IAEA Regional Training Course on Radiation Protection of

IAEA Regional Training Course on Radiation Protection of patients for Radiographers, Accra, Ghana, 11 -15 July 2011 Optimization of protection in radiography – What radiographers can do? IAEA International Atomic Energy Agency

What is optimization in radiography? To obtain diagnostic images Lcontaining required diagnostic information Mwith the minimum patient exposure Ewithin prevailing resource limitations IAEA 15. 1: Optimization of protection in radiography: technical aspects 2

How to optimize? l Which aspects to consider ? üEquipment üExamination/technique üInterpretation IAEA 15. 1: Optimization of protection in radiography: technical aspects 3

Outline • Optimization in conventional radiography - Technical aspects - Radiation protection aspects • Optimization in digital imaging IAEA What radiographers can do in optimization 4

Optimization in Conventional Radiography IAEA What radiographers can do in optimization 5

Image formation in film-screen imaging Film, fluorescent screen or image intensifier Scattered radiation « Latent » radiological image Bone X Soft tissue Air Primary collimation Antiscatter Grid IAEA Beam intensity at detector level What radiographers do in optimization 6

• 1. Screen film system: A particular intensifying screen used with a particular type of film • Screen-film combination should be selected according to manufacturer’s recommendations • Identification of screen by type and format • type mismatch (use of different types of screens) FOR THE SAME FORMAT is not ADVISABLE • Screen film contact • loss of spatial resolution, blurred image • Cleanliness IAEA What radiographers can do in optimization 7

2. Film processing: automatic processors • • Constant temperature Constant processing time Automatic replenishment of chemicals Drying of films BUT • Can introduce artifacts IAEA What radiographers can do in optimization 8

Film processor QC • Most important QC features: • • • proper film storage cassette and screen care processor chemical care Identify artifacts processor cleanliness IAEA What radiographers can do in optimization 9

Manual Processing • There are many places where X Ray films are processed manually, in open tanks • Manual processing can be very effective, BUT there can be many quality problems IAEA What radiographers can do in optimization 10

Dark room conditions in some hospitals IAEA What radiographers can do in optimization 11

Basic film processing Requirements • Temperature - constant and optimum • Time - measured • Developer activity (chemical condition) fresh and unoxidised IAEA What radiographers can do in optimization 12

Dark room Darkroom characteristics • Safelight • number (as low as possible), distance from the table • type and colours of filters • bulb color (red) or adapted to film • • External light tightness Hygrometry (30 - 60%) Room temperature < 20° Film storage conditions IAEA 15. 1: Optimization of protection in radiography: technical aspects 13

3. Viewing box characteristics Since the viewing conditions are essential for a good interpretation of the diagnostic images, the viewing conditions must be optimal • Cleanliness of external/internal surface • Brightness • homogeneity within the same viewing box • Coloring • color mismatch must be avoided • Environment • ambient light level: 50 lux maximum IAEA 15. 1: Optimization of protection in radiography: technical aspects 14

Viewing box color and brightness 5700 5810 3510 6200 5920 3870 BLUE COLOR 4160 5860 2150 WHITE COLOR 3110 WRONG CONFIGURATIONS (cd/m 2) IAEA What radiographers can do in optimization 15

Example of poor viewing box IAEA What radiographers can do in optimization 16

Radiation protection aspects • Optimization of patient radiation protection requires periodic evaluation of doses and image quality. • Operators of the X Ray system should be aware of the interdependence between technical parameters, dose and image quality • Procedures should be established for each examination to ensure a proper use of equipment. IAEA What radiographers can do in optimization 17

1. Skin focus distance • In general radiography (except dental), the skinfocus distance should not be lower than 30 cm • In radiography with fixed equipment, the skin-focus distance should not be lower than 45 cm • Usually chest x-ray examinations ( chest stand; FFD= 180 (140 -200) cm • Abdominal x-ray examinations: FFD= 115 (100150) cm IAEA What radiographers can do in optimization 18

2. Awareness • e. g. when there are suspicions about a malfunctioning of the X Ray unit or of the imaging chain in a room that might affect the protection of the patient (i. e. , because the images become over or underexposed without changing the technique), this should be reported to the responsible person of the room in order to reevaluate the equipment if necessary and to introduce corrective actions. IAEA What radiographers can do in optimization 19

