Trends of increasing medical radiation exposure in a population hospitalized for cardiovascular disease (1970-2009)

BACKGROUND

High radiation doses employed in cardiac imaging may increase cancer frequency in exposed patients after decades. The aim of this study was to evaluate the relative trends in medical radiation exposure in a population hospitalized for cardiovascular disease.

METHODS AND RESULTS

An observational single-center study was conducted to examine 16,431 consecutive patients with heart disease admitted to the Italian National Research Council Institute of Clinical Physiology between January 1970 and December 2009. In all patients, the cumulative estimated effective dose was obtained from data mining of electronic records of hospital admissions, adopting the effective dose typical values of the American Heart Association 2009 statement and Mettler's 2008 catalog of doses. Cumulative estimated effective dose per patient in the last 5 years was 22 (12-42) mSv (median, 25(th)-75(th) percentiles), with higher values in ischemic heart disease (IHD), 37 (20-59) vs non-IHD, 13 (8-22) mSv, p<0.001. Trends in radiation exposure showed a steady increase in IHD and a flat trend in non-IHD patients, with variation from 1970-74 to 2005-2009 of +155% for IHD (p<0.001) and -1% in non-IHD (NS). The relative contribution of different imaging techniques was remodeled over time, with nuclear cardiology dominating in 1970s (23% of individual exposure) and invasive fluoroscopy in the last decade (90% of individual exposure).

CONCLUSION

A progressive increase in cumulative estimated effective dose is observed in hospitalized IHD patients. The growing medical radiation exposure may encourage a more careful justification policy regarding ionizing imaging in cardiology patients applying the two main principles of radiation protection: appropriate justification for ordering and performing each procedure, and careful optimization of the radiation dose used during each procedure.

Cardiovascular studies and the radiation dose

In a previous editorial, I commented on ionizing radiation associated with multislice computed tomographic angiography and x-ray coronary angiography performed in the catheterization laboratory. I mentioned that just by living, all of us are exposed to a background radiation dose, probably in the neighborhood of 3.6 millisieverts per year.

Interventional cardiovascular procedures in Belgium: effective dose and conversion factors

Effective dose (E), representing the risk of late radiation-induced effects, can be estimated by the use of conversion factors (CF), converting direct measurable quantities such as dose-area-product into E. Eight Belgian hospitals participated in the study with a total number of 318 procedures. E-values, calculated with PCXMC, were compared for the different hospitals for diagnostic and therapeutic procedures separately. E-values varied significantly depending on the hospital where the procedure was performed (P < 0.001), on filtration insertion (P < 0.001), on whether a centre is a training centre or not, the dose conscious action of the cardiologists and the complexity of the procedure (P < 0.001). Hospital-specific CF were calculated. An average CF of 0.185 mSv Gycm(-2) was obtained with a satisfactory correlation (r = 0.966, P < 0.001). The differences in CF between hospitals were due to, a large extent, the availability of additional filtration in cinegraphy mode (P < 0.001) and not to the differences in irradiation geometries in the clinical protocol of the interventional procedures.

Interventional radiology procedures: addressing the needs of the cardiovascular patient

Interventional radiologists perform a wide range of procedures on virtually every organ system in the body. Technological advances continue to expand the repertoire of procedures in this field, challenging the frontiers of medical science and individual expertise. With cardiovascular disease being the number 1 cause of death in the United States and an aging population before us, physicians who perform minimally invasive procedures must be knowledgeable regarding unique aspects of cardiovascular management as it pertains to the catheterization laboratory. Specific areas addressed in this review include anesthesia, hypertension, and chronic kidney disease.

It is time to test low level laser therapy in Great Britain

Low level laser therapy (LLLT) has been used in Eastern Europe and Asia for the treatment of a wide range of conditions for many years. Its continued acceptance in these populations reflects the efficacy with which it is regarded both by clinicians and their patients. Although there have been a substantial number of reports on its clinical benefit and some practitioners have used the technique in North America and Australasia it has yet to be subjected to detailed assessment through randomised clinical trials. The purpose of this review is to stimulate interest in the technique and to encourage rigorous research into its potential value.

A comparison of polyacrylamide gels and radiochromic film for source measurements in intravascular brachytherapy

For intravascular brachytherapy with catheter-based systems, AAPM Task Group 60 has recommended measurements that should be made to characterize the sources. Beta emitters, including (90)Sr/(90)Y are ideal for intravascular brachytherapy, but problems arise in measuring dose distributions in the high dose gradient region at short distances from the source. In this paper, measurements of radial and orthogonal dose distributions and dose profiles for a (90)Sr/(90)Y source train using polyacrylamide gel (PAG) dosimetry and a high-field 4.7 Tesla MRI scanner are presented and compared with measurements made with two types of radiochromic film, MD-55 and HD-810. For the PAG system, the dose distributions were determined with in-plane resolutions of 0.4 mm and 0.2 mm. The measurements of absorbed dose distributions both orthogonal and parallel to the source axis show good agreement between the PAG and radiochromic film. The absolute dose at a radial distance of 2 mm in the central 32 mm of a line parallel to the axis was measured. For the PAG the measured absorbed dose was 1.25% lower, for MD-55 4% higher and for the HD-810 1.6% higher when compared with the value given by the source calibration. These results confirm that both absorbed dose and dose distributions for high gradient vascular brachytherapy sources can be measured using PAG but the disadvantages of gel manufacture and the need for access to a high resolution scanner suggests that the use of radiochromic film is the method of choice.

