Patient dose during carotid artery stenting with embolic-protection devices: evaluation with radiochromic films and related diagnostic reference levels according to factors influencing the procedure.

PURPOSE: To measure the maximum entrance skin dose (MESD) on patients undergoing carotid artery stenting (CAS) using embolic-protection devices, to analyze the dependence of dose and exposure parameters on anatomical, clinical, and technical factors affecting the procedure complexity, to obtain some local diagnostic reference levels (DRLs), and to evaluate whether overcoming DRLs is related to procedure complexity. MATERIALS AND METHODS: MESD were evaluated with radiochromic films in 31 patients (mean age 72 ± 7 years). Five of 33 (15 %) procedures used proximal EPD, and 28 of 33 (85 %) procedures used distal EPD. Local DRLs were derived from the recorded exposure parameters in 93 patients (65 men and 28 women, mean age 73 ± 9 years) undergoing 96 CAS with proximal (33 %) or distal (67 %) EPD. Four bilateral lesions were included. RESULTS: MESD values (mean 0.96 ± 0.42 Gy) were <2 Gy without relevant dependence on procedure complexity. Local DRL values for kerma area product (KAP), fluoroscopy time (FT), and number of frames (NFR) were 269 Gy cm(2), 28 minutes, and 251, respectively. Only simultaneous bilateral treatment was associated with KAP (odds ratio [OR] 10.14, 95 % confidence interval [CI] 1-102.7, p < 0.05) and NFR overexposures (OR 10.8, 95 % CI 1.1-109.5, p < 0.05). Type I aortic arch decreased the risk of FT overexposure (OR 0.4, 95 % CI 0.1-0.9, p = 0.042), and stenosis ≥ 90 % increased the risk of NFR overexposure (OR 2.8, 95 % CI 1.1-7.4, p = 0.040). At multivariable analysis, stenosis ≥ 90 % (OR 2.8, 95 % CI 1.1-7.4, p = 0.040) and bilateral treatment (OR 10.8, 95 % CI 1.1-109.5, p = 0.027) were associated with overexposure for two or more parameters. CONCLUSION: Skin doses are not problematic in CAS with EPD because these procedures rarely lead to doses >2 Gy.

Proposed local diagnostic reference levels in angiography and interventional neuroradiology and a preliminary analysis according to the complexity of the procedures.

The aim of this study was to propose local diagnostic reference levels (DRL) for exposure to radiation during diagnostic procedures and neuroradiological interventions such as cerebral angiography and embolisation of cerebral aneurysms (intra-cranial aneurysms and arteriovenous malformations). Hospitals should adopt the national DRLs for use locally or establish their own DRLs based on local practice, if sufficient local data are available. For this purpose we studied a sample of 113 cerebral angiography procedures and 82 embolisations of cerebral aneurysms. The data recorded included the kerma-area product (KAP), the fluoroscopy time and the number of frames for each procedure: third quartiles from the total dosimetric databank were calculated and proposed as provisional local DRL. Since the complexity of a procedure must be taken into account when evaluating the radiation dose, in the case of embolisation of aneurysms (intra-cranial), in this initial phase we assessed whether the complexity of the embolisation procedure is related to the size of the aneurysm and/or its site. We, therefore, re-calculated the DRL for only intra-cranial aneurysms, leaving aside the arteriovenous malformations. Considering that the DRL calculated for all the therapeutic procedures are similar to those calculated considering only intra-cranial aneurysms, at the moment we propose, besides the DRL for cerebral angiography, a single DRL for all interventional procedures, even when the clinical pictures are very different. Local preliminary DRLs were proposed as follows: 180 Gy cm(2), 12 min and 317 frames for cerebral angiography and 487 Gy cm(2), 46 min and 717 frames for interventional procedures (intra-cranial aneurysms and arteriovenous malformations).

Measurement of patient skin dose in vertebroplasty using radiochromic dosimetry film.

STUDY DESIGN: We studied the radiation doses to which patients were exposed during 17 vertebroplasty operations. OBJECTIVE: The radiation doses during vertebroplasty were measured to determine maximum skin dose (MSD), a measure of the likelihood of radiation-induced skin effects. SUMMARY OF BACKGROUND DATA: Vertebroplasty is performed with use of fluoroscopic guidance for needle placement and to monitor bone cement injection. This procedure requires relatively long duration of fluoroscopic guidance, and so, it demands dose measurements for patients. METHODS: From May 2006 to April 2008, 16 patients (7 men and 9 women; mean age 70.19 years, range 30-87 years) underwent a total of 17 vertebroplasty procedures. Total dose-area product (DAP), duration of fluoroscopy, and the parameters for anteroposterior (AP) and lateral (LAT) fluoroscopic and fluorography projections were recorded for each procedure. Gafchromic films were placed on the patients' skin to measure entrance surface dose and to evaluate the MSD. RESULTS: The MSD and DAP were higher in the LAT plane than in the AP plane. These results were expected because the fluoroscopy time was longer, and the number of fluorography runs was higher in the LAT plane than in the AP plane.The MSD values for the AP plane ranged between 0.184 Gy and 1.834 Gy, whereas those for the LAT plane ranged between 0.417 Gy and 2.362 Gy. The frequency distribution of values for both planes showed that most MSD values were in the range of 0 to 0.5 Gy and 0.5 to 1 Gy for the AP plane and 0.5 to 1 Gy and 1 to 1.5 Gy for the LAT plane. There was great variability in the MSD at each value for the parameters among individual instances. CONCLUSION: When evaluating the MSD to a patient, a distinction should be made between AP and LAT projections, because an overall mean MSD value underestimates the contribution of x-ray absorption on the LAT plane. The use of radiochromic films to estimate radiation damage to the skin has been shown to have the limitation of relying on DAP values only.