CT pediatry: influence of new technologies on patient dose
Redefining the Rules of clinical CT Imaging with Spectral
Imaging and Iterative Reconstruction techniques
Johan de Mey PhD. MD Head of Radiology Department
Koenraad Nieboer MD Head of Emergency RadiologyNico Buls PhD.
MScMedical Imaging and Physical Sciences Gert Van Gompel PhD.
MScMedical Imaging and Physical SciencesToon Van Cