Real-time measurement of skin radiation during cardiac catheterization

What are useful methods to reduce occupational radiation exposure among radiological medical workers, especially for interventional radiology personnel?

Protection against occupational radiation exposure in clinical settings is important. This paper clarifies the present status of medical occupational exposure protection and possible additional safety measures. Radiation injuries, such as cataracts, have been reported in physicians and staff who perform interventional radiology (IVR), thus, it is important that they use shielding devices (e.g., lead glasses and ceiling-suspended shields). Currently, there is no single perfect radiation shield; combinations of radiation shields are required. Radiological medical workers must be appropriately educated in terms of reducing radiation exposure among both patients and staff. They also need to be aware of the various methods available for estimating/reducing patient dose and occupational exposure. When the optimizing the dose to the patient, such as eliminating a patient dose that is higher than necessary, is applied, exposure of radiological medical workers also decreases without any loss of diagnostic benefit. Thus, decreasing the patient dose also reduces occupational exposure. We propose a novel four-point policy for protecting medical staff from radiation: patient dose Optimization, Distance, Shielding, and Time (pdO-DST). Patient dose optimization means that the patient never receives a higher dose than is necessary, which also reduces the dose received by the staff. The patient dose must be optimized: shielding is critical, but it is only one component of protection from radiation used in medical procedures. Here, we review the radiation protection/reduction basics for radiological medical workers, especially for IVR staff.

Planned versus bailout rotational atherectomy: A systematic review and meta-analysis

BACKGROUND/PURPOSE

Rotational atherectomy (RA) plays a central role in the treatment of heavily calcified coronary artery lesions. Our aim was to compare periprocedural characteristics and outcomes of planned (PA) vs. bailout (BA) rotational atherectomy.

METHODS

We conducted a systematic review and performed a meta-analysis on studies which compared PA vs. BA strategy.

RESULTS

Five studies fulfilled the inclusion criteria, pooling a total of 2120 patients. There was no difference in procedural success, PA vs. BA risk ratio (RR) 1.03 and 95% confidence interval (95% CI) 0.99-1.07. Compared to BA, PA was associated with a shorter procedural time [mean difference (MD) -25.88 min, 95% CI -35.55 to -16.22], less contrast volume (MD -43.71 ml, 95% CI -69.17 to -18.25), less coronary dissections (RR 0.50, 95% CI 0.26-0.99), fewer stents (MD -0.20, 95% CI -0.29 to -0.11), and a trend favouring less periprocedural myocardial infarctions (MI) (RR 0.77, 95% CI 0.54-1.11). There was no difference in major adverse cardiovascular events on follow-up (RR 1.04, 95% CI 0.62-1.74), death (RR 0.98, 95% CI 0.59-1.64), MI (RR 1.16, 95% CI 0.62-2.18), target vessel revascularization (RR 1.40, 95% CI 0.83 to 2.36), stroke (RR 1.50, 95% CI 0.46-4.86) or stent thrombosis (RR 0.82, 95% CI 0.06-10.74); all PA vs. BA comparisons.

CONCLUSIONS

Compared to bailout RA, planned RA resulted in significantly shorter procedural times, less contrast use, lesser dissection rates and fewer stents used. The bailout RA approach appears to enhance periprocedural risk, but there is no difference on mid-term outcomes.

An initial investigation of a wireless patient radiation dosimeter for use in interventional radiology

Radiation exposure during interventional radiology (IR) procedures is a critical issue. We have developed a wireless real-time dosimeter for IR patients that use nontoxic phosphor (four sensors). We evaluated the basic performance parameters (such as dose linearity, batch uniformity, reproducibility, and wireless-communication conditions) of the developed system using an IR X-ray system. Further, we investigated the influence of noise from other medical equipment on our wireless real-time dosimeter in the IR X-ray room. Overall, our wireless system exhibited excellent performance in terms of uniformity, reproducibility, and linearity; moreover, the wireless communication performance was better. The developed system enabled real-time visualization of patient radiation dose, without noise contamination from other medical equipment. In addition, the wireless system can be easily installed in a location where the PC screen (display) can be readily viewed by the IR physician. Hence, we developed a wireless system that can display the patient radiation dose data in real time; the system performed satisfactorily upon application in radiation dosimetry. Therefore, our wireless system will facilitate the real-time monitoring/management of patient radiation dose during IR.

Fast skin dose estimation system for interventional radiology

To minimise the radiation dermatitis related to interventional radiology (IR), rapid and accurate dose estimation has been sought for all procedures. We propose a technique for estimating the patient skin dose rapidly and accurately using Monte Carlo (MC) simulation with a graphical processing unit (GPU, GTX 1080; Nvidia Corp.). The skin dose distribution is simulated based on an individual patient's computed tomography (CT) dataset for fluoroscopic conditions after the CT dataset has been segmented into air, water and bone based on pixel values. The skin is assumed to be one layer at the outer surface of the body. Fluoroscopic conditions are obtained from a log file of a fluoroscopic examination. Estimating the absorbed skin dose distribution requires calibration of the dose simulated by our system. For this purpose, a linear function was used to approximate the relation between the simulated dose and the measured dose using radiophotoluminescence (RPL) glass dosimeters in a water-equivalent phantom. Differences of maximum skin dose between our system and the Particle and Heavy Ion Transport code System (PHITS) were as high as 6.1%. The relative statistical error (2 σ) for the simulated dose obtained using our system was ≤3.5%. Using a GPU, the simulation on the chest CT dataset aiming at the heart was within 3.49 s on average: the GPU is 122 times faster than a CPU (Core i7-7700K; Intel Corp.). Our system (using the GPU, the log file, and the CT dataset) estimated the skin dose more rapidly and more accurately than conventional methods.

