Radiation Protection in Paediatric Radiology Part No...., Module No....Lesson No Module title Radiation Protection in Paediatric Radiology Radiation Protection of Children During Computed Tomography L06 IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology 1

Educational objectives At the end of the programme, the participants should: Recognize that CT is a relatively higher dose imaging procedure. Understand dose management strategies for computed tomography in children. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Answer True or False Reduction of kVp in CT reduces the dose. CT contributes 60-70 % of the dose from radiological examinations in developed countries. The same CT protocol used for children and adults will result in a higher dose to adults. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Contents Overview of CT systems: SDCT and MDCT. Dose levels in CT and risk attributable to paediatric CT. Importance of application of justification in paediatric CT. Optimization of image quality and patient dose in paediatric CT. Selection of appropriate technical parameters. Use of shielding devices in paediatric CT. Dose management strategies in paediatric CT. Requirements for staff: experience and training. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Computed Tomography Computed tomography (CT) is the method that extends the clinical capabilities of X-ray imaging: High contrast sensitivity for visualizing soft tissues. Production of configurable data sets. Three-dimensional (3D) representations Multiplanar depictions “Volume” CT Dynamic (e.g. perfusion, cardiac) information Tissue characterization (dual energy technology) Advances in computed tomography (CT) technology have continued to improve existing and open new clinical applications. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Nobel prize for medicine 1979 Computed Tomography Since 1972; then… Hounsfield Cormack Nobel prize for medicine 1979 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Computed Tomography ..and now… Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Modern CT Scanners Modern CT scanners are 3rd generation, that is the tube and detectors rotate together around the patient Slip ring technology allows for spiral hence volume scanning Principle of spiral CT. Patient is transported trough the gantry, x-ray tube traces spiral path around the patient when acquiring data M. Mahesh, MDCT physics, the basic technology, image quality and radiation dose, Wolters Kluwer, 2009 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Single Detector (SDCT) vs Multi-detector (MDCT) Computed Tomography SDCT and MDCT design. The difference is the presence of multiple-row detectors in the longitudinal direction with MDCT yielding multiple slice options for single rotation M. Mahesh, MDCT physics, the basic technology, image quality and radiation dose, Wolters Kluwer, 2009 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Multi-detector (MDCT) Computed Tomography MDCT detectors M. Mahesh, MDCT physics, the basic technology, image quality and radiation dose, Wolters Kluwer, 2009 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

CT and Paediatric Radiology The patient dose in CT is an important issue for children. In some centres, the exposure factors used for scanning children are the same as for adults. CT scanning contributes most to collective dose from exposures from medical imaging due both to relatively high dose per exam and to the increasing use of this modality. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Facts About CT… Facts about CT… 69 million CT examinations per year for all ages in USA in 2007. Approximately 10% growth rate per year 7 million CT examinations per year in children 40-50 % increase in paediatric CT from 2005/06. Up to 31% of paediatric body CT examinations are multiphase in some reports Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Facts About CT… The frequency of CT examinations is evenly distributed at all ages: 33% are performed in children under age of 10 Repeated examination: 30% of adults and children have three or more CT scans METTLER, F.A., et al., J. Radiol. Prot. 20 4 (2000) 353-359 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

CT as a Dose Contributor Part No...., Module No....Lesson No Module title CT as a Dose Contributor CT examinations: comprise only 17% of all radiological examinations, but... contributes to 49% of the effective dose all radiological examinations Mettler et al. Helath Phys 2008, 95:502-7 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

Amount of Radiation Resulting From CT Examination Effective Dose (mSv) Chest X-ray Equivalents 3-view ankle radiography 0.0015 0.07 2-view chest radiography 0.02 1 Radionuclide cystogram 0.18 9 Flouroscopic cystogram ~0.33 ~16 Radionuclide bone scan ~5 ~250 Brain CT 2 100 Chest CT up to 3 up to 150 Abdominal CT up to 5 up to 250 Frush D, et al, CT and Radiation Safety: Content for Community Radiologists www.imagegently.org Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Part No...., Module No....Lesson No Module title Why is this so? Radiography CT Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

Why is this so? Dose distribution* *in relative units Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Risk of CT Examination Unique consideration in children: Life time to manifest the bioeffects More radiosensitive tissues Dose is considered cumulative over time Risk is higher for females and younger age groups From a single abdominal CT in paediatric age, lifetime estimated risk for fatal cancer is 1: 1000 - 1: 2000. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Risk Versus Benefit Important to distinguish between individual risks and collective, public-health risks The individual risks are small, so the benefit / risk ratio for any child will generally be very large, …but the exposed population (~7.0 million children/yr in the US) is large Even a very small individual radiation risk, when multiplied by a large (and increasing) number of children, is likely to produce a significant long-term public health concern Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

