1. Part No...., Module No....Lesson No
Module title
Olivera Ciraj-Bjelac, Milojko Kovacevic, Danijela Arandjic, Djordje Lazarevic
Vinca Institute of Nuclear Sciences
Radiation and Environmental Protection Department
Laboratory for Radiation Measurements
Belgrade, Serbia
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
DOSIMETRY FOR MEDICAL APPLICATION OF IONIZING RADIATIONS: Calibration requirements and clinical applications
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

2. Content Global trends in medical exposures
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Global trends in medical exposures
Dosimetric quantities and units
Dosimetry in diagnostic radiology
Metrology and calibration requirements
Clinical application

3. Medical exposure to ionizing radiation
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Medical exposure contributes 99% of man-made radiation exposure to humans
The concept of risk is used to quantify possible detrimental effects
Total dose from man-made sources of radiation> mSv
Medical: 0.6 mSv (> 99.97%)
Source: United Nations Scientific Committee for Effect of Atomic Radiation (UNSCEAR), 2010

4. Medical exposure to ionizing radiation
Dose?
The role of dosimetry is to determine the amount of radiation received by a person from the radiological examination

5. Dosimetry in diagnostic radiology
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Patient dose assessment
Establishment of Diagnostic Reference Levels (DRL), optimisation of protection
Assessment of x-ray equipment performance
Standards of good practice
Assessment of radiation detriment

6. Global trend
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
3,6 billion radiological examinations in the period
Increase of 50% compared to previous decade
Significant increase of CT practice:
Examination frequency
Dose per examination
Interventional procedures

7. Dose to patient Depends on the examination type
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Depends on the examination type
Variations for the same type of procedure
2 mSv
100CxR
5-20 mSv
CxR
mSv
50 chest radiographies= annual natural background radiation dose

8. Problems
Effects
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Dose for the same examination type varies up to 2 orders of magnitude
Increased utilization of high-dose procedures CT
Interventional procedures
Increase of probability for stochastic effects, in particular in the case of the repeated examinations
Possible radiation injuries in high-dose procedures

9. Was this possible 10 years ago?
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Was this possible 10 years ago?
More than 400 cases in the last few years have been reported….

10. Radiation injuries ICRP 85
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
ICRP 85

11. Basic metrology elements
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
International Measurements System (IMS)
Framework for dosimetry in diagnostic radiology
Consistency in radiation dosimetry

12. International Measurements System (IMS)
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Bureau International des Poids et Mesures (BIPM)
National Primary Standard Dosimetry Laboratories (PSDL)
Secondary Standards Dosimetry Laboratories (SSDL)
Users performing measurements

13. Traceability chain Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

14. Metrology and traceability
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Dosimeters used to determine doses received by individuals
Measurements need to be traceable though an unbroken chain of comparisons to national and international standards
Traceability is needed to ensure accuracy and reliability
Legal and economic implications

15. Role of the SSDL The prime function: to provide a service in metrology
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
The prime function: to provide a service in metrology
Designated by the competent national authorities
SSDL-Secondary standards, calibrated against the primary standards of laboratories participating in the IMS
Designated by the competent national authorities to undertake the duties of a calibrating laboratory within that country

16. Journal of the ICRU Vol 5 No 2 (2005) Report 74
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Journal of the ICRU Vol 5 No 2 (2005) Report 74

17. Dosimetric quantities in units in diagnostic radiology
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Basic dosimetric quantity: Air kerma
Easy to measure
Calibration:
Dosimeters calibrated in terms of air kerma
Clinical application:
Quantities derived from air kerma for different imaging modalities

18. Dosimetric quantities
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Basic dosimetric quantities
Application specific dosimetric quantities
Quantities for risk assessment
Conversion coefficient for tissue and organ dose assessment

19. Basic dosimetric quantities
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Energy fluence
Unit:J/m2
Kerma
Unit:J/kg, Gy
Absorbed dose
The ICRU report on patient dosimetry in diagnostic radiology divides dosimetric quantities into basic and application specific quantities. Besides fundamental quantities (fluence, energy fluence, kerma, absorbed dose and energy imparted), specific i.e. practical dosimetric quantities used in DR are…

