Download Low dose CT of the lumbar spine has better image quality than

Low dose CT of the lumbar spine has better image quality
than lumbar spine radiography at similar dose levels
Poster No.:
C-0064
Congress:
ECR 2015
Type:
Scientific Exhibit
Authors:
M. Alshamari , M. Geijer , E. Norrman , M. Lidén , W. Krauss , F.
1
3
2
1
1
1 1
2
3
1
Wilamowski , H. Geijer ; Örebro/SE, Lund/SE, Stockholm/SE
Keywords:
Quality assurance, Physics, Diagnostic procedure, CT,
Conventional radiography, Musculoskeletal spine
DOI:
10.1594/ecr2015/C-0064
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Aims and objectives
Despite recent abundant evidence of the limited value of lumbar spine radiography (1,2),
it is still the most common radiologic investigation of the lumbar spine region. Clinicians
try to use conventional radiography as much as possible to avoid or minimize the use
of unnecessary "standard" CT imaging as radiography has a low radiation level with the
effective dose being about 1 mSv level (3,4). The awareness of both the hazards of
medical ionizing radiation and the need to reduce it as much as possible have been
raised (5,6).
However, is possible to perform CT at much lower dose settings than with standard CT,
at the expense of increased image noise and reduced image quality; it can even be done
using the same relatively low radiation dose as lumbar spine radiography (7). The current
study was performed to evaluate and compare image quality and anatomic and some
diagnostic information from low dose CT of the lumbar spine, at about 1 mSv, with lumbar
spine radiography.
Methods and materials
Patients
After approval from the regional ethics committee patients referred for lumbar spine
radiography were invited to participate in the study. Inclusion criteria were adults
referred for lumbar spine radiography. Exclusion criteria were age below 18 years,
pregnancy, coma, dementia or inability to understand oral or written instructions. The
study cohort consisted of a convenience sample of 51 patients, 16 males and 35 females.
Patient length and weight were recorded for body mass index (BMI) calculations. The
patients were classified according to BMI (8) as being of normal weight (BMI 18.5-24.9),
overweight (BMI 25.0-29.9), or obese (BMI > 30.0).
Imaging
Each patient was examined by lumbar spine radiography and low dose CT the same day.
Lumbar spine radiography was performed our institute standard clinical settings. Low
dose CT was performed using a Somatom Definition AS scanner (Siemens, Erlangen,
Germany; 40 channels), using the settings determined in a previously reported phantom
study, giving about 1 mSv effective dose (9); tube potential 120 kV, reference mAs 30,
Page 2 of 17
collimation 40x0.6 mm, rotation time 0.5 s, pitch 1.4, FOV 200x200 mm, convolution
filter B41f (medium plus), with automatic dose modulation. Multiplanar reformations
(MPRs) were performed with 2 mm thickness and 2 mm increment. Several low dose CT
images are shown in Fig. 1 and 2 which demonstrates the sharp reproduction of different
anatomical structures of lumbar spine.
Image evaluation
The 102 examinations (51 low dose CT and 51 lumbar spine radiography studies) were
presented in random order. Five reviewers independently scored all studies blinded to
patient information as follows:
A. Scoring of image quality according to a modification of the European guidelines on
image quality for computed tomography (EUR 16262) (10) and diagnostic radiographic
images (EUR 16260) (11). Each reviewer scored the following criteria from 0 to 4:
1 Sharp reproduction of the disc profile and the upper and lower-plate surfaces of
vertebrae
2 Sharp reproduction of the cortical (cortex) and the trabecular bone
3 Sharp reproduction of the intervertebral foramina and pedicles
4 Sharp reproduction of the intervertebral joints
5 Sharp reproduction of the spinous and transverse processes
6 Reproduction of the adjacent soft tissues
7 Sharp reproduction of the sacro-iliac joints (the included part of the joints in the
examination)
8 Absence of any obscuring superimposed abdominal contents or gastrointestinal gas
The scoring levels for each criterion were:
0 Confident that the criterion is not fulfilled
1 Somewhat confident that the criterion is not fulfilled
2 Indecisive whether the criterion is fulfilled or not
3 Somewhat confident that the criterion is fulfilled
4 Confident that the criterion is fulfilled
Page 3 of 17
One reviewer scored all examinations again six month later to assess intra-observer
agreament.
B) The time needed to review each case.
Radiation dose
For lumbar spine radiography the dose-area product (DAP) measured with a DAP meter
integrated in the equipment was recorded for each projection. The PCXMC computer
program v2.0 (Finnish Radiation and Nuclear Safety Authority, Helsinki, Finland) was
used to calculate the effective dose from the average DAP of each projection. For the
CT examination the calculations were done with the software CT-Expo v 2.3 (SASCRAD,
Buchholz, Germany).
Statistical analysis
The data were analyzed as pooled data for all reviewers' first observation with visual
grading regression (VGR) (12), which is an ordinal logistic regression. VGR coefficient
and odds ratio were estimated. Negative values of the VGR coefficient and its confidence
interval limits, which consequently lead to estimation of odds ratios with confidence
intervals greater than one, indicate that low dose CT is significantly better than the
reference radiography. The calculations were performed with IBM SPSS Statistics for
Windows (version 22, IBM Corp., Armonk, NY, USA).
