Ανάπτυξη μεθόδου εκτίμησης της δόσης ασθενών από ακτινοσκοπικά καθοδηγούμενες επεμβατικές εξετάσεις με την εφαρμογή υπολογιστικών τεχνικών Monte Carlo
Στρατάκης, Ιωάννης Εμμ.
Aim: To investigate radiation dose and associated risks associated with fluoroscopically
guided interventional (IR) procedures.
Methods: A method for the calculation of organ and effective doses, normalized to dose–
area product (DAP), were estimated for IR procedures with use of a Monte Carlo
transport code and an adult mathematical phantom.
Exposure parameters from consecutive patients were used to determine average
examination parameters for biliary (PTB), and angioplasty interventions.
Thermoluminescent dosimeters were used in an anthropomorphic phantom to verify
Monte Carlo calculations. Radiation-induced cancer and genetic risks were estimated.
To investigate doses imparted to IR personnel scattered air-kerma dose rates were
measured for neck, waist, and gonad levels at various sites in the interventional radiology
laboratory. Dose rate values were converted to dose-area product (DAP)–normalized airkerma
values. In addition, sets of thermoluminescent dosimetry crystals were placed in
both hands of the interventional radiologist to monitor doses.
Results: The results consist of doses normalized to DAP so patient dose from any
technique and x-ray unit can be easily calculated for left and right biliary drainage and/or
stenting and for iliac and renal angioplasty procedures. The average effective dose varied
from 1.8 to 5.4 mSv depending on biliary procedure approach (left vs right access) and
procedure scheme. A maximum effective dose of 13 mSv was estimated for 30 minutes of
fluoroscopy for PTB procedures. For iliac and renal angioplasty, the average effective
dose varied from 15 to 24.5 mSv depending on procedure scheme and the sex of the
patient. A good agreement was found between Monte Carlo–calculated data and data
derived from thermoluminescent dosimetry.
Isodose maps of DAP-normalized air-kerma doses in the interventional laboratory for
projections commonly used in PTB procedures are presented. To facilitate effective dose
estimation, normalized dosimetric data at the interventional radiologist’s position are
presented for left and right access drainage procedures, metallic stent placement only, and
drainage and metallic stent placement in one-session procedures with and without undercouch
shielding. Doses to the hands of interventional radiologists are presented for left
and right transhepatic biliary access and metallic stent placement.
Conclusions: Radiation-induced cancer risk may be considerable for younger individuals
undergoing transluminal angioplasty with stent placement. Doses delivered to patients
undergoing PTB procedures are comparable to those that arise from computed
tomography protocols. Radiation-induced cancer risk may be considerable for young
patients undergoing PTB drainage and stent implantation procedures.
Body level–specific normalized air-kerma distributions from commonly used projections
in PTB procedures may be useful to accurately quantify dose, maximum workloads, and
possible radiogenic risks delivered to medical personnel working in the interventional
radiology laboratory. Normalized dose data presented will enable occupational exposure
estimation from other institutions.
Most PTA/stenting procedures can result in considerable radiation doses to the patient,
even when performed with modern fluoroscopic equipment. Even higher radiation doses
can be imparted due to multiple procedures, extended exposure times affected by the
clinical condition of the patient and the level of experience of the interventional
radiologist. Genetic risks were considered minimal. However, fatal cancer risks cannot be
neglected especially for relatively young individuals.