20. Basic dosimetric quantities
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Charged-particle equilibrium
Absence of bremsstrahlung losses
The ICRU report on patient dosimetry in diagnostic radiology divides dosimetric quantities into basic and application specific quantities. Besides fundamental quantities (fluence, energy fluence, kerma, absorbed dose and energy imparted), specific i.e. practical dosimetric quantities used in DR are…

21. Application specific dosimetric quantities
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Quantity
Symbol
Unit
Equation
Incident air kerma Ki Gy
Entrance -surface air kerma Ke
Air-kerma area product
PKA
Gym2
Air-kerma length product
PKL
Gym
X-ray tube output
Y(d)
Gy/As
Basic dosimetry instrument in DR is ionizing chamber which is used as a standard for air kerma. This is an precise instrument with suitable energy dependence and few other complicating parameters. The design and performance of an ionizing chamber should match the need for clinical measurement, so in most cases cylindrical and PP chambers are used.
Other devices with special properties, TLDs and semiconductor detectors are also used, but they have to be calibrated against ionizing chambers which is a standard of air kerma.
Other QC tools used in DR (non-invasive kVp measuring devices, timers..) also have to be calibrated having a valid calibration certificate.

22. Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

23. Application specific dosimetric quantities: computed tomography
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

24. Application specific dosimetric quantities: computed tomography
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Quantity
Symbol
Unit
Equation
CT air-kerma index (free in air)
Ca,100 Gy
CT air-kerma index (in standard phantom)
CPMMA, 100
Weighted CT air kerma index Cw
Normalized weighted CT air kerma index
nCw
Gy/As
Air-kerma length product
PKL
Gym

25. Quantities describing risk
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Organ and tissue dose
Equivalent dose
Effective dose
Dose-conversion coefficients for assessment of organ and tissue doses

26. The Use of Effective Dose (E)
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
E is a risk-related quantity and should only be used in the low-dose range
Primary use:
to demonstrate compliance with dose limits
in regulation, for prospective planning of radioprotection
Not for:
detailed retrospective dose and risk assessments after exposure of individuals
epidemiological studies, neither in accidents.
In the last cases: organ doses are needed !
continuing use of effective dose as a radiological protection quantity for prospectively estimating risks in the population
and to demonstrate compliance with dose limits.
The use of effective dose allows exposures in very different situations (e.g., internal and external exposure by different types of radiation) to be combined in a single value. As a consequence, the primary exposure limits can be expressed in terms
of a single quantity. This facilitates the system of dose limitation and record-keeping.
Effective dose is used to limit the occurrence of stochastic effects (cancer and heritable effects) and is not applicable to the assessment of the possibility of tissue reactions.
Effective dose provides a convenient quantity for the assessment of overall radiation exposure, taking account of all exposure
pathways, internal and external, for dose record keeping and regulatory purposes.
Used in this way effective dose is a valuable quantity for practical radiological protection purposes although it is not individual-specific but applies to a Reference Person. In retrospective situations the assessment of effective dose
gives an insight into the quality of radiological protection and gives information on whether the dose limits could have been exceeded.
(B 232) However, there are situations in which the use of effective dose is not appropriate, and individual organ and tissue absorbed doses should be used instead.
These include epidemiological studies, assessment of the probability of causation of
cancer, assessments of the possibility of tissue reactions, or assessments of doses
when treatment or medical surveillance are needed.
(B 64) In order to provide a practicable approach for the assessment of effective
dose, coefficients relating it to physical quantities, e.g., particle fluence or air kerma
for external exposure or activity intake for internal exposure, are calculated for standard
conditions (e.g., mono-energetic radiations, standard irradiation geometries, selected
chemical compounds labelled with radionuclides, models for the transfer of
radionuclides in the body) in anthropomorphic phantoms with clearly defined geometries.
ICRP 103, ICRP 105

27. Effective Dose in Medical Exposure
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
The relevant quantity for planning the exposure of patients and risk-benefit assessments is the equivalent dose or the absorbed dose to irradiated tissues.
The assessment and interpretation of E is very problematic when organs and tissues receive only partial exposure or a very heterogeneous exposure (x-ray diagnostics)
E can be of value for comparing doses from
different diagnostic procedures
similar procedures in different hospitals and countries
different technologies for the same medical examination.
However, for planning the exposure of patients and risk-benefit assessments, the equivalent dose or the absorbed dose to irradiated tissues is the relevant quantity.
ICRP 103, ICRP 105

28. Dosimeters in diagnostic radiology
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Tube voltage keV, various A/F combinations, various modalities
Ionization chambers
Accurate
Good energy dependence
Design for different application (cylindrical, parallel-plate, different volumes..)
Semiconductor dosimeters
Compact
Energy dependant
Others
TLD
OSL
Film (radiochromic)
Scintillation
(kVp meters)
Basic dosimetry instrument in DR is ionizing chamber which is used as a standard for air kerma. This is an precise instrument with suitable energy dependence and few other complicating parameters. The design and performance of an ionizing chamber should match the need for clinical measurement, so in most cases cylindrical and PP chambers are used.
Other devices with special properties, TLDs and semiconductor detectors are also used, but they have to be calibrated against ionizing chambers which is a standard of air kerma.
Other QC tools used in DR (non-invasive kVp measuring devices, timers..) also have to be calibrated having a valid calibration certificate.
PSDL/SSDL
user

29. Dosimetry standards in diagnostic radiology
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
IEC 61674: Dosimeters with ionization chambers and/or semi-conductor detectors as used in X-ray diagnostic imaging
Diagnostic dosimeter: detector and measuring assembly
IEC 60580: Dose area product meters

30. Requirements for dosemeters
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
User
IEC 61674
Ionization chambers
Semiconductor detectors
SSDL
Ionization chamber of reference class

31. Calibrations in diagnostic radiology
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Air kerma:
Radiography and mammography
Kerma-length product
Dosimeters in CT
Kerma-area product
Radiography and fluoroscopy
PPV: kVp meters
Frequency: according to national regulations
Due to variety of imaging techniques used in DR, dose descriptors vary from one technique to another. These dose descriptors require calibration of instruments in terms of basic physical quantities. The one of the main tasks of SSDL is to disseminate units of the basic physical quantities through appropriate instrument calibration.
All measuring equipment used for calibration at SSDL shall be of reference class and available in duplicate. Thos is valid for ionization chambers and other equipment (electrometers, barometers, thermometers), as well. To ensure traceability, instruments have to be periodically calibrated, and stability checks have to be performed.
Also, SSDL shall be accommodated in the room with controlled environmental conditions, with stabilized T, P and air humidity. 31

32. Calibration in diagnostic radiology
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
SSDL with relevant measurement capabilities
General requirements: beam qualities, tube voltage and filtration measurements
Dosimeter of reference class (with electrometer)
Calibrated
Quality control
Traceability for all beam qualities
Auxiliary equipment: electrometers, thermometers, barometers…
Environmental conditions
Due to variety of imaging techniques used in DR, dose descriptors vary from one technique to another. These dose descriptors require calibration of instruments in terms of basic physical quantities. The one of the main tasks of SSDL is to disseminate units of the basic physical quantities through appropriate instrument calibration.
All measuring equipment used for calibration at SSDL shall be of reference class and available in duplicate. Thos is valid for ionization chambers and other equipment (electrometers, barometers, thermometers), as well. To ensure traceability, instruments have to be periodically calibrated, and stability checks have to be performed.
Also, SSDL shall be accommodated in the room with controlled environmental conditions, with stabilized T, P and air humidity.

33. Equipment Dosimetry Radiation source Ionization chambers
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Dosimetry
Radiation source
Ionization chambers
Position system
HV supply for monitor and reference class ionization chamber
Electrometer
X-ray generator, kVp, kVp
Ripple less than 10% for radiography and less than 4% for mammography
Beam qualities according IEC 61267
“Shutter” mechanism
Filters and attenuators
Tube voltage meter (ppv, ±1.5%)

34. Reference class dosemeter
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Application
Type of
chamber
Range tube
voltage (kV)
Intrinsic
uncertainty
(k=2)
Maximum variation
of response (%)
Range of air
kerma rate
Unatte-
nuated
beam
Attenuated
General
radiography
cylindrical or
plane parallel
60-150
3.2
±2.6
1 mGy/s-
500 mGy/s
10 μGy/s-
5 mGy/s
Fluoroscopy
50-100
0.1 μGy/s-
100 μGy/s
Mammogra-
phy
22-40
10 mGy/s CT
cylindrical
0.1 mGy/s-
50 mGy/s
Dental
50-90
1 μGy/s-

