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Radiation Protection in Paediatric Radiology. Radiation Protection of Children During Computed Tomography. L06. Educational objectives. At the end of the programme, the participants should: Recognize that CT is a relatively higher dose imaging procedure.

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Radiation protection in paediatric radiology

Radiation Protection in Paediatric Radiology

Radiation Protection of Children During Computed Tomography

L06


Educational objectives
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
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
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

  • 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


Computed tomography1
Computed Tomography

  • Since 1972; then…

Hounsfield

Cormack

Nobel prize for medicine 1979

Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography


Computed tomography2
Computed Tomography

  • ..and now…

Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography


Modern ct scanners
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
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
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
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…

  • 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 ct1

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

Facts About CT…

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
CT as a Dose Contributor all ages:

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


Amount of radiation resulting from ct
Amount of Radiation Resulting From CT all ages:

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


Why is this so
Why is this so? all ages:

Radiography

CT

Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography


Why is this so1
Why is this so? all ages:

Dose distribution*

*in relative units

Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography


Risk of ct examination
Risk of CT Examination all ages:

  • 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
Risk all ages: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
CT in Paediatric Radiology all ages:

  • 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
In all ages: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 radiology1
In all ages:Paediatric Radiology…

  • It estimated that between a third and halfof 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
Justification and CT all ages:

  • 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
Justification for CT: all ages: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 advice1
Justification for CT: all ages: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
How to achieve the objective? all ages:

  • 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 objective1
How all ages: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
Optimisation and CT all ages:

One size does not fit all...

Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography


Optimisation and ct1
Optimisation and CT all ages:

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 re commendation
General all ages: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
Generic Requirements for Optimisation all ages:

  • 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 optimisation1
Generic Requirements for Optimisation all ages:

  • 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
Equipment, Protocol, Dose and Image Quality all ages:

  • 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, Pediatr Radiol, 2010

Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography


Equipment protocol dose and image quality1
Equipment, Protocol, Dose and Image Quality all ages:

  • 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


Equipment protocol dose and image quality2
Equipment, Protocol, Dose and Image Quality all ages:

  • 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 quality3
Equipment, Protocol, Dose and Image Quality all ages:

  • 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 quality4
Equipment, Protocol, Dose and Image Quality all ages:

  • 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 quality5
Equipment, Protocol, Dose and Image Quality all ages:

  • 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 quality6
Equipment, Protocol, Dose and Image Quality all ages:

  • 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 quality7
Equipment, Protocol, Dose and Image Quality all ages:

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 beachieved

    • tube current (mA) can beautomatically 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 quality8
Equipment, Protocol, Dose and Image Quality all ages:

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 quality9
Equipment, Protocol, Dose and Image Quality all ages:

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 indose 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 quality10
Equipment, Protocol, Dose and Image Quality all ages:

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 quality11
Equipment, Protocol, Dose and Image Quality all ages:

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 quality12
Equipment, Protocol, Dose and Image Quality all ages:

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 quality13
Equipment, Protocol, Dose and Image Quality all ages:

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
Radiation Dose Indices for CT all ages:

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
Dose Indices for CT all ages:

  • 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
Computed Tomography Dose Indices all ages:

  • 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
Typical Doses in Paediatric CT all ages:

*"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 quality14
Equipment, Protocol, Dose and Image Quality all ages:

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 quality15
Equipment, Protocol, Dose and Image Quality all ages:

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 quality16
Equipment, Protocol, Dose and Image Quality all ages:

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
Shielding all ages:

  • 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 quality17
Equipment, Protocol, Dose and Image Quality all ages:

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
Training all ages:

  • 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
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 responsibilities1
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
Radiologists, Physicists and Technologists’ Advice Responsibilities

  • 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


Radiation protection in paediatric radiology

http://rpop.iaea.org/RPoP/RPoP/Content/index.htm Responsibilities

Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography


Http www pedrad org associations 5364 ig
http://www.pedrad.org/associations/5364/ig/ Responsibilities

Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography


Summary
Summary Responsibilities

  • 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 false1
Answer True or False Responsibilities

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 false2
Answer True or False Responsibilities

  • 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
References Responsibilities

  • 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

Additional material Responsibilities


Practical optimisation in paediatric ct i
Practical Optimisation in Paediatric CT (I) Responsibilities

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
Practical Optimisation in Paediatric CT (II) Responsibilities

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
Practical Optimisation in Paediatric CT (III) Responsibilities

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
Practical Optimisation in Paediatric CT(IV) Responsibilities

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
Practical Optimisation in Paediatric CT (V) Responsibilities

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

Tube current modulation: Responsibilities

Based on patient's size

Longitudinal (z-axis)

Angular (xy-axis)

Combined

Tube Current Modulation Options

Thin patient

Thick patient

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Tube current modulation options1
Tube Current Modulation Options Responsibilities

Dose reduction based on patient anatomy.

Lower mA in AP, higher mA in lateral directions.

200 mA

180 mA

150 mA

130 mA

150 mA

180 mA

210 mA

200 mA

170 mA

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

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Tube potential kvp
Tube potential (kVp) Responsibilities

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

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Tube potential kvp1
Tube potential (kVp) Responsibilities

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

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Guidelines
Guidelines Responsibilities

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/

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Radiation protection in paediatric radiology

A Practice Quality Responsibilities

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

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Example of successful story i
Example of successful story I Responsibilities

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

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Example of successful story ii
Example of successful story II Responsibilities

Wallace, et al. Proceedings of IRPA 12, Buenos Aires, 2008, FP0227:

Eight paediatric hospitals

Training and seminars on optimisation

Dose reduction greater than 50%

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