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Interventional Cardiology

Cardiologists are among the most intensive users of fluoroscopy in the medical profession, if not the most frequent. However, many of them are unaware that they may be exposing patients to relatively high levels of radiation during cardiac catheterization procedures - levels much higher than those handled by many radiologists. While staff protection is definitely important, there are bigger issues of patient protection in interventional procedures using X rays. For description of radiation units and dose quantities, please click here..

Patient protection

Staff protection - Some of the measures to reduce patient dose will also result in a reduction of staff dose

1. Are radiation induced skin injuries common among patients undergoing interventions?

No. Radiation induced skin injuries happen very rarely and the rough estimate is around one in 10,000 interventions. This figure can vary by a large margin as many injuries go unreported. The skin injuries can vary from mild erythema to deep skin ulceration. Many interventionalists still do not acknowledge that skin injuries have or could occur. Such denial has led, in many cases, to uncertain and ill-directed care for some patients. Injuries occur weeks or months after the interventional procedure was performed and could create problems in diagnosis. Most of these injuries can be avoided by using established radiation protection approaches.

Further details are available »

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2. What problems are associated with diagnosis of such injuries?

Experience has shown that patients normally go to a physician or dermatologist when symptoms are detected. The delay between the interventional procedure and occurrence of symptoms coupled with the lack of instruction by the interventionalist to report back to him if there is any skin irritation on ports of entries of the X ray beam (typically patient's back), are responsible for misdiagnosis. There have been situations of misdiagnosis as insect bites, electrical burns, chemical burns or contact dermatitis. Typically in radiation induced injuries, normal methods of treatment with creams fail to give relief to the patient.

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3. Can radiation injuries be prevented?

In most, if not all cases, the answer is ‘yes’, at least as far as the severe injuries are concerned. The experience from a centre where cardiologists were trained in radiological protection and the equipment was monitored and covered by a quality control programme indicates an absence of skin injuries in patients who underwent 5-7 PTCAs and 5-14 additional angiographies [VA1].

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4. How high is the patient exposure in cardiac interventions in comparison to chest radiograph?

Entrance exposure to patients in diagnostic and therapeutic angiography might be a few hundreds to even a thousand times more than in a chest radiograph.

It must be emphasized that this way of comparing is an over-simplification as exposure situations are not similar.

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5. Which factors can affect patient dose in cardiac interventions?

There are patient, equipment and procedure dependent factors.

Patient factors include: : body mass or body thickness in the beam, complexity of the lesion and anatomic target structure, radiosensitivity of some patients (ataxia telangiectasia); connective tissue disease and diabetes mellitus.

Equipment factors include: setting done by the manufacturer on fluoro- and cine mode, appropriate quality control, existence of cine loop, last image hold, pre-selectable number of radiographic frames per run and virtual collimation.

The main procedure related factors are: number of radiographic frames per run, collimation, the fluoroscopic and radiographic acquisition modes, fluoroscopy time, wedge filter, magnification, distance of patient to image receptor (image intensifier or flat panel detector), distance between X ray tube and patient and tube angulations. For further details please consult the references below.

Further details are available »

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6. How can I manage patient exposure?

Patient’s anatomic state, e.g. weight and the complexity of intervention are relevant and may be fixed, but a number of factors can help the interventionalist in patient exposure management. Collimation, a commonly neglected factor can prove to be the most efficient influencing factor. Restriction to the essential number of radiographic frames and to adequate (required image information) instead of best-possible image quality are more efficient than the potential of optimisation of fluoroscopy time. Further, adequately short radiographic runs, inspiration during radiography, avoid irradiating arms and breast, use means to monitor exposure, preference of less irradiating angulations, e.g. short skin-to-image-intensifier distance, use of the lowest image magnification compatible with the clinical objective [KU].

Further details are available »

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7. What adverse effects could occur as a result of dose reduction actions?

Optimization of protection requires that exposure of patients be the minimum necessary to achieve the required diagnostic (BSS) and therapeutic objective of the interventional procedure. By no means should dose reduction compromise clinical information and outcome. If overlooked, the adverse effects may be quality and extent of information.

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8. Is the exposure to the cardiologist much higher than to non-interventionalists?

The radiation exposure of the cardiologist is of significance principally for following three reasons:

  1. location - has to work inside and near the X ray tube and cannot be too far away from the patient;
  2. time - the radiation 'ON' time in a well utilized catheterization laboratory is typically a few hours per day (say 60-200 minutes) in contrast to a radiography room where it is generally two-four minutes for a workload of 100-200 radiographs per day; and
  3. shielding - attenuation by lead apron can be to the order of 90-97% depending upon the lead content of the apron whereas higher attenuation is possible with structural shielding for those who work at the console outside the X ray room.

