Radiation dose optimization in coronary angiography and percutaneous coronary intervention (PCI). II. Clinical evaluation

In a previous part of this study, the fluoroscopy dose rate was reduced in a cardiac catheterization laboratory. The objectives of the present study were to evaluate the effects in a clinical population undergoing percutaneous coronary intervention (PCI) of the dose-reducing measures detailed previously. Kerma area-product (KAP) values were first recorded for 154 patients undergoing PCI. Then, the fluoroscopy KAP rate was reduced from 44 to 16 mGy cm²/s by increasing filtration and reducing the image intensifier dose request. After this optimization, KAP was recorded for another 138 PCI procedures. After adjustment for differing proportions of combined procedures (coronary angiography+PCI), the total KAP was reduced to 67% of the original value with a 95% confidence interval from 57 to 78%, statistically significant. The mean total KAP values were 93.6 Gy cm² before and 69.1 Gy cm² after optimization. The KAP for digital acquisition did not change significantly. It is possible to make a large dose reduction in PCI by reducing the fluoroscopy dose rate. This dose reduction is beneficial for both patients and staff. Electronic Publication     

Impact of digital imaging on radiation doses to the patient during X-ray examination of the urinary tract

Purpose: To compare radiation doses given to patients undergoing IVU (intravenous urography) before and after digitalization of our X-ray department.

Material and Methods: IVU examinations were monitored with dose area product meters before and after the X-ray department changed to digital techniques. The first step was a change from film-screen to storage phosphor plates, while the second step involved changing to a flat panel detector. Forty-two patients were included for the film-screen situation, 69 when using the storage phosphor plates, and 70 using the flat panel detector.

Results: A dose reduction from 41.8 Gycm² to 31.5 Gycm² was achieved with the first step when the film-screen system was replaced with storage phosphor plates. A further reduction to 12.1 Gycm² was achieved using the flat panel detector.

Conclusion: The introduction of the flat panel detectors made a considerable dose reduction possible.     

Evaluation of patient-absorbed doses during coronary angiography and intervention by femoral and radial artery access

The aim of this study was to compare the radiation dose to patients during coronary angiography (CA) and coronary intervention (percutaneous transluminal coronary angioplasty, PTCA) by the femoral or radial artery access routes. A plane-parallel ionisation chamber, mounted on an under-couch X-ray tube (Siemens Coroskop TOP with an optional dose reduction system), recorded the dose-area product (DAP) to the patient from 40 coronary angiographies and 42 coronary interventions by the femoral route. The corresponding numbers for radial access were 36 and 24, respectively. Using a human-shaped phantom, conversion factors between maximum entrance surface dose and DAP were derived for CA and CA plus PTCA, respectively. The dose to the staff was measured with TL dosimeters for 22 examinations. Fluoroscopy time and DAP were significantly (p=0.003) larger using the radial access route for coronary angiography (7.5 min, 51 Gy cm²) than the corresponding values obtained from femoral access route (4.6 min, 38 Gy cm²). For CA plus PTCA the fluoroscopy time and DAP were larger for radial access (18.4 min, 75 Gy cm²) than for femoral access (12.5 min, 47 Gy cm²; p=0.013). In our experience, radial access did significantly prolong the fluoroscopy time and increase the patient doses.     

Effective techniques for reduction of radiation dosage to patients undergoing invasive cardiac procedures