Inter-observer agreementaccording to free-marginal multirater kappa (multirater #free)
was estimated (13). Data from the first observations of all five reviewers was used. The
scoring scale was converted from a 5 grade scale to 3 grades (1-2 as 1, bad; 3 as 2,
moderate; and 4-5 as 3, good). Data from the first and second observation of one of
the reviewers was used to estimate free marginal kappa to evaluate the intra-observer
agreement. Calculations were performed with an online kappa calculator (14).
Images for this section:
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Fig. 1: Low dose CT of a 27-year old woman of normal weight with good image quality.
Page 5 of 17
Fig. 2: Axial images of low dose CT of an overweight 64-year old man which
demonstrates the sharp reproduction of different anatomical structures of the lumbar
spine.
Page 6 of 17
Results
Mean age of our sample was 58 years (SD 13.9, range 21-81 years). Average weight
was 79.6 kg (SD 15.6, range 55-125 kg), average length 169 cm (SD 9.3, range 152-194
cm). Average BMI was 27.7 (SD 4.0, range 20-38). The average number of exposures
in radiography was 3.5 (range 2-5).
CT was scored higher than radiography on all criteria except on "Sharp reproduction of
cortical and trabecular bone", as shown in Fig. 3 and 4. According to the visual grading
regression (VGR) analysis low dose CT had significantly higher image quality compared
with lumbar spine radiography in all criteria except "Sharp reproduction of the cortical
and the trabecular bone" as shown in (Table 1).
Criterion
VGR coefficient
(95% CI limits)
Odds ratio (95% CI
limits)
Interpretation
Disc profile
-0.96 (-1.31, -0.61)
2.61 (1.84, 3.70)
+
Cortical &
trabecular bone
1.19 (0.86, 1.53)
0.30 (0.22, 0.42)
-
Intervertebral
-2.01 (-2.40, -1.63)
foramina & pedicles
7.48 (5.09, 10.97)
+
Intervertebral joints
-4.87 (-5.53, -4.21)
130 (67.3, 251)
+
Spinous &
transverse
processes
-2.29 (-2.67, -1.92)
9.88 (6.79, 14.4)
+
Adjacent soft
tissues
-1.30 (-1.62, -0.97)
3.65 (2.63, 5.07)
+
Sacro-iliac joints
-1.76 (-2.12, -1.40)
5.82 (4.06, 8.35)
+
Absence of
-5.73 (-6.68, -4.79) 308 (120,792)
+
superimposed
contents & gas
+ Significantly superior image quality for low dose CT compared with lumbar spine
radiography
- Significantly inferior image quality for low dose CT compared with lumbar spine
radiography
Page 7 of 17
In the VGR analysis the criterion "Cortical and trabecular bone" was scored significantly
better for radiography regardless of BMI. All other criteria were scored significantly better
for low dose CT with the exception for the criterion "Disk profile" where there was no
significant difference for obese patients, but significantly better scoring for CT in normalweighted and overweight patients. Some examples which demonstrate higher image
quality of low dose CT compared with radiography are shown in Fig 5, 6 and 7.
There were good inter- and intra-observer agreements for all reviewer´s observations of
most of criteria 1, 3-5, 7 and 8 on CT images. The free-marginal multirater Kappa range
was 0.8-1.0 except for two criteria; "sharp reproduction of cortical and trabecular bone"
and "reproduction of adjacent soft tissues" which had low kappa values. There was a
generally low observer agreement for radiography.
The average time to review the studies was 204 s (95% CI 194-214 s) for low dose CT
and 152 s (95% CI 146-158 s) for lumbar spine radiography.
Using the average DAP the effective dose of three-image radiography (the frontal, lateral
and lumbosacral projections) was calculated to 0.6 mSv.
The dose from the scanogram was estimated to 0.1 mSv resulting in a total effective dose
of 1.0 mSv for low dose CT.
Images for this section:
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Fig. 3: Rating scores for all reviewers (R1-5) on all criteria for low dose CT. Full score
for each criterion is 1020 (4 max score x 5 reviewers x 51 cases).
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Fig. 4: Rating scores for all reviewers (R1-5) on all criteria for lumbar spine radiography.
Full score for each criterion is 1020 (4 max score x 5 reviewers x 51 cases).
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Fig. 5: A 73-year-old overweight man with obscuring superimposed gastrointestinal gas
on lumbar spine radiography but no effect on the image quality of low dose CT.
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Fig. 6: A 64-year-old man with unilateral spondylolysis at the L5-S1 level, well
demonstrated at low dose CT compared with radiography.
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Fig. 7: A 55-year-old woman with bilateral spondylolysis at the L4-L5 and at L5-S1 levels,
well demonstrated at low dose CT compared with radiography.
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Conclusion
The results from the current study have shown that low dose CT improves visualization
of most anatomical structures.