Further factors to consider are:

  • radiation intensity - in the fluoroscopy mode, intensity is lower by a factor of few tens as compared to the radiography or cine mode;
  • exposure parameters - typically they are automatically controlled by equipment and are higher for patients with high body mass;
  • cardiologists may work in the catheterization laboratory only few days a week (against five or six days a week for the staff at the console).

Considering all these factors, the exposure to intervantionalists can be many times higher than a staff who works only at the console located just outside the X ray room. [RE].

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9. Is there a risk of cataract after several years of work in a catheterization laboratory?

Proper use of radiation protection tools (most importantly the protective screens or lead glass barrier) and techniques can prevent effects such as cataracts for work in catheterization laboratory to cover full professional life.

At the moment, it is not clear if these early changes will lead to lens opacity. The interventional practice is increasing and some interventionalists perform many procedures (aproximately 1000 procedures per year or more). Measurements and calculations indicate that if radiation protection devices and procedures are not used, the threshold for cataract can be exceeded with possibility of radiation induced lens injury. At the same time, it is clear that proper use of radiation protection can avoid lens injuries even with high workload.

There is a published report of radiation induced cataracts of one interventional radiologist and two nurses [VA]. Results from recent studies conducted by the IAEA reveal the prevalence of radiation associated posterior lens opacities ranged from 38 - 52% for interventional cardiologists, 21 - 45% for nurses. Estimated cumulative ocular doses ranged from 0.01 Gy to 43 Gy. [CI; VA2]

The subject of radiation induced cataract is under review by the International Commission on Radiological Protection (ICRP).

http://rpop.iaea.org/RPOP/RPoP/Content/News/relid-cataract-study.htm

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10. Can I work my full professional life in a catheterization laboratory and have no radiation effects?

Yes it is possible. Under optimized conditions when the equipment is periodically tested and it is operating properly, when personal protective devices (lead apron of suitable lead equivalence of 0.25 to 0.5 mm and wrap around type, protective eye wears or protective shields are used for head/face and leg region), when proper technique is employed, it is possible to achieve negligible probability of all known radiation effects during a full professional life. There are situations where patient protection poses a great challenge, not so much in staff protection where it can reasonably achieved.

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11.What are the typical radiation doses associated with diagnostic and therapeutic interventional procedures?

Typical values in terms of effective dose and dose area product (DAP) values are presented in Tables 1 and 2 below:

Table 1 Mean effective doses and DAP values from diagnostic interventional procedures

Diagnostic interventional radiological/cardiological procedures Mean Effective doses(mSv) Mean DAP value (Gy.cm2) Equivalent number of PA chest radiograph(each 0.02 mSv)
Upper extremity angiography [BO] 0.56 12 28
T-Tube cholangiogram [HA] 2.6 10 130
Cerebral angiography [BO] 3 85.7 150
Coronary angiography [HA] 3.1 26 155
Lower extremity [BO] 3.5 14 175
ERCP [HA] 3.9 15 195
Thoracic aortography [HA] 4.1 34.5 205
Pulmonary angiography [ME] 5   250
Arterial pressures* [HA] 7   350
Peripheral arteriography [HA] 7.1 27.2 355
Abdominal aortography [ME] 12   600
Renal angiography [BO] 13.7 86 685
Mesenteric angiography [HA] 22.1 85 1105

* Fluoroscopically guided catheterization for the measurement of pulmonary artery pressure

Table 2 Mean effective doses and DAP values from therapeutic interventional procedures

Interventional Radiological /cardiological therapeutic procedures Mean Effective doses (mSv) Mean DAP value (Gy.cm2) Equivalent number of PA chest radiograph (each 0.02 mSv)
Upper extremity arterography [BO] 0.9 18 45
Nephrostomy [HA] 3.4 13 170
Thrombolysis [HA] 3.5 13.5 175
Pacemaker implant [HA1] 4 17 200
Lower extremity arterography [BO] 4.5 18 225
Ureteric stenting [HA] 4.7 18 235
Cerebral embolisation [HA] 5.7 202 285
Vascular stenting [HA] 10.4 40 520
Renal angiography [BO] 11.7 81 585
Insertion of caval filters [HA] 12.5 48 625
Kidney stent insertion [HA] 12.7 49 635
Biliary intervention [MA]   54  
PTCA, stent placement [HA] 15.1 58 755
Bile duct drainage [MI] 18.4 70.6 920
Cardiovascular embolisation [HA] 19.5 75 975
Radio frequency ablation [PA] 20.3 54.6 1015
Valvuloplasty [HA] 29.3 162 1465
TIPS [HA] 53.6 206 2680
Pelvic vein embolisation [ME] 60   3000
Uterine fibroid embolisation [MI] 77.5 298.2 3875

Typical radiation doses from other fluoroscopy procedures

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References


 
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