Radiographic
Inspections
Procedures for Digital and
Conventional Radiographic
Imaging Systems
Lee W. Goldman
Hartford Hospital
Filling in the Gap
Reasons for Rad or R/F Inspection
State regulatory requirement
 3rd party payer requirement
 Employer expectations (see following)
 Standards of good practice (see above)

It is not uncommon that “inspections” include the
minimum set of tests and evaluations needed to
fulfill the expectation or legal requirement
(perhaps due to time constraints and priorities)
Philosophy of Inspections
The goal of radiographic and fluoroscopic (R/F)
inspections should be to provide value by
evaluating and (if necessary) improving:
radiation safety
 image quality
 image consistency

This may entail going beyond commonly
accepted standards to striving for stricter yet
generally achievable performance levels
Philosophy of Inspections
Accomplishing this goal require thoroughness
on the part of the inspecting physicist. Since
“time is money”, emphasis must be placed on:
efficiency of inspection methodology
 organization of work
 attention to frequent problem areas

Sources of Requirements/Guidelines
Radiographic and Fluoroscopic Units
Visual Inspection/general
Collimation:
PBL (if so equiped)
Grid alignment and focusing
Light field illumination
Half-value Layer
Exposure timer accuracy
Exposure reproducibility
Exposure rates (mR/mAs):
mA/mAs Linearity:# 0.1
kVp accuracy
Focal spot size
SID Indication Accuracy
AEC (phototiming):
Fluoro min source-skin distance
Max fluoro entrance exposure rates (EER)
Typical EER measurements
Spot film exposures and rates
Automatic brightness control function
Fluoro resolution and sensitivity
Fluoro/TV system lag, flare
Criteria
NCRP
AAPM
ACR
ACMP
CFR
CFR
CFR
Annual
Semiann
Semiann
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
New
Annual
Semiann
Annual
Semiann
Semiann
Semiann
Semiann
Semiann
Semiann
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
New
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
--Annual
Annual
Annual
Annual
Annual
Annual
--Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
--Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Annual
CFR
CFR
CFR
CFR
CFR
CFR
CFR
CFR
Annual
Annual
Annual
Annual
Annual
----
Guidelines and Acceptance Limits

Many items commonly evaluated physicists have
performance levels specified by the Code of
Federal Regulations (CFR) 21 Part 1020

For other items, recommendations from various
organizations (AAPM, etc)are fairly consistent

State law may impose stricter limits, require more
frequent evaluations and include more test items

If not legally mandated, acceptance criteria may
depend on environment, equipment used, etc.

Might recommend stricter criteria if reasonably
achievable and provides appropriate benefits
Efficiency of Methodology
Combination of tests where appropriate
 Time saving tools
 Minimizing cassette/film usage (trips to the
darkroom)

Organization of Work



Concise data forms: avoid multiple pages
Sensible order: verify detents before AEC tests
Effective reports: Clear summary, recommendations
MODEL:____________________________________MAX mA:___________________
TUBE SER #:______________________________ CHAMBER:_________________
KVP ACCURACY AND EXPOSURE (mR/mAs):
SELECTED TECHNIC
kVp
mA
Sec
mAs
Focal-Chamber Distance:
MEASURED KVP
kV-1
SURVERYOR:_______________
CHAM CF:__________________
kV-2
kV-3
EXPOSURE (mR)
AVG
mR-1
mR-2
mR-3
CF:
AVG
CF mR/mAs
60
80
100
120
EXPOSURE LINEARITY, REPRODUCIBILITY AND TIMER ACCURACY:
kVp:_________
Frequency of Radiographic Findings
Year
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
Total:
Total Collim
kVp Reprod Linear Tim er
SID
Grid
Fog
33
34
43
38
33
38
17
24
31
25
9%
18%
26%
26%
36%
39%
18%
33%
26%
28%
30%
21%
30%
24%
18%
11%
12%
29%
32%
28%
9%
6%
2%
5%
15%
3%
12%
0%
0%
8%
24%
21%
35%
32%
27%
13%
12%
17%
35%
28%
6%
3%
2%
5%
6%
3%
6%
0%
3%
4%
6%
12%
12%
5%
6%
3%
6%
0%
0%
4%
33%
35%
42%
42%
39%
29%
24%
33%
13%
8%
0%
6%
0%
0%
6%
11%
0%
8%
6%
8%
316
26%
24%
5.7%
25%
3.8%
5.7%
31%
4.4%
Other: mR/mAs (1), HVL (1), Focal Spot (1), Artifacts (2)
Inspection Factors for Digital Systems