The strengths of the current study are that five reviewers took part in this study providing
a wide range of experience in evaluating image quality, and that the study included tests
of intra-individual and inter-individual agreement and an evaluation of whether BMI was
a confounder.
The protocol for low dose CT at 1 mSv level used in the current study was derived from
a previous phantom study (9). The effective dose level was set as the average effective
dose of lumbar spine radiography in Sweden, 1.1 mSv, according to a report from 2010
(3). In the current study the effective dose to a standard sized patient was estimated
to 1 mSv for low dose CT and 0.6 mSv for radiography. Risk from medical radiology is
described using broad categories: negligible, < 0.1 mSv; minimal, 0.1-1 mSv; very low,
1-10 mSv; and low, 10-100 mSv (15).
CT at the low dose set in the current study, about 1 mSv, has a high possibility to
become part of the clinical routine in imaging the lumbar spine. The CT protocol can be
further developed by adapting the settings of other parameters than reference mAs, tube
potential (kV) and convolution filter, or by applying other reconstruction techniques such
as iterative reconstructions (5,16).
In conclusion, low dose CT of the lumbar spine at 1 mSv has superior image quality
to lumbar spine radiography. Low dose CT may give more anatomical and diagnostic
information than lumbar spine radiography and thus can replace radiography in daily
clinical practice.
Personal information
Muhammed Alshamari, M.D.
Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro,
Sweden;
[email protected]
Page 14 of 17
Mats Geijer, M.D., Ph.D.
Department of Medical Imaging and Physiology, Skåne University Hospital, Lund, Lund
University, Sweden.
Eva Norrman, Ph.D.
Department of Medical Physics, Faculty of Medicine and Health, Örebro University,
Örebro, Sweden.
Mats Lidén, M.D., Ph.D.
Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro,
Sweden.
Wolfgang Krauss, M.D.
Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro,
Sweden.
Franciszek Wilamowski, M.D.
Department of Radiology, Ersta Hospital, Stockholm, Sweden.
Håkan Geijer, M.D., Ph.D.
Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro,
Sweden;
[email protected]
References
1. Miller P, Kendrick D, Bentley E, et al. Cost-effectiveness of lumbar spine radiography
in primary care patients with low back pain. Spine 2002;27:2291-2297
2. Venkatesan M, Fong A, Sell PJ. CT scanning reduces the risk of missing a fracture of
the thoracolumbar spine. J Bone Joint Surg Br 2012;94:1097-1100
Page 15 of 17
3. Leitz W, Almén A. 2010:14 Patient doses from X-ray examinations in Sweden Development 2005-2008 [Report in Swedish] Stockholm: Swedish Radiation Safety
Authority, 2010.
4. Hart D, Hillier M, Shrimpton PC. Doses to patients from radiographic and fluoroscopic
X-ray imaging procedures in the UK - 2010 Review. In: The Health Protection Agency
(HPA), Centre for radiation, chemical and environmental hazards(CRCE); 2012.
5. McCollough CH, Chen GH, Kalender W, et al. Achieving routine submillisievert CT
scanning: report from the summit on management of radiation dose in CT. Radiology
2012;264:567-580
6. Amis ES, Jr., Butler PF, Applegate KE, et al. American College of Radiology white
paper on radiation dose in medicine. J Am Coll Radiol 2007;4:272-284
7. Gleeson TG, Byrne B, Kenny P, et al. Image quality in low-dose multidetector computed
tomography: a pilot study to assess feasibility and dose optimization in whole-body bone
imaging. Can Assoc Radiol J 2010;61:258-264
8. WHO. Obesity: preventing and managing the global epidemic. Report of a WHO
Consultation. WHO Technical Report Series 894. Geneva: World Health Organization,
2000.
9. Alshamari M, Geijer M, Norrman E, et al. Low-dose computed tomography of the
lumbar spine: a phantom study on imaging parameters and image quality. Acta Radiol
2014;55:824-832
10. Bongartz G, Golding SJ, Jurik AG, et al. European Guidelines for Multislice Computed
Tomography, European Commission.
http://www.msct.eu/CT_Quality_Criteria.htm. (accessed December 2014).
11. European Commission. European guidelines on quality criteria for diagnostic
radiographic images-UR 16260. Luxembourg, 1996.
12. Smedby O, Fredrikson M. Visual grading regression: analysing data from visual
grading experiments with regression models. Br J Radiol 2010;83:767-775
13. Warrens MJ. Inequalities between multi-rater kappas. Advances in Data Analysis and
Classification 2010;4:271-286
14. Randolph JJ. Online Kappa Calculator http://justus.randolph.name/kappa. (accessed
November 12 2014).
15. Martin CJ. Effective dose: how should it be applied to medical exposures? Br J Radiol
2007;80:639-647
Page 16 of 17
16. Yang CH, Wu TH, Chiou YY, et al. Imaging quality and diagnostic reliability of lowdose computed tomography lumbar spine for evaluating patients with spinal disorders.
Spine J 2014;14:2682-2690
Page 17 of 17