CT in Paediatric Radiology The frequency of paediatric CT examinations has been increasing over the past 20 years Reduced requirements for sedation and allowance of examination of younger, sicker and less co-operative children Increased speed of acquiring diagnostic information Increased number of multiple scans Attention must be given to adapting protocols to suit children taking into account that they are more sensitive than adults Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

In Paediatric Radiology… If identical CT head examination protocol is used: Adult dose: 1.5 mSv Child dose: 6 mSv Huda et al. Radiology, 1997, 203:417-22 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

In Paediatric Radiology… It estimated that between a third and half of the examinations occurring have questionable indications. Many are conducted using inappropriate technical factors. Frush, RSNA, 2006, Berenner Pediatr. Radio.l 32 (2002) 228 – 231, Oikarinen et al. Eur Radiol 19 (2009) 1161-5 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Justification and CT It is very important that each examination is rigorously justified, thus… Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Justification for CT: Practical Advice Justify CT examination rigorously and eliminate inappropriate referrals. Perform only necessary CT examinations. Reduce the number of multiple phase scans. Work to account for previous procedures. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Justification for CT: Practical Advice Use referral guidelines and appropriateness criteria when available Use alternative approaches, such as ultrasound, MRI where appropriate Include justification in clinical audit Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

How to achieve the objective? Respect age-specific pathology and its prognosis. Consider potential contribution of the scan to patient management and outcome. Consider the patient’s medical imaging record with respect to ionizing radiation Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

How to Achieve the Objective? Respect cost and radiation exposure. Replace CT by examination with no or with lower radiation exposure (e.g. US, MRI). Delay/cancel follow-up examination unless a decision based on scan is needed now. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Optimisation and CT One size does not fit all... Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Optimisation and CT For paediatric CT examinations, the use of specific radiographic technical parameters should be promoted as: Child size the kVp and mA.  One scan (single phase) is often enough.  Scan only the indicated area. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

General Recommendation You must use paediatric protocols to reduce the dose for the same image quality as in adults Make sure there are no inappropriate high (e.g. adult) parameter settings behind the name paediatric protocols Plan paediatric scans according to patient’s size and age Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Generic Requirements for Optimisation Inform and prepare the patient and accompanying person(s). Be familiar with CT dose descriptors. Realise lower noise usually means higher doses; accept noise if scan is diagnostic. Make sure operating conditions balance image quality and radiation exposure.  Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Generic Requirements for Optimisation Optimize scan parameters within the axial plane. Optimize a set of tube current settings for paediatric examinations. Optimize scan parameters for volume coverage. Scan minimal length and minimise repeated scanning at identical areas. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality In most children a tube voltage of 80–100 kVp will suffice, especially in children with a body weight <45 kg. In adolescents, a tube voltage of 100 kVp for the thorax and 120 kVp for the abdomen is usually sufficient Recent studies with phantoms suggest that the optimal tube voltage in children may be even lower (60kVp) at least for some indications Nievelstein Nievelstein, Pediatr Radiol, 2010 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality Part No...., Module No....Lesson No Module title Equipment, Protocol, Dose and Image Quality Spiral or helical scanning is preferable in paediatrics as an entire volume is imaged Short tube rotation times reduce movement artefacts and provide more detailed cardiac imaging One main benefit for MDCT scanners is speed of acquisition rather than dose reduction Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

