University of Pennsylvania
Radiation Safety Office

Diagnostic Energized Equipment
Radiation Safety Manual

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Outline

A. Radiographic Units
B. Fluoroscopic Units
C. Mobile Diagnostic Units
D. Computed Tomography Units
E. Dental units

A. Patient Shielding
B. Personnel Shielding
C. Structural Shielding

A. Personnel Dosimeter Policy
B. Dosimeter Placement
C. Dose Reports
D. Pick-up and Drop-off of Dosimeters

A. Reject-Repeat Analysis Program
B. Film Processors
C. Radiographic X-Ray Units
D. Fluoroscopic X-Ray Units
E. Computed Tomographic X-Ray Units
F. Dental X-Ray Units
G. Inspection of Protective Garments
H. Response to the Reported Problems
I. Visual Inspection

A. Registration of diagnostic units
B. Acquisition of new diagnostic units
C. Disposal of diagnostic units

A. Proper Operating Procedures for Radiographic Units

1. Limit the x-ray primary beam to the smallest area possible consistent with the objectives of the clinical examination.

2. Align the x-ray beam properly with the patient and the image receptor.

3. Remain behind a protective barrier (i.e., a leaded glass wall or a leaded door) during the entire radiographic exposure and observe the patient during the exposure from this protected area.

4. NCRP Report 102, 3.4 (h): "No person should routinely hold patients during diagnostic examinations. When a patient must be held in position for radiography, a mechanical supporting or restraining device should be used. Pregnant women or persons under the age of 18 years should not be permitted to hold patients. If a patient must be held by someone, that individual shall be protected with appropriate shielding devices such as protective aprons and gloves. Positioning should be arranged so that no part of the holder's torso, even if covered by protective clothing, will be struck by the useful beam and so that the holder's body is as far as possible from the useful beam."

5. Do not use expired radiographic films; protect unprocessed film adequately.

6. Provide protective garments (lead aprons and shielding) for all individuals whose presence is necessary during the radiographic exposure.

B. Proper Operating Procedures for Fluoroscopic Units

1. Only persons required for the fluoroscopic procedure should be in the room during the procedure.

2. As in a radiographic procedure, use the smallest possible beam area to reduce patient exposure and scatter radiation.

3. Perform visual observation of the alignment of the image intensifier, x-ray tube, and the patient prior to the initiation of a fluoroscopy procedure.

4. Minimize fluoroscopic doses by reducing the fluoroscopic time used. Fluoroscopic time, of course, varies with different patients, the type of the examination, and the complexity of the clinical study. Perform quarterly outputs for Entrance Skin Exposure (ESE) rates for all fluoroscopes. Post the ESE rates in the fluoroscopy room for reference by physician/radiologist.

5. Operators should use the timing device to indicate a preset time, which will serve as a reminder to keep it as short as possible. According to State regulations, the predetermined time should not exceed 5 minutes (PA 221.38).

6. Use the shortest possible distance from the image intensifier to the patient. For fluoroscopes that are equipped with AEC; AEC operations provide for automatic compensation so that when longer distances are used, a higher radiation dose is given to the patient.

7. The fluoroscopist should wear a thyroid shield, leaded gloves, and glasses to reduce exposure to the thyroid, extremities, and eyes.

C. Proper Operating Procedures for Mobile Diagnostic Units

If proper care is not taken, mobile equipment has a greater potential than standard diagnostic equipment for unnecessary radiation exposure of personnel and patients. In mobile units, variations can occur in exposures due to line voltage fluctuations which can affect the output of the machine. Rechargeable units & capacitor discharge units are not affected.

1. If possible, stand at least 2 meters away from the tube head and the patient (PA 221.47 c(2)). Distance is often the best possible protection from radiation.

2. It is important that only individuals necessary for the diagnostic examination be in the vicinity. Other individuals who are required to remain in the room should wear protective clothing or should be located behind a protective shield.

3. Wear protective garments .

4. In mobile or portable radiographic systems, ensure that the source to skin distance is not less than 30 centimeters. [PA 221.42.c]

5. Mobile fluoroscopes shall provide image intensification (PA 221.40).

D. Proper Operating Procedures for Computed Tomography Units

1. Use a scan plane position device, such as a light or lights, to indicate directly or indirectly the position of the slice plane(s) on the patient within 2 mm (NCRP 3.9.1(e)).