The goal of this study was to improve radiation dose reduction techniques in invasive cardiology and after patients' radiation data had approached minimal levels, to evaluate predictors of their radiation exposure resulting from invasive cardiac procedures. Over the course of 1 year (and 1996 procedures) we minimized cinegraphic frames and runs, as well as fluoroscopy time, and trained ourselves to achieve effective fluoroscopy-saving positioning of blinds and filters toward the regions of interest. We were consequently able to reduce the mean dose-area products (DAP) for coronary angiography and angioplasty, combined interventions, high-frequency rotational atherectomy, and excimer laser angioplasty: from levels of 53.9 Gy cm(2), 79.6 Gy cm(2), 112.3 Gy cm(2), 119.4 Gy cm(2), and 168.0 Gy cm(2) as currently reported in the literature, to 12.9 Gy cm(2), 13.3 Gy cm(2), 25.9 Gy cm(2), 33.0 Gy cm(2), and 27.1 Gy cm(2), respectively. The mean DAP due to interventions in acute myocardial infarction was 38.3 Gy cm(2). DAP was influenced by body mass index, complexity of coronary artery disease, tube angulation, documented structure, coronary recanalization, emergency circumstances, and the percutaneous transluminal coronary angioplasty (PTCA) target vessel involved, but not by stent implantation. By favouring radiation-reducing cranial posteroanterior views over standard left anterior oblique views for visualization of the left anterior descending and the diagonal artery, we consequently achieved mean PTCA-DAPs of 10.4 Gy cm(2) and 8.6 Gy cm(2), respectively: levels significantly lower than those for PTCA of the right coronary artery (13.3 Gy cm(2)), left circumflex artery (13.7 Gy cm(2)), and obtuse marginal branch (16.9 Gy cm(2)). In conclusion, enhanced knowledge of radiation dose-reduction techniques significantly reduces patient radiation hazards in invasive cardiology.     

Comparison of Patient Dose in Two-Dimensional Carotid Arteriography and Three-Dimensional Rotational Angiography

Background and Purpose It is known that interventional neuroradiology (IN) involves high radiation dose to both patients and staff even if performed by trained operators using modern fluoroscopic X-ray equipment and dose-reducing technology. Therefore, every new technology or imaging tool introduced, such as three-dimensional rotational angiography (3D RA), should be evaluated in terms of radiation dose. 3D RA requires a series with a large number of images in comparison with 2D angiography and it is sometimes considered a high-dose IN procedure. The literature is scarce on the 3D RA radiation dose and in particular there are no data on carotid arteriography (CA). The aim of this study was to investigate patient dose differences between 2D and 3D CA. Methods The study included 35 patients undergoing 2D CA in hospital 1 and 25 patients undergoing 3D CA in hospital 2. Patient technical data collection included information on the kerma area product (KAP), fluoroscopy time (T), total number of series (S), and total number of acquired images (F). Results Median KAP was 112 Gy cm² and 41 Gy cm² for hospitals 1 and 2, respectively, median T was 8.2 min and 5.1 min, median S was 13 and 4, and median F was 247 and 242. Entrance surface air-kerma rate, as measured in “medium” fluoroscopy mode measured in 2D acquisition using a 20 cm phantom of polymethylmethacrylate, was 17.3 mGy/min for hospital 1 and 9.2 mGy/min for hospital 2. Conclusion 3D CA allows a substantial reduction in patient radiation dose compared with 2D CA, while providing the necessary diagnostic information.     

Tips to minimize radiation exposure

The use of cardiac computed tomography (CT) to noninvasively visualize the coronary arteries has rapidly increased during the last few years but thereby also has raised concerns about the amount of radiation exposure and its potentially associated hazards. In this article, we summarize several strategies and new scanning techniques for dose reduction in cardiac CT, including the following: 1) Coronary CT angiography should not be performed in patients with extensive coronary calcifications because the probability to rule out obstructive coronary artery disease diminishes with increasing coronary artery calcium scores; 2) The scan length in CT angiography should be individually adjusted to the minimum needed length; 3) electrocardiogram-correlated modulation of the tube current should be applied in all patients with stable sinus rhythm; 4) The tube voltage should be reduced to 100 kV in non-obese patients (patient weight <85-90 kg); and 5) A sequential scan mode with prospective electrocardiogram triggering should be considered in patients with a stable heart rate ≤63 beats/min. With the appropriate use of these strategies for dose reduction, the diagnostic image quality is maintained. Therefore, these strategies should be rigidly applied in daily practice to obtain diagnostic images with the lowest possible radiation dose in every patient.     