Many inspection components--no difference
– kVp, mR/mAs, linearity, timer accuracy, HVL)

For beam measurements (kVp, mR/Mas, etc)
– Move tube off of digital receptor if possibile
– If not, use lead blocker

Some (may) require digital receptor to record
– Collimation
– Grid alignment
– Focal spot size
– SID Indication
---?
Cardboard Cassettes or ReadyPack
Radiographic Inspection Components






Visual Inspection
Beam Measurements (kVp, mR, HVL, etc)
Receptor Tests: Grids, PBL, Coverage
Tube Assembly Tests: Collim, Foc Spot, SID
AEC (table and upright)
Darkroom Tests (if applicable)
Visual Inspection
 Visually
evident deficiencies
often ignored/worked
around by staff
 Reporting deficiencies often
leads to corrective actions
 Include:
–Lights/LEDs working
–Proper technique indication
–Locks and interlocks work
–No broken/loose dials, knobs
–Any obvious electrical or
mechanical defects
X-ray Beam Measurements
kVp accuracy AND reproducibility
 Exposure rates (mR/mAs)
 mA linearity

– Adjacent station
– Overall

Exposure control
– Timer accuracy
– Timer and/or mAs linearity
Reproducibility
 Half-Value Layer

kVp Evaluation: Significance
Total
kVp
Reprod
 Among
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
33
34
43
38
33
38
17
24
31
25
30%
21%
30%
24%
18%
11%
12%
29%
32%
28%
5%
– Increase dose if kV’s too low
15%
– Cause poor mA linearity,
3%
12%leading to possible repeats
 0%
Image contrast: affected,
0%
but relatively minor effect
8%
Total:
316
23.7%
most common
issue,
even
with
HF
9%
generators
6%
 2%
Poor kV calibration can:
for ranges of miscalibration
usually encountered
5.7%
Causes of kV Miscalibration

Inadequate provisions for kV adjustments
– May have only one overall kV adjustments to
raise or lower all kVps and one to adjust kV ramp
– Result: difficult to properly calibration all stations

Miscalibrated compensation circuits:
– Initial sags or spikes as tube begins to energize
– May significantly affect short exposure times

Important to evaluate kV accuracy at several
mA/kV combinations, and possibly all mA’s.
Causes of HF kVp Miscalibration
Pulse freq calibration: infrequent but seen on units
invasively calibrated at generator rather than at tube
 Power line limitations: more common if powered by
1-phase line with inadequate power
 Units incorporating energy storage device helps

Measuring kV: Yesterday
Measuring kVp: Today
kVp Measurements (Con’t)

Invasive measurement:
– still standard for many service personnel)

Non-invasive kV meters (highly
recommended):
– Measurements at many settings practical--allows
comprehensive eval of accuracy & reproducibility

Understand characteristics of your kV meter
–
–
–
–
–
Minimum exposure time for accurate measurement
Accuracy ~2%: beware of imposing tight limits
Effect of mid- or HF (meters that sample waveform)
Selection of waveform type
Properly calibrated filtration range
Effect of Filtration on kV
Meters
Measured kVp
mm added
Filtration
Meter 1
Meter 2
MultiFunc
0
2 AL
0.1 Cu + 1 Al
0.2 Cu + 1 Al
79.2
79.8
81.1
83.8
80.1
82.5
84.8
82.2
79.1
79.2
79.2
79.3
kVp Waveforms

