Anjali (qa qc on cr dr)

PRESENTED BY
ANJU THAKUR
FINAL YEAR
DEPARTMENT OF RADIODIAGNOSIS AND IMAGING
PGIMER, CHANDIGARH

QA-it is the planned $ systematic action that a
diagnostic x-ray facility will produe consistently high
images with min exposure of patient $ healing arts
personnel.

QC-it deals with the technique used in the
monitoring (or testing) and maintenance of the
technical elements or components of an X-ray system.

(CR) Computed Radiography

Digital way of doing general radiography
with Conventional X-ray machines

is a process of capturing radiographic data from a
conventional X-ray machine and processing the
data digitally to produce crisp and high quality
radiographic images

Basic Components of CR
Preview & ID Station
ID Tablet
Cassette with
Imaging Plate

Digitizer Laser Camera
Processing Server

M A IX 3300
TR LR

CR WORKFLOW

M A IX 3300
TR LR

Rx Exposure
Printing
Network

Processing server
Identification Digitizer

Digital Radiography

 Performed by digital X-ray machines
with flat panel detectors

INTRODUCTION to QA QC of CR and
DR
Direct digital radiography (DR) and computerized
radiography (CR) systems are now being used routine for
radiography Screening Programme

Routine quality control (QC) is essential to ensure that the
equipment is performing as expected meets standards

Recommended routine QC tests
for DR systems
Frequency Test Section

Daily Checks on acquisition and reporting monitors
Daily System check
Daily Printer checks using test pattern
Weekly Check of contrast-to-noise ratio
Weekly Image quality tests
Weekly Uniformity check
Monthly AEC thickness check
Monthly Test of reporting monitors
Monthly Mechanical safety and function checks
As required Detector flat-field calibration
As required Repeat analysis
As required Printer checks following software upgrade

Recommended routine QC tests
for CR systems
 Frequency Test Section
 Daily Checks on acquisition and reporting monitors
 Daily System check
 Daily Printer checks using test pattern
 Weekly Check of contrast-to-noise ratio
 Weekly Image quality tests
Weekly Uniformity check
 Monthly AEC thickness check
 Monthly Test of reporting monitors
 Monthly Mechanical safety and function checks
Six monthly Image plate matching and artefact check
 As required Image plate erasure
 As required Image plate cleaning
 As required Repeat analysis
 As required Printer checks following software upgrade

Artifacts
CR- Dust on the ip, scraches/cracks on ip,dirt on reader,roller
marks

DR- faulty individual pixel,cluster of pixel, loss of resolution in
one or both direction

MONITOR- CRT(distortion,possibly due to interference from
other electrical devices)

PRINTER- if artifacts not seen on hard copy then it is caused
by printer, bandling, streaking, fine line in direction of film appear

Artifacts in computed
radiography
 Hardware artifacts

 Soft ware artifacts

11

Hard ware artifacts
Appearance
Reasons
 dust particle
&scratches
 Damage to the laser
beam head of CR
system
Remedy
Head has to be cleaned by
Camel hair brush by vendor Dust on the laser beam head appear
engineer as an irregular white lines
12

Damaged laser beam head in CR
reader
Appearance
Appears as multiple linear white line

Remedy
Laser beam head
Has to be replaced

13

Software artifacts

A Excessive edge enhancement B

Artifact simulate acute phase of Paget's disease as a result
Of excessive edge enhancement .(B) normal E.E 14

Computed Radiography and
Quality Control
 Computed radiography still uses conventional
radiographic equipment so basic radiography quality
control testing is still needed. This would include:
 Calibration of the generator
 Collimation
 Beam Alignment
 Linearity of exposure
 Spatial resolution (focal spot)

MONITOR CHECKS

 Monitor checks should be performed on both
the acquisition and reporting* monitors
under recommended working conditions. It
should be noted that cathode ray tube (CRT)
and flat panel displays (FPD) may have
different types of problems.

