A novel approach for superficial intraoperative radiotherapy (IORT) using a 50 kV X‐ray source: a technical and case report

Abstract

The use of IORT as a treatment modality for patients with close or positive margins has increased over the past decade. For situations where a flat area (up to 6 cm in diameter) has to be treated intraoperatively, new applicators for superficial treatment with a miniature X‐ray source (INTRABEAM system) were developed. Here we report our evaluation of the dosimetric characteristics of these new applicators and their first clinical use. Each of these flat and surface applicators consists of a radiation protective metal tube and a flattening filter, which converts the spherical dose distribution of the X‐ray source into a flat one. The homogeneity of each dose distribution and depth‐dose measurements were evaluated using film dosimetry in a solid water phantom and a soft X‐ray ionization chamber in a water tank. The first patient was treated with 5 Gy delivered in 5 mm using a 4 cm FLAT applicator over 21 minutes. The flat applicators show the maximum homogeneity, with a uniformity ratio of 1.02‐1.08 in certain depths. In 1 mm depth surface applicators show a uniformity ratio of 1.15‐1.28. They also show a higher dose rate and a steeper dose gradient compared to the flat applicators. The results of this investigation demonstrated that the flat and surface applicators have unique dosimetric characteristics that need to be considered during the treatment planning stages. This work also showed that it is possible to perform a superficial localized IORT which provides new application possibilities for use of the INTRABEAM system.PACS number: 87.55.ne

Comparison and uncertainty evaluation of different calibration protocols and ionization chambers for low‐energy surface brachytherapy dosimetry

“…A high dose rate (HDR) surface electronic brachytherapy (EBT) device, which is in fact an x-ray generator with specific applicators that collimate the beam, offers an alternative solution to external beam electron radiotherapy and HDR radionuclide-based brachytherapy. Currently, there are three EBT systems, used clinically with applicators, specifically designed for surface treatments: the 50 kVp Xoft Axxent ® (iCad, San Jose, CA) with a 1.0, 2.0, 3.5, and 5.0 cm diameter applicators, [5][6][7] the 50 kVp Zeiss INTRABEAM ® (Carl Zeiss Surgical Gmbh, Oberkochen, Germany), with 1-6 cm diameter applicators, 8,9 and the 69.5 kVp Esteya ® (Elekta Brachytherapy, Veenendaal, The Netherlands) with 1.0, 1.5, 2.0, 2.5, and 3.0 cm diameter applicators. 3,10 Low-energy (<100 kVp) x-ray beams present several dosimetric challenges that need to be addressed.…”

The Dosimetric Characteristics and Potential Limitation in Clinical Application of a Low Energy Photon Intra-Operative Radiotherapy System

“…Water tank/ionization chamber has the highest accuracyamong those instruments [13]. Schneider et al have compared homogeneity of each dose distribution and depth-dose measurements for flat and surface applicators using film dosimetry in a solid water phantomand a soft X-ray ionization chamber in a water tank [10]. One of the important factors influencing the accuracy of the measurement is the relative position error of X-ray source to ionization chamber due to sharp attenuation of low energy X-ray in the water.…”

“…Dose measurement tools used for INTRABEAM system include water tank/ionization chamber [10] [11], film/ solid water phantom [11], Thermo-luminescence [12], etc. Water tank/ionization chamber has the highest accuracyamong those instruments [13].…”

Electronic brachytherapy—current status and future directions

“…11 Solid spherical applicators were developed to deliver intraoperative radiotherapy (IORT) to the tumour bed for breast cancer, as described below. Further applicators have been designed for gynaecological, skin and kyphoplasty treatments, 12,19,20 but only a few clinical results have been reported. 21,22 The Xoft® Axxent® system (iCAD Inc., Nashua, NH) is a miniature X-ray tube integrated with a cooling sheath into a multilumen catheter, first released in 2006 (Figure 1b).…”