Aim and Objectives
This work is a cross-section study result of the experience of a single Stroke Hub Centre (including 24/7/365 h neurology service, interventional neuroradiology and neurosurgery) which aims to identify which are parameters that can influence the complexity of stroke endovascular treatment in terms of exposure. In addition, it is proposed to derive the DRL (Typical values) according to ICRP 135[1], in the absence of DRL at national level.
Method and Material
Data from 145 stroke patient treated between January 1, 2017, and May 31, 2019, were retrospectively analyzed. For each patients, the local Pacs was used to collect parameters summarized in table 2.
Table 2. List of collected parameters.
Dosimetric data
|
Fluoroscopy KAP, Acquisition KAP, Total KAP, Ka,r for frontal and lateral tubes (case of biplane), fluoroscopy time, Number of images
|
Patients data
|
Sex, Age
|
Anatomical features
|
Thrombus location, Type of Aortic Arch, Type of Carotid Siphon, Type of sheath, Type of aspiration catheter(ACE o SOPHIA), Number of aspiration ADAPT, use of Stent Retriever
|
Other parameters
|
Operator expertise, radiological equipment (monoplane/biplane system)
|
Procedures were performed in two angiographic rooms equipped with a Philips Allura Xper FD20 (S1) monoplane system and a Philips Allura Xper FD2020 (S2) biplane system. The two angiographic systems are comparable in terms of both input dose and image quality.
According to the experience of our department, endovascular treatment of patients with acute ischemic stroke has been performed by direct thrombectomy with the ADAPT technique as a first therapeutic choice [3]. When the direct thrombectomy with ADAPT technique is unsuccessful (after 2/3 attempts) it is followed by thrombus removal by stent-retriever; the purpose is trying to obtain the best vascular recanalization in the shortest procedural time, taking into account the age and clinical conditions of the patients, the site of vascular occlusion and the anatomical conditions found.
To identify which clinical parameters influence the complexity of the procedure and therefore which parameters contribute to increasing patient exposure, a univariable analysis was performed followed by a multivariable for the total KAP (primary endpoint) and for the other dosimetric data.
By subdividing the procedures according to complexity (simple, medium, complex), the median value of the distribution of all dosimetric data was calculated to obtain the typical values as defined by the ICRP[1].
Results
The Total KAP multivariable analysis shows significant correlation (p<0.05) with sex, operator experience, thrombus location and use of stents. The same results were obtained in the air kerma and number of image multivariablee analysis. The number of images is also influenced by the type of radiological equipment. As regard fluoroscopy time, there is a significant dependence (p<0.05) on operator experience, use of stent and patient’s age (Figure 1).
Fig. 1: Clinical and technical parameters that influence dosimetric data.
The Total KAP was used as reference to derived the complexity index of procedures. Figure 2 summarizes the results of the multivariable analysis and shows the weight factors to be used to derive the complexity index as proposed in the pilot study reported in IAEA report No. 59. of 2009[2]. By our choice, the weight factors were obtained by multiplying the coefficients of the multivariable analysis by 10.
CI = age weight factor + sex weight factor + operator weight factor + location weight factor + catheter weight factor + angiographic system weight factor + stent weight factor.
The procedures were divided into three complexity levels:
-
simple: CI ≤7
-
medium :7< CI ≤15
-
complex: CI >15
Fig. 2: Graphic representation of Total KAP dependencies. The variables that do not intercept the vertical red line are the statistically significant parameters. On the side is the ratio (95%) between the factors, the minimum and maximum value in brackets, the p-value and the weight factor useful to obtain the complexity index.
To obtain typical values, the median value of each dosimetric data distribution was calculated distinguishing the three different complexity classes (Table 3).
Table 3. Typical values related to procedure complexity.
Typical Values vs Complexity
|
|
FT (min)
|
Fluoroscopy KAP
(Gy.cm2)
|
Acquisition KAP
(Gy.cm2)
|
Total KAP
(Gy.cm2)
|
Total Ka,r
(Gy)
|
NI
|
Low
|
12
|
35
|
53
|
90
|
0,36
|
110
|
Medium
|
27
|
83
|
126
|
222
|
0,82
|
230
|
Complex
|
30
|
125
|
169
|
345
|
1,58
|
268
|
Discussion
The main purpose of this work is to highlight which clinical and technical parameters affect patient exposure.
Figure 3 justifies the criteria chosen to analyze the complexity.
Fig. 3: Criteria chosen to analyze the complexity.
KAP and Ka,r should be analyzed based on body size: this is not required for cerebral procedures as there is a little variation in size when it comes to head anatomy[8].