Daily checks on acquisition and reporting monitors

Method

• Check for obvious faults such as flicker, gross distortion,
artefacts
• Check general condition.
• Clean if necessary (follow the supplier’s instructions).
• Look at the text and lines on the screen – are they sharp and
straight?
• Keep a record of all checks, note any problems and take
action to get them corrected

Monthly test of reporting
monitors
 Using the SMPTE Test Pattern

SMPTE
This organization developed a test pattern that can be used to
determine grey scale image quality on videos and computer
display monitor.
Other parameter which can be evaluated are-
 Spatial resolution
 Brightness
 Contrast
 Aliasing

19

Contt…………..
 There should be no blurring or bleeding of bright display areas into dark
areas or aliasing of the spatial imaging patterns.
 All monitors used for interpretation should be tested at least monthly.
 For the dynamic range test, both the 5% and 95% contrast areas should
be visible and distinctly different than the adjacent 0% and 100% areas.
 Therefore: The brightness and contrast of the monitor is adequate if the
5% squares at both ends of the gray scale are visible.
 The gray scale is shown as a series of squares in the center of the image
that range from black (0%) to white (100%).
 It may be difficult to get the monitor to show both of these inner
squares perfectly.
 Most monitors do better showing the 95% square than the 5% square.
 However, you might try adjusting the ambient light to improve the
visibility of the 5% square.

Diagnostic video monitor
luminance & uniformity
 For Digital Systems:
 • Display SMPTE test pattern to evaluate initial quality of
monitor
 Determine manufacturers recommended settings
– ensure monitor is set accordingly

 • If no guidance material available follow:
– Video Monitor Manual Brightness & Contrast Setting
Procedure
 Diagnostic quality monitors typically include this
measurement in calibration check
- perform test following vendor recommendations

21

Luminance and uniformity
contd

•Use the TG-18 UNL -80 or SMPTE test
pattern ,or set an entirely white display
•Use a photo timer to measure luminance
-Measure maximum luminance in the
centre and four corners of display
-Measure minimum luminance in centre
of display

22

Diagnostic video monitor
luminance & uniformity

•Determine monitor type

•Calculate % difference of each of corners to
centre

23

Monitor type Maximum luminance
Color CRT > 80 Cd/m2
Color LCD > 100Cd/m2
Grey scale CRT secondary > 150 Cd/m2

Grey scale diagnostic >200 Cd/m2
Grey scale LCD 350 Cd/m2
Minimum luminance
CRT <1.0 Cd/m2
LCD <1.5 Cd/m2
% diff
All With in 15%
24

Image quality
uniformity & artifacts

25

Image quality
high contrast (spatial) resolution
For photo stimulable phosphor systems
 Determine standard set up& technical factors- do once
- low KVp, Extended SID
 use a lead –bar resolution test pattern phantom
- slightly angle phantom
 Minimize moiré &line pairing pattern
 Process with high-contrast algorithm

26

Image quality
low contrast resolution
(delectability)
 photo stimulable phosphor systems:
 erase cassettes
 Obtain several contact images of a low contrast phantom

 process using a high –contrast algorithm & edge enhancement
algorithm.

27

Image quality low contrast resolution
(delectability)

28

Weekly check of contrast-to-
noise ratio (CNR)

If region of interest (ROI) facility is available
Method
• Use the image of the test object from the daily test
• Draw two ROIs
• Record the mean (M1) and standard deviation (SD) of the pixel value in ROI
1.
• Record the mean (M2) of the pixel value in ROI 2.
• Subtract M2 from M1 and divide by SD to calculate the signal-to-noise ratio
(CNR):

CNR =M1- M2
SD
CNR baseline ± 20%
If this level is exceeded then take action to correct the problem.

Reader reboot

Reboot weekly Or as required
Follow the schedule as prescribed by the
manufacture
Daily wiping of the insertion slot
reduces the chance of dust getting
into the readout chamber

30

Daily wiping of the insertion
slot reduces the chance of
dust getting into the readout
chamber

31

Weekly uniformity check
 Uniformity should be visually checked on a weekly basis
using the image of the test object or plain Perspex

 from the daily test. By setting a narrow grey scale
window areas of non-uniformity will be seen. Magnify or
zoom the image electronically and inspect it in a
systematic fashion to look for artefacts such as faulty
clusters of pixels or areas of unusually low noise (where
the background mottle appears blurred or smoother than
otherareas of the image). This is particularly important
for some DR systems

Monthly AEC thickness check
Set up test just as done for film
Make Ist exposure on the thinner phantom
- expose thicker phantom at the same setting
- record the mAs
If a printer is available , print both images and measure optical
densities.
If using the on screen tool , select same size region- of – interest
(ROI) at same location on both images and record average
measurement.
 If region of interest (ROI) facility is available
 • Measure SNR and compare with baseline values
 • Measure CNR and compare with baseline values
 Remedial levels
 Detector dose indicator baseline for that thickness ± 10%
 SNR baseline for that thickness ± 20%
 CNR baseline for that thickness ± 20%
 No disturbing artefacts should be visible.
 If any of the levels are exceeded then take action to correct the problem.