Direct Dose Measurement On Patient During Percutaneous Coronary Intervention Procedures Using Radiophotoluminescence Glass Dosimeters

The purpose of this research was to measure accurate patient entrance skin dose and maximum skin absorbed dose (MSD) to prevent radiation skin injuries in percutaneous coronary interventions (PCIs). We directly measured the MSD on 50 PCIs by using multiple radiophotoluminescence glass dosimeters and a modified dosimetry gown. Also, we analysed the correlation between the MSD and indirect measurement parameters, such as fluoroscopic time (FT), dose-area product (DAP) and cumulative air kerma (C-AK). There were very strong correlations between MSD and FT, DAP and C-AK, with the correlation between MSD and C-AK being the strongest (r = 0.938). In conclusion, the regression lines using MSD as an outcome value (y) and C-AK as predictor variables (x) were y = 1.12x (R2 = 0.880). From the linear regression equation, MSD is estimated to be ~1.12 times that of C-AK in real time.

Fundamental study on the characteristics of a radiophotoluminescence glass dosemeter with no energy compensation filter for measuring patient entrance doses in cardiac interventional procedures

Cardiac interventional procedures have been increasing year by year. However, radiation skin injuries have been still reported. There is a necessity to measure the patient entrance skin dose (ESD), but an accurate dose measurement method has not been established. To measure the ESD, a lot of radiophotoluminescence dosemeters (RPLDs) provide an accurate measurement of the direct actual ESD at the points they are arrayed. The purpose of this study was to examine the characteristics of RPLD to measure the ESD. As a result, X-ray permeable RPLD (with no tin filter) did not interfere with the percutaneous coronary intervention procedure. The RPLD also had good fundamental performance characteristics. Although the RPLD had a little energy dependence, it showed excellent dose and dose-rate linearity, and good angular dependence. In conclusion, by calibrating the energy dependence, RPLDs are useful dosemeter to measure the ESD in cardiac intervention.

Radiation-induced noncancer risks in interventional cardiology: optimisation of procedures and staff and patient dose reduction

Concerns about ionizing radiation during interventional cardiology have been increased in recent years as a result of rapid growth in interventional procedure volumes and the high radiation doses associated with some procedures. Noncancer radiation risks to cardiologists and medical staff in terms of radiation-induced cataracts and skin injuries for patients appear clear potential consequences of interventional cardiology procedures, while radiation-induced potential risk of developing cardiovascular effects remains less clear. This paper provides an overview of the evidence-based reviews of concerns about noncancer risks of radiation exposure in interventional cardiology. Strategies commonly undertaken to reduce radiation doses to both medical staff and patients during interventional cardiology procedures are discussed; optimisation of interventional cardiology procedures is highlighted.

Physician-received scatter radiation with angiography systems used for interventional radiology: comparison among many X-ray systems

Radiation protection for interventional radiology (IR) physicians is very important. Current IR X-ray systems tend to use flat-panel detectors (FPDs) rather than image intensifiers (IIs). The purpose of this study is to test the hypothesis that there is no difference in physician-received scatter radiation (PRSR) between FPD systems and II systems. This study examined 20 X-ray systems in 15 cardiac catheterisation laboratories (11 used a FPD and 9 used an II). The PRSR with digital cineangiography and fluoroscopy were compared among the 20 X-ray systems using a phantom and a solid-state-detector electronic pocket dosemeter. The maximum PRSR exceeded the minimum PRSR by ~12-fold for cineangiography and ~9-fold for fluoroscopy. For both fluoroscopy and digital cineangiography, the PRSR had a statistically significant positive correlation with the entrance surface dose (fluoroscopy, r = 0.87; cineangiography, r = 0.86). There was no statistically significant difference between the average PRSR of FPDs and IIs during either digital cineangiography or fluoroscopy. There is a wide range of PRSR among the radiography systems evaluated. The PRSR correlated well with the entrance surface dose of the phantom in 20 X-ray units used for IR. Hence, decreasing the dose to the patient will also decrease the dose to staff.

Evaluating the maximum patient radiation dose in cardiac interventional procedures

Many of the X-ray systems that are used for cardiac interventional radiology provide no way to evaluate the patient maximum skin dose (MSD). The authors report a new method for evaluating the MSD by using the cumulative patient entrance skin dose (ESD), which includes a back-scatter factor and the number of cineangiography frames during percutaneous coronary intervention (PCI). Four hundred consecutive PCI patients (315 men and 85 women) were studied. The correlation between the cumulative ESD and number of cineangiography frames was investigated. The irradiation and overlapping fields were verified using dose-mapping software. A good correlation was found between the cumulative ESD and the number of cineangiography frames. The MSD could be estimated using the proportion of cineangiography frames used for the main angle of view relative to the total number of cineangiography frames and multiplying this by the cumulative ESD. The average MSD (3.0 ± 1.9 Gy) was lower than the average cumulative ESD (4.6 ± 2.6 Gy). This method is an easy way to estimate the MSD during PCI.

