Guidance

National Diagnostic Reference Levels (NDRLs) from 20 November 2024

Updated 20 November 2024

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Introduction

National Diagnostic Reference Levels (NDRLs) for the UK are listed in the following tables.

National Dose Reference Levels for radiotherapy planning CT scans are also listed.

The NDRL values should be considered by employers when setting their local DRLs as required by the Ionising Radiation (Medical Exposure) Regulations 2017 and the Ionising Radiation (Medical Exposure) Regulations (Northern Ireland) 2018 (as amended).

The UK National DRLs are based on body region examined and, where appropriate, the clinical requirement for the examination.

A list of the published reports used as the sources of the NDRL values are provided at the end of this page. These reports contain dose information which may be of use for setting local DRLs for radiographic procedures where there was insufficient data to formally recommend a NDRL.

National DRLs for computed tomography

Table 1. Adult CT examinations

Examination Clinical Indication Scan region / technique CTDI vol per sequence (mGy) DLP per complete examination (mGy cm) Year NDRL adopted
Head(1) Acute stroke All sequences 47 790 2022
Paranasal sinuses(1) Sinus disease All sequences 12 160 2022
Cervical spine(1) Fracture All sequences 16 400 2022
Neck, chest, abdomen and pelvis(1) Cancer All sequences   850 2022
Chest(1) Lung cancer All sequences 8.5 290 2022
Chest and Abdomen(1) Lung cancer All sequences   470 2022
Chest-high resolution(1) Interstitial lung disease Helical 8 300 2022
Chest, abdomen, pelvis(1) Cancer All sequences   660 2022
CT Pulmonary Angiography (CTPA)(1) Pulmonary embolism All sequences 9.1 310 2022
Abdomen and pelvis(1) Abscess All sequences 10 530 2022
Virtual colonoscopy(1) Polyps/Tumour All sequences   690 2022
Kidneys, ureters, bladder(1) Stones/Colic All sequences 6.3 290 2022
Urogram(1) Tumour/Stones/Colic All sequences   890 2022
Coronary CT angiography (CTA)(2)   Prospective, no padding   170 2018
    Prospective, with padding   280 2018
    Retrospective, with gating   380 2018

Note: Doses for the head and paranasal sinus examinations refer to measurements in the 16cm standard CT dosimetry phantom. All other doses refer to measurements in the 32cm standard CT dosimetry phantom.

Caution is required when comparing your local dose values with the NDRL for the chest exam. There are separate NDRLs for ‘chest’ and ‘chest and abdomen’, covering the appropriate body regions. However, the descriptor for the ‘chest’ exam for the previous NDRL (based on the 2011 survey) extended to the liver region, and therefore may not be directly comparable.

Table 2. Paediatric CT examinations

Examination Clinical indication Scan region / technique CTDIvol per sequence (mGy) DLP per complete examination (mGy cm) Year NDRL adopted
Paediatric head:
0 to <1 y		 Trauma All sequences 19 290 2022
Paediatric head:
1 to <5 y		 Trauma All sequences 24 420 2022
Paediatric head:
5 to <10y		 Trauma All sequences 36 570 2022
Paediatric head:
10 to <15y		 Trauma All sequences 46 690 2022
Paediatric head:
15 to <18y (adult head CT values applied)		 Acute Stroke All sequences 47 790 2022
Paediatric chest:
0 to <5kg		 Query cancer All sequences 0.44 8 2022
Paediatric chest:
5 to <15kg		 Query cancer All sequences 0.86 18 2022
Paediatric chest:
15 to <30kg		 Query cancer All sequences 2.0 40 2022
Paediatric chest:
30 to <50kg		 Query cancer All sequences 2.6 62 2022
Paediatric chest:
50 to <80kg		 Query cancer All sequences 3.8 110 2022

Note: Doses for the head examination refer to measurements in the 16 cm standard CT dosimetry phantom. Doses for chest examinations refer to measurements in the 32 cm standard CT dosimetry phantom.

For paediatric head (15 to less than 18 years) adult head values are applied.

For the paediatric chest 0 to less than 5kg and 50 to less than 80kg categories, the values are based on sample sizes smaller than commonly used to set NDRLs. The application of these NDRLs should therefore be carefully considered by the Medical Physics Expert (MPE).

Values taken from ‘Analysis and results from a UK national dose audit of paediatric CT examinations’.

