The equivalent dose HT takes into account that the energy dose©in©©scabies has the probability© of a stochastic effect (cancer, leukemia©) varies with radiation. It results from©the product of the absorbed dose©and DT of the radiation characteristics© of the radiological weighting factor©WR (equal to©1 for X-rays). It is expressed in Sievert (Sv). The effective dose E takes into account the particular sensitivity© of each tissue to cancer©. It is the sum of each equivalent dose©of HT received by an organ or tissue exposed© to T multiplied by©WT, relative tissue weighting factor©: E = sum WT. HT. It is expressed in sieverts (Sv). In interventional radiology, the risk lies in the skin. The maximum dose for the skin is therefore the most robust dosimetric indicator. The others (reference point kerma, kerma surface product and copy time) are not directly (and not linearly) correlated with skin dose. However, they can be useful when PPD is not accessible and serve as a reference for physicians, for example.
The energy emitted in the form of X-rays interacts with matter (air, tissue). Kerma (Gy) represents all the energy deposited in matter. Some of this energy is absorbed, the other is transferred. The dose (Gy) represents the part absorbed by the material. It must therefore be connected to the medium in which it is measured or estimated. For radiology radiographic energies, the kerma in air and the dose in air are considered equivalent. The amplitude of the thresholds for the occurrence of deterministic effects is given as a dose range in the following table after the article by Stecker et al. Know the definition of the incoming dose and©the dose©of the product x surface. ® Their value corresponds to that of the virtual dose© equivalent which, applied uniformly throughout the body,©© would entail the same risk of stochastic effects.
By replacing all doses received from different organs or tissues with a single value, it is possible to compare different©procedures©©and add them up for equilibrium purposes. The diagnostic reference value (DRN) of an exposed examination is the 75th percentile of the dose distribution (value© exceeded©© only in 25% of cases), measured©in a group of patients or with a typical imagination: input dose or surface dose product©in conventional diagnostic radiology; © dose index tomography©©©and length of dose index in computed tomography©. The dose at the surface of the entry, also known as© the dermal dose, is the dose absorbed©at the intersection of the axis of the X-ray beam with the skin surface©of the inlet©© into the air, including scattered radiation©. It is usually©©expressed© in milligrays (mGy). This is the dose in the air at the level of the patient`s skin. Expressed in mGy, it makes it possible to quantify the maximum energy deposited at a point of the field or fields used during the intervention. This indicator is therefore by far the most robust, because it allows access to a dose for the tissue. However, it is very difficult to measure. However, this is possible through the use of radiochromic film. Most often it is estimated by a subsequent calculation.
Dose is a measurable physical quantity. It is a quantity of energy deposited in matter by ionization. She speaks in grey. In imaging, it will be easier to talk about MilliGrays (mGy). The thresholds for good radiation protection practice (including a maximum dermal dose of 3000 mGy) are empirical thresholds. They thus allow a reasonable management of the radiological risk. It is important to note that these cutaneous deterministic effects are not expected in the average population for dermal doses below 6000 mGy. However, this may not apply to patients with biological factors associated with higher radiation sensitivity. The Monte Carlo statistical method was used to estimate the uncertainty of the emissivity of grey surfaces at room temperature obtained by double-spectrum infrared radiometry. Eine große Anzahl von Simulationen wurde durchgeführt, indem ein breites Spektrum von Werten aus Parametern ausgewählt wurde, die den resultierenden Emissionsgrad direkt beeinflussen: den Emissionsgrad der Zieloberfläche, die Hintergrundtemperatur der umgebenden Oberflächen, den maximalen Fehler der Detektoren sowie die Breite und spektrale Position der Bänder der Detektoren. This is the dose, in mGy, absorbed through the skin in the middle of the field. It integrates the dose in the air with the radiation scattered via a backscatter factor.
This factor depends on the kilovoltage (FDR = 1.35 between 60 kV and 80 kV). The absorbed dose at DT is the average value of the absorbed X-ray energy divided by the mass of radioexposed©©© T-tissue. It is expressed in joules per kilogram (J.kg-1 ©©) called© gray (Gy). It makes it possible to quantify the deterministic effects (dh for the skin, burns©.) At high doses, in radiotherapy©©©for example. The explanation is simple: the dose decreases with the square of the distance (example: at 4 m it is divided by 16), while the area increases in equal proportions. The PDS is determined by the installation. Interventional radiology is a deterministic activity with radiological risk. Obviously, the American (SIR) and European (CIRSE) learned societies, as well as the High Authority for Health, have defined standards to help you implement an effective radiovigilance strategy.
We present here some elements to understand the dose indicators as well as the bases of a radiovigilance strategy in interventional radiology. Finally, we provide you with an implementation checklist that you can use in your services. External beam radiation therapy techniques©to the prostate are described©, both during irradiation of the prostate in place and after prostatectomy, including or without pelvic lymph node areas. The following points are presented©: indications for radiation, total dose and fractionation, recording of CT design images, lineation of volumes of interest (target volumes and organs at risk) and definition of© margins, planning by intensity-modulated©©© radiotherapy (IMRT) and associated©dose constraints and©finally image-guided©radiotherapy. ©©© The surface product of the kerma in air (or dose-surface product) represents the cumulative energy over the entire field. It is therefore the total amount of energy emitted by the beam (Gy.cm2); For each examination, we must be able to estimate the dose delivered.