Does a flat panel detector reduce the patient radiation dose in interventional cardiology?

The role of a commercial radiation dose index monitoring system in establishing local dose reference levels for fluoroscopically guided invasive cardiac procedures

PURPOSE

The primary goal was to evaluate local dose level for fluoroscopically guided invasive cardiac procedures in a high-volume activity catheterization laboratory, using automatic data registration with minimal impact on operator workload. The secondary goal was to highlight the relationship between dose indices and acquisition parameters, in order to establish an effective strategy for protocols optimization.

METHODS

From September 2016 to December 2018, a dosimetric survey was conducted in the 2 rooms of the catheterization laboratory of our institution. Data collection burden was minimized using a commercial Radiation Dose Index Monitoring System (RDIMs) that analyzes dicom files automatically sent by the x-ray equipment. Data were combined with clinical information extracted from the HIS records reported by the interventional cardiologist. Local dose levels were established for different invasive cardiac procedures.

RESULTS

A total of 3029 procedures performed for 2615 patients were analyzed. Median KAP were 21 Gycm² for invasive coronary angiography (ICA) procedures, 61 Gycm² for percutaneous coronary intervention (PCI) procedures, 59 Gycm² for combined (ICA+PCI) procedures, 87 Gycm² for structural heart intervention (TAVI) procedures. A significant dose reduction (51% for ICA procedures and 58% for PCI procedures) was observed when noise reduction acquisition techniques were applied.

CONCLUSIONS

RDIMs are effective tools in the establishment of local dose level in interventional cardiology, as they mitigate the burden to collect and register extensive dosimetric data and exposure parameters. Systematic review of data support the multi-disciplinary team in the definition of an effective strategy for protocol management and dose optimization.

TAGUCHI METHOD-BASED OPTIMIZATION OF THE MINIMUM DETECTABLE DIFFERENCE OF A CARDIAC X-RAY IMAGING SYSTEM USING A PRECISE LINE PAIR GAUGE

Objective: To optimize the minimum detectable difference (MDD) of a cardiac X-ray imaging system using the Taguchi L8(27) analysis and a precise line pair (LP) gauge. Methods: The optimal combination of the four critical factors of the cardiac X-ray imaging system, namely X-ray focus, kilovoltage (kVp), milliamper-seconds (mAs) and source image distance (SID), providing the MDD was calculated via the Taguchi analysis and experimentally verified. Two (low and high) levels were assigned for each factor, and eight combinations of four factors were used to acquire instant X-ray images using an NDT commercial LP gauge (with a gauge length of 64[Formula: see text]mm and a width of [Formula: see text][Formula: see text]mm). The latter had five lines and was split gradually from top to bottom for the inspection of X-ray images, whose quality was ranked by three well-trained radiologists according to the double-blind criterion. The ranking grade was given by sharp contrast, low noise and precision to distinguish the LP. Accordingly, the MDD was derived to represent the spatial resolution of instant X-ray images by the revised Student’s [Formula: see text]-test analysis. The optimal combination of factors was experimentally identified and clinically verified in the follow-up inspections. Results: For the conventional setting, Group No. 7 (which obtained the highest grade among eight groups) and the optimal setting, the obtained MDD values were [Formula: see text], [Formula: see text] and [Formula: see text][Formula: see text]mm, respectively, while the LP (line pair/mm) interpolated from the gauge scale amounted to [Formula: see text], [Formula: see text] and [Formula: see text][Formula: see text]LP/mm, respectively. Conclusion: The Taguchi L8 analysis was proved to be instrumental in optimizing the cardiac X-ray imaging system MDD and is recommended to be used jointly with the revised Student’s [Formula: see text]-test analysis for improving the spatial resolution of instant X-ray images.

Radiation dose from percutaneous transluminal coronary angioplasty procedure performed using a flat detector for different clinical angiographic projections

The radiation dose from complex cardiac procedures is of concern due to the lengthy fluoroscopic screening time and vessel complexities. This study intends to assess radiation dose based on angiographic projection and vessel complexities for clinical protocols used in the performance of percutaneous transluminal coronary angioplasty (PTCA). Dose-area product (DAP), reference air kerma (K _a,r) and real-time monitoring of tube potentials and tube current for each angiographic projection and dose setting were evaluated for 66 patients who underwent PTCA using a flat detector system. The mean DAP and cumulative K _a,r were 32.71 Gy cm² (0.57 Gy), 51.24 Gy cm² (0.9 Gy) and 102.03 Gy cm² (1.77 Gy) for single-, double- and triple-vessel PTCA, respectively. Among commonly used angiographic projections, left anterior oblique 45°-caudal 35° reached 2 Gy in 55 min using a low-dose fluoroscopy setting and 21 min for a medium-dose setting. Use of a low-dose setting for fluoroscopic screening showed a radiation dose reduction of 39% compared with a medium-dose setting.

Radiation doses and estimated risk from angiographic projections during coronary angiography performed using novel flat detector

Coronary angiography (CA) procedure uses various angiographic projections to elicit detailed information of the coronary arteries with some steep projections involving high radiation dose to patients. This study intends to evaluate radiation doses and estimated risk from angiographic projections during CA procedure performed using novel flat detector (FD) system with improved image processing and noise reduction techniques. Real‐time monitoring of radiation doses using kerma‐area product (KAP) meter was performed for 140 patients using Philips Clarity FD system. The CA procedure involved seven standard projections, of which five were extensively selected by interventionalists. Mean fluoroscopic time (FT), KAP, and reference air kerma (Ka,r) for CA procedure were 3.24 min (0.5–10.51), 13.99 Gycm² (4.02–37.6), and 231.43 mGy (73.8–622.15), respectively. Effective dose calculated using Monte Carlo‐based PCXMC software was found to be 4.9 mSv. Left anterior oblique (LAO) 45° projection contributed the highest radiation dose (28%) of the overall KAP. Radiation‐induced risk was found to be higher in females compared to males with increased risk of lung cancer. An increase of 10%–15% in radiation dose was observed when one or more additional projections were adopted along with the seven standard projections. A 14% reduction of radiation dose was achieved from novel FD system when low‐dose protocol during fluoroscopy and medium‐dose protocol during cine acquisitions were adopted, compared to medium‐dose protocol.

PACS number(s): 87.50.cm, 87.55.de, 87.55.N, 87.59.cf, 87.59.Dj

Transition from image intensifier to flat panel detector in interventional cardiology: Impact of radiation dose

Flat panel detector (FPD) technology in interventional cardiology is on the increase due to its varied advantages compared to the conventional image intensifier (II) systems. It is not clear whether FPD imparts lower radiation doses compared to II systems though a few studies support this finding. This study intends to compare radiation doses from II and FPD systems for coronaryangiography (CAG) and Percutaneous Transluminal Coronary Angioplasty (PTCA) performed in a tertiary referral center. Radiation doses were measured using dose area product (DAP) meter from patients who underwent CAG (n = 222) and PTCA (n = 75) performed using FPD angiography system. The DAP values from FPD were compared with earlier reported data using II systems from the same referral center where the study was conducted. The mean DAP values from FPD system for CAG and PTCA were 24.35 and 63.64 Gycm(2) and those from II system were 27.71 and 65.44 Gycm(2). Transition from II to FPD system requires stringent dose optimization strategies right from the initial period of installation.