3. Procedures • Image annotation (patient ID, exam date, markers ) on film • Patient instructions and patient positioning • The usual radiological technique for each projection on a given equipment, with details of the associated image device should be written and be readily accessible, close to the control panel. It should be specified for patients of standard as well as uncommon size IAEA What can radiographers do in optimization 20

………Procedures • It is advisable to use the highest k. Vp (and the lowest m. As) compatible with the image that one expects to obtain. In this way the patient irradiation will be lower, although it might get lower image contrast. Therefore the optimization is to find the proper balance between contrast and dose • The shortest exposure time as possible should be selected, above all when examining noncollaborating patients (shorter time means reduction in kinetic blurring) IAEA What can radiographers do in optimization 21

…. Procedures: x-ray beam limitation • The smallest film and cassette size compatible with the expected image must be used together with automatic collimation. Otherwise the patient would be over-irradiated, by receiving radiation over a larger volume and transversal surface, and the raise in scattered radiation would reduce the image quality and increase the operating personnel doses. • When using equipment without automatic X Ray beam collimation, it should be verified that the radiation field is reduced up to the smallest size compatible with the required image. IAEA What can radiographers do in optimization 22

Periodic evaluation of the image quality • A periodic evaluation (at least once a year) of the image quality obtained in each room allows the detection of malfunctioning in the imaging chain or in the generator (almost always associated to high patient doses and poor image quality) • A periodic evaluation of the number of rejected and repeated radiographs and the analysis of the causes of rejects and retakes allow the detection of failures in the X Ray equipment, associated image devices, as well as in the examination procedures and in the skill and training of the staff IAEA What can radiographers do in optimization 23

Corrective actions • When some corrective measures are proposed after the detection of a malfunctioning, recording the follow up of their implementation is advisable (in a logbook) IAEA What can radiographers do in optimization 24

Optimization in Digital imaging IAEA What can radiographers do in optimization 25

Radiation dose in digital radiology Ø Conventional films allow to detect mistakes if a wrong radiographic technique is used: images are too white or too black Ø Digital technology provides user always with a “good image” since its dynamic range compensates for wrong settings even if the dose is higher than necessary IAEA What radiographers can do in optimization 26

Ø Underexposure results in a “too noisy” image Ø Overexposure yields good images with unnecessary high dose to the patient Exposure level 2, 98 IAEA Exposure level 2, 36 What radiographers can do in optimization 27

An underexposed image is “too noisy” Exposure level 1, 15 IAEA Exposure level 1, 87 20: Digital Radiology 28

Three approaches to digital radiography I. II. III. Translate developed film into digital form (Digitizing conventional films). Capture the radiographic projection by nonphotographic method and digitize during development (Computed radiography, CR) Capture the radiographic projection or its fluorescence directly in digital form (Direct radiography, DR). IAEA 15. 1: Optimization of protection in radiography: technical aspects 29

Typical CR system IAEA 15. 1: Optimization of protection in radiography: technical aspects 30

Typical DR system IAEA 15. 1: Optimization of protection in radiography: technical aspects 31

How to move from film-screen to digital? • Typically the initial setting for the automatic exposure control using CR, should be the same or similar to the existing with film-screen. Optimisation (including possible k. V changes) and potential dose reduction should be initiated later once radiologists become familiar with digital. • Audit DICOM header. It contains a lot of useful information. IAEA Radiation Protection in Digital Radiology L 01 Fundamentals of Digital Radiography 32

What can a radiographer do? Generally as for film screen imaging • Image annotation • Patient positioning and collimation • Radiographic exposure per examination • Image viewing conditions • Patient dose and image quality evaluation IAEA 15. 1: Optimization of protection in radiography: technical aspects 33

Specific for digital imaging • Exposure parameters and image processing (follow manufacturer guidance • Lower m. As than in film–screen • High or low k. Vp? (generally lower than in film-screen • protective shielding (assure that area being examined is not covered) • Post processing (adequate, avoid too much processing since artifacts can result) • Image viewing conditions (calibrated to fit purpose) • Cleanliness (extremely important-to avoid artifacts) IAEA What radiographers can do in optimization 34

Improper collimation cause an incorrect exposure indicator value: Fuji CR S = 183, L = 1. 9 IAEA S = 578, L=1. 8 35

