gamma analyses of all 56 plans exhibited a ≥90% pass for all criteria except for 1% DD-1-mm DTA. Better results were obtained in the DCAT technique because of the sharper dose gradients in the VMAT technique [Table 4]. We observed that the DCAT plans were more applicable according to 3% DD-1-mm DTA criteria. The percentage difference of PTVD1 dose in MC and Compass-collapse cone (CC) was 6.71% ± 2.87% with DCAT and 5.60% ± 3.16% with VMAT (P = 0.016), irrespective of the plus and minus directions. The percentage difference of PTVmean dose in Monaco-MC and Compass-CC was 5.02% ± 2.67% with DCAT and 5.60% ± 3.16% with VMAT (P = 0.009). The percentage difference of PTVD99 dose in Monaco-MC and Compass-CC was 3.16% ± 2.49% with DCAT and 4.50% ± 2.89% with VMAT (P = 0.186). [Figure 1], [Figure 2], [Figure 3] exhibit the respective differences between the PTVD1, PTVmean, and PTVD99 doses in Monaco and Compass TPSs. [Figure 4] shows the gamma analysis of the two dose distributions observed with the Compass TPS and the Dolphin measurements.
Table 4: Three-dimensional gamma index results of volumetric modulated arc therapy and dynamic conformal arc therapy plans

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Figure 1: Percentage difference of planning target volume D1 dose in Monaco- and Compass treatment planning system calculations

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Figure 2: Percentage difference of planning target volume mean dose in Monaco- and Compass treatment planning system calculations

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Figure 3: Percentage difference of planning target volume D99 dose in Monaco- and Compass treatment planning system calculations

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Figure 4: Comparison of dose distributions at Compass treatment planning system

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We also performed DVH-based plan QA analyses of the mean and V6 and V12 doses of the brain [Table 5]. The dose distributions calculated by the MC algorithm in Monaco TPS, by the CC algorithm in Compass TPS, and the measured fluence by the Dolphin detector via the CC algorithm were comparatively analyzed. The results obtained with DCAT and VMAT and Monaco TPS and Compass TPS calculations were all comparable. However, the mean brain doses and the V6 and V12 achieved with Dolphin-CC results were higher than the Monaco-MC and the Compass-CC. The V12 and V6 of the brain were higher with DCAT than the VMAT plans, probably as a result of the superior GI values obtained with the VMAT technique. According to QA results, significantly lower mean brain dose, V6, and V12 values were obtained by VMAT then the DCAT technique in all three of the Monaco-MC, Compass-CC, and Dolphin-CC, respectively [Table 5].
Table 5: Comparison of brain mean, V12, and V6 doses

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 > Discussion Top


In an effort to add to the literature, we intended to dosimetrically objectively compare the VMAT- and DCAT-based SRS/SRT plans in patients presenting with single brain metastasis. Our results revealed that VMAT was more efficient than the DCAT plans in offering altogether more conformal SRS/SRT plans with steeper dose falloff beyond the target volumes. Nevertheless, these vital advantages were achieved at the cost of higher MU and directly associated longer beam-on times, suggesting the determination of the choice of treatment as per patient basis with regard to the lesion location and the general health status of the patient, which may impact the tolerability of longer treatment durations.

Several techniques can be efficiently utilized for the LINAC-based intracranial SRS/SRT applications for patients presenting with intracranial benign or malignant tumors including the brain metastases: the historical arc-based use of circular collimators, or more recent static beams, conformal arc therapy, dynamic conformal arc therapy, IMRT, and VMAT techniques.[20],[21],[22],[23] As a result of the notable innovations in the MLC structure and speed, and TPS technologies, currently, it is more permissive than ever to generate more homogeneous and conformal SRS/SRT plans with improved PTV coverage and maximum avoidance of the neighboring healthy tissues in LINAC devices.[20],[24] Nevertheless, it is imperative to objectively compare different modern techniques in terms of plan quality indices and QAs to determine the SRS/SRT treatment plans with the highest conformity and lowest treatment durations which will clinically translate into lower treatment-related severe late toxicities with sequent better long-term quality of life measures and patient convenience during the treatment sessions. Therefore, our present dosimetric study represents such an effort comparing the intensity-modulated VMAT and segment shape-optimized DCAT field-based SRS/SRT plans to define the best-fit technique for patients presenting with brain metastasis.

