| Περίληψη: | Nowadays, many diagnostic and therapeutic interventions are performed fluoroscopically guided. Fluoroscopy is widely used in cardiology, orthopedics and urology and is a method of real-time imaging of the tissues and internal structures of the human body using x-rays. X-rays belong to the category of ionizing radiation and have the ability to interact with matter and cause ionization in it. However, ionizing radiation poses a radiation risk to both the patient and the medical staff who is on the patient’s side during the fluoroscopically guided procedures. So, it is necessary to control their application and investigate the radiation hazards on patients and staff. For this reason, in recent years the scientific community has become increasingly interested in the doses of the patients and the medical staff with ionizing radiation.
The present study focuses on the investigation of the patient radiation dose and the radiation hazards of patients undergoing interventional cardiology procedures performed in two different angiographic systems from two hospitals of Patras. Specifically, the dose record files of the hemodynamic laboratory of the Private Clinic “Olympion” of Patras (Hospital A) and the University General Hospital of Patras (Hospital B) were studied. The dose record files refer to two cardiac catheterization procedures: Coronary Angiography (CA) and Percutaneous Transluminal Coronary Angioplasty (PTCA). The patient’s radiation hazards were calculated using published conversion factors from DAP values to effective dose. Furthermore, in this thesis the effect of complexity procedure (varying degree of complexity vs. high degree of complexity) and the effect of patient’s gender in high complexity cases (Hospital A) were studied on time of fluoroscopy, patient dose (Dose-Area Product, DAP) and radiation hazard (effective dose). Finally, the 75th percentile of the total DAP and the fluoroscopy time of the patients who underwent coronary angiography and coronary angiography with PTCA of high complexity were estimated. These values were compared with respect to the national DRLs, as well as with respect to the international DRLs.
Thirty cases of coronary angiography and 30 cases of coronary angiography and PTCA of high complexity each of them, were studied for Hospital A, while for Hospital B 33 cases of CA and 30 cases of CA+PTCA of varying complexity were studied too. An interventional cardiac procedure is defined as highly complex due to the patient pathology (angioplasty in two or three vessels) and the patient anatomical features (difficulty of passing through a vessel).
For Hospital A it is observed that the patient radiation dose during hemodynamic procedures has a large variation [standard deviation of the total DAP for CA: 40.6 (Gy⸱cm2) and for CA + PTCA: 67.3 (Gy⸱cm2)] due to the different anatomical patient characteristics and the high complexity of the invasive cardiology procedures performed. In cases of high complexity, the orientation of the x-ray tube - detector system is frequently changed in order to obtain a satisfactory image. Changing the position of the X-ray tube affects the dose that patient receives. Also, for the sample of cases of high complexity (Hospital A) the time of fluoroscopy required to perform coronary angiography with PTCA [(25.0 ± 8.6) min] is higher than the time of fluoroscopy in coronary angiography [(7.8 ± 3.7) min] (Student's t-test, p-value <0.05). The same is observed for total DAP [(226.8 ± 67.3) (Gy⸱cm2)] and effective dose [(38.8 ± 12.0) mSv] in coronary angiography with PTCA compared to the total DAP [(87.9 ± 40.6) (Gy⸱cm2)] and effective dose [(14.7 ± 7.3) mSv] in coronary angiography (Student's t-test, p-value <0.05). At the same time, in Hospital A it was observed that the value of DAP [(139.7 ± 51.1) (Gy⸱cm2)], during fluoroscopy has statistically significant difference (Student's t-test, p-value <0.05) from that of DAP [(87.1 ± 32.8) (Gy⸱cm2)] during cine acquisition mode for the interventional procedure of coronary angiography with PTCA (CA + PTCA) because cine mode only operates for a few projections. The same is observed in the effective dose for both interventional procedures. The effective dose obtained during fluoroscopy [CA: (10.2 ± 6.3) mSv, CA + PTCA: (28.3 ± 10.4) mSv] contributes more to the total effective dose [CA: (14.7 ± 7.3) mSv, CA + PTCA: (38.8 ± 12.0) mSv] than the effective dose received during cine mode [CA: (4.5 ± 2.1) mSv, CA + PTCA: (10.5 ± 3.9) mSv] (Student's t-test, p-value <0.05).