35. Specification of the x-ray beam
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Spectrum
X-ray beam quality:
First half-value layer (HVL1)
Second half-value layer (HVL2)
Homogeneity coefficient:
Tube voltage
Total filtration

36. Radiation beam qualities (IEC 61267)
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Radiation quality
Radiation origin
Phantom material
Application
RQR
Unfiltered beam emerging from x-ray assembly
No phantom
General radiography, fluoroscopy, dental radiology
RQA
Radiation beam from an added filter
Aluminium
Measurements behind the patient (on the image intensifier)
RQT
Copper
CT applications (free in air)
RQR-M
Mammography (free in air)
RQA-M
Measurements behind the patient
Radiation qualities for calibration shall be established in accordance with recommendation given IEC
Radiation qualities are described in terms of tube voltage, first and second HVL, i.e. homogeneity coefficient.
For conventional diagnostic range reference quality is RQR5 and at least two additional qualities in the range kVp shall be established. Interpolation can be done for intermediate points.
The radiation qualities of the RQA series represent simulation of the radiation field behind a patient while RQT series simulate the untenanted beam used in CT, RQT is applied when CT chamber calibration is to be performed.
For mammography dosemeters calibration a molybdenum anode tube with molybdenum filtration and x-ray unit capable to produce radiation qualities denoted as RQR-M. Although it has been shown that good mammography dosimeters (reference class chambers) can be calibrated with almost any of the beams studied in a mammography range, SSDL shall establish at least three radiation qualities from 20 kV to 35 kV.

37. Typical calibration set up
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
X-ray tube window
Focal
spot
Shutter
Apertures
Additional filtration
Monitor chamber
Test point
The general principle for calibration of dosemeters used in diagnostic radiology is similar to those used in RT calibrations.
SSDL shall provide calibration coefficient in terms of air kerma. A schematic view of calibration set up is given in Figure on the slide.
A chamber positioning device is required in order to minimize positioning errors and keeps them in accordance with laboratory’s uncertainty goals.
The test point should be selected so that scattered radiation shall not introduce an uncertainty inconsistent with laboratory’s goals.
The shutter situated between the x-ray tube and the monitor chamber must be ticked enough to reduce the transmitted air kerma to 0.1% for the radiation quality with the highest mean energy to be used. The aperture should be placed after and close to added filtration to limit the beam area to required size.
The beam shall be large enough to ensure that both standard chamber and instrument to be calibrated are irradiated completely.
A monitor chamber shall be positioned in the beam after and close to the field-limiting aperture. The monitor chamber should be an unsealed transmission ionization chamber with an associated measuring assembly.
For suppression of low energy part of spectrum aluminum and/or copper filters are used in position between the shutter and aperture. They should have a certified purity at least 99.9 % and their thickness should be known to within uncertainty of 10 μm. The absorbers for measuring HVL should have at least the same purity.

38. Calibration procedures
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Procedures before calibration (acclimatization, positioning, stabilization…)
Calibration procedures (methods, number of measurements, interval between measurements…corrections…
Procedures following calibration (uncertainty budget, certificate…)

39. Dosimetry formalism Air kerma:
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Air kerma:
Reference conditions: set of influencing quantities
Influencing condition: quantities that are not subject of mesusremst but have an impact on the result
Air density correction:
Beam quality correction:

40. Calibrations of dosemeters for CT
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Traditionally, irradiation of the whole volume
Contras:
Information on chamber response only
Size on active volume only assumed
Far from real situation

41. Calibration for CT: air kerma length product
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Cylindrical chamber, 100 mm
Non-uniform irradiation
Uniform response
RQT 9 (120 kVp, HVL: 8.5 mm Al)
Focal spot
Monitor chamber
Aperture
Ionization chamber w da dr
CT chamber has been designed for non-uniform exposure from a single scan.
Primary beam is not more than 10 % of the full length of the chamber. However, the sensitive volume of the pencil chamber extends over a much larger axial length.
The calibration is performed in air in a uniform x-ray field with known air kerma rate by irradiation of a well defined fraction of the useful volume of the chamber.
The calibrated quantity is the air kerma length. The calibration arrangement is shown in Figures on the slide. Beam quality RQT9 should be used.
A rectangular lead aperture should be positioned at 5 cm in front of CT chamber. The calibration coefficient is determined by formula shown on the slide, based on conventional true value, reading of user chamber and geometrical relationships. 41

42. Calibration for fluoroscopy: air kerma area product
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
In laboratory (SSDL)
Field calibration
Film
10 cm
Ref. chamber
KAP meter indicates is the integral of the air kerma over the area of the X-ray beam. The calibration of such a device needs to include the ionization response and the correct beam area. The calibration can be performed in laboratory or in situ ,i.e. field calibration.
Laboratory calibration by mapping X-ray field to account for field heterogeneity also includes extra focal radiation, providing a calibration factor independent on geometry. The reported overall uncertainty of laboratory calibration method is ± 3% .
However, such calibration is time consuming and inappropriate for field application. In practice, simplified calibration is employed, based on measurements of beam area and air kerma in reference point. This method results with calibration factor deviating by up to 20 % from calibration factor obtained in laboratory.
Field calibration is performed in the geometry used clinically. Air kerma area product is determined as the product of the air kerma on the central axis and nominal beam area. After reference chamber irradiation, film-screen cassette (or film or direct film) is positioned perpendicularly to beam axis to determine the beam area.
If possible, the couch is removed during calibration at over couch installation to avoid backscattered radiation registration. In the case of calibration at under couch installation, patient couch should not be removed. In such case attenuation in the couch and scattered radiation from the couch should be taken into account.
Calibration coefficient, for both over couch and under couch installations is calculated as ratio of reference chamber reading multiplied by the beam area and KAP meter reading.
Cekerevac at al, Poster B3

43. Calibration in terms of practical peak voltage
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
X-ray tube voltage measurements
Practical Peak Voltage (ppv):
Property of the whole exposure cycle
Related to image contrast
Invasive or non-invasive measurements
Voltage divider
For carrying out calibrations of non-invasive tube voltage measuring devices, SSDL has to be equipped with suitable means…
Using non-invasive instrument that is capable to measure practical peak voltage as a traceable standard. Procedure is to irradiate the calibrated device to obtain an analysis of the waveform at the same time as the user’s non-invasive instrument. Also, substitution technique could be used, depending on stability of x-ray source. The user’s instrument is calibrated by comparison of it reading with SSDL’s calibrated device;
This method is derived from the previous. In this case a calibrated instrument with analogue or digital output is used to derive x-ray tube voltage waveform. The waveform is converted to practical peak voltage by means of computer code [17,18];
Invasive voltage divider is used in this method as a traceable standard. This method has the greatest accuracy. In order to minimize the effect of connecting cables to x-ray tube voltage, the cables should be kept as short as possible. Also, the branching point should for integrating the divider into circuit should be close to x-ray tube. Long exposure times should be used. The voltage waveform is converted to practical peak voltage. This method is based on use of analogue-to-digital converter (ADC). The ADC shall be either supplied with a calibration certificate from which information about accuracy and linearity are obtained. If ADC is not supplied with such information, SSDL should derive this information from measurements performed with the voltage supply and digital voltmeter used for determining the calibration coefficient of the electrometers. 43

44. Uncertainty budget Uncertainty of the reference standard
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Uncertainty of the reference standard
Uncertainty of user’s instrument
Uncertainty due to calibration set up
Uncertainty of the evaluation procedure

45. Uncertainty budget Air kerma: ± 2.7 %
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Air kerma: ± 2.7 %
Air kerma length product: ± 3.0 %
Air kerma area product: ± 15 %
Non-invasive tube voltage measuring devices: 2.5 %
The level of uncertainty should be appropriate to the use of the measurement, and it should be derived by the calibration laboratory.
It is based on the complete analysis of the sources of uncertainties associated with the measurements and shall be established and continuously maintained.
There are certain recommendations about uncertainty level as a goal of an SSDL, but SSDL shall determine its own values.
They are expressed as an combined, expanded uncertainty.
Using previously described calibration procedures, work examples for different calibration types are given with stated overall uncertainty of.. 45

46. Quality Management System
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Goal: minimal uncertainty
Assurance and control of traceability
Quality manual: technical details, methods, traceability, uncertainty budget, QC, safety….
Continuous improvements and reviews
External peer review/audit
The primary goal of any calibration laboratory is to disseminate standards with the smallest possible uncertainty. To accomplish this, it is necessary to institute procedures for the management of quality operation.
Laboratory shall provide, control and assure traceability, as a general metrology principle.
The technical requirements of the QA are based on the guidelines described in the ISO series documents. The QA programme includes a quality manual that describes the main activities of the laboratory, the organizational details and management structure….. QA also includes quality audits that are held at regular intervals and record keeping procedures.
In addition to quality manual, documents such a relevant regulation, standards, specifications and instruction manuals for all equipment should be available.
Once the quality system is established, the laboratory should maintain and update it. Peer reviews of laboratory procedures may also be useful to foster increased communications and encourage suggestions for improving quality.

47. Patient dose assessment
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

48. Clinical dosimetry Direct measurement on patients or phantoms
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Direct measurement on patients or phantoms
Indirect measurements on patients or phantoms
Output of the X-ray tube, scaled for exposure and geometry

49. Dosimetric quantites Quantities
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Quantities
incident air kerma, entrance surface air kerma and kerma-area product (radiography);
kerma-area product and entrance surface air kerma rate (fluoroscopy);
incident and entrance surface air kerma (mammography); and
kerma-length product (computed tomography)
BSF
KAP Ke

50. Patients and phantoms Patient Phantoms Real situation
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Patient
Phantoms
Real situation
Objects that simulate real patients in terms of interaction of radiation with matter
Easy to perform
Standardized

51. Radiography Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

52. Fluoroscopy Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

53. Mammography Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

54. Computed tomography Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

55. Patient dose levels Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

56. Uncertainty of clinical dose assessment
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Radiographers taking the x-ray images
Determining tube output
Calculation of individual patient doses
Determining dose to an average patient
Use of k=2 for expression of uncertainty of dose assessment
Typically >10% and close to 25%*
*if correction for beam quality and for individual patient is not applied

57. Form measurements towards risk assessment
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Conversion coefficients
Conversion of measured quantity into organ doses and effective dose
Ratio of the dose to a specified tissue or effective dose divided by the normalization quantity
Measured using phantoms or calculated using computer models
Voxel phantoms based on images of human anatomy

58. Organ dose assesment Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

59. ICRU 74 Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
ICRU 74

60. Optimization of protection
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences

61. Application of DRLs
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Values of measured quantities above which some specified action or decision should be taken
Values must be specified
Action must be specified
DRLs will be intended for use as a convenient test for identifying situations where the levels of patient
dose are unusually high.
Quantities that are easily measured!

62. Diagnostic Reference Levels
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Distributions of X-ray room mean entrance surface dose values for AP abdomen from surveys in the UK in 1995, 2000 and The dotted lines show the 75 percentile values of the distributions which are 7.2, 5.6 and 4.3 mGy, respectively.
Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK—2005 review. HPA RPD-029, HPA; 2007.

63. Re-cap
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Diagnostic radiology is major contribution to total dose from man-made sources of radiation
Dose measurements: population dose assessment, optimization of practice
Application-specific dosimetric quantities (patients, phantoms)
Calibration of dosimeters in the conditions that are similar to the clinical environment, in terms of
air kerma
kerma-area product
kerma-length product

64. Milojko Kovacevic, MSc, Head of MDL, radiation physicist
Radiation and Environmental Protection Laboratory
Vinca Institute of Nuclear Sciences
Olivera Ciraj-Bjelac, PhD, research associate, dosimetry and radiation physics
Milojko Kovacevic, MSc, Head of MDL, radiation physicist
Danijela Arandjic, MSc, PhD student, dosimetry and radiation physics
Djordje Lazarevic, MSc, PhD student, dosimetry and radiation physics
Dragana Divnic, technician
Milos Jovanovic, technician
Nikola Blagojevic , technician