As seen by radiologist IAEA Actual radiation field 36

Incorrect collimation cause inappropriate image processing: Agfa CR Automatic processing IAEA Radiation Protection in Digital Radiology Manual reprocessing L 06 Avoiding Artefacts in Computed Radiography 37

Gonadal shielding has drawbacks • Ovary locations vary • Shield may obscure clinical features • Shield may interfere with automatic image processing Processed IAEA Unprocessed 38

Image quality and dose • Diagnostic information content in digital radiology is generally higher than in conventional radiology if equivalent dose parameters are used • The wider dynamic range of the digital detectors and the capabilities of post processing allow to obtain more information from the radiographic images IAEA What radiographers can do in optimization 39

Exposure level b. Some digital systems provide the user with a so called “exposure level” index which expresses the dose level received at the digital detector and orientates the operator about the goodness of the radiographic technique used b. The relation between dose and exposure level is usually logarithmic: doubling the dose to the detector, will increase the “exposure level” to a factor of 0. 3 = log(2). IAEA What radiographers can do in optimization 40

Difficulty to audit the number of images per procedure • Deleting useless images before sending them to the PACS is also very easy in digital fluoroscopy • This makes difficult any auditing of the dose imparted to the patient • The same applies to projection radiography to audit the retakes. IAEA What radiographers can do in optimization 41

Actions that can influence image quality and patient doses in digital radiology (2) • Eliminate post-processing problems, digitizer problems, local hard disk, fault in electrical power supply, network problems during image archiving etc. • Avoid loss of images in the network or in the PACS due to bad identification or others • Reduce artifacts due to incorrect digital postprocessing (creation of false lesions or pathologies) IAEA What radiographers can do in optimization 42

Diagnostic reference levels • In digital radiology, the evaluation of patient doses should be performed more frequently than in conventional radiology: • Easy improvement of image quality • Unknown use of high dose technique • Re-assessment of local reference levels when new digital techniques are introduced is recommended to demonstrate the optimization of the systems and to establish a baseline value useful for future patient dose assessment IAEA 43

Conventional Reason for Repeated Exam • • • Artefacts Mispositioning Over-collimation Patient motion Double exposure Inadequate inspiration IAEA • • • Overexposed - too dark Underexposed - too light Marker missing or wrong Wrong exam Wrong patient Film lost in processor Radiation Protection in Digital Radiology L 03 Optimisation in CR and DR 44

CR/DR Reason for Repeated Exam • • • Artefacts Mispositioning Over-collimation Patient motion Double exposure Inadequate inspiration • Overexposed - high exposure index • Underexposed - low exposure index • • Marker missing or wrong Wrong exam Wrong patient Lost image • corrupt data, cannot transfer • deleted by operator (waste bin) IAEA Radiation Protection in Digital Radiology L 03 Optimisation in CR and DR 45

Remember digital imaging can lead to many artefacts • PSP Plates • Scratches in the plate. • Abdomen of a 3 rd trimester pregnant woman. IAEA 46

CR Imaging plates do not last forever Imaging plate artefact Agfa plate defect IAEA Same defect, different orientation Artefact remedy: The Imaging plate (IP) must be replaced when cracks occur in clinically useful areas 47

Imaging plate artefact • PSP Plates • Artifact due to humidity IAEA 48

Imaging plate artefact Phosphor plate misused. Impossible to clean. IAEA 49

Dust on collection optics causes line in slow-scan dimension (Fuji CR) • Dirt on the light guide in the CR reader. The light guide collects light emitted from the imaging plate when it is scanned by the laser. • Artefact remedy: the light guide of the photomultiplier tube was cleaned by service personnel. IAEA Radiation Protection in Digital Radiology L 06 Avoiding Artefacts in Computed Radiography 50

Plate reader artefact • Digitiser • Processing IAEA Radiation Protection in Digital Radiology L 06 Avoiding Artefacts in Computed Radiography 51

Summary • Digital radiology requires some specific training to benefit of the advantages of this new technique. • Image quality and diagnostic information are closely related with patient dose. • The transmission, archiving an retrieving of images can also influence the workflow and patient doses • Quality assurance programs are specially important in digital radiology due to risk of increasing patient doses IAEA 52

THANK YOU! IAEA 53