Equipment, Protocol, Dose and Image Quality An increase in pitch can result in a shorter scan time and (in some scanner types) in a dose reduction In modern MDCT scanners this may not be the best option (due to overranging) If effective mAs is used, an increase in pitch will result in an increase in the tube current Therefore, it is usually more dose efficient to keep the pitch as low as possible (<1) and if needed manually decrease the tube current Nievelstein, Pediatr Radiol, 2010 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality Multi-slice scanners have potential to deliver higher dose by having a wider beam irradiating a number of detector rows to achieve multiple slices simultaneously as well as owing to more extensive clinical use However.… Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality Strategies for dose reduction in MDCT: Hardware improvements Software improvements, as tube current modulation, image reconstruction algorithms, … Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality Modern scanners give automatic or semiautomatic correction of tube current (mA) for patient size (mA modulation). Significant dose reduction (20–50%) without appreciative loss of image quality. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality Image thickness: Should be chosen depending on the size of the child and the application Use maximal acquisition collimation (assuming this would result in scanning at lower mA) appropriate for specific diagnosis Narrow collimation in MSCT and 1 mm slices on some SDCT result in a higher dose (increase in mAs to maintain image quality) Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 2. Pitch: SDCT: a pitch factor 1.5 is recommended for most examinations 25% reduction in dose compared with using a pitch of 1 MDCT: reduction in dose due to greater pitch may not be achieved tube current (mA) can be automatically adjusted to keep the dose and noise the same Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 3. Tube potential (kVp) There are few advantages to using a high tube potential (kV). Without a reduction in tube current (mA) this leads to a significantly higher dose. 100 kVp or 80 kVp is usually adequate for children. Lowering of kVp enhances contrast 10 kg patient transmits 3-4% while an adult transmits less than 0.1%. Be aware that images with high noise, even if they do not look very crisp, may provide the diagnostic information. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 4. Lower tube current (mA): Lower tube current (mA) should be used for scanning kids. High tube current is required only when there is a need for high image detail ( in low contrast settings) Decrease of mA according to body diameter and use of exposure charts if AEC is not available (dose reduction 70-80%), Lucaya, et al, 2000, AJR 175:895-92 Use of tube current modulation technology results in dose reduction by 60% for paediatric scanning, Kalra et al, 2004, Radiology, 233:649-57 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 5. Gantry Tilt A straight gantry results in irradiation of a smaller volume of tissue compared with a tilted gantry and is recommended. Exception: tilt is used to avoid unnecessary exposure of sensitive tissues, e.g. in brain CT for avoiding the orbits. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 6. Scan Length Scan the minimum length required and be restrictive in defining upper and lower limits. Optimise scan parameters for volume coverage by using representative volume sample(s) when the entire volume is not needed (by sequential scans with gaps) to reduce dose-length product Vock and Wolf , Dose Optimization and Reconstruction in CT of children, in Radiation Dose from Adult and Paediatric MDCT, Springer, 2007 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 7. Reconstruction Algorithm Appropriate reconstruction algorithms, window levels and window settings should be used Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 8. Dose Indices Protocols must be adjusted by the operator to take into account the patient's age and weight (size). Newer scanners indicate the volumetric CT dose index (CTDIvol ) and Dose-length product (DLP) on the console (Requirement from IEC 60601-2-44). This allows the user to automatically: See the relative effect on dose owing to changes in kVp, mA, collimation and pitch, Estimate the effective dose to patient. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Radiation Dose Indices for CT Dose displays on modern multislice scanners: Volume CTDI (CTDIvol) Dose Length Product (DLP) Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Dose Indices for CT CTDI is a local per scan dose and is dependent on kVp, mAs and slice collimation. DLP is an integral dose over the scan length and number of series and depends on pitch and dose Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Computed Tomography Dose Indices Effective dose, E, provides risk estimate which depends on the body size and organs imaged as well as on the integral dose. E is calculated as the product of DLP and conversion factors Shrimpton et al, BJR (2006) 79, 968-980 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Typical Doses in Paediatric CT Exam type Relevant organ Range of absorbed organ doses (mGy) Range of effective doses (mSv) Head unadjusted* (200 mAs) Brain 23- 49 1.8 - 3.8 Head adjusted (100 mAs) 11 - 25 0.9 - 1.9 Abdomen unadjusted Stomach 21 - 43 11 - 24 Abdomen adjusted (50 mAs) 5 - 11 6 - 12 *"Unadjusted" refers to using the same settings as for adults. "Adjusted" refers to settings adjusted for body weight. NCI: www.cancer.gov/cancertopics/causes/radiation-risks-pediatric-CT Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 9. Viewing Conditions: Make sure windows levels and settings are adequate and that the monitors are calibrated. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 10. Shielding: Lead shielding can be place over the male gonads if: the edge of the volume of investigation is less than 10-15cm away it does not interfere with the image Dauer, et al, BMC Medical Imaging 2007, 7:5 doi:10.1186/1471-2342-7-5 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 10. Shielding: The use of reusable bismuth attenuation shields is possible for sensitive organs such as the eyes, gonads, breasts and thyroid. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Shielding The bismuth eye shield is simple to place and covers only the eye In-plane shields are associated with greater image noise and streak artifacts. However, shields reduce radiation dose. Automatic exposure control did not increase radiation dose when using a shield. Karla et al, Korean J Radiol. 10:156-63, 2009 This adult patient has a 3 layer bismuth latex eye shield in place. While artefact is seen into the globe, no artefact is transmitted into the brain. Standoff pads can reduce surface artefact Hopper KD, et al, Am J Neuroradiol 22:1194–1198,2001 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Equipment, Protocol, Dose and Image Quality 11. Training The examination should always be supervised by a radiologist experienced in paediatric imaging If all listed factors are taken into consideration, significant dose reduction can be achieved Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Training Following options are available on modern scanners Tube current modulation (mA, mA/slice, effective mAs), pitch, noise level setting, field-of-view for bow tie filter, kVp, beam (vs slice) collimation… This requires a skilled operator: Who knows well the model of the scanner using Trained in paediatric imaging to adjust the examination parameters according to examination type, age and/or size of the child Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Radiologists, Physicists and Technologists’ Responsibilities Improve awareness of need to decrease CT radiation dose to children. Be committed to make a change in daily practice by team work between radiologists, technologists, referring healthcare providers and parents. Medical physicists, radiologists, technologists and department managers should review vendor or other CT protocols and “down-size” them for children. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Radiologists, Physicists and Technologists’ Responsibilities Single phase scans are often adequate Pre- and post-contrast or delayed scans rarely add additional information in children, but can double or triple the dose. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Radiologists, Physicists and Technologists’ Advice Scan only the indicated area. If a patient has a possible small dermoid on ultrasound, there may not be a need to scan the entire abdomen and pelvis. Be involved with your patients. Be the patient’s advocate. Ask the questions required to ensure that you “child-size” the scan. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