Comparison of the radiation dose in a cardiac IVR X-ray system

In this study, the entrance surface dose rates received by a phantom during cineangiography and fluoroscopy were compared. The X-ray conditions used in the measurements were those normally used in facilities performing percutaneous coronary intervention. Although, today, the entrance surface doses (cineangiography and fluoroscopy) of X-ray equipment used for cardiac interventional radiology (IVR) tends to be lower than they were previously, some equipment produces a high radiation dose. Therefore, the X-ray equipment used for cardiac IVR procedures must be maintained in good repair and must be carefully calibrated. In addition, periodic measurement of the radiation dose from the X-ray equipment used for both cineangiography and fluoroscopy for cardiac IVR is necessary. If the radiation dose of the X-ray system in use is too high, the IVR staff should determine the reason and make an effort to reduce it. Hence, the IVR staff must be adequately trained in radiation protection.

Radiation dose and radiation protection for patients and physicians during interventional procedure

Although the wide acceptance of interventional radiology (IVR) procedures has led to increasing numbers of interventions being performed, the radiation doses from IVR are higher. Increasing numbers of case reports of patient radiation injury resulting from IVR are being published. Therefore, radiation protection during IVR poses a very important problem. To protect against radiation injury, the evaluation of radiation dose is essential. The radiation dose must be evaluated for each IVR x-ray machine and each laboratory, because it varies greatly. To obtain this information easily, and to ensure practical use of the radiation information, good relationships between interventionists and medical physicists are essential.

Patient radiation doses in interventional cardiology procedures

Interventional cardiology procedures result in substantial patient radiation doses due to prolonged fluoroscopy time and radiographic exposure. The procedures that are most frequently performed are coronary angiography, percutaneous coronary interventions, diagnostic electrophysiology studies and radiofrequency catheter ablation. Patient radiation dose in these procedures can be assessed either by measurements on a series of patients in real clinical practice or measurements using patient-equivalent phantoms. In this article we review the derived doses at non-pediatric patients from 72 relevant studies published during the last 22 years in international scientific literature. Published results indicate that patient radiation doses vary widely among the different interventional cardiology procedures but also among equivalent studies. Discrepancies of the derived results are patient-, procedure-, physician-, and fluoroscopic equipmentrelated. Nevertheless, interventional cardiology procedures can subject patients to considerable radiation doses. Efforts to minimize patient exposure should always be undertaken.

X-ray burns--painful, protracted, and preventable

Very high doses of x-ray may produce deep burns in the backs of patients having fluoroscopically guided cardiac interventional procedures. While these incidents are uncommon they can be prevented by judicious limitation of fluoroscopy and timely repositioning of the x-ray tube. Better education and improved methods for dose mapping should make these distressing complications a thing of the past.

Methods to reduce patients' maximum skin dose during percutaneous coronary intervention for chronic total occlusion

OBJECTIVES

The purpose of this research is to assess the patient's entrance skin dose (ESD) during percutaneous coronary intervention (PCI) for chronic total occlusion (CTO), and discuss methods to reduce the maximum ESDs.

BACKGROUND

Only a few reports are available on the methods to reduce patients' maximum ESD during the procedures.

METHODS

This study included consecutive 30 patients who underwent PCI procedures for CTO in the three institutions. Pearson correlation test was employed to determine the relationship between total fluoroscopic time (TFT) and the maximum ESD, dose area product (DAP) value, and the maximum ESD in each institution.

RESULTS

There were significant correlations between the TFT and maximum ESD (Institution 1: P = 0.000410, Institution 2: P = 0.000525), and between the DAP and the maximum ESD (Institution 2: P < 0.0001). In Institution 1, TFT of 60 min was set as the upper limit, and the maximum ESDs were controlled within 7 Gy. In Institution 2, the angiographic unit was a biplane system, and two skin sites were exposed, corresponding to the angulation of each X-ray tube. In Institution 3, the interventionalist changed the beam angulations frequently by several degrees during the procedures, and the maximum ESD was controlled within 3 Gy even during procedures with a TFT of more than 1 hr.

CONCLUSIONS

The TFT and DAP, the latter of which is preferable, are useful to estimate the maximum ESD. Limiting the TFT or DAP, or changing the beam angulations is important to control ESD during prolonged procedures.

Optimisation in fluoroscopy

Optimisation of radiation protection in fluoroscopy is important since the procedure could lead to relatively high absorbed doses both in patients and personnel resulting in acute radiation injury. Optimisation procedures include adjustment of the fluoroscopy equipment such as exposure factors as well as proper use of automatic brightness control and pulsed fluoroscopy. It is also important to gain the benefits of image processing and the higher sensitivity of flat panel detectors as compared to image intensifier-TV systems.

Proper positioning of the patient with respect to detector and X-ray tube is of fundamental importance to image quality and radiation dose to the patient. Both image quality and radiation dose are also affected by the methodology used with parameters such as magnification factor, increased filtration, use of last-image-hold and the use of a grid.

There is a direct relation between patient dose and the absorbed dose to the personnel since this is mostly due to scattered radiation from the patient. If the correct methodology and the correct radiation protection devices are used, the absorbed dose to the personnel could be minimised to acceptable levels even for those working with complex procedures.

In order to have an organised review of all aspects of optimisation, it is recommendable to have an active quality system at the department. This system should define responsibilities and tasks for persons involved.

Kodak EDR2 film for patient skin dose assessment in cardiac catheterization procedures

Patient skin doses were measured using Kodak EDR2 film for 20 coronary angiography (CA) and 32 percutaneous transluminal coronary angioplasty (PTCA) procedures. For CA, all skin doses were well below 1 Gy. However, 23% of PTCA patients received skin doses of 1 Gy or more. Dose-area product (DAP) was also recorded and was found to be an inadequate indicator of maximum skin dose. Practical compliance with ICRP recommendations requires a robust method for skin dosimetry that is more accurate than DAP and is applicable over a wider dose range than EDR2 film.

Skin entrance radiation dose in an interventional radiology procedure

Monitoring of skin entrance radiation exposure in lengthy interventional procedures has been recommended because of the potential for skin injury. Fluoroscopy duration and dose-area product (DAP) are readily available real-time measurements. It would be of interest to study the correlation of these parameters and skin entrance radiation. Twenty neurological interventional procedures performed through the aortic arch were monitored. Two pieces of GafChromic XR Type R film were placed between the patient and the examination table. An observer recorded the fluoroscopy duration and DAP for each phase of the procedure. Each film was scanned post-procedure in RBG mode, and then the image was analyzed for peak skin entrance radiation dose (in air kerma). All DAP values were corrected according to a calibration with an ion chamber. With the DAP values for the respective phases of a procedure, the effective dose in a Reference Man was calculated. For these twenty cases, the means and standard deviations were 17.2+/-6.4 min for x ray on-time, 256+/-65 Gy cm (-2) for DAP, 94+/-34 cGy for peak skin entrance dose in air kerma, and 19.2+/-5.0 mSv for effective dose, respectively. The peak skin entrance dose was correlated to fluoroscopy duration, DAP, and effective dose with the r(2)-values of 0.48, 0.46, and 0.09, respectively. The correlation with DAP or fluoroscopy duration was not sufficiently strong to infer skin entrance dose from either of these parameters. Therefore, skin entrance dose should be determined directly.

Factors That Influence Radiation Dose in Percutaneous Coronary Intervention

AIM

To explore the factors that may influence the radiation dose imparted to the patient in PCI, and investigate whether the use of the latest digital X-ray system based on FP detector technology can have an impact on dose.

MATERIALS AND METHOD

Demographic and clinical data such as number of lesions treated, number of stents placed, grade of tortuosity, and stage of occlusion, as well as use of double wire and double balloon technique, ostial stenting or bifurcation stenting, and presence of major complications were recorded, together with radiation parameters.

RESULTS

The factors that increased patient radiation dose were (1) patient gender, as men exhibited higher doses than women; (2) complex lesion; (3) increasing number of stents; (4) position of stent; (5) grade of tortuosity; and (6) stage of occlusion. The FP digital system appeared to be settled in a lower-dose rate for fluoroscopy (a factor of 6) and higher for dose per frame in cine (a factor of 3) in comparison with the image intensifier (II) system. There was a marked reduction of DAP when the FP technology was introduced.

CONCLUSION

More extensive studies should be performed in the future so as to further investigate the influence of the FP detector in IC.

Radiosensitive Functional Dye: Clinical Application for Estimation of Patient Skin Dose

Institutional review board approval and informed patient consent were obtained. The purpose of the study was to prospectively evaluate the use of radiosensitive indicators to estimate patient entrance skin dose (ESD). Forty-six patients wore a jacket with 48 or 52 indicators adhered to the back during percutaneous coronary interventions; they had eight additional indicators on their upper arms. The patients' ESDs were calculated according to the change in color of the indicators. There were good correlations between the ESDs estimated by using color measurements performed with an optical instrument and those estimated at visual observation (P < .001) and between the ESDs estimated by using a thermoluminescent dosimeter and those estimated by using color measurements (P < .001). The radiosensitive indicator method seems to be useful for estimating ESDs and their distribution during percutaneous coronary intervention; however, visual observation is reliable for estimating doses of up to 5 Gy only. (c) RSNA, 2006.

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.

Patient skin dose in cardiac interventional procedures: Conventional fluoroscopy versus pulsed fluoroscopy

OBJECTIVES

To investigate whether pulsed fluoroscopy reduces a patient's exposure compared with the exposure owing to conventional (continuous) fluoroscopy, we simulated the skin radiation doses of patients at cardiac catheterization facilities with various X-ray systems used in fluoroscopically guided intervention procedures.

BACKGROUND

Although many reports have noted that "pulsed fluoroscopy" provides important further reductions in radiation exposure, it has been determined that when comparing dose rates between different vendor systems, "pulsed fluoroscopy" does not reduce patients' exposure as compared with "conventional fluoroscopy".

METHODS

We examined 13 X-ray systems; 10 used pulsed fluoroscopy and three used conventional fluoroscopy. The entrance surface doses with fluoroscopy were compared for the 13 X-ray systems by using acrylic plates (20-cm thick) and a skin dose monitor. The X-ray conditions used in the measurements were those normally used in the facilities performing percutaneous coronary intervention.

RESULTS

The average surface dose for systems from three different vendors producing conventional fluoroscopy systems was 23.93+/-2.77 mGy/min vs. an average surface dose of 22.52+/-4.50 mGy/min from five vendors of pulsed fluoroscopy systems (25, 30, and 50 pulses/sec) (P=0.646). The average entrance surface dose was significantly (P<0.0001) higher with conventional fluoroscopy and pulsed fluoroscopy at 25, 30, and 50 pulses/sec (23.05+/-3.78 mGy/min) than with pulsed fluoroscopy at 15 pulses/sec (13.86+/-3.22 mGy/min).

CONCLUSIONS

Pulsed fluoroscopy did not in itself reduce radiation exposure. In general, the use of pulsed fluoroscopy at a pulse rate lower than 25 pulses/sec should reduce the skin dose in fluoroscopically guided intervention procedures. Nevertheless, some X-ray systems are not designed to reduce the dose rate as the number of pulses per second is decreased. Physicians should be aware of the entrance surface dose of the X-ray system that they use for cardiac IVR.

Indicators of the maximum radiation dose to the skin during percutaneous coronary intervention in different target vessels

OBJECTIVES

To evaluate whether the maximum radiation dose to the patient's skin (MSD) can be estimated during percutaneous coronary intervention (PCI) procedures, we investigated the relationship between the MSD and fluoroscopic time, dose-area product (DAP), and body weight, separately analyzing the relationships for different target vessels.

BACKGROUND

Many cases of skin injury caused by excessive radiation exposure during cardiac intervention procedures have been reported. However, real-time maximum-dose monitoring of the skin is unavailable for many cardiac intervention procedures.

METHODS

We studied 197 consecutive PCI procedures that involved a single target vessel and were conducted. The DAP was measured, and the MSD was calculated by a skin-dose mapping software program (Caregraph). The target vessels of the PCI procedures were divided into four groups based on the AHA classification system: AHA 5-10, left anterior descending artery domain (LAD), AHA 11-15, left circumflex artery domain (LCx), AHA 1-3 = R 1-3, and AHA 4 = R 4.

RESULTS

The correlation coefficient (r) between the MSD and fluoroscopic time was higher for the right coronary artery (RCA) vessels (R 1-3, 0.852; R 4, 0.715) than for the left coronary artery (LCA) vessels (LAD, 0.527; LCx, 0.646), and the r value between the MSD and DAP was higher for the RCA vessels (R 1-3, 0.871; R 4, 0.898) than for the LCA vessels (LAD, 0.628; LCx, 0.694). Similarly, the correlation coefficient between the MSD and weight x fluoroscopic time (WFP) was higher for the RCA vessels (R 1-3, 0.874; R 4, 0.807) than for the LCA vessels (LAD, 0.551; LCx, 0.735).

CONCLUSIONS

The DAP and WFP can be used to estimate the MSD during PCI in the RCA but not in the LCA, especially the LAD.

Radiation Exposure to Patient's Skin During Percutaneous Coronary Intervention for Various Lesions, Including Chronic Total Occlusion

BACKGROUND

Radiation skin injuries have been reported as a result of various procedures, so in the present study the patients' entrance skin dose (ESD) during percutaneous coronary intervention (PCI) was evaluated.

METHODS AND RESULTS

ESDs were assessed during 97 procedures (13 for chronic total occlusion (CTO), 14 for multivessel stenoses, 22 for single-vessel multiple stenoses, and 48 for single stenosis). The patients wore jackets that had 48 or 52 radiosensitive indicators placed on the back during the PCI procedures, with 8 other indicators placed on both upper arms. After the procedure, the color of the indicators was analyzed with a color measuring instrument, and the patients' ESDs were calculated from the color difference of the indicators. The average maximum ESDs of the patients were 4.5 +/- 2.8 Gy (median: 4.6 Gy) for CTO, 2.3 +/- 0.7 Gy (median: 2.4 Gy) for multivessel stenoses, 1.8 +/- 1.0 Gy (median: 1.5 Gy) for single-vessel multiple stenoses, and 1.4 +/- 0.9 Gy (median: 1.2 Gy) for single stenosis.

CONCLUSIONS

Skin injury can occur during PCI, especially for CTO, so it is important to estimate each patient's ESD and attempt to reduce it.

Patient dosimetry approaches in interventional cardiology and literature dose data review

Interventional radiology contributes a significant proportion of the collective dose of the population from medical exposures. Interventional radiology procedures are usually fluoroscopy-guided diagnostic and therapeutic interventions. When complex procedures are performed or procedures are repeated for the same patient, high-radiation dose levels can occur because procedures often require long fluoroscopy times and require high-quality images. For all of these reasons, dosimetric evaluations in interventional radiology are widely increasing. Patient dosimetry methods currently used in interventional radiology may be divided into three categories according to dosimetry purpose: (I) dosimetry for stochastic risk evaluation, (II) dosimetry for quality assurance and (III) dosimetry to prevent the deterministic effects of radiation. A short description of dosimetric methods used in interventional cardiology practice and relevant published dosimetric data are reported.