Table 3. Adult CT examinations as part of PET-CT and SPECT-CT examinations

Examination Clinical indication Scan region / technique CTDIvol per sequence (mGy) DLP per complete examination (mGy cm) Year NDRL adopted
PET half body attenuation correction and localisation of the nuclear medicine signal All sequences 4.3 400 2018
SPECT bone scan attenuation correction and localisation of the nuclear medicine signal All sequences 4.9 150 2018
SPECT parathyroid attenuation correction and localisation of the nuclear medicine signal All sequences 5.6 170 2018
SPECT post-thyroid ablation attenuation correction and localisation of the nuclear medicine signal All sequences 5.9 210 2018
SPECT mIBG/octreotide attenuation correction and localisation of the nuclear medicine signal All sequences 5.5 240 2018
SPECT cardiac attenuation correction All sequences 2.1 36 2018

Note: Doses refer to measurements in the 32cm standard CT dosimetry phantom.

Values taken from ‘A national survey of computed tomography doses in hybrid PET-CT and SPECT-CT examinations in the UK’.

National DRLs for general radiography and fluoroscopy

Table 4. Individual radiographs on adult patients

Radiograph ESD per radiograph (mGy) DAP per radiograph (Gy cm 2 ) Year NDRL adopted
Abdomen AP 4 2.5 2016
Chest AP 0.2 0.15 2016
Chest LAT 0.5   2016
Chest PA 0.15 0.1 2016
Cervical spine AP   0.15 2016
Cervical spine LAT   0.15 2016
Knee AP 0.3   2016
Knee LAT 0.3   2016
Lumbar spine AP 5.7 1.5 2016
Lumbar spine LAT 10 2.5 2016
Pelvis AP 4 2.2 2016
Shoulder AP 0.5   2016
Skull AP/PA 1.8   2016
Skull LAT 1.1   2016
Thoracic spine AP 3.5 1.0 2016
Thoracic spine LAT 7 1.5 2016

Values taken from ‘HPA-CRCE-034: Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK (2010 review)’.

Table 5. Diagnostic radiography examinations on adult patients

Examination DAP per exam (Gy cm2) Fluoroscopy time per exam (minutes) Year NDRL adopted
Abdomen 4.4   2016
Barium (or water soluble) enema 21 2.6 2016
Barium small bowel enema 23 8.9 2016
Barium follow through 8.4 2.0 2016
Barium meal 12 2.6 2016
Barium meal & swallow 10 2.3 2016
Barium (or water soluble) swallow 7.5 2.1 2016
Barium swallow (video) 3.4 3.5 2016
Chest 0.3   2016
Coronary angiography
[note 1]		 31 4.3 2016
Coronary graft angiography
[note 1]		 47 13 2016
Femoral angiography 56 5.9 2016
Fistulography 8 6.7 2016
Hysterosalpingography 2 0.7 2016
Intravenous Urography (IVU) 14   2016
Lumbar spine 6   2016
Micturating Cystourethrography (MCU) 7 1.6 2016
Nephrostography 9 3.9 2016
Proctography 14 1.3 2016
Sialography 2.8 1.5 2016
Sinography 7 1.7 2016
T-tube cholangiography 5 1.8 2016

Fluoroscopy time: time during a procedure that fluoroscopy is used, excluding cine acquisition imaging.

Note 1: Mean patient weight range 75 to 85kg

Values taken from ‘HPA-CRCE-034: Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK (2010 review)’.

Table 6. Interventional procedures on adult patients

Interventional procedure DAP per exam (Gy cm2) Fluoroscopy time per exam (minutes) Year NDRL adopted
Biliary intervention (3) 43 14 2016
Facet joint injection (3) 6 1.4 2016
Hickman line insertion (3) 3 1.5 2016
Nephrostomy (3) 13 6.7 2016
Oesophageal stent (3) 13 5 2016
Pacemaker (permanent) (3) 7 6 2016
Percutaneous transluminal coronary angioplasty (PTCA) (single stent)
[note 1] (3)		 40 11.3 2016
Endovascular Aneurysm Repair (EVAR) (4) 160   2024
Thoracic endovascular aortic repair (TEVAR) (4) 180   2024
Branched endovascular aneurysm repair (BEVAR) or fenestrated endovascular aneurysm repair (FEVAR) (4) 270   2024

Fluoroscopy time: time during a procedure that fluoroscopy is used, excluding cine acquisition imaging.

Note 1: Mean patient weight range 75 to 85kg.