For Hospital B (interventional cardiac procedures of varying degree of complexity) the mean time of fluoroscopy (9.2 min), the mean DAP (73.5 (Gy⸱cm2)) and the mean effective dose (11.6 mSv) for the coronary angiography with PTCA are higher than mean time of fluoroscopy (3.3 min), mean DAP (26.6 (Gy⸱cm2)) and mean effective dose (4.2 mSv) obtained on coronary angiography.
In addition, it was observed that the mean DAP [26.6 (Gy⸱cm2)] for CA and the mean DAP [73.5 (Gy⸱cm2)] for CA+PTCA performed in Hospital B were much lower than the mean DAP for CA [(87.9 ± 40.6) (Gy⸱cm2)] and for CA+PTCA [(226.8 ± 67.3) (Gy⸱cm2)] performed in Hospital A respectively. Therefore, patients undergoing hemodynamic procedures at Hospital A receive higher dose than patients undergoing the same interventional procedures at Hospital B. This is mainly due to the different degree of complexity of the interventional procedures, in Hospital A, the sample concerns interventional cardiac procedures of high degree of complexity, while in Hospital B the sample concerns interventional cardiac procedures of varying degree of complexity. Also, this difference is due to the type of angiographic system, the insertion of different filters in each angiographic system during normal mode operation, as well as due to the experience of each invasive cardiologist. This difference is also seen in the times of fluoroscopy needed to perform the interventional procedures. The mean time of fluoroscopy for diagnostic [(7.8 ± 3.7) min] and therapeutic [(25.0 ± 8.6) min] high complexity procedures (Hospital A) is much higher than the mean time of fluoroscopy for diagnostic (3.3min) and therapeutic (9.2 min) procedures of variable degree of complexity (Hospital B).
For the sample of patients who underwent interventional cardiac procedures of high complexity (Hospital A) there is no statistically significant difference (Student’s t-test, p-value> 0.05) between the dose received by females [CA: (69.2 ± 29.3) (Gy⸱cm2), CA + PTCA: (199.6 ± 47.1) (Gy⸱cm2)] and the dose received by males [CA: (98.8 ± 42.9) (Gy⸱cm2), CA + PTCA: (240.5 ± 72.7) (Gy⸱cm2)]. In fact, males receive higher dose than females. The reason that there was no statistically significant difference between males and females in the present study is attributed to the fact that the sample under study was small (30 cases).
In addition, the dose received for Hospital A is increased in relation to the National Diagnostic Reference Levels (DRLs). This difference is due to the fact that all cases of Hospital A were of high degree of complexity in diagnostic and therapeutic procedures, while DRLs have resulted from variable degree of complexity cases (including low, medium and high degree of complexity cases). Other contributing factors are the different patient pathology, the different body mass index (BMI) of each patient, as well as the accuracy of the DAP meters. Also, for the interventional procedure of PTCA, the comparison with the national DRLs is not objective because the total DAP in Hospital A was not monitored exclusively for PTCA, but also for coronary angiography (CA). Therapeutic procedures, as defined in this study, were combined procedures in which a therapeutic intervention immediately followed a diagnostic examination.
Finally, there was a large variation in the DRLs of different countries which is initially due to the varying degree of complexity, the different number of centers of each country participating, the different number of CA and PCI performed in each country and the different calculation method that each country utilizes to find their national DRLs (75th percentile of all the values or the 75th percentile of the mean values). Also, the different body mass index, the different pathology of the patient and the accuracy of DAP meters are some of the factors that contribute to the heterogeneity shown by the DRLs of different countries. Through the study of DRLs at national and international level compared to the 75th percentile of the dose of Hospital A for a sample of high degree of complexity of interventional procedures, it is concluded that there is a need for estimating/reporting patient dose (updating DRLs) with respect to procedure complexity.
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