http://rpop.iaea.org/RPoP/RPoP/Content/index.htm Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

http://www.pedrad.org/associations/5364/ig/ Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Summary CT can be a relatively high dose diagnostic imaging procedure Rigorous justification of CT for children is required Good practice in paediatric CT: Optimisation of the CT examination protocol based on patient size (lower kVp and mA) Acceptance of images with greater noise One scan (single phase) is often enough - Reduce repeat scanning of identical body areas Scan only the indicated area Use of shielding devices Trained and experiences staff Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Answer True or False Reduction of kVp in CT reduces the dose. CT contributes 60-70 % of the dose from radiological examinations in developed countries. 3. The same CT protocol used for children and adults will result in a higher dose to adults. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 63

Answer True or False Тrue - Reduced kVp reduce the dose in children while maintaining image quality. Тrue - It is a high dose modality and with 10% contribution to number of all radiological examination it gives 60-70% of dose. False- It is opposite, the same protocol will give a few time higher dose to children. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

References BRENNER, D.J., ELLISTON, C.D., HALL, E.J., BERDON, W.E., Estimated risks of radiation-induced fatal cancer from paediatric CT, Am. J. Roentgenol. 176 (2001) 289-296. BRENNER, D.J., Estimating cancer risks from paediatric CT: going from the qualitative to the quantitative, Pediatr. Radio.l 32 (2002) 228 – 231. FRICKE, B.L., et.al., In-plane bismuth breast shields for pediatric CT: effects on radiation dose and image quality using experimental and clinical data, Am. J. Roentgenol. 180 (2003) 407 – 411. HOPPER, K.D.,et al, The breast: in-plane x-ray protection during diagnostic thoracic CT - shielding with bismuth radioprotective garments, Radiology 205 (1997) 853 – 858. KILJUNEN, T., JÄRVINEN, H., SAVOLAINEN, S., Diagnostic reference levels for thorax X-ray examinations of paediatric patients, Br. J. Radiol. 80 (2007) 452-9. BOONE, J.M., et. al., Dose reduction in paediatric CT: a rational approach, Radiology 228 (2003) 352-360. LUCAYA, J., et. al., Low-dose high-resolution CT of the chest in children and young adults: dose, cooperation, artefact incidence and image quality, Am. J. Roentgenol. 175 (2000). 985-992. INTERNATIONAL ATOMIC ENERGY AGENCY, Dose Reduction in CT while Maintaining Diagnostic Confidence: A Feasibility/Demonstration Study, IAEA-TECDOC-1621, IAEA, Vienna, (2009). KALRA, M.K., et. al., Techniques and applications of automatic tube current modulation for CT, Radiology 233 (2004) 649-657. INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, ICRP Publication 102: Managing Patient Dose in Multi-Detector Computed Tomography (MDCT), Annals of the ICRP Volume 37/1, Elsevier, (2007). D. Tack,Pierre A Gevenois, Radiation Dose from Adult and Pediatric Multidetector Computed Tomography, Springer, 2007 Karla et al, In-plane shielding for CT: effect of off-centering, automatic exposure control and shield-to-surface distance, Korean J Radiol. 2009 Mar-Apr;10(2):156-63.. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