Patient dose values in a dedicated Greek cardiac centre

The purpose of this study was to collect information on the practice and patient doses in a major Greek cardiac centre, investigate differences between senior cardiologists of various levels of experience and compare results with the literature, in order to optimize angiographic and interventional cardiology procedures. Radiation doses from 292 patients have been studied, 195 of which had undergone coronary angiography and 97 percutaneous transluminal coronary angioplasty. All procedures were undertaken on a Siemens Angioscop X-ray equipment. The system performed under automatic exposure control using pulsed fluoroscopy of 12.5 pulses s(-1) and cine frame rate of 25 frames s(-1). Dose-area product values, fluoroscopy times, total number of cine frames as well as operator's name were collected for each patient. Only senior cardiologists have participated in the study. Median values for dose-area product were 39.1 Gy cm(2) for coronary angiography and 58.3 Gy cm(2) for percutaneous transluminal coronary angioplasty. Median fluoroscopy time was 5.0 min and 9.7 min and median number of frames was 1588 and 1823 for coronary angiography and percutaneous transluminal coronary angioplasty, respectively. Comparison showed that patient dose-area product values were lower than other studies and fluoroscopy time values were comparable. However, the total number of frames used was much higher than other published results. Differences between cardiologists with increased experience have been found. Analysis of the patient dose values obtained initiated a program of radiation protection optimization. The need for continuous training in radiation protection for interventionalists has been verified.     

Radiation dose optimization in coronary angiography and percutaneous coronary intervention (PCI). I. Experimental studies

The objectives of this study were to evaluate the influence on image quality and dose to the patient and operator of various equipment settings for percutaneous coronary intervention (PCI), and to optimize the set-up. With an Alderson phantom, different settings, such as projection, protective screens, filtration, image intensifier size and collimation, were evaluated. Kerma-area product (KAP) was recorded as a measure of patient dose and scattered radiation was measured with an ionization chamber. Effective dose for a standardized PCI procedure was measured with thermoluminescent dosimeters inside the phantom. Image quality was evaluated with a contrast-detail phantom. Based on these findings, the equipment set-up was optimized to a low fluoroscopy dose rate with a sufficient image quality. Several operating parameters affected dose, particularly scattered radiation. The optimization reduced the fluoroscopy KAP rate from 44 to 16 mGy cm(2)/s using 15 cm of acrylic. The effective dose was reduced from 13 to 4.6 mSv for a standardized PCI procedure. Radiation dose to patient and operator in PCI is heavily dependent on both equipment set-up and operating parameters which can be influenced by the operator. With a careful optimization, a large reduction of radiation dose is possible.     

Comparison of a conventional and a flat-panel digital system in interventional cardiology procedures

The purpose of the study was to analyse the technical characteristics of a newly installed flat-panel fluoroscopy (FPF) system in an interventional cardiology (IC) department and compare it with an older conventional system. A patient survey was performed to investigate the radiation doses delivered by the X-ray systems. Finally, methods of technique optimization regarding the new digital system were investigated. Dose rates in all fluoroscopic and cine modes were measured and image quality assessed using a dedicated test tool. 200 patients were investigated, half using the conventional and half using the digital FPF system. Patient data collected were: sex, age, weight, height, dose-area product (DAP), fluoroscopy time (T) and total number of frames (F). Our results are: (1) Digital FPF system: high contrast resolution (HCR) is not affected by fluoroscopic mode, whereas low contrast resolution (LCR) is slightly decreased in the low mode. (2) The digital FPF system has 2.5 times better HCR than the conventional system, with 5 times lower dose in the fluoroscopy mode. (3) Median values of DAP, T and F, respectively, in coronary angiography (CA) are: 27.7 Gycm(2), 4.1 min and 876 for the digital and 39.3 Gycm(2), 5.3 min and 1600 for the conventional system. Median values for percutaneous transluminal coronary angioplasty (PTCA) are: 51.1 Gycm(2), 12.7 min and 1184 for the digital and 44.3 Gycm(2), 7.4 min and 1936 for the conventional system. Digital DAP in CA is reduced by 30%, suggesting that a dose reduction in the FPF system is possible. The results of the study concerning the FPF system lead to the conclusion that the lowest fluoroscopic mode and the lowest frame rate should be used in routine practice.     