Obtainable with meters having computer output
Very useful to recognize cause of calibration
problems(ramps, spikes, dropped cycles or phases)
kV Waveform
70
60
50
kV

40
30
20
10
0
0
10
20
30
m illiseconds
40
50
60
kVp: Action Limits

CFR: refers only to manufacturer’s specifications
Manufacturer specs: often quite loose (eg, +/-7%)
Common recommendations: 5% or 4-5 kV

For consistency:


differences between kV calibration at different mA
stations may be more important than across-theboard errors: eg:
100 mA --> 80 kVp measured to be 84
200 mA --> 80 kVp measures to be 76
Both may yield similar intensities at receptor!!
kVp Action Limits-Considerations




Inconsistencies may be more important than
across-the-board errors
More important for multi-unit sites (technique
consistency matters more)
Older Generators:
– Often difficult to accurately calibrate all mA/kV
– Recalibrations may shift error to other ranges
– More important to accurately calibrate limited
but clinically important limited range
May attempt improvements during next service or
during servicing for other corrective actions
X-ray Beam Measurements
kVp accuracy AND reproducibility
 Exposure rates (mR/mAs)
 mA linearity
 Exposure control
 reproducibility
 Half-Value Layer

Beam Exposure Measurements
Year
Total
Repro
Linear
Timer
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
33
34
43
38
33
38
17
24
31
25
9%
6%
2%
5%
15%
3%
12%
0%
0%
8%
24%
21%
35%
32%
27%
13%
12%
17%
35%
28%
6%
3%
2%
5%
6%
3%
6%
0%
3%
4%
Total:
Other:
316
5.7%
25.3%
mR/mAs (1), HVL (1)
3.8%
PROBLEM FREQUENCIES
 Poor linearity (adjacent or a
common problem
 Timer and Reproducibility
issues occur less frequently
 Problems may appear only:
– with certain mA settings
– Under certain conditions
– At certain kV ranges
Important to evaluate
many kV/mA settings!!
Efficient Beam Measurements
Valuable to make both kV and exposure
measurements at many kV/mA settings.
 Appropriate to measure kV and exposure
measurements simultaneously.
 May accomplish this via:

– Appropriate (multipe) tools and test geometry
– Multifunction meters
Efficient Beam Measurements
Multiple Meters
Geometry with Multiple Detectors


Scatter from kV meter
(or other material) can
significantly affect
exposure measurement
Procedures:
– Tight collimation
– Block scatter from
dosimeter (air gap,
foam spacer, lead
blocker
Efficient Beam Measurements
Multifunction Meters
X-ray Beam Measurements
kVp accuracy AND reproducibility
 Exposure rates (mR/mAs)
 mA linearity
 Exposure control
 reproducibility
 Half-Value Layer

Exposure Rates (mR/mAs)

Measure at several mA/kV settings covering
the commonly used clinical ranges
– Can measure along with kVp (no add’l exposures)
– Measure at relevant distance (eg, 30”)

Normal ranges very broad:
– Affected by filtration, age, kV and mA calibration
– Common range (30”): 12 +/- 50% (3-phase, HF)
– Narrow limits which have been published (6
mR/mAs +/- 1 at 100 cm) are not realistic

Greatest value is for patient dose estimates
X-ray Beam Measurements
kVp accuracy AND reproducibility
 Exposure rates (mR/mAs)
 mA linearity
 Exposure control
 reproducibility
 Half-Value Layer

Evaluating Linearity
Both adjacent-station linearity as well as overall
linearity (between any two mA stations) are important
mA Linearity (con’t)

