Radiation Safety for Physicians, Technologists and R.N.’s - PowerPoint Presentation

1. Radiation Safety for Physicians, Technologists and R.N.’s Utilizing Fluoroscopy Equipment

2. OverviewALARA (As Low as Reasonably Achievable)Image Wisely, Image Gently, Step-LightlyBiological effects of radiation exposureMinimizing radiation exposures to patients and staffTechniques to optimize dose for pediatric and adult patients in FluoroscopyThe following topics will be covered

3. ALARAAs Low As Reasonably AchievableTime - Reduce the time spent near the source of radiation as well as the amount of time the source is exposed.Distance - Keep as far away from the source of radiation as possible. Doubling your distance from source decreases dose rate by factor of 4. Tripling your distance decreases dose rate by factor of 9.Shielding – Place shielding between radiation source and yourself.

4. Image WiselyTo put my patients' safety, health and welfare first by optimizing imaging examinations to use only the radiation necessary to produce diagnostic-quality images.To convey the principles of the Image Wisely® program to the imaging team in order to ensure that my facility optimizes its use of radiation when imaging patients.To communicate optimal patient imaging strategies to referring physicians, and to be available for consultation.To routinely review imaging protocols to ensure that the least radiation necessary to acquire a diagnostic-quality image is used for each examination.To monitor examination radiation dose indices to enable comparison to established diagnostic reference levels.

5. Image GentlyThe goals of Image Gently are to raise all stakeholders' awareness about the three key principles of radiation protection: justification, optimization, and dose limits. Justification: Do the benefits outweigh the risks? Optimization: CT protocols are adjusted for the size of the infant and child rather than a one-size-fits-all protocol. Justification: Physics and technical parameters are key to know how to use the lowest possible radiation dose necessary to achieve image quality.

6. Step-Lightly FluoroscopyStep Lightly: Pediatrics and AdultsTap on pedal and examine still image on monitor, minimize live fluoroscopic time Position with fluoroscopy off Use pulse fluoroscopy when possible. Use a low pulse rate rather than high pulse rates or continuous fluoroscopy; for example, decrease from 7.5 pulses to 3 pulses a second whenever possible. Collimate tightly. Decreasing the area of patient exposure directly decreases patient dose. Collimate to avoid dose to the eyes, thyroid and gonads whenever possible

7. Radiation unitsRoentgen (R)- measures ExposureRad - measures Absorbed DoseRem - indicates radiation dose with same biological equivalenceS.I. Units:1 Gray = 100 rad1 Sievert = 100 rem

8. Occupational Radiation Protection Dose LimitsWhole body - 5 rem per yearIndividual organs - 50 rem per yearEye dose - 15 rem per yearHands, skin - 50 rem per yearDeclared Pregnant worker - 0.5 rem per 9 monthsMember of general public - 0.1 rem per year

9. Background Radiation DoseRadon - 228 mrem/yearCosmic - 33 mrem/yearTerrestrial - 21 mrem/yearInternal - 29 mrem/yearTotal = 311 mrem/yearNaturally occurring sources

10. Man-made Radiation DoseMedical - 300 mrem/yearConsumer products - 13 mrem/yearIndustrial - 0.3 mrem/yearOccupational exposure - 0.5 mrem/yearNatural+man-made = 620 mrem/yr

11. Types of Radiation EffectsDeterministic effectsFrom acute exposureThreshold level for effectSeverity depends on doseStochastic effectsFrom long-term exposureNo assumed threshold for effectRisk of effect increases with doseSeverity does not depend on dose

12. Threshold Doses for Deterministic EffectsEffectDose (Rem)Erythema200 – 500Epilation300 - 700Bone Marrow Syndrome300 – 700GI Syndrome1000

13. Risk for Stochastic EffectsNatural risk of fatal cancer approx. 210,000 per millionExcess Fatal Cancer Incidence per Million*Cancer typeExcess incidence per remBreast101Lung305Acute Leukemia51Stomach, liver, colon94Uterus, ovary, bladder65Other146Pancreas, lymphatic tissues2-5