Relationship between fluoroscopic time, dose-area product, body weight, and maximum radiation skin dose in cardiac interventional procedures

OBJECTIVE: Real-time maximum dose monitoring of the skin is unavailable on many of the X-ray machines that are used for cardiac intervention procedures. Therefore, some reports have recommended that physicians record the fluoroscopic time for patients undergoing fluoroscopically guided intervention procedures. However, the relationship between the fluoroscopic time and the maximum radiation skin dose is not clear. This article describes the correlation between the maximum radiation skin dose and fluoroscopic time for patients undergoing cardiac intervention procedures. In addition, we examined whether the correlations between maximum radiation skin dose and body weight, fluoroscopic time, and dose-area product (DAP) were useful for estimating the maximum skin dose during cardiac intervention procedures. MATERIALS AND METHODS: Two hundred consecutive cardiac intervention procedures were studied: 172 percutaneous coronary interventions and 28 cardiac radiofrequency catheter ablation (RFCA) procedures. The patient skin dose and DAP were measured using Caregraph with skin-dose-mapping software. RESULTS: For the RFCA procedures, we found a good correlation between the maximum radiation skin dose and fluoroscopic time (r = 0.801, p < 0.0001), whereas we found a poor correlation between the maximum radiation skin dose and fluoroscopic time for the percutaneous coronary intervention procedures (r = 0.628, p < 0.0001). There was a strong correlation between the maximum radiation skin dose and DAP in RFCA procedures (r = 0.942, p < 0.0001). There was also a significant correlation between the maximum radiation skin dose and DAP (r = 0.724, p < 0.0001) and weight-fluoroscopic time product (WFP) (r = 0.709, p < 0.0001) in percutaneous coronary intervention procedures. CONCLUSION: The correlation between the maximum radiation skin dose with DAP is more striking than that with fluoroscopic time in both RFCA and percutaneous coronary intervention procedures. We recommend that physicians record the DAP when it can be monitored and that physicians record the fluoroscopic time when DAP cannot be monitored for estimating the maximum patient skin dose in RFCA procedures. For estimating the maximum patient skin dose in percutaneous coronary intervention procedures, we also recommend that physicians record DAP when it can be monitored and that physicians record WFP when DAP cannot be monitored.     

Does coronary stenting following balloon angioplasty improve myocardial fractional flow reserve?

Purpose: Suboptimal distal coronary flow reserve after successful balloon angioplasty has been attributed to angiographically unrecognized inadequate lumen expansion, and adjunct coronary stenting has been shown to improve coronary flow reserve. The aim of this study was to investigate whether myocardial fractional flow reserve (FFRmyo) would increase further after coronary stenting compared with balloon angioplasty alone in the same patient group. Methods: FFRmyo and quantitative coronary angiography were obtained before and after pre-stent balloon dilation, and again after stent placement in 11 patients (7 left anterior descending artery, 3 right coronary artery and 1 left circumflex artery). FFRmyo was calculated as the ratio of Pd/Pa during intracoronary adenosine 5′-triphosphate (50 μg and 20 μg in the left and right coronary arteries, respectively)-induced maximum hyperemia, where Pd represents mean distal coronary pressure measured by a 2.1 Fr infusion catheter and Pa represents mean aortic pressure measured by the guiding catheter. Results: Percent diameter stenosis significantly decreased after balloon angioplasty (74% ± 15% vs 37% ± 17%, p < 0.001), and decreased further after stent placement (18% ± 10%, p < 0.001 vs baseline and balloon angioplasty). FFRmyo after coronary stenting (0.85 ± 0.09) was significantly higher than that at baseline (0.51 ± 0.16, p < 0.001) and after balloon angioplasty (0.77 ± 0.11, p < 0.05). There was a significant correlation between angiographic variables and FFRmyo. The increase in lumen dimensions after coronary stenting was followed by a further significant improvement of FFRmyo. Conclusion: These results suggest that coronary stenting may provide a more favorable functional status and lumen geometry of residual coronary stenosis compared with balloon angioplasty alone.     