2. Observe the patient during the CT exposures.

3. Only individuals whose presence is necessary should be in the CT x-ray room during exposures. All such individuals should be protected with leaded aprons and/or portable shields.

E. Proper Operating Procedures for Dental Units

1. Only persons required for a radiographic procedure should be in the radiographic room during exposure. All persons must be adequately protected by protective garments (NCRP 35,4.4).

2. Align the x-ray beam and film very carefully with the area to be radiographed.

3. Stand behind protective barrier and observe the patient during the dental exposure.

4. Neither the operator nor the assistant shall hold the film in place for the patient during the exposure. Use the film holder devices to hold the film in place.

Control radiation exposure levels via four basic methods:

A. Maximize the distance from radiation source.
B. Minimize the radiation exposure time.
C. Shield the radiation source properly.
D. Shield patients and personnel.

A. Patient Shielding

"Sensitive body organs (e.g., lens of eye, gonads) should be shielded whenever they are likely to be exposed to the useful beam provided that such shielding does not eliminate useful diagnostic information or proper treatment. Shielding should never be used as a substitute for beam collimation"(NCRP Report 102, Section 2.2 (d)).

Gonadal Shielding

Shield the gonads with at least 0.25 mm of lead equivalence during diagnostic procedures in which gonads are in the useful beam, except for cases in which this would interfere with the diagnostic procedure.

B. Personnel Shielding

Personnel who remain in the room during examinations must be protected by proper shielding.

1. All personnel in the room during an exposure should wear leaded aprons .

2. Personnel who are likely to be exposed to high levels of scattered radiation to the thyroid during any procedure should wear thyroid shields.

3. Leaded glasses can greatly reduce the exposure of eye lenses to scattered radiation in fluoroscopy, especially for physicians.

4. Any person who must have his or her hand near the primary beam (as in cases in which no other means is available to immobilize a patient) should wear leaded gloves to reduce exposure of the extremities.

C. Structural Shielding

Each radiographic room has been designed with sufficient shielding in the walls to provide protection to anyone outside of the room. Do not tamper with the integrity of the shielded walls. If any personnel notice structural changes, such as holes drilled into walls, Radiation Safety should be notified as soon as possible.

A. Patient

Special consideration must be given to the protection of the embryo or fetus of women known to be, or potentially, pregnant. A patient of childbearing age should be questioned to ascertain the likelihood of pregnancy. If the patient is found to be pregnant or likely to be pregnant, the physician or radiologist should be consulted to decide whether this radiation dose to the patient is justified.

B. Personnel

An employee should contact the Radiation Safety Office either directly or through a supervisor when she knows or suspects that she is pregnant. If for personal reasons an employee does not wish to disclose pregnancy to her supervisor, confidential disclosures can be made directly to the Radiation Safety Office.

A. Personnel Dosimeter Policy

The Radiation Safety Office (RSO) uses personnel monitoring to identify inadequate or improper radiation safety practices and potentially serious radiation exposure situations. The RSO will issue proper personnel dosimeters when evaluation of equipment reveals that the radiation dose to personnel could potentially be larger than ALARA limits per calendar quarter to the whole body (125 mrem).

Radiation workers are monitored by the University of Pennsylvania Radiation Safety Office. All radiation workers must conscientiously wear the radiation monitoring devices provided by the RSO. These devices may include:

1. A Film Badge to monitor doses to the whole body

2. A Ring Dosimeter to monitor extremity doses

3. A TLD badge for whole body measurements

B. Dosimeter Placement

Interpretation of the measured dose depends on the placement of the dosimeter. All personnel must wear their dosimeters correctly. The following list indicates where the dosimeters are to be worn:

1. Film Badge with no TLD Badge: wear the film badge above any protective clothing at collar level.

2. Film Badge with a TLD Badge: wear the film badge under the lead apron and the TLD above the apron at collar level.

3. Ring Dosimeter: wear ring dosimeters so that the employee's name faces outwards.

Do not expose personnel monitoring devices to extreme heat or humidity. They are screened monthly. If any dosimeter has received a dose higher than the values shown below, the employee will be notified and the reason for the high reading will be investigated. Measures will be taken to keep radiation doses below these limits whenever possible:

All personnel must return all monitoring devices promptly every month.