14. Factors that affect patient doseSource-to-skin distance – should be maximized.Image receptor should be as close to patient as possible.Filtration will remove low energy x-rays and reduce patient dose. Image ReceptorTubePatientFilters

15. Factors that affect patient doseX-ray technique factorskVpmAPulse widthContinuous or pulsedPulse rate/frame rateExposure timeMagnificationUsually controlled by systemAdjustable by operator** Available options vary by system

16. Grid RemovalFor some small patients, (less than 10 cm thick) the grid can be removed without significant loss in image contrast. This will significantly reduce the dose rate.For many systems such as mobile C-arms and some interventional systems, grid cannot be easily removed.

17. Automatic Brightness ControlThe fluoroscope will automatically adjust technique factors to achieve the dose at the image receptor necessary to produce an image with the desired noise level (unless it is placed into manual mode)Anatomical programs will optimize the technique parameters based on the body part being examined, the patient thickness, and type of contrast material.Designed to optimize image contrast and noise while minimizing patient dose.

18. Low Dose settingsLow dose settings will reduce dose to the patient. Always use first, and turn off if improved image quality is needed.

19. High Level Fluoro/BoostHigh Dose, or ‘Boost’ settings will increase the dose rate beyond standard fluoro setting.Used if especially high quality is needed, or to penetrate very large patients.This setting may allow the patient dose rate to exceed the standard regulatory limitLimit in Normal fluoro mode = 10 R/minLimit in High Level mode = 20 R/minA special tone will sound while exposing in High Level mode.Use this mode sparingly.Dose rate can be 2 – 3 times higher than normal.

20. Continuous vs. Pulsed FluoroContinuous Fluoro - X-ray beam is continuous. Image is updated 30 times per second.Pulsed Fluoro – X-rays are emitted in short pulses (about 3 to 10 millisecond).The dose required for each fluoro frame is the same for both pulsed and continuous fluoro.Because the fluoro pulse is shorter, the mA is increased in pulsed mode to compensate.

21. Pulsed FluoroBecause each pulsed fluoro frame is acquired over shorter time, motion unsharpness is decreased in pulsed mode.Lower pulse frequencies can be selected to reduce dose rate.15 frames per second (fps) – ½ dose of 30 fps7.5 fps – ¼ dose of 30 fpsTemporal resolution is sacrificed at lower pulse rates.

22. Cine/DSA Acquisition ModeProduces high quality digital images.Necessary for visualization of small, low contrast objects.Uses short, intense pulses of x-rays.Dose rate is typically 10x higher than fluoroscopy.As with fluoroscopy, low dose modes are typically available for cine/DSA.Use the lowest frame rate appropriate for the procedure.

23. CollimationThe amount of scattered radiation is directly proportional to the area of the primary x-ray beam.Fluoroscopy systems have adjustable size collimators to limit the size of the field.Always reduce the size of x-ray field to exclude anatomy that is outside the area of interest.Modern fluoroscopes will allow you to adjust the collimator position using the last image hold.Collimation will reduce risk to patient, reduce scatter exposure to staff, and reduce chances of physician’s hands getting into the beam.

24. Electronic MagnificationMost modern fluoroscopes will have at least one magnification mode available. Some have several.Mag mode will reduce the Field of View (FOV)Displayed image will be magnified, spatial resolution is improved.Patient dose rate is increased to compensate.

25. Electronic MagnificationFOV12”(Norm)9” (Mag1)6”(Mag2)Exposure Rate (R/min)1.22.13.3OEC 9900, Adult PhantomUse the largest FOV which provides adequate image quality.Increase magnification only if higher detail is needed.

26. Last Image Hold/SaveAll modern fluoroscopes will continue to display the last acquired fluoroscopic image after the exposure is ended.This allows the physician to examine the image without further exposure to the patient.On some units with Fluoro Save, you can save and archive this image along with other radiographic images that were acquired. This can save the patient the additional dose required to acquire another radiographic image (at 10x the dose) if the fluoro frame image quality is adequate.