Uterine arterial embolization: factors influencing patient radiation exposure

PURPOSE: To investigate patient radiation exposures during uterine arterial embolization and the factors responsible for those exposures. MATERIALS AND METHODS: Clinical and procedural factors were evaluated for 42 consecutive procedures performed in 39 patients by one operator. Seven patients were excluded because of early termination (n = 1) or unusual conditions that necessitated extended procedures (n = 6). Fluoroscopic time, number of images acquired, height, and weight were available in the 35 remaining patients, and dose-area product (DAP) was available in 20. Equipment factors were evaluated by using a Lucite phantom in four angiography units from three manufacturers. RESULTS: The mean fluoroscopic time per case decreased from 30.6 to 14.2 minutes between the 1st and 5th quintiles. Mean DAP decreased from 211.4 to 30.6 Gy. cm(2) with dose reduction techniques; this primarily reflected a decreased number of acquired images. Phantom studies demonstrated many significant dose variations with magnification and equipment position. Low-dose and pulsed fluoroscopic modes reduced exposure rates in units so equipped, but roadmapping caused a silent switch to continuous fluoroscopy in two such units, which doubled the exposure rate. CONCLUSION: With operator experience and careful technique, uterine arterial embolization can be performed at radiation exposures comparable to those used in routine diagnostic studies. However, operators must be familiar with the technical parameters of their angiographic equipment.     

Factors affecting patient radiation exposure during routine coronary angiography in a tertiary referral centre

Cardiac catheterization is carried out by an increasing number of operators from district hospitals as well as tertiary referral centres. Procedures are not standardized and are at the discretion of individual operators. The purpose of this study was to describe the pattern of patient radiation dose and screening times associated with diagnostic cardiac catheterization, and explore determinants of radiation dose to patients and staff. Data were collected from 1337 diagnostic procedures carried out in two cardiac catheterization laboratories from January to June 1998. Screening time and radiation dose measured by dose-area product (DAP) meter were recorded. Status of the operator and type of investigation were determined. 22 operators had performed at least 15 left ventriculograms with coronary angiography (total 944 procedures). The average (+/- SD) was 40 (+/- 22) per operator. Screening times for individual operators varied from 2.0 (+/- 1.3) min to 5.0 (+/- 4.3) min with no relationship between time and number of cases. Consultants and visiting physicians had longer screening times and greater patient DAP readings. In comparison with 115 cases of coronary angiography alone, left ventriculography increased DAP reading from 14.24 (+/- 11.7) Gy cm2 to 20.26 (+/- 0.47) Gy cm2 (p < 0.0001). In 106 cases of coronary artery bypass graft angiography, an aortogram (n = 53) did not add significantly to radiation dose or screening time. A right heart catheter added approximately 5 min to screening time (9.13 (+/- 0.63) min with right heart (n = 83) vs 3.96 (+/- 0.12) min without right heart (n = 1234)), but did not affect radiation dose significantly. There is a wide range of screening times and radiation doses related to diagnostic cardiac catheterization. Visiting and consultant staff use greater radiation doses. Left ventriculography adds significantly to patients' radiation exposure. Aortography does not add significantly to radiation dose in cases of graft angiography.     

二代双源CT对冠状动脉支架的显示及辐射剂量的研究

目的 对比分析二代双源CT前瞻性心电触发高螺距螺旋扫描模式(Flash模式)和回顾性心电门控螺旋扫描模式(常规模式)下冠状动脉支架的显示质量和辐射剂量.方法 常规模式和Flash模式下共计120例患者的155个冠状动脉植入支架纳入本研究,平均年龄(64.9±10.6)岁,所有患者的心率均控制在≤65次/min,且心律规则.所有患者分成两组,分别接受Flash模式和常规模式的冠状动脉成像.冠状动脉原始图像均进行Kernel B26和Kernel B46的数据重建,并由两位医师对支架的显示质量进行独立的4级评分.两种模式下的冠状动脉显示质量利用卡方检验进行统计分析,而不同冠状动脉扫描模式下的容积CT剂量指数值(CTDIvol)和剂量长度乘积值(DLP),利用t检验进行辐射剂量的对比研究.结果 2位医师对所有冠状动脉支架显示质量的评分具有较好的一致性(Kappa=0.764,P＜0.001),Flash模式和常规模式的平均评分分别为:1.61±0.77和1.65±0.82.两种冠状动脉扫描模式的图像质量差异无统计学意义(x2=0.865,P=0.834).Flash模式的CTDIvol(3.24±1.21)明显低于常规模式(31.26±10.79),差异有统计学意义(t=19.83,P<0.001);Flash模式的DLP(54.61±19.88)同样低于常规模式(468.30±174.88),差异有统计学意义(t=18.06,P＜0.001).结论 控制患者心率≤65次/min且心律规则,Flash模式在降低辐射剂量的前提下可获得与常规模式相同质量的冠状动脉支架图像.