Optimization of a 90Sr/90Y radiation source train stepping for intravascular brachytherapy

A steepest-descent gradient algorithm is developed to optimize the stepping of a 90Sr/90Y radiation source train (RST) for intravascular brachytherapy (IVB). The objective function is to deliver a uniform dose in a coronary target vessel and minimize the dose in adjacent normal vessel tissue at the proximal and distal edges of the coronary target vessel. Based on the target length and number of dwell points (number of steps), the algorithm modulates the dwell times and corresponding dwell positions that optimize the weighted addition of staggered EGS4 Monte Carlo (MC) calculated dose distribution from a single RST. Stepping treatment plans are generated for target vessel lengths of 3.0, 3.3, and 3.8 cm. For both the unoptimized and optimized plans, the dose heterogeneity in the target vessel wall, and length of nontarget vessel receiving 3 Gy, is assessed to compare plans. Optimization results show a 14% dose uniformity within the target is achievable for all vessel lengths. Further, the dose in the adjacent normal tissue is lower in the optimized plans than the unoptimized plans. The work presented in this paper provides a model to address the finite length of RST in IVB treatments. While the results presented are specific to the 90Sr/90Y RST, the methods should apply to other finite length RSTs.

[Use of radiotherapy in cardiovascular disease. Radiophysical basis, current results, indications and perspectives]

Restenosis is the main limitation of percutaneous angioplasty, especially in vessels of small diameters such as the coronary arteries, the femoro-popliteal and tibial-peroneal arteries and the arterio-venous dialysis grafts. The extensive use of tents has not entirely prevented its occurrence, whereas treating in-stent restenosis gives even more uncertain results. Endovascular radiotherapy has emerged over the past few years as a promising approach to both prevent and cure it. The analogy between the tumour-like cellular proliferations observed in post-angioplasty restenosis and tumour processes prompted pioneering works to study the effect of ionizing radiations in animal models of arterial restenosis. The demonstrated feasibility, tolerance and efficacy of this approach lead to test this strategy in humans. The results of 3 recently presented randomized double-blind trials in the treatment of coronary in-stent restenosis have been so promising that endovascular brachytherapy might now be considered the treatment of choice in this indication. Other randomized trials are currently carried out to test whether endovascular brachytherapy may prevent restenosis in coronary and femoro-popliteal arteries as well as in hemodialysis shunts. In the present review, we describe the basics of the biological effects of ionizing radiations, the technical modalities to deliver endovascular radiations, our current knowledge about their effects on the vascular wall and the restenosis mechanisms, and the results of the first clinical studies. Finally, we address the remaining problems in the use of endovascular curietherapy and question the promises and challenges of its clinical application.

A high-precision, high-resolution and fast dosimetry system for beta sources applied in cardiovascular brachytherapy

A fast dosimetry system based on plastic scintillator detectors has been developed which allows three-dimensional measurement of the radiation field in water of beta-sources appropriate for application in cardiovascular brachytherapy. This system fulfills the AAPM Task Group 60 recommendations for dosimetry of cardiovascular brachytherapy sources. To demonstrate the use of the system, measurements have been performed with an 90Y-wire source. The dose distribution was determined with a spatial resolution of better than 0.2 mm, with only a few minutes needed per scan. The scintillator dosemeter was absolutely calibrated in terms of absorbed dose to water with a precision of +/-7.5%. The relative precision achievable is +/-2.5%. The response of the system is linear within +/-2% for dose rates from 0.5 mGy s(-1) to 500 mGy s(-1).

[Aspects of radiation protection in cardiovascular brachytherapy]

In the scope of cardiovascular brachytherapy beta- as well as gamma-ray emitting radionuclides are used. The handling of radioactive sources is within the range of the radiation protection regulations (Strahlenschutzverordnung [StrlSch V]). According to EU guidelines an amendment of the StrlSch V is required by May 2000. The connected reduction of dose limits now should already be taken into consideration when planning irradiation facilities, likewise in cardiovascular brachytherapy. Temporary regulations for equipment that was already in operation before May 2000 are not planned in the new StrlSch V.

Improving the patient evaluation process in a cardiovascular and interventional radiology department

Brigham & Women's Hospital (BWH) has adopted total quality management (TQM) to increase productivity and efficiency and to improve the quality of patient care services. This article reports on a quality improvement project in the department of radiology designed to improve the process of pre-procedure workup of patients referred for cardiovascular and interventional radiology (CVIR) procedures. The project was initiated, led, and conducted by a physician.