Retrospective evaluation of occurrence of skin injuries in interventional cardiac procedures

Interventional cardiology procedures can involve high doses to patients and, in particular, to patients' skin, the tissue at greatest risk of deterministic injuries. The evaluation of skin dose from interventional procedures is recommended, but difficult because of the amount of different X-ray fields and projections used in a procedure. For this reason, a retrospective follow-up study has been developed to identify skin injuries in patients submitted to one or more cardiac interventions in the Udine hospital between 1998 and 2002. Seventy-eight patients with a cumulative dose-area product >300 Gy cm2 were selected from 3332 patients, who underwent 5039 procedures. In this group the maximum skin dose was 6.7 Gy. The clinical follow-up, performed using the LENT-SOMA methodology, has not detected skin injuries and this result allows a frequency to be estimated for skin injuries in patients undergoing repeated cardiac procedures of <3 x 10(-4) in our centre.

Characteristics of dosemeter types for skin dose measurements in practice

A growing number of papers report deterministic effects in the skin of patients who have undergone interventional radiological procedures. Dose measurements, and especially skin dose measurements, are therefore increasingly important. Methods and acceptable dosemeters are, however, not clearly defined. This paper is the result of a literature overview with regard to assessing the entrance skin dose during radiological examinations by putting a dosemeter on the patient's skin. The relevant intrinsic characteristics, as well as some examples of clinical use of the different detector types, are presented. In this respect, thermoluminescence, scintillation, semiconductor and film dosemeters are discussed and compared with respect to their practical use.

Reference levels in PTCA as a function of procedure complexity

The multicentre assessment of a procedure complexity index (CI) for the introduction of reference levels (RLs) in percutaneous transluminal coronary angioplasties (PTCA) is presented here. PTCAs were investigated based on methodology proposed by Bernardi et al. Multiple linear stepwise regression analysis, including clinical, anatomical and technical factors, was performed to obtain fluoroscopy time predictors. Based on these regression coefficients, a scoring system was defined and CI obtained. CI was used to classify dose values into three groups: low, medium and high complexity procedures, since there was good correlation (r = 0.41; P < 0.001) between dose-area product (DAP) and CI. CI groups were determined by an ANOVA test, and the resulting DAP and fluoroscopy time third quartiles suggested as preliminary RLs in PTCA, as a function of procedure complexity. PTCA preliminary RLs for DAP are 54, 76 and 127 Gy cm2, and 12, 20 and 27 min for fluoroscopy time, for the three CI groups.

Patient dosimetry during coronary interventions: a comprehensive analysis

BACKGROUND

We performed a detailed analysis of patient radiation during coronary interventions, comparing dose measurements to established dose reference levels, assessing coronary artery doses, and estimating total radiation risk of fatal cancer.

METHODS

We prospectively examined 281 patients who were subjected to 307 percutaneous coronary interventions.

RESULTS

The mean kerma area product (KAP) per procedure was 82.1 +/- 47.9 Gy x cm2. Corresponding values for fluoroscopy and digital cineangiography were 28.3 +/- 25.5 Gy x cm2 and 53.8 +/- 35.5 Gy x cm2, respectively, and exposure times were 13.1 +/- 6.8 minutes (87%) and 2.0 +/- 1.5 minutes (13%), respectively. The right anterior oblique caudal and left anterior oblique cranial projections accounted for the highest amount of KAP (24.0% and 23.1%, respectively) compared with other projections. The maximum recorded skin-dose was 182 mGy. Performing a representative procedure on a phantom, the effective dose was 14.9 mSv. The mean coronary dose was 61.7 +/- 38.2 mGy, with a highest calculated dose of 220.1 mGy. The third quartile of KAP measurements was 105 Gy x cm2, the 95th percentile was 175 Gy x cm2, and the mean value of KAP measurements was 82 Gy x cm2. The total risk for the development of fatal cancer was calculated as 83 cases for every 100,000 patients subjected to coronary intervention.

CONCLUSIONS

A detailed analysis of patient radiation during coronary interventions is presented. Coronary doses and total radiation risk of fatal cancer are also calculated, and a method for establishing dose reference level values is proposed.

Radiation doses in interventional radiology procedures: the RAD-IR study: part II: skin dose

PURPOSE

To determine peak skin dose (PSD), a measure of the likelihood of radiation-induced skin effects, for a variety of common interventional radiology and interventional neuroradiology procedures, and to identify procedures associated with a PSD greater than 2 Gy.

MATERIALS AND METHODS

An observational study was conducted at seven academic medical centers in the United States. Sites prospectively contributed demographic and radiation dose data for subjects undergoing 21 specific procedures in a fluoroscopic suite equipped with built-in dosimetry capability. Comprehensive physics evaluations and periodic consistency checks were performed on each unit to verify the stability and consistency of the dosimeter. Seven of 12 fluoroscopic suites in the study were equipped with skin dose mapping software.