Abstract：

Objective To compare a prospective ECG-gated high-pitch spiral technique (Flash) and conventional retrospective ECG-gated spiral technique for the image quality of coronary artery stent and radiation dose with a dual source CT.Methods One hundred and fifty five coronary stents in one hundred and twenty patients (mean age 64.9 ± 10.6 years,heart rates≤65 bpm) were examined using a dual source CT.All patients were divided in two groups,receiving either Flash or conventional coronary artery CT angiography separately.After images of coronary artery were reconstructed using both the smooth (B26) and sharp (B46) kernel,the coronary stent image quality and stent lumen were scored by two observers individually using four point scale (1 = excellent,4 = unvaluable) .The effective radiation dose of volume CT dose index (CTDIvol,mGy) and dose length product (DLP,mGy x cm) were also calculated for each patient.x2-test analysis of image quality and t-test analysis of radiation dose were used respectively for statistical difference between two groups.Results Interobserver agreement for stent image quality was good (Kappa =0.764,P＜0.001).The mean scores were 1.61 ±0.77 and 1.65 ±0.82 in Flash group and conventional group respectively.There was no significant difference in image quality between the two groups (x2 = 0.865,P = 0.834).The effective radiation dose in Flash group was significantly lower than that in conventional group.The mean values of CTDIvol were 3.24 ± 1.21 in Flash group and 31.26 ± 10.79 in conventional group (t = 19.83,P < 0.001) ,and the mean values of DLP in Flash group and conventional group were 54.61 ±19.88 and 468.30 ± 174.88,respectively (t = 18.06,P < 0.001).Conclusions Compared with the conventiaonal coronary artery CT angiography,the Flash coronary artery CT angiography technique has a similar coronary stent image quality,but at a lower radiation dose in patients with heart rates lower than 65 beats per minute.     

Evaluation and estimation of entrance skin dose in patients during diagnostic and interventional radiology procedures

A study was performed to evaluate the total entrance skin dose (ESD) of patients during diagnostic and interventional radiology procedures (IVR) and to estimate ESD with body mass index (BMI) and fluoroscopy time. The study included 26 cases of transcatheter arterial embolization therapy (TAE) for hepatocellular carcinoma (HCC) and 19 cases of diagnostic digital subtraction angiography (DSA) for HCC. The ESD of patients was evaluated with a zinc-cadmium sensor linked to a digital counter (SDM: skin dose monitor). Exposure doses were measured with SDM attached to the front of the X-ray beam-limiting device like a dose area product monitor. ESD was calculated from the measured exposure dose. In 26 TAE for HCC, ESD was 1793.7+/-739.1 mGy, with the mean fluoroscopic time of 23.5 minutes and 4.4 DSA acquisitions. The fluoroscopic dose rate was 52.4+/-11.5 mGy/min. In 19 diagnostic DSA for HCC, ESD was 962.9+/-375.2 mGy, with the mean fluoroscopic time of 11.1 minutes and 4.0 DSA acquisitions. The fluoroscopic dose rate was 32.7+/-12.7 mGy/min. Although 33.2% of ESD was from fluoroscopy in diagnostic procedures, the figure was 68.8% in TAE procedures. It was demonstrated that the increase in ESD during IVR was caused by the rise of fluoroscopy dose rate caused by high-magnification fluoroscopy and the extension of fluoroscopy time. In order to reduce ESD, it is necessary to use a low fluoroscopy dose rate with low-rate pulse fluoroscopy, in addition to shortening fluoroscopy time. Fluoroscopy time was a poor predictor of risk because it did not correlate well with ESD during IVR (diagnostic procedures r(2)= 0.897, IVR r(2)= 0.594). However, ESD correlated well with the product of BMI and fluoroscopy time (diagnostic procedures r(2)= 0.910, IVR r(2)= 0.783). The linear relationship between ESD and the product of BMI and fluoroscopy time provides a simple monitoring mechanism of the ESD delivered to the patient during interventional radiology procedures. This linear relationship needs to be established for other types of interventional procedures.     