A significant finding of the present dosimetric investigation was the exhibition of fundamentally superior CI (P < 0.001) and GI (P < 0.001) values with VMAT than the DCAT-based SRS/SRT plans for brain metastases, which even become more prominent in relatively larger target volumes [Table 2]. These remarkable discoveries reasonably infer that it is more probable to achieve more conformal dose distributions with accompanying lower doses (steeper dose falloff) beyond the target volumes by means of VMAT than the DCAT SRS/SRT plans. The CI represents an objective dosimetric measure of how well the prescribed SRS/SRT dose fits in with the target volume. Notwithstanding, the lower but yet significant doses unavoidably cover notable amounts of normal tissue beyond the prescription isodose volume: the major source of most late severe normal tissue complications, such as brain necrosis. Therefore, considering the severe toxicity risk after the SRS/SRT, the GI which is a reliable measure of dose falloff beyond the target volume is of equivalent significance as the CI for any given isocenter configuration. In this respect, regardless of the SRS/SRT technique, our outcomes seem to land additional support on the published findings of Paddick and Lippitz, which emphatically recommended the use of the GI in conjunction with the traditional CI to achieve the best conformal SRS/SRT plan with the steepest dose falloff past the target volume.[13] In addition, lower results were obtained with VMAT at V12 and V6 doses in the brain [Table 5]. Therefore, VMAT technique is more advantageous for radionecrosis.[25],[26],[27]

The intricate relationship between the CI, HI, and GI and their direct influences on the clinical results have been previously investigated. In the study by Balagamwala et al.,[28] the authors examined the possible link between the CI, HI, and GI in patients undergoing SRS for meningiomas and displayed that a high GI was related to a lower HI value which implies that more homogenous SRS plans resulted in more gradual dose falloff beyond the target volume. The authors further marked that higher HI was associated with the development of dizziness, whereas a lower GI was associated with motor deficits and auditory changes. Scientifically basing on these results, the researchers recommended that the ideal CI, HI, and GI for such patients were ≤2.0, ≤2.0, and ≤3.0, separately. In another study, Dellaretti et al. compared the IMRT and DCAT plans for intracranial SRS in terms of the CI, HI, GI, and critical structure doses in 21 patients with benign tumors.[20] Even though the GI was comparable between the two procedures, the investigators enthusiastically recommended the preferred use of VMAT for intracranial benign tumors which are close to critical structures, as they got essentially superior HI and CI values with VMAT. In the same manner, our present outcomes additionally exhibited the plausibility of accomplishing fundamentally superior CI, GI, HDS%, and mean, V6, and V12 brain doses with VMAT than the DCAT plans, with hypothetically decreased severe toxicity risks.

