Early clinical experience with a degraded 4 MeV electron beam in radiotherapy of superficial basal cell carcinoma.

The most common non-melanoma skin cancer is basal cell carcinoma (BCC). Surgery is the gold standard treatment but also non-surgical alternatives are needed. The purpose of this work was to present the early clinical experiences of degraded 4 MeV electron beam as a treatment method for superficial BCC. Twelve patients underwent two weeks radiation therapy treatment with either 5 × 7 Gy or 2 × 12 Gy. There were no significant differences in treatment outcome with different fractionations or lesion locations. The degraded beam method is a safe and valid non-surgical solution for suitable patients with superficial lesions.

Modification of the 4 MeV electron beam from a linear accelerator for irradiation of small superficial skin tumors.

Uniform dose distribution with steep lateral gradient within depth range of 0-0.5 cm is crucial to be able to treat small skin lesions. The standard nominal 4 MeV electron beam from Elekta Versa HD linear accelerator was modified with degrading filter to remove the lateral scatter from treatment head and minimize the penumbra. The energy degrading method was verified based on dosimetric properties and output factors (OFs) with comparison of four types of measurement methods. The properties of degraded 4 MeV electron beam and developed electron applicators seem optimal for treating small targets near the skin surface.

Compass model-based quality assurance for stereotactic VMAT treatment plans.

PURPOSE: To use Compass as a model-based quality assurance (QA) tool for stereotactic body radiation therapy (SBRT) and stereotactic radiation therapy (SRT) volumetric modulated arc therapy (VMAT) treatment plans calculated with Eclipse treatment planning system (TPS). MATERIALS AND METHODS: Twenty clinical stereotactic VMAT SBRT and SRT treatment plans were blindly selected for evaluation. Those plans included four different treatment sites: prostate, brain, lung and body. The plans were evaluated against dose-volume histogram (DVH) parameters and 2D and 3D gamma analysis. The dose calculated with Eclipse treatment planning system (TPS) was compared to Compass calculated dose (CCD) and Compass reconstructed dose (CRD). RESULTS: The maximum differences in mean dose of planning target volume (PTV) were 2.7 ±â€¯1.0% between AAA and Acuros XB calculation algorithm TPS dose, -7.6 ±â€¯3.5% between Eclipse TPS dose and CCD dose and -5.9 ±â€¯3.7% between Eclipse TPS dose and CRD dose for both Eclipse calculation algorithms, respectively. 2D gamma analysis was not able to identify all the cases that 3D gamma analysis specified for further verification. CONCLUSIONS: Compass is suitable for QA of SBRT and SRT treatment plans. However, the QA process should include wide set of DVH-based dose parameters and 3D gamma analysis should be the preferred method when performing clinical patient QA. The results suggest that the Compass should not be used for smaller field sizes than 3 × 3 cm2 or the beam model should be adjusted separately for both small (FS ≤ 3 cm) and large (FS > 3 cm) field sizes.