双轴旋转造影在冠心病诊断中的安全性观察及应用体会

目的 观察双轴旋转冠状动脉造影(DARCA)在中国人群冠心病诊断中的安全性,探讨其临床应用.方法 选取2010年3月至12月在我院行诊断性DARCA患者共74例,其中后期34例于DARCA时对等中心调整方法进行了改良.于造影前后即刻观察记录患者血压、心率以及症状,并记录造影所用对比剂用量、射线剂量及操作时间.计量资料比较采用Student＇st检验,若呈非正态分布则采用秩和检验,以中位数(M)和四分位数间距(QR)表示;计数资料采用x2检验行统计学分析.结果 (1)临床安全性:所有患者于造影过程中均无胸痛症状,仅1例(1％)于造影后出现短阵室性心动过速,约6s后自行恢复窦性心律.造影前后左冠状动脉收缩压及心率稍降低[收缩压分别为(116±20)、(111±18) mm Hg(1 mm Hg=0.133 kPa),t =3.303,P=0.001;心率的M(QR)分别为73(65 ～84)、71 (64 ～78)次/min,Z=-4.789,P=0.00l],但均在临床正常值内.(2)对比剂、射线剂量及操作时间:所有患者完成造影所需对比剂用量、射线剂量和操作时间分别为28(25 ～34) ml、8979(6733～12 363)mGycm2和200(164 ～ 270)s.等中心调整方法改良后的DARCA其左冠状动脉造影射线剂量及总射线剂量较改良前明显减少[左冠状动脉剂量分别为4004( 2932～5772)、5808 (4798 ～ 8838) mGycm2,Z=-3.471,P=0.001;总剂量分别为(8116±2493)、(11 371±4122) mGycm2,t=-4.176,P=0.001],左冠状动脉造影操作时间及总操作时间也明显减少[左冠状动脉操作时间分别为120(80 ～ 180)、150( 126 ～214)s,Z=-2.836,P=0.005;总操作时间分别为180( 139 ～ 240)、220( 186～308)s,Z=-3.004,P=0.003],但对比剂用量差异无统计学意义[分别为30 (25～35)、27(25 ～34)ml,Z=-0.906,P=0.365].结论 DARCA在中国人群冠心病诊断中具有可靠的安全性,且改良后的DARCA等中心调整方法较常规等中心调整方法在简化操作的基础上可显著减少射线剂量和操作时间,可代替常规法,但临床推广还需大样本随机双盲对照研究结果的支持.     

An investigation into patient and staff doses from X-ray angiography during coronary interventional procedures

Radiation doses to patients from interventional coronary X-ray procedures are relatively high when compared with conventional radiographic procedures. These high patient doses can translate into high staff doses owing to scattered radiation. This study investigates patient doses by means of dose-area product (DAP) meters installed in six rooms in two hospitals. DAP measurements in each room ranged from 28.0-39.3 Gy cm2 for coronary angiography and from 61.3-92.8 Gy cm2 for percutaneous transluminal coronary angioplasty, with the mean effective doses calculated to range between 5.1-6.6 mSv and 11.2-17.0 mSv, respectively. These values are comparable with those found in recent literature. DAP measurements were found to correlate strongly (correlation coefficient of 79%) with patient weight. The non-uniform scatter radiation fields surrounding the irradiated area during coronary angiography were also investigated using a tissue equivalent phantom and an ionization chamber. Exposure rates of scattered radiation from digital acquisition were found to be around 16 times higher than those generated from fluoroscopy, and oblique-angled imaging led to greater amounts of scatter owing to the increase in related exposure factors. The distribution of scatter from oblique projections confirms that X-ray photons in the diagnostic energy range are preferentially scattered backwards, toward the X-ray tube. These concepts are a major consideration when training individuals working in the angiography suite in order to keep doses "as low as reasonably practicable".     

