A dosimetric analysis of volumetric-modulated arc radiotherapy with jaw width restriction<i>vs</i>7 field intensity-modulated radiotherapy for definitive treatment of cervical cancer

The aim of this study was to find optimal planning approach for large planning targets with complicated geometry requiring wide field openings. The study presents a novel approach for arc geometry design for pelvic targets with extensive nodal involvement. A total of 15 patients with anorectal carcinoma or vulvar cancer were selected retrospectively. For each patient, one seven‐field IMRT plan and three VMAT plans were calculated: one with two 360° arcs with no limitations for the field size (VMATw); one with two asymmetrically field‐size‐restricted 360° arcs (VMATr); and the proposed novel approach which consisted of one 360° arc with the field size restricted to the central PTV, and another arc divided into two 180° arcs, restricting the field sizes with the focus on the lymph nodes. The techniques were compared in terms of PTV coverage false(normalVPTVfalse(95%false)false), dose maximum (D(max)), dose conformity index (CI), homogeneity index (HI), and organs at risk doses. The proposed novel approach with one full and two half arcs tended to have better PTV coverage (normalVPTVfalse(95%false)=97%±2%, compared to 95%±3%,95%±3%, and 97%±2% in VMATw, VMATr, and 7f‐IMRT, respectively) and lower maxima (Dfalse(maxfalse)=107%±1%, compared to 110%±3%,110%±4%, and 110%±4% in VMATw, VMATr, and 7f‐IMRT, respectively); and lower or equal organs at risk doses. The superiority of the proposed technique false(CI=1.16±0.05,HI=9±2false) was more pronounced compared with the VMATw plans (CI=1.41±0.10, paired t‐test p<0.001;HI=12±2,p<0.001), but the proposed technique was slightly better also in comparison with the VMATr plans false(CI=1.21±0.07,p<0.001;HI=11±4,p=0.015false) and 7f‐IMRT plans false(CI=1.18±0.03,p=0.016;HI=10±2,p=0.215false). Radiotherapy treatment planning for large and complicated treatment volumes benefits not only from restricting the field size but also from careful field design that considers PTV geometry. This optimizes multileaf collimator movements, leading to better dose conformity and homogeneity.PACS number(s): 87.53.Jw, 87.55.D, 87.56.jk:

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A novel arc geometry setting for pelvic radiotherapy with extensive nodal involvement

Rossi

Boman

Skyttä

et al. 2016

Fully automated searching for the optimal VMAT jaw settings based on Eclipse Scripting Application Programming Interface (ESAPI) and RapidPlan knowledge‐based planning

Huang

Yue

Wang

et al. 2018

PurposeEclipse treatment planning system has not been able to optimize the jaw positions for Volumetric Modulated Arc Therapy (VMAT). The arbitrary and planner‐dependent jaw placements define the maximum field size within which multi‐leaf‐collimator (MLC) sequences can be optimized to modulate the beam. Considering the mechanical constraints of MLC transitional speed and range, suboptimal X jaw settings may impede the optimization or undermine the deliverability. This work searches optimal VMAT jaw settings automatically based on Eclipse Scripting Application Programming Interface (ESAPI) and RapidPlan knowledge‐based planning.Methods and materialsUsing an ESAPI script, the X jaws of rectal VMAT plans were initially set to conform the planning‐target‐volume (PTV), and were gradually extended toward the isocenter (PTV center) in 5–7 mm increments. Using these jaw pairs, 592 plans were automatically created for 10 patients and quantitatively evaluated using a comprehensive scoring function. A published RapidPlan model was evoked by ESAPI to generate patient‐specific optimization objectives without manual intervention. All candidate plans were first stored as text files to save storage space, and only the best, worst, and conformal plans were consequently recreated for comparison.ResultsAlthough RapidPlan estimates dose‐volume histogram (DVH) based on individual anatomy, the geometry‐based expected dose (GED) algorithm does not recognize different jaw settings but uses PTV‐conformal jaws as default; hence, identical DVHs were observed regardless of planner‐defined jaws. Therefore, ESAPI finalized dose‐volume calculation and eliminated the plans with unacceptable hotspots before comparison. The plan quality varied dramatically with different jaw settings. Trade‐offs among different organs‐at‐risk (OARs) were collectively considered by the proposed scoring method, which identified the best and worst plans correctly. The plans using conformal jaws were neither the best nor the worst of all candidates.Conclusions VMAT plans using optimal jaw locations can be created automatically using ESAPI and RapidPlan. Conformal jaws are not the optimal choice.

Plan quality and treatment efficiency assurance of two VMAT optimization for cervical cancer radiotherapy

Huang,

Mai,

Liu

et al. 2023

To investigate the difference of the fluence map optimization (FMO) and Stochastic platform optimization (SPO) algorithm in a newly‐introduced treatment planning system (TPS). Methods: 34 cervical cancer patients with definitive radiation were retrospectively analyzed. Each patient has four plans: FMO with fixed jaw plans (FMO‐FJ) and no fixed jaw plans (FMO‐NFJ); SPO with fixed jaw plans (SPO‐FJ) and no fixed jaw plans (SPO‐NFJ). Dosimetric parameters, Modulation Complexity Score (MCS), Gamma Pass Rate (GPR) and delivery time were analyzed among the four plans. Results: For target coverage, SPO‐FJ plans are the best ones (P ≤ 0.00). FMO plans are better than SPO‐NFJ plans (P ≤ 0.00). For OARs sparing, SPO‐FJ plans are better than FMO plans for mostly OARs (P ≤ 0.04). Additionally, SPO‐FJ plans are better than SPO‐NFJ plans (P ≤ 0.02), except for rectum V45Gy. Compared to SPO‐NFJ plans, the FMO plans delivered less dose to bladder, rectum, colon V40Gy and pelvic bone V40Gy (P ≤ 0.04). Meanwhile, the SPO‐NFJ plans showed superiority in MU, delivery time, MCS and GPR in all plans. In terms of delivery time and MCS, the SPO‐FJ plans are better than FMO plans. FMO‐FJ plans are better than FMO‐NFJ plans in delivery efficiency. MCSs are strongly correlated with PCTV length, which are negatively with PCTV length (P ≤ 0.03). The delivery time and MUs of the four plans are strongly correlated (P ≤ 0.02). Comparing plans with fixed or no fixed jaw in two algorithms, no difference was found in FMO plans in target coverage and minor difference in Kidney_L Dmean, Mu and delivery time between PCTV width≤15.5 cm group and >15.5 cm group. For SPO plans, SPO‐FJ plans showed more superiority in target coverage and OARs sparing than the SPO‐NFJ plans in the two groups. Conclusions: SPO‐FJ plans showed superiority in target coverage and OARs sparing, as well as higher delivery efficiency in the four plans.