Since the SRS/SRT is a viable yet remarkably time-consuming treatment strategy, the total irradiation duration is a parameter to be kept as low as feasible for the comfort of the treated patient and the prosperity of the treatment sites, especially for the vigorously stacked radiation oncology facilities. Furthermore, without any doubt, not only the tolerability of the treatment is remarkably lower in patients with poor general health status, but also the risk for intrafractional motion also increases with longer treatment times. The latter can become critical in treating the tumors close to the critical OAR, such as the brainstem or optic chiasm/nerves, or re-irradiation instances. In this respect, similar to the others, we demonstrated that the DCAT plans offered 25.1% (P < 0.001) lower MU and 19.9% (P < 0.001) shorter beam-on times compared to the VMAT procedure, which appeared to be even more profound in large target volumes: 42.7% for the MU and 28.6% for the beam-on times, respectively. Molinier et al. also compared the coplanar VMAT and coplanar DCAT with noncoplanar VMAT and noncoplanar DCAT SRS plans created for intracranial lesions.[29] The authors reported the lowest MU esteems with DCAT for single intracranial lesions, where the MU was 34.5% lower with the noncoplanar DCAT than noncoplanar VMAT. On that account, due to the ability of the noncoplanar DCAT to provide a profoundly conformal and homogenous plan with an accompanying better sparing of the healthy brain tissue, the authors recommended the noncoplanar DCAT as the planning method to be preferred for single brain lesions. However, we reasonably believe that the lower MU and shorter beam-on times ought to not be considered as the ultimate goals for any SRS/SRT circumstances and other plan quality indices such as the CI, HI, and GI ought to be also respected while deciding the best-fit treatment plans for the management of intracranial lesions.

Since small fields are used in SRS/SRT treatments, both the accuracy of the measurement systems and the small field uncertainties have a very important role in the treatment verification. Therefore, 3D gamma index and DVH-based QA analysis were performed. Better results were obtained in the DCAT technique because of the sharper dose gradients and smaller segments in the VMAT technique [Table 4]. Although the small-field dosimetry has uncertainty, similar results were found in the Compass-CC, Monaco-MC calculations, and Dolphin-CC measurements comparison.

Formerly, analogous to our analyses, Nakaguchi et al. performed 3D dose reconstruction (Compass) and new transmission detector (Dolphin) analysis in SBRT treatments and asserted the admirable precision of the Compass with Dolphin for SBRT using MLC test patterns and clinical SBRT cases.[18] The authors, moreover, objectively compared the results between the Compass, the TPS, the Kodak EDR2 film, and the MC calculations. For MLC test patterns, the diversity between the Compass and MC were assuredly found to be around 3%. The researchers reported that the Compass with the Dolphin system showed sufficient resolution in SBRT and Compass also exhibited great concurrency with the MC framework. Based on these harmonious results, it was proposed that the Compass was able to accurately detect subtle variations for the dose profile and DVH for clinical applications. This study is notable for the fact that the feasibility of SBRT QA by utilizing the Compass system with Dolphin was established. In this respect, our current results appear to strengthen Nakaguchi et al.'s published findings at another tumor site, namely for the single brain metastasis treated with SRS.


 > Conclusions Top


The results of our dosimetric study convincingly demonstrated that the VMAT was adequately equipped for offering altogether more conformal SRS/SRT plans with steeper dose falloff beyond the target volumes, in spite of the fact that the MU and associated beam-on times were higher with VMAT than the DCAT plans. However, lower MU and shorter beam-on times ought to not be considered as the definitive criteria in the proper management of intracranial lesions with SRS/SRT; thus, other plan quality indices such as the CI, GI, HI, and HDS% ought to be carefully respected for choosing the ideal SRS/SRT plan as per patient basis.

Data sharing statement

Data cannot be shared publicly because the data are owned and saved by Yeni Yuzyil University Gaziosmanpasa Hospital. Data are available from the Yeni Yuzyil University Gaziosmanpasa Hospital Institutional Data Access/Ethics Committee (contact via Yeni Yuzyil University for researchers who meet the criteria for access to confidential data: contact address, [email protected]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 > References Top

1.
Saenz DL, Li Y, Rasmussen K, Stathakis S, Pappas E, Papanikolaou N. Dosimetric and localization accuracy of Elekta high definition dynamic radiosurgery. Phys Med 2018;54:146-51.  Back to cited text no. 1
    
2.
Leksell L. The stereotaxic method and radiosurgery of the brain. Acta Chir Scand 1951;102:316-9.  Back to cited text no. 2
    
