Real-time radio-transparent dosimeter for X-ray imaging system
Introduction
The use of X-ray radioscopy devices allows the physician to simplify the surgery in some cases. During the intervention, the surgeon introduces small instruments in the patient body using a catheter and performs the therapeutic work with the aid of a real-time movie produced by an X-ray detector. The movie is made up of images obtained with short X-ray pulses of few milliseconds. The image rate, usually equal to 25 images/s, is high enough to ensure a visual comfort. The voltage and the current of the X-ray tube are automatically calculated by the device based on the intervention type and the patient corpulence in order to optimize the image contrast. The main disadvantage of this procedure is the high dose delivered by the X-ray tube to the patient during the intervention time. Skin diseases leading to tumors can be the consequences of an extreme exposition of the patient to X-ray (few Grays). In order to reduce the dose absorbed by the patient, the use of a dosimeter is needed during the surgical intervention. However, there are no available commercial devices matching to the constraints of the surgery which are real time information, radio-transparency and large sensitive surface. The dosimeter presented in this paper allows the physician to measure in real time the dose absorbed by the patient skin on the whole surface potentially exposed. In the case where the dose reaches a dangerous defined threshold, the surgeon can change the angular view of the radioscopy device in order to distribute the global dose on a larger surface. A file is created providing the dose history of the patient and allowing the physician to follow the eventual consequences. This file can also provide elements in the case of lawsuit between the patient and his surgeon. This paper presents the development of the dosimeter and the first results obtained.
Section snippets
Material and methods
The sensitive part of the dosimeter is based on a thin detector placed between the patient and the X-ray tube at the skin level. The detector is transparent to the X-ray and introduced no artifact in the radioscopy image. The surface is large enough to cover the body part potentially exposed to the X-ray. A typical skin surface exposed is about . The dose measured by the dosimeter is similar to the dose absorbed by the skin which is the most relevant in this context. A
Results and discussion
The dosimeter has been tested with a radioscopy device where it was possible to set manually the X-ray tube parameters. Fig. 4 shows a very good linearity between the counting rate and the beam intensity. The measurement has been done by only changing the X-ray tube current keeping the voltage at . The expected behavior is observed when the X-ray tube voltage is changed keeping the current at (Fig. 5). A comparative measurement has been done with an ionization chamber reference
Conclusions
The realization of an original dosimeter for radioscopy application has been presented. An accurate measurement of the dose absorbed by the patient skin is performed in real time during the surgical interventions without any perturbation. The map of the dose is given by the software allowing the physician to monitor the exposition of the patient to the X-ray during the surgery. A study with a large number of patients is scheduled to evaluate the benefit of this dosimeter during the surgery. A
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