Table 7a. Diagnostic radiography examinations on paediatric patients: micturating cystourethrography (MCU)

Standard age (y) DAP per examination (Gy cm2) Year NDRL adopted
0 0.1 2016
1 0.3 2016
5 0.3 2016
10 0.4 2016
15 0.9 2016

Table 7b. Diagnostic radiography examinations on paediatric patients: barium meal

Standard age (y) DAP per examination (Gy cm2) Year NDRL adopted
0 0.1 2016
1 0.2 2016
5 0.2 2016
10 0.7 2016
15 2.0 2016

Table 7c. Diagnostic radiography examinations on paediatric patients: barium swallow

Standard age (y) DAP per examination (Gy cm2) Year NDRL adopted
0 0.2 2016
1 0.4 2016
5 0.5 2016
10 1.8 2016
15 3.0 2016

Values taken from ‘HPA-CRCE-034: Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK (2010 review)’.

National DRLs for dental radiography

Table 8a. National DRLs for intra-oral radiography

Radiograph Patient size Patient entrance dose (PED) per radiograph (mGy) Year NDRL adopted
Intra-oral mandibular molar Adult 1.2 2019
  Child 0.7 2019

Table 8b. National DRLs for panoramic, cephalometric, and CBCT radiography

Radiograph Patient size (clinical indication) DAP per radiograph (mGy cm2) Year NDRL adopted
Panoramic (full jaw) Adult 81 2019
  Child 60 2019
Lateral cephalometric Adult 35 2019
  Child 24 2019
Dental CBCT Adult (imaging prior to placement of a maxillary molar implant) 265 2019
  Child (imaging of an impacted maxillary canine of a 12-year-old child) 170 2019

Values taken from ‘Dental radiographic X-ray imaging: dose to patients’.

National DRLs for screening mammography

This value was proposed to the UKHSA NDRL working group by the Breast Screening Physics Clinical Professional Group (formerly National Breast Screening QA Co-ordinating Group for Physics), and the National Co-ordinating Centre for the Physics of Mammography (NCCPM).

Table 9. National DRLs for screening mammography

Radiograph Mean glandular dose (MGD) (mGy) Year NDRL adopted
Screening mammography 2.5 2022

Average mean glandular dose (MGD) for mediolateral oblique breast exposures of a sample of 50mm to 60mm thick breasts using at least 10 patients, 2D full field digital mammography in screening using DR systems. Please note that only DR systems are used in the NHSBSP.

Value based on data from ‘Radiation doses in the United Kingdom breast screening programmes 2016–2019’.

National DRLs for radiotherapy planning CT Scans

Radiotherapy planning CT scans are not considered diagnostic scans, and therefore the use of the term Diagnostic Reference Levels is not appropriate. However, the use of dose reference levels is a useful method of demonstrating dose optimisation has taken place. The following table provides dose index values, which can be taken to be equivalent to formal NDRLs.

Table 10. National DRLs for radiotherapy planning CT Scans

Examination CTDIvol per sequence (mGy) DLP per complete examination (mGy cm) Scan length (mm) Year NDRL adopted
Breast 10 390 360 2018
Gynaecological 16 610 400 2018
Lung 3D 14 550 390 2018
Lung 4D 63 1750 340 2018
Prostate 16 570 340 2018
Brain 50 1500 290 2018
Head and Neck 49 2150 420 2018

Doses for the brain and ‘head and neck’ examinations only refer to measurements in the 16cm standard CT dosimetry phantom. All other doses refer to measurements in the 32cm standard CT dosimetry phantom.

Values taken from ‘IPEM topical report: the first UK survey of dose indices from radiotherapy treatment planning computed tomography scans for adult patients’.

References

  1. UKHSA. ‘UKHSA-RCE-1 Doses from computed tomography examinations in the UK (2019 review)’

  2. Castellano IA and others. ‘A prospective national survey of coronary CT angiography radiation doses in the United Kingdom’ Journal of Cardiovascular Computed Tomography 2017: volume 11, pages 268 to 273

  3. Radiographic, fluoroscopic and dental x-rays. ‘Patient dose audits’

  4. Tsitsiou Y and others. ‘National UK Survey of Radiation Doses During Endovascular Aortic Interventions’: volume 92, pages 92 to 100

  5. Worrall M and others. ‘Analysis and results from a UK national dose audit of paediatric CT examinations’ British Journal of Radiology 2021: volume 95, issue 1129

  6. Iball GR and others. ‘A national survey of computed tomography doses in hybrid PET-CT and SPECT-CT examinations in the UK’ Nuclear Medicine Communications 2017: volume 38, issue 6, pages 459 to 470

  7. Loveland J, Young KC, Oduko JM and Mackenzie A. ‘Radiation doses in the United Kingdom breast screening programmes 2016–2019’ British Journal of Radiology 2022: volume 95, issue 1135

  8. Wood TJ and others. ‘IPEM topical report: the first UK survey of dose indices from radiotherapy treatment planning computed tomography scans for adult patients’ Physics in Medicine and Biology 2018

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