C. Dose Reports

The Radiation Safety Office sends dose summary reports on a monthly and an annual basis. Post these reports in a conspicuous location in the department.

D. Pick-up and Drop-off of Dosimeters

The Radiation Safety Office delivers new dosimeters to each department on the last Wednesday of each month. Each group should have one person who is responsible for the distribution of dosimeters. The old dosimeters should be returned to the designated personnel. The Radiation Safety Office will pick these up by the first Wednesday of the following month for analysis.

The quality assurance program will ensure that doses to patients are in accordance with the standards of good practice.

A. Reject-repeat analysis program

The analysis of the rejected radiographs provides information about the different aspects of radiological imaging.

B. Film processors

Test each film processor daily for temperature, contrast, density, and speed. A graph of results of daily measurements will show deviation from normal behavior.

C. Radiographic x-ray units

Annually test the beam defining system, focal spot size, accuracy of field size, x-ray field and field alignment, and SID calibration. The radiation safety characteristics from the unit should comply with NCRP report NO. 33 as well as FDA and PA State regulations. Evaluate generator performance by testing the accuracy of the tube potential, timer, and tube current linearity, and the reproducibility of the x-ray output. In the absence of the mAs indicator, evaluate the phototimer response. Check the beam quality. Record and the measurement and compare it to that of the entrance skin exposure for typical patient examinations.

D. Fluoroscopic x-ray units

Test the exposure rate from the unit under both manual and automatic operation with simulated patient conditions. The maximum exposure rate should be less than 10 R/min. Test the high- and low- contrast resolution of the image intensifier. Measure the half-value layer, effective focal spot size, and minimum SSD. Test the entrance skin exposure during cine procedures for cardiology equipment. Measure the Entrance-Skin exposure rates for all fluoroscopes in each quarter of the calendar year. The radiation safety characteristics of the machine must meet the recommendations of NCRP Report NO. 33, as well as FDA and PA state regulations. Make exposure measurements of scattered radiation under simulated patient conditions.

E. Computed tomographic x-ray units

Test the resolution of the imaging system for high and low contrast. Measure the patient dose with a phantom under simulated patient conditions. Using contrast, calculate the noise level. Check the accuracy of tube current and take a measurement of the scatter radiation. The radiation safety characteristics of the machine must meet the recommendation of NCRP Report NO. 33, as well as FDA and PA state regulations.

F. Dental x-ray units

Annually measure focal spot size, collimation, field alignment, and SSD. Evaluate generator performance by testing the accuracy of the tube potential, timer, and tube current linearity, as well as the reproducibility of the x-ray output. Check the beam quality. Record the entrance skin exposure for a typical patient for typical patient examination and compare it with the measured doses. The radiation safety characteristics from the unit should comply with NCRP recommendation report NO. 33, as well as FDA and PA State regulations. In addition, perform a follow-up survey on all units with major non-compliance problems. Do a follow-up to ensure that required repairs are being performed.

G. Inspection of protective garments

Perform an annual inspection of the shielding garments, such as lead aprons and lead gloves.

H. Response to reported problems

Make all repairs on the units as soon as possible. Send repair documentation to authorized personnel upon completion of the repairs.

I. Visual inspection

Report all conspicuous problems with energized equipment or with shielded rooms, as well as any other safety problems observed by personnel to the Radiation Safety Office immediately.

A. Registration of Diagnostic Units

According to Section 216.2 of 25 PA Code, Chapter 216, all radiation-producing equipment must be registered with the Department of Environmental Resources. This registration is currently done by the RSO on an annual basis. The RSO maintains a listing of all units currently registered.

B. Acquisition of New Diagnostic Units

It is the responsibility of clinical personnel to notify the RSO upon acquisition of any new diagnostic equipment. Authorized RSO personnel will conduct a radiation safety survey on all new units prior to use.

C. Disposal of Diagnostic Units

Clinical personnel must notify the RSO of any diagnostic equipment intended for disposal. The RSO will work in cooperation with the Environmental Health & Safety Office to ensure safe disposal of diagnostic units.

Radiation Safety Office of the University of Pennsylvania: 898-7187