27. Last Fluoro Loop Replay (LFLR)On some modern systems, the last fluoro sequence can be stored and archived by pressing a button after the pedal is released.If the sequence provides the necessary clinical information, additional cine runs can be avoided, reducing patient dose.

28. Intermittent UseFluoroscopy should be exposed only when necessary.Never press the pedal while looking away from the viewing monitor.Always have the fluoroscope positioned at the area of interest before beginning the exposure.

29. Fluoro Dose DisplayAir Kerma is the dose to air, typically measured in milli-Gray (mGy).Air Kerma Rate is the dose rate to air, typically measured in milli-Gray per minute (mGy/min).All fluoro units manufactured after 2006 will display the current Air Kerma Rate during exposures. This should be visible to the operator.When the exposure is terminated, the cumulative Air Kerma will be displayed.The Air Kerma value is accurate at the Interventional Reference Point, which varies between fluoro systems.

30. Air Kerma Display

31. Fluoroscopy Dose TrackingDuring the procedure, the cumulative Air Kerma is monitored by staff.When the first notification level is reached (3 Gy, or 3,000 mGy), the physician is notified.The physician is notified at each subsequent increase of 1 Gy, or 1,000 mGy.If the ‘Substantial Radiation Dose Level’ (SRDL) of 5,000 mGy is reached, arrangements for follow-up with the patient will be made after the procedure.

32. Peak Skin Dose20 mGy20 mGyThe dose from each exposure is 20 mGy.The peak skin dose is 40 mGy because the fields partially overlap.40 mGy

33. Reducing Peak Skin DoseIn addition to the usual dose reduction practices,the angle of the c-arm should be varied throughout the procedure to avoid areas of high peak skin dose.

34. Scattered RadiationScatter from patient is primary source of staff exposure.Highest levels always on tube side of patient.If c-arm is positioned laterally, it is better to stand on the side of the image receptor.Always best to keep tube under table if possible.Distribution of radiation near the table

35. Scattered RadiationThe dose rate from scatter at 1 meter from the patient is about 1/1000 of the dose rate to the patient.Dose to staff will be reduced by anything that reduces the area of the x-ray beam or reduces dose to the patient.Stand as far away as possible.Utilize shielding devices as much as possible.Minimize LAO angle (Scatter dose rate at 60° is up to 3 times the dose at 30°. Dose rate at 90° is up to 8 times the dose rate at 30°.)

36. Shielding DevicesCeiling mounted shields will typically have at least 0.5 mm lead equivalent, and will shield at least 95% of scatter.Lead drapes for table are effective at shielding scatter on the x-ray tube side of the patient, where scatter rates are the highest.

37. Personal Protective Equipment (PPE)All staff in the room during the fluoro procedure must wear a lead apron.If you may be working with your back toward the patient, the apron should be a wrap around style.For high dose or interventional procedures, should also wear thyroid collar.Staff with potential for high radiation exposures should also wear leaded glasses for eye protection.

38. Personnel DosimetryAll personnel likely to receive exposures >10% of limit will be issued a dosimeter monthly.If you have been issued a single dosimeter, it is worn on the collar level, outside of protective aprons.Individuals issued two badges will wear one on the collar outside the apron, and one at waist level under the apron.Do not take badge home or leave in x-ray room.Notify supervisor if your badge is lost, damaged, or was left inside the x-ray room.Return badges on time.

39. SummaryTo optimize patient dose:Use appropriate anatomical programPlace patient far from x-ray tubePlace image receptor close to patientCollimate to area of interestUse largest FOV consistent with examUtilize low dose modes, lower pulse ratesPractice intermittent fluoroscopy.Remove grid if possible for small pediatric patients.Utilize Last Image Hold, Fluoro save, and Fluoro Loop Relay.Adjust tube angle during long c-arm procedures to reduce peak skin dose.

40. SummaryTo minimize staff dose:Minimize patient dose = reduced staff doseStand farther away from patient & X-ray tube.Step back farther during cine/dsa runs.Keep x-ray tube under table if possible.Use available shielding devices.Always wear lead apron.Wear dosimeters in correct locations.At all times follow the ALARA Principle, Image Wisely, Image Gently and Step-Lightly Principles