Fluoroscopy: patient radiation exposure issues.

Fluoroscopic procedures (particularly prolonged interventional procedures) may involve high patient radiation doses. The radiation dose depends on the type of examination, the patient size, the equipment, the technique, and many other factors. The performance of the fluoroscopy system with respect to radiation dose is best characterized by the receptor entrance exposure and skin entrance exposure rates, which should be assessed at regular intervals. Management of patient exposure involves not only measurement of these rates but also clinical monitoring of patient doses. Direct monitoring of patient skin doses during procedures is highly desirable, but current methods still have serious limitations. Skin doses may be reduced by using intermittent exposures, grid removal, last image hold, dose spreading, beam filtration, pulsed fluoroscopy, and other dose reduction techniques. Proper training of fluoroscopic operators, understanding the factors that influence radiation dose, and use of various dose reduction techniques may allow effective management of patient dose.     

The Diagnostic Accuracy, Image Quality and Radiation Dose of 64-Slice Dual-Source CT in Daily Practice: a Single Institution's Experience

Objective

We wanted to evaluate the image quality, diagnostic accuracy and radiation exposure of 64-slice dual-source CT (DSCT) coronary angiography according to the heart rate in symptomatic patients during daily clinical practice.

Materials and Methods

We performed a retrospective search for the DSCT coronary angiography reports of 729 consecutive symptomatic patients. For the 131 patients who underwent invasive coronary angiography, the image quality, the diagnostic performance (sensitivity, specificity, positive predictive value [PPV] and negative predictive value [NPV] for detecting significant stenosis ≥ 50% diameter) and the radiation exposure were evaluated. These values were compared between the groups with differing heart rates (HR): mean HR < 65 or ≥ 65 and HR variability (HRV) < 15 or ≥ 15.

Results

Among the 729 patients, the CT reports showed no stenosis or insignificant coronary artery stenosis in 72%, significant stenosis in 26% and non-diagnostic in 2%. For the 131 patients who underwent invasive coronary angiography, 95% of the patients and 97% of the segments were evaluable, and the overall per-patient/per-segment sensitivity, the perpatient/per-segment specificity, the per-patient/per-segment PPV and the per-patient/per-segment NPV were 100%/90%, 71%/98%, 95%/88% and 100%/97%, respectively. The image quality was better in the HR < 65 group than in the HR ≥ 65 group (p = 0.001), but there was no difference in diagnostic performance between the two groups. The mean effective radiation doses were lower in the HR < 65 or HRV < 15 group (p < 0.0001): 5.5 versus 6.7 mSv for the mean HR groups and 5.3 versus 9.3 mSv for the HRV groups.

Conclusion

Dual-source CT coronary angiography is a highly accurate modality in the clinical setting. Better image quality and a significant radiation reduction are being rendered in the lower HR group.     

钙化积分扫描缩短冠脉CTA扫描范围及降低辐射量的作用

目的:探讨使用钙化积分扫描缩短增强扫描范围以降低后门控冠状动脉CTA检查辐射量的临床应用价值。方法:40例患者行冠脉钙化积分及冠脉CTA检查,其增强扫描的实际扫描范围根据钙化积分扫描图像来决定,即冠状动脉树上缘1cm至心尖部心包影即将消失的层面。并按常规方法在定位像上测量增强扫描的预计扫描范围,即气管隆突下1cm至心脏下缘2cm。比较两种扫描范围及相应的辐射剂量的差异。结果:实际扫描范围比预计扫描范围平均缩短(2.09±0.76)cm(t=17.31,P<0.01),冠状动脉CTA各序列总剂量较常规方法平均减少(1.51±0.87)mSv,差异有极显著性意义(t=10.92,P<0.01),相当于各序列平均剂量总和的9.20%。结论:使用钙化积分扫描图像能有效缩短增强扫描的范围,从而明显降低冠状动脉CT血管成像的辐射量。