DETECTOR FLAT-FIELD CALIBRATION
(DR SYSTEMS ONLY)
 Some DR detectors may have a non-uniform response (due to variations
in sensitivity, faulty pixels etc). Also,there are non-uniformities in the x-
ray beam due to the anode heel effect and x-ray beam divergence.
 Some DR systems correct for these inherent non-uniformities by a
process of flat-fielding. Flat-field correction maps are obtained using a
standard beam attenuator (usually a Perspex block) for one or more
exposure conditions
 (eg different target/filter combinations and focal spot sizes).

Some system require the user to carry out this flat-fielding process
periodically, and it is therefore included here although it is not strictly a
QC test. On other systems this is carried out by the service engineer at
routine service visits.

Method

• Carry out the flat field calibration according to manufacturer’s
protocols.
• Record and initial that the procedure has been performed.

IMAGE PLATE (IP) CHECKS (CR
SYSTEMS ONLY)
 Image plate erasure
 It is recommends that any cassettes left in the x-ray
room, or left un-used for a few days (eg over a weekend)
 should be erased using the image reader ‘secondary
erasure’ cycle before use, to remove any ‘fog’ from the
IP.

Six-monthly image plate
matching and artefact check
 This procedure should also be carried out on new image plates.
Image plates and cassettes should be matched
 in both their sensitivity (S value per unit exposure) and in the mAs
derived under automatic exposure control.
 Full size Perspex blocks are preferable for these tests so that the
whole IP can be checked for artefacts.
Method
Using each IP in turn:
• Conduct primary erasure before starting.
• Place 4 cm thickness of Perspex on the table (if more convenient, other
thicknesses such as 4.5 or 5 cm would also be suitable).
• Place IP cassette in the bucky.
• Operate the unit in a fixed kV, automatic mAs mode – select kV in
normal use,
• Make an exposure and record the mAs value.
• Read the IP after a standard delay time (eg 1 minute) –

• Record the S value.
• View image with a narrow display window and check for
artefacts.
• Repeat for each IP.
Then:
• Calculate the mean (average) mAs value for all IPs.
• Calculate the mean S value for all IPs.
Remedial levels
mAs value mean ± 5%
S value mean ± 10% (this allows for variation due to mAs and
variation in IP sensitivity).
Plates showing scratches or marks should be cleaned and the
test repeated. Plates with permanent scratches or marks should
be removed from service

MONTHLY MECHANICAL SAFETY AND
FUNCTION CHECKS
 Check the safety and function of the system. It is
recommended that a local checklist is drawn up for each
system to identify relevant features to be checked (eg items
that are safety-critical or areas known to be prone to faults).
 the local system, for example:
 • environmental checks (some digital systems are
particularly sensitive to environmental conditions such as
temperature and humidity)
 • checks relating to the reporting workstation .
 Keep a record of all checks, note any problems and take
action to get them corrected

PRINTER CHECKS

 The printer is set up on installation when the
engineer should ensure that the hard copy
matches the soft copy image.

 Daily printer checks using test pattern
 Printer checks should be carried out using standard viewing
conditions each day that the printer is used. Print
 SMPTE test pattern or the manufacturer supplied test
pattern and perform the following checks:

 • Geometrical distortion – check image is printed without
geometrical distortion; borders should be completely visible
and straight lines should be straight.

 • Contrast visibility – SMPTE test pattern, the 5% and 95%
squares should be clearlyvisible.

• Printer artefacts – check test pattern for printer
artefacts no disturbing artefacts should
be visible.
• If a densitometer is available, measure densities
and compare with baseline values
.
Printer checks following software upgrade
After software changes or an upgrade, it may be
advisable to print both a test pattern and a clinical
image to confirm that the hard copy remains
similar to the soft copy display

Anjali (qa qc on cr dr)

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