Definition:
L = (RmA-1 - RmA-2)/(RmA-1 + RmA-2)
where R is mR/mAs at mA-1 and mA-2
Usual Requirement: L < 0.1 for any pair of
adjacent mA stations
 Exposure rates may differ by ~20% yet pass
 Prob signif contributor to technique errors
 We recommend: L < 0.1 for any pair of mA
L < 0.05 for adjacent pairs

mA Linearity (con’t)
For some HF and Falling Load Generators:
 Don’t allow selection of mA
 May allow selection of load:
– 60%/80%/100%
– Low/Half/Full, etc)
May evaluate linearity for different load
Note: For these (and some other HF) units,
linearity of mAs rather than mA may be
more pertinent

X-ray Beam Measurements
kVp accuracy AND reproducibility
 Exposure rates (mR/mAs)
 mA linearity
 Exposure control

– Timer accuracy
– Timer or mAs linearity
reproducibility
 Half-Value Layer

Timer Accuracy
Exposure Control & Timer Accuracy

Measure as part of linearity tests
– Also at longer and shorter times if necessary

For HF generators:
– exposures terminated at desired mAs, not time.
– More meaningful to evaluate exposure control
via linearity of exposure versus mAs
Timer Accuracy: Action Limits
1-Phase
CFR
AAPM1
ACMP 2
NCRP 3
Hendeei4
Manuf
Not specif
Not separately specif
1 pulse if >1/20 sec
0 pulses if < 1/20 sec
1 pulse if >1/10 sec
0 pulses if < 1/10 sec
3-phase
>10 mSec < 10 mSec
Manuf
Manuf
5%
10%
5%
20%
5%
5%
5%
20%
1
- AAPM Report 74, July 2002
2
- ACMP Report #1, Jnauary 1986
3
- NCRP Report 99, December 1988
4
- HEW Publ (FDA) 79-8094

Recommend:
– Greater attention to mAs and timer exposure linearity
– Attention to accuracy of short exposure times
– Awareness of non-invasive timer characteristics
X-ray Beam Measurements
kVp accuracy AND reproducibility
 Exposure rates (mR/mAs)
 mA linearity
 Exposure control
 reproducibility
 Half-Value Layer

Reproducibility
Usual Criteria: coeff of variaton < 0.05
 Our experience: Rarely a problem per se
 Causes when found:

– Abnormally terminated exposures (errors)
– Tripped circuit breaker
– Often occur only at certain technique settings
CFR test: 10 exposures within 1 hour,
checking line voltage prior to each exposure
 We recommend: limited test (3 exposures) at
several settings, with followup if necessary

X-ray Beam Measurements
kVp accuracy AND reproducibility
 Exposure rates (mR/mAs)
 mA linearity
 Exposure control
 Half-Value Layer

HVL Measurement





Failures do occur
Should test new tubes
prior to clinical use
Test procedure should
allow easy setup, proper
geometry (adequate
space between dosimeter
and aluminum sheets
Measure at desired
measured kVp
Criteria from CFR
Collimation
X-ray/light field congruence and alignment
 Light field Illumination
 Anode cutoff
 Damaged off-focus radiation limiters
 Positive Beam Limitation

Collimation: Congruence
Collimation: Congruence





Simple tools can suffice
Relatively frequent issue,
particularly for portables
Some uncertainty in
marking light field edges
CFR Criteria: 2% of SID
for L/X congruence and
indicator accuracy
(1.5” at 72” SID !!)
Can usually do better: try
for 1% of SID congruence
Light Field Illumination/Contrast
 CFR
Specifications:
– Illum: >160 lux at 100 cm
– Contrast: I1/I2 > 4
(I1,I2 are illuminations 3
mm in and out from light
edge, respectively)
 Often
never inspected
 Common problem on
some collim designs
 Recommend: test if
visually dim or edge
definition is poor
Anode Cutoff and Off-focus Limiters



Evaluated from full-field exposures:
– both lengthwise and crosswise orientations
– May combine with PBL or grid alignment tests
Anode Cutoff: failure to reach anode edge of film
with adequate intensity
Off-focus limiters:
– Can become bent inward, blocking primary x-ray
– Poorly delineated edge of x-ray field occuring
before reaching each of image receptor
Positive Beam Limitation