3.
Tas B, Durmus IF, Okumus A, Uzel OE. Correlation between heterogeneity index (HI) and gradient index (GI) for high dose stereotactic radiotherapy/radiosurgery (SRT/SRS). AIP Conf Proc 2017;1815:1. doi.org/10.1063/1.4976462.  Back to cited text no. 3
    
4.
Ballangrud A, Kuo LC, Happersett L, Lim SB, Beal K, Yamada Y, et al. Institutionalexperience with SRS VMAT planning for multiple cranial metastases. J Appl Clin Med Phys 2018;19:176-83.  Back to cited text no. 4
    
5.
Dimitriadis A, Palmer AL, Thomas RAS, Nisbet A, Clark CH. Adaptation and validation of a commercial head phantom for cranial radiosurgery dosimetry end-to-end audit. Br J Radiol. 2017 Jun;90(1074):20170053.doi:10.1259/bjr.20170053.  Back to cited text no. 5
    
6.
Ong CL, Verbakel WF, Cuijpers JP, Slotman BJ, Lagerwaard FJ, Senan S. Stereotactic radiotherapy for peripheral lung tumors: A comparison of volumetric modulated arc therapy with 3 other delivery techniques. Radiother Oncol 2010;97:437-42.  Back to cited text no. 6
    
7.
Thaper D, Kamal R, Singh G, Oinam AS, Yadav HP, Kumar R, et al. Dosimetric comparison of dynamic conformal arc integrated with segment shape optimization and variable dose rate versus volumetric modulated arc therapy for liver SBRT. Rep Pract Oncol Radiother 2020;25:667-77.  Back to cited text no. 7
    
8.
Tas B, Durmus IF. Dose verification with different ion chambers for FFF energy plans. Int J Eng Sci 2018;7:66-9.  Back to cited text no. 8
    
9.
Low DA, Harms WB, Mutic S, Purdy JA. A technique for the quantitative evaluation of dose distributions. Med Phys 1998;25:656-61.  Back to cited text no. 9
    
10.
Low DA, Dempsey JF. Evaluation of the gamma dose distribution comparison method. Med Phys 2003;30:2455-64.  Back to cited text no. 10
    
11.
Paddick I. A simple scoring ratio to index the conformity of radiosurgical treatment plans. J Neurosurg 2000;93 Suppl 3:219-22.  Back to cited text no. 11
    
12.
van't Riet A, Mak AC, Moerland MA, Elders LH, van der Zee W. A conformation number to quantify the degree of conformality in brachytherapy and external beam irradiation: Application to the prostate. Int J Radiat Oncol Biol Phys 1997;37:731-6.  Back to cited text no. 12
    
13.
Paddick I, Lippitz B. A simple dose gradient measurement tool to complement the conformity index. J Neurosurg 2006;105 Suppl: 194-201.  Back to cited text no. 13
    
14.
Shaw E, Kline R, Gillin M, Souhami L, Hirschfeld A, Dinapoli R, et al. Radiation Therapy Oncology Group: Radiosurgery quality assurance guidelines. Int J Radiat Oncol Biol Phys 1993;27:1231-9.  Back to cited text no. 14
    
15.
Bezjak A, Paulus R, Gaspar LE, Timmerman RD, Straube WL, Ryan WF, et al. Safety and Efficacy of a Five-Fraction Stereotactic Body Radiotherapy Schedule for Centrally Located Non-Small-Cell Lung Cancer: NRG Oncology/RTOG 0813 Trial. J Clin Oncol. 2019 May 20;37:1316-25. doi: 10.1200/JCO.18.00622.  Back to cited text no. 15
    
16.
Videtic GM, Paulus R, Singh AK, Chang JY, Parker W, Olivier KR, et al. Long-term follow-up on NRG oncology RTOG 0915 (NCCTG N0927): A randomized phase 2 study comparing 2 stereotactic body radiation therapy schedules for medically inoperable patients with stage I peripheral non-small cell lung cancer. Int J Radiat Oncol Biol Phys 2019;103:1077–84.  Back to cited text no. 16
    
