Dose response of irradiated XRCT radiochromic film

Gafchromic XRCT radiochromic film is a self developing high sensitivity radiochromic film product which can be used for assessment of delivered radiation doses which could match applications such as Computed Tomography (CT) dosimetry. The dose response of Gafchromic XRCT radiochromic film has been measured with reflectance spectrophotometry and desktop scanners. The film automatically changes colour upon irradiation, changing from a yellow to a green/brown colour. Results show a high sensitivity to delivered dose compared to other conventional radiochromic films which is well suited to CT applications where lower applied doses are delivered. Sensitivity is found for this film with a 1cGy applied dose, producing an approximate net optical density change of 0.3 at 636nm and 0.2 net OD using broad band white light. This high sensitivity combined with its relatively energy independent nature around the 100kVp to 150kVp x-ray energy range provides a unique enhancement in dosimetric measurement capabilities over currently available dosimetry films for CT applications

Practical IMRT QA dosimetry using Gafchromic film: a quick start guide

This work outlines a method for using Gafchromic film for dosimetry purposes, by scanning it with currently available commercial scanners. The scanners used were: Epson V800, Epson V700, Epson V37 series, specifically a V370 and a Canon multi-function office printer/scanner. The Epson scanners have 16 bit RGB resolution, the Canon has 8 bit RGB (Red Green Blue) resolution, and the V800 and V700 allow scanning in transmission mode. The V700 uses an Epson White Cold Cathode Florescent Lamp; the recently released V800 uses an Epson light emitting diode (LED) light source, while the V37 series uses a reflective mode and the Epson LED light source. The Epson V37 series scanners are designed for non-professional use so the cost has been kept at a low entry level point, so they would be a suitable option for a department wanting to use Gafchromic film or with limited needs that did not justify a more sophisticated and expensive unit. Note that the V800 or V700 scanners are not expensive in context, costing approximately the same as a 25 sheet box of Gafchromic film. The Canon was included to demonstrate that a scanner with 8 bit RGB resolution can be used for dosimetry. These general multi-function units are available in most departments, and they would allow Gafchromic film to be evaluated as a dosimetry tool without a significant investment. Furthermore, they are generally capable of scanning large format film (425 x 350 mm) in one part. Although this is not necessary for dosimetry, it is often useful for machine QA, where dividing the film into two parts to ensure accurate measurements is not practical. Moreover, this analytical method uses software that is freely or commonly available, particularly the image processing package ImageJ. Note ImageJ v1.48 was the version used. The results demonstrate that this method used with the scanners evaluated is a practical method of using Gafchromic film as a dosimeter for IMRT QA

Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures

Purpose: The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures. Methods: The calibration and reproducibility of the MOSkin detector and its dependency on different radiation beam qualities were carried out using RQR standard radiation qualities in free-in-air geometry. Studies of the other characterization parameters, such as the dose linearity and dependency on exposure angle, field size, frame rate, depth-dose, and source-to-surface distance (SSD), were carried out using a solid water phantom under a clinical x-ray unit. Results: The MOSkin detector showed good reproducibility (94%) and dose linearity (99%) for the dose range of 2 to 213 cGy. The sensitivity did not significantly change with the variation of SSD (±1%), field size (±1%), frame rate (±3%), or beam energy (±5%). The detector angular dependence was within ±5% over 360◦ and the dose recorded by the MOSkin detector in different depths of a solid water phantom was in good agreement with the Markus parallel plate ionization chamber to within ±3%. Conclusions: The MOSkin detector proved to be reliable when exposed to different field sizes, SSDs, depths in solid water, dose rates, frame rates, and radiation incident angles within a clinical x-ray beam. The MOSkin detector with water equivalent depth equal to 0.07 mm is a suitable detector for in vivo skin dosimetry during interventional radiology procedures

A comparison of entrance skin dose delivered by clinical angiographic c-arms using the real-time dosimeter: the MOSkin

Coronary angiography is a procedure used in the diagnosis and intervention of coronary heart disease. The procedure is often considered one of the highest dose diagnostic procedures in clinical use. Despite this, there is minimal use of dosimeters within angiographic catheterisation laboratories due to challenges resulting from their implementation. The aim of this study was to compare entrance dose delivery across locally commissioned c-arms to assess the need for real-time dosimetry solutions during angiographic procedures. The secondary aim of this study was to establish a calibration method for the MOSkin dosimeter that accurately produces entrance dose values from the clinically sampled beam qualities and energies. The MOSkin is a real-time dosimeter used to measure the skin dose delivered by external radiation beams. The suitability of the MOSkin for measurements in the angiographic catheterisation laboratory was assessed. Measurements were performed using a 30 × 30 × 30 cm3 PMMA phantom positioned at the rotational isocenter of the c-arm gantry. The MOSkin calibration factor was established through comparison of the MOSkin response to EBT2 film response. Irradiation of the dosimeters was performed using several clinical beam qualities ranging in energy from 70 to 105 kVp. A total of four different interventional c-arm machines were surveyed and compared using the MOSkin dosimeter. The phantom was irradiated from a normal angle of incidence using clinically relevant protocols, field sizes and source to image detector distance values. The MOSkin was observed to be radiotranslucent to the c-arm beam in all clinical environments. The MOSkin response was reproducible to within 2 % of the average value across repeated measurements for each beam setting. There were large variations in entrance dose delivery to the phantom between the different c-arm machines with the highest observed cine-acquisition entrance dose rate measuring 326 % higher than the lowest measured cine-acquisition entrance dose rate and with the highest measured fluoroscopic entrance dose rate measuring 346 % higher than the lowest measured fluoroscopic entrance dose rate. This comparison of entrance dose delivery across local clinical c-arms demonstrated the disparity in entrance dose delivery across catheterisation laboratories and outlined a need for real-time dose monitoring systems for patients during angiographic procedures. Through use of our calibration method, an average MOSkin calibration of 7.37 mV/cGy was established. The calibration method allowed entrance dose to be measured across a range of beam energies and beam qualities without the input of the c-arm beam characteristics. This calibration factor was proven to reproduce entrance dose values to within 5 % value of the reference dosimeter’s response, suggesting potential for further studies and utilisation of the dosimeter in this field

Characterization of XR-RV3 GafChromic® films in standard laboratory and clinical conditions and means to evaluate uncertainties and reduce errors

Artikkelissa tutkitaan GafChromic-filmin käyttökelposuutta ja ominaisuuksia potilaan ihoannoksen määrittämiseen toimenpideradiologiassa ja –kardiologiassa. Perinteisesti filmiannosmittauksiin on liitetty suuri annoksen epävarmuus, ja tässä työssä on tutkittu merkittävimpiä epävarmuuden lähteitä ja kuinka niitä voidaan pienentää. Lopputuloksena todetaan, että filmiä käyttäen potilaan ihoannos voidaan määrittää noin 10 % epävarmuudella. Mikäli mittauksiin ja filmin lukuun kiinnitetään erityistä huomiota, saadaan epävarmuus tätäkin pienemmäksi, noin 5 prosenttiin. Täten filmimittausten tarkkuus riittää hyvin toimenpideradiologian ja –kardiologian ihoannosmittauksiin