No longer FDA-required
Still available/common for non-digital systems
Test for each cassette size
Can often use single test cassette by overriding
PBL or switching to manual mode
Place angled cassette on table of in front of
receptor to capture full field
Limits: from CFR
Common causes of Failure:
– Mechanical failure of sensors
– Calibrated for metric but english sizes used, etc

Measurement:
–OK to use star pattern test
with digital image but
–difficult to properly expose
with NEMA kV, mA (need
lowest mAs, 1 mm Cu)


Results rarely useful
Pinhole/slit tests:
–Not clinically relevant
–Needed to resolve failure

Resolution-based test
(as in MQSA) at appropriate
distance/position could be
useful (limits?)
Focal Spot Size
SID Accuracy

Measurement:
– Location of focal spot usually not marked or visible
– Determine magnification of known-object size:
convenient to combine with star pattern f.s. test
– Digital displays: should check 2-3 distances


Criteria: 2% of SID
Causes of failure: New installations:
– incorrectly located/mounted scale
– miscalibrated digital display

Causes of Failure: Existing installations
– incorrect or mispositioned tape measure
– Incorrectly used tape (tape handle ‘tip’ or ‘flat’)
Grid Alignment/Appropriateness
Common problem area due to:




Incorrect grid: 72” upright grid for orthopedic office
Angulation due to installation errors or sag (with age)
Incorrect lateral detents (table and upright receptors)
Stationary grid artifacts with CR (“corduroy” effect)
Grid Cutoff vs Lateral Misalignment
Grid cutoff (absorption of primary x-rays) versus
amount of lateral decentering of x-ray tube focal
spot from the grid focal line. Lateral decentering
is relatively common due to misplacement or
changes in detent positions (measurements are
for a typical 10:1 grid, 103 lines/inch)
Distance (in):
% absorbed:
0
0%
0.5
12%
1
24%
1.5
41%
2
53%
2.5
71%
3
82%
3.5
92%
Stationary Grid Artifacts with CR

Problem if grid
lines parallel to
CR horizontal
scan direction

Need > 65-70
lines/cm for
clinically
acceptable
images
Testing Grids

If exposure possible with tube off lat detent:
–
–
–
–
–
–
–

Load cassette crosswise in receptor
Position x-ray at lateral detent and proper SID
Expose (~3 mAs at 50 kVp) with full x-ray field
Repeat with lateral shift of +/- 1” and +/-2”
Can use one cassette, exposing narrow strips
Maximum density of signal should be at detent
Image density or signal should be rel uniform
If cannot move off detent:
– one exposure--should have relatively uniform
signal or density across image
Radiograpic Inspection: Summary
1) Visual inspection and recording of information
2) kVp and mR/mAs together at 4 kVs, 3 mA’s
3) mR at fixed mAs for all mA; also measure time, kVp
4) HVL measurement
5) Light/X-ray field alignment
6) Star pattern focal spot test with SID verification
7) PBL test with film 14x17” test inspected for coverage
8) Grid alignment (also inspected for coverage)
9) Table and upright receptor AEC tests (if applicable)
10) Darkroom fog evaluation (if applicable)
11) Vendor-specific digital receptor tests, if available
Portable Radiography Inspection

Battery-powered:
– mR/mAs and kV
formerly frequent
problems; rare with
modern versions

Capacitor-discharge
– More uncommon
– Difficult to test

Outlet-powered and
all portable types:
– Collimation most
frequent problem
Ports
Total
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
7
5
8
9
9
10
4
3
4
4
HVL
13%
Collim
kVp
20%
13%
11%
56%
30%
100%
33%
50%
25%
20%
Reprod
11%
33%
20%
50%
67%
25%
25%
11%
11%
Total:
63
10%
32%
22%
Other: mR/mAs (0), Reprod (0), SID (0)
Linearity (NA), timer (0), Foc Spot (0)
3%
10%
50%
33%
25%