Additional material

Practical Optimisation in Paediatric CT (I) Reduce mAs according to body weight/diameter or composition and/or Use dose modulation (angular/longitudinal) Use maximal slice reconstruction thickness to reduce noise and potentially dose appropriate for specific diagnosis. Decrease kVp for thin (small) patients and high contrast exams (CT angiography, chest, musculoskeletal ) Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 67

Practical Optimisation in Paediatric CT (II) Normally use shortest rotation time available. Use representative volume sample when entire volume is not needed. Use spiral scan with pitch greater than 1 (eg.: 1.5), provided this does not automatically increase the mA. Use newer dose reduction strategies such as iterative reconstruction and adaptive modulation (to reduce over ranging) Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 68

Practical Optimisation in Paediatric CT (III) Be restrictive in defining upper-most and lower-most scan range Use localising projection scan extending just minimally beyond scan limits. Consider low kVp and single AP topogram Reconstruct additional thick noise-reduced slices without increase in exposure. Avoid major overlap when scanning adjacent areas with different protocols Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 69

Practical Optimisation in Paediatric CT(IV) Avoid additional non-enhanced scans unless specifically justified. Optimise the protocol to obtain all the information requested during one scan. Minimise the number of scans in multi-phase scanning. In case of multi-phase scanning use shorter scan length for additional scans. Use lower dose for non-enhanced or repeat scans unless high quality is needed. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 70

Practical Optimisation in Paediatric CT (V) Minimise length of scans and fluoroscopy time in interventional applications. Use low mA with CT fluoroscopy Replace test bolus/bolus triggering by standard can delay unless timing is very critical. Use additional protection devices where indicated such as bismuth shields (lens, thyroid, breast, gonads). Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 71

Tube Current Modulation Options Based on patient's size Longitudinal (z-axis) Angular (xy-axis) Combined Thin patient Thick patient Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 72

Tube Current Modulation Options Part No...., Module No....Lesson No Module title Tube Current Modulation Options 200 mA 150 mA 130 mA 180 mA 210 mA 170 mA Dose reduction based on patient anatomy. Lower mA in AP, higher mA in lateral directions. Methods Patient attenuation measured during scout scan (AP & Lat) and alter mA for each gantry rotation (Smart mA1, Real AEC2) or “on-the-fly” (Care dose3) 1 GE, 2 Toshiba and 3 Siemens MDCT Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 73 IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

kV = dose Tube potential (kVp) Part No...., Module No....Lesson No Module title Tube potential (kVp) Decreasing kVp significantly reduces dose, typically: 80 kV – 0.5 mSv 100 kV – 1 mSv 120 kV – 1.6 mSv 140 kV – 2.3 mSv kV = dose Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 74 IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

Tube potential (kVp) CT examinations with a high intrinsic contrast (chest, bones) justify lowering the tube voltage to 80–100 kVp However, bony examinations can be performed with very low current 25-70mA Nievelstein, Pediatr Radiol, 2010 Cook, Imaging, 2001 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 75

Guidelines FDA Public Health Notification: Reducing Radiation Risk from Computed Tomography for Paediatric and Small Adult Patients, November 2nd, 2001 National Cancer Institute: Radiation Risks and Paediatric Computed Tomography (CT): A Guide for Health Care Providers, http://www.cancer.gov/cancertopics/causes/radiation-risks-pediatric-CT Image Gently: http://www.pedrad.org/associations/5364/ig/ Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 76

Protocols for Children? A Practice Quality Improvement (PQI) Program in CT Scans in Children: The PQI module capture how your practice performs CT scans in children, and allows you to compare your practice to “safe practice” guidelines in the literature. How to Develop CT Protocols for Children? Provide guidance in developing CT protocols for children and periodically verifying that your current protocols are appropriate Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 77

Example of successful story I Arch and Frush, AJR 2008;191:611–617: Since 2001, kVp and mA settings, two principal parameters determining radiation dose, have decreased significantly for paediatric body MDCT It is a reasonable assumption that these changes are due to efforts to increase awareness about the risks of radiation Paediatric chest CT Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 78

Example of successful story II Wallace, et al. Proceedings of IRPA 12, Buenos Aires, 2008, FP0227: Eight paediatric hospitals Training and seminars on optimisation Dose reduction greater than 50% Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 79