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Chapter 12: THE CHEST ROENTGENOGRAM AND CARDIAC FLUOROSCOPY CARDIAC FLUOROSCOPY

Cardiac radiography deals primarily with anatomic details by filming at short exposure times that stop the motion. Cardiac fluoroscopy, on the other hand, explores the dynamic features of the organ that are discernible only in motion.28 The two techniques are mutually complementary.

Description

A good-quality image intensifier is a prerequisite for the proper performance of cardiac fluoroscopy.2!9 The modern intensifier with cesium iodide phosphors has increased the brightness of the fluoroscopic image at least 10,000 times. Television viewing permits cone vision under dim light with better perception of detail. The attached videotape or videodisk recorder providesa means for instant playback as well as future analysis of the fluoroscopic observations.

The milliamperage and kilovoltage of the fluoroscope should be adjusted according to the patient's size in different projections. The milliamperage ranges from 1.5 to 3.5 mA, and the kilovoltage varies between 90 and 120 kV. Too high a kilovoltage tends to reduce the contrast, and excessive milliamperage blurs the margin of the image. The shortest fluoroscopic time and the smallest shutter opening are employed to keep the dose of radiation to the patient to the minimum. The average examining time for this author is 3 min.

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The patient is routinely examined in the erect position with four views. The patient should be asked to stop breathing during the brief moment of fluoroscopy. A barium meal is given only after a thorough search for cardiac calcifications is completed. Occasionally, a recumbent position is used for better visualization of small calcifications, as well as for a critical evaluation of cardiac asynergy. The cardiac output increases and the heart rate decreases on assuming recumbency, thereby giving a truer and more representative picture of the left ventricular contractility. In obese patients, the thick layer of soft tissue over the thorax is compressed and pushed aside, thereby improving the fluoroscopic image significantly.

Results

When performed properly, cardiac fluoroscopy is useful in the following areas of investigation: (1) assessment of cardiovascular dynamics, (2) detection of small cardiovascular calcifications, (3) visualization of important anatomic landmarks, e.g., subepicardial fat stripes, (4) differentiation of cardiac from noncardiac disease, and (5) evaluation of cardiac valve prostheses, pacemakers, and radiopaque foreign bodies.

Precautions

Although no complication from modern fluoroscopy has been reported, both the patient and the examiner should be protected from excessive radiation. Even with an image intensifier, a routine cardiac fluoroscopy still involves more radiation than does two-view chest roentgenography. Therefore, the fluoroscopist should accomplish the task within the shortest possible period of time. Although all aspects of the heart are surveyed briefly, one should emphasize special areas of interest for each patient, as suggested by the baseline radiographs. If coarctation of the aorta is suspected in a patient older than 40 years of age, for instance, particular attention should be paid to finding calcium in a stenotic bicuspid aortic valve. Applications

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