17.
Ahnesjö A. Collapsed cone convolution of radiant energy for photon dose calculation in heterogeneous media. Med Phys 1989;16:577-91.  Back to cited text no. 17
    
18.
Nakaguchi Y, Ono T, Maruyama M, Shimohigashi Y, Kai Y. Validation of a method for in vivo 3D dose reconstruction in SBRT using a new transmission detector. J Appl Clin Med Phys 2017;18:69-75.  Back to cited text no. 18
    
19.
Conover WJ. On methods of handling ties in the Wilcoxon signed-rank test. J Am Stat Assoc 1973:68:985-8.  Back to cited text no. 19
    
20.
Dellaretti M, Barbosa Pereira JL, Tagawa E, Pedrini M. Stereotacticradiosurgery of intracranial tumors: A comparison of intensity-modulated radiosurgery and dynamic conformational arc. J Radiosurg SBRT 2012;1:273-80.  Back to cited text no. 20
    
21.
Baumert BG, Norton IA, Davis JB. Intensity-modulated stereotactic radiotherapy vs. stereotactic conformal radiotherapy for the treatment of meningioma located predominantly in the skull base. Int J Radiat Oncol Biol Phys 2003;57:580-92.  Back to cited text no. 21
    
22.
Bourland JD, McCollough KP. Static field conformal stereotactic radiosurgery: Physical techniques. Int J Radiat Oncol Biol Phys 1994;28:471-9.  Back to cited text no. 22
    
23.
Ding M, Newman F, Kavanagh BD, Stuhr K, Johnson TK, Gaspar LE. Comparative dosimetric study of three-dimensional conformal. Dynamic conformal arc, and intensity modulated radiotherapy for brain treatment using Novalis system. Int J Radiot Oncol Biol Phys 2006;66:S82-6.  Back to cited text no. 23
    
24.
Perks JR, St George EJ, El Hamri K, Blackburn P, Plowman PN. Stereotactic radiosurgery XVI: Isodosimetric comparison of photon stereotactic radiosurgery techniques (gamma knife vs micro multileaf collimator linear accelerator) for acoustic neuroma – And potential clinical importance. Int J Radiat Oncol Phys 2003;57:1450-9.  Back to cited text no. 24
    
25.
Korytko T, Radivoyevitch T, Colussi V, Wessels BW, Pillai K, Maciunas RJ, et al. 12 Gy Gamma Knife radiosurgical volume is a predictor for radiation necrosis in non-AVM intracranial tumors. Int J Radiat Oncol Biol Phys 2006;64:419-24.  Back to cited text no. 25
    
26.
Minniti G, Clarke E, Lanzetta G, Osti MF, Guido T, Bozzao A, et al. Stereotactic radiosurgery for brain metastases: Analysis of outcome and risk of brain radio-necrosis. Radiat Oncol 2011;6:48.  Back to cited text no. 26
    
27.
Potrebko PS, Keller A, All S, Sejpal S, Pepe J, Saigal K, et al. GammaKnife versus VMAT radiosurgery plan quality for many brain metastases. J Appl Clin Med Phys 2018;19:159-65.  Back to cited text no. 27
    
28.
Balagamwala EH, Suh JH, Barnett GH, Khan MK, Neyman G, Cai RS, et al. The importance of the conformality, heterogeneity, and gradient indices in evaluating Gamma Knife radiosurgery treatment plans for intracranial meningiomas. Int J Radiat Oncol Biol Phys 2012;83:1406-13.  Back to cited text no. 28
    
29.
Molinier J, Kerr C, Simeon S, Ailleres N, Charissoux M, Azria D, et al. Comparison of volumetric-modulated arc therapy and dynamic conformal arc treatment planning for cranial stereotactic radiosurgery. J Appl Clin Med Phys 2016;17:92-101.  Back to cited text no. 29
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

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