RESULTS

Over a 3-year period, skin dose data were recorded for 800 instances of 21 interventional radiology procedures. Wide variation in PSD was observed for different instances of the same procedure. Some instances of each procedure we studied resulted in a PSD greater than 2 Gy, except for nephrostomy, pulmonary angiography, and inferior vena cava filter placement. Some instances of transjugular intrahepatic portosystemic shunt (TIPS) creation, renal/visceral angioplasty, and angiographic diagnosis and therapy of gastrointestinal hemorrhage produced PSDs greater than 3 Gy. Some instances of hepatic chemoembolization, other tumor embolization, and neuroembolization procedures in the head and spine produced PSDs greater than 5 Gy. In a subset of 709 instances of higher-dose procedures, there was good overall correlation between PSD and cumulative dose (r = 0.86; P <.000001) and between PSD and dose-area-product (r = 0.85, P <.000001), but there was wide variation in these relationships for individual instances.

CONCLUSIONS

There are substantial variations in PSD among instances of the same procedure and among different procedure types. Most of the procedures observed may produce a PSD sufficient to cause deterministic effects in skin. It is suggested that dose data be recorded routinely for TIPS creation, angioplasty in the abdomen or pelvis, all embolization procedures, and especially for head and spine embolization procedures. Measurement or estimation of PSD is the best method for determining the likelihood of radiation-induced skin effects. Skin dose mapping is preferable to a single-point measurement of PSD.

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.

Radiation dose reduction in invasive cardiology by restriction to adequate instead of optimized picture quality

In this study, the cinegraphic image intensifier entrance dose level for coronary angiography was changed in four steps from dose level A (0.041 microGy frame(-1)), allowing high contrast, but coarse mottled background, to level D (0.164 microGy frame(-1)), affording high transparency and sharpness. Using this new approach throughout the course of 404 consecutive cardiac catheterizations, we reduced patient radiation exposures down to 11 to 16% of currently typical values: i.e., mean dose area products of 5.97 Gy cm2 (n = 91), 6.73 (n = 113), 8.11 (n = 91), and 8.90 (n = 109); cinegraphic dose area products of 2.34, 3.64, 4.56, and 5.49; and cinegraphic dose area products frame(-1) of 13.3, 19.8, 27.0, and 30.2 mGy cm2, for levels A, B, C, and D, respectively. The number of cinegraphic frames ranged within 168 to 182 per case. Our results show that during catheterization interventionalists should vary image intensifier entrance dose levels in accordance with documented structure, angulation, and body mass index. With the exception of cases with special requirements, lower dose levels typically guarantee an adequate image quality.

Minimizing radiation-induced skin injury in interventional radiology procedures

Skin injury is a deterministic effect of radiation. Once a threshold dose has been exceeded, the severity of the radiation effect at any point on the skin increases with increasing dose. Peak skin dose is defined as the highest dose delivered to any portion of the patient's skin. Reducing peak skin dose can reduce the likelihood and type of skin injury. Unfortunately, peak skin dose is difficult to measure in real time, and most currently available fluoroscopic systems do not provide the operator with sufficient information to minimize skin dose. Measures that reduce total radiation dose will reduce peak skin dose, as well as dose to the operator and assistants. These measures include minimizing fluoroscopy time, the number of images obtained, and dose by controlling technical factors. Specific techniques-dose spreading and collimation-reduce both peak skin dose and the size of skin area subjected to peak skin dose. For optimum effect, real-time knowledge of skin-dose distribution is invaluable. A trained operator using well-maintained state-of-the art equipment can minimize peak skin dose in all fluoroscopically guided procedures.

Radiation injuries after fluoroscopic procedures

Fluoroscopically guided diagnostic and interventional procedures have become much more commonplace over the last decade. Current fluoroscopes are easily capable of producing dose rates in the range of 0.2 Gy (20 rads) per minute. The dose rate often changes dramatically with patient positioning and size. Most machines currently in use have no method to display approximate patient dose other than the rough surrogate of total fluoroscopy time. This does not include patient dose incurred during fluorography (serial imaging or cine runs), which can be considerably greater than dose during fluoroscopy. There have been over 100 cases of documented radiation skin and underlying tissue injury, a large portion of which resulted in dermal necrosis. The true number of injuries is undoubtedly much higher. The highest dose procedures are complex interventions such as those involving percutaneous angioplasties, stent placements, embolizations, and TIPS. In some cases skin doses have been in excess of 60 Gy (6000 rads). In many instances the procedures have been performed by physicians with little training in radiation effects, little appreciation of the radiation injuries that are possible or the strategies that could have been used to reduce both patient and staff doses. Almost all of the severe injuries that have occurred were avoidable.

Usefulness of rotational spin for coronary angiography in patients with advanced renal insufficiency

Coronary angiography in patients with advanced renal insufficiency is typically restricted to cases of life-threatening circumstances such as acute myocardial infarction and unstable angina. To gather a large amount of visual information with a minimum number of cine runs, and consequently, with a minimum volume of contrast medium, we rotated the gantry at 40 degrees /s throughout an angle of 120 degrees, from the right toward the left anterior oblique positions. This technique of rotational spin during cinegraphic runs has not yet become established in invasive cardiology. Three experienced cardiologists independently evaluated all coronary segments in rotational versus standard coronary angiography modes for 15 patients, on the basis of an 11-point scale (0 = cardiac spin far better to 10 = standard mode far better). A score of 5 signified that there was no difference in quality between the 2 modes. The arithmetic mean of the assessment values was 4.9 +/- 0.3 for coronary segments, 5.4 +/- 1.3 for coronary lesions, 5.1 +/- 1.4 for bifurcations, and 5.0 +/- 0.1 for coronary flow. The arithmetic means for the volume of contrast medium (25 +/- 4 ml), for the overall dose area product (8.6 +/- 4.5 Gy x cm(2)), and for the number of cine graphic frames (203 +/- 65) for a diagnostic cardiac spin were significantly below published typical values in standard mode. Cardiac spin enables 3-dimensional coronary impression under conditions of adequate image quality and represents a new, useful, and beneficial method in invasive cardiology for applications involving the special indication of advanced renal insufficiency.

