Dose indices of radiation to skin in fluoroscopically guided invasive cardiology procedures.

Tissue injury depends on the extent as well as the intensity of the assault. It would be helpful to develop skin dose indices that are more descriptive of the skin area receiving radiation above a threshold value of potential injury. For monitoring radiation exposure to patients, radiochromic film was placed close to the skin of a patient undergoing cardiac catheterization procedures. With the approval of the Institutional Review Board, films from 36 patients were scanned. Contours were drawn at the increment of 100 cGy in air kerma. Using each contour value as a threshold, the area exceeding this threshold and the average dose within this area were computed. For the four patients who had skin doses exceeding the 200 cGy threshold, the peak entrance doses have a range from 230 cGy to 409 cGy. However, these high radiation exposures were confined to limited skin areas and support the absence of any significant skin injury in these patients. The area exceeding a chosen threshold value and the average dose within the area circumscribed might therefore serve as helpful measures of the assault to the skin. This investigation has demonstrated the technical feasibility of providing such dose indices.

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.

Measurement of dose-area product with GafChromic XR Type R film.

Many of the newer X-ray machines are equipped with electronic means to provide dose-area product (DAP) information. For machines without that ability, an alternative method is to record radiation on a film that can handle a large amount of cumulative exposure. The use of GafChromic XR Type R film was investigated for this purpose by placing it at the X-ray tube assembly to record the radiation in interventional radiological procedures. Dose-area product was determined with a reflective densitometer and then with a flatbed scanner. Precisions were demonstrated to be 5% and 2%, respectively. In a comparison with the machine-recorded DAP, a regression analysis showed the validity of both techniques for values less than 1200 Gy-cm2.

Energy dependence of photostimulable phosphor.

In this study, phantoms were used to illustrate the dependence of photostimulable phosphor's characteristic response on beam quality. These phantoms, consisting of sheets of acrylic and aluminum, represented an extremity, an abdomen, a skull and a chest. Images were taken with 50 to 65 kVp, 60 to 110 kVp, 65 to 80 kVp and 70 to 120 kVp, respectively. In general, the amount of resulting luminescence of the photostimulable phosphor per unit of air kerma (exposure) increased with kVp.