Comparison of four techniques to estimate radiation dose to skin during angiographic and interventional radiology procedures

PURPOSE

Four techniques used to estimate radiation risk were compared to determine whether commonly used dosimetry measurements permit reliable estimates of skin dose. Peak skin dose (PSD) is known to be the most reliable estimate of risk to skin. The purpose of this study is to determine peak skin dose with use of real-time software measurements and to correlate other measures of dose with PSD.

MATERIALS AND METHODS

Two hundred twelve patients undergoing arch aortography and bilateral carotid arteriography (referred to as "carotid"), abdominal aortography and bilateral lower extremity runoff ("runoff"), or tunneled chest wall port placement ("port") were studied. Fluoroscopy time, dose-area product (DAP), and cumulative dose at the interventional reference point were recorded for all procedures; PSD was recorded for a subset of 105 procedures. The dose index, defined as the ratio between PSD and cumulative dose, was also determined.

RESULTS

In general, correlation values for comparisons between fluoroscopy time and the other measures of dose (r =.29 to.78) were lower than values for comparisons among DAP, cumulative dose, and PSD (r =.52 to.94). For all procedures, pair-wise correlations between DAP, cumulative skin dose, and PSD were statistically significant (P <.01) The ratio between PSD and cumulative skin dose (dose index) was significantly different for ports versus other procedures (carotid, Z = 4.62, P <.001; runoff, Z = 4.52, P <.001), but carotid and runoff procedures did not differ significantly in this regard (Z = 0.746, P =.22). Within each individual procedure type, the range of values for the dose index varied 156.7-fold for carotid arteriography, 3.2-fold for chest ports, and 175-fold for aortography and runoff.

CONCLUSION

Fluoroscopy time is a poor predictor of risk because it does not correlate well with PSD. Cumulative dose and DAP are not good analogues of PSD because of weak correlations for some procedures and because of wide variations in the dose index for all procedures.

CT fluoroscopy--guided interventional procedures: techniques and radiation dose to radiologists

PURPOSE

To determine the radiation dose to radiologists who perform computed tomographic (CT) fluoroscopic interventional procedures by using a quick-check method and a low-milliampere technique.

MATERIALS AND METHODS

Two hundred twenty CT fluoroscopy--guided interventional procedures were performed in 189 patients. Procedures included 57 spinal injections, 17 spinal biopsies, 24 chest biopsies, 20 abdominal aspirations, 44 abdominal biopsies, and 58 abdominal drainages. Procedure details were prospectively recorded and included site, depth, target diameter, milliampere value, kilovolt peak, fluoroscopic time, and CT technique (continuous CT fluoroscopy, quick-check method, or a combination of these techniques). An individual collar and finger radiation detector were worn by each radiologist during each procedure to determine the dose per procedure.

RESULTS

The quick-check technique was performed in 191 (87%) of 220 procedures. Four procedures were performed with continuous CT fluoroscopy, and a combination technique was used for 25 (11%) procedures. The overall mean CT fluoroscopic time was 17.9 seconds (range, 1.2--101.5 seconds). The mean milliampere value was 13.2 mA (range, 10--50 mA). The overall mean radiologist radiation dose per procedure was 2.5 mrem (0.025 mSv) (whole body). Individual procedure doses ranged from 0.66 to 4.75 mrem (0.007--0.048 mSv). The finger radiation dose was negligible.

CONCLUSION

By using a low-milliampere technique and the quick-check method, CT fluoroscopic time and radiation exposure can be minimized.

Evaluation of physical performance of a scintillation dosemeter for patient dosimetry in diagnostic radiology

The physical performance of the patient scintillation dosemeter Skin Dose Monitor (SDM) was evaluated for use in diagnostic radiology. The SDM response was found to be linear, with output air kerma and output air kerma rate having a reproducibility in time lower than +/- 2.4%) (one standard deviation). A calibration protocol taking into account the more significant parameters, such as radiation quality dependence and the relative sensitivity of SDM detectors of the same batch, can be applied so that the maximum overall uncertainty is +/- 18% at the 95% confidence level. The SDM detectors did not show any loss of sensitivity during the 5-month period of evaluation. SDM performance was evaluated against thermoluminescent dosemeters (TLDs) (GR200A) by monitoring chest X-rays in 18 adult patients. The difference in entrance surface dose (ESD) values between the SDM and TLDs was less than 10%, but a lack of accuracy in ESD values of less than 0.3 mGy was observed. The main benefit of the SDM device compared with TLDs is the real-time read-out of dose combined with a better flexibility and rapidity of use for approximately the same cost per measurement. The SDM device is a good candidate for regular measurement of patient doses in diagnostic imaging departments as required under implementation of the European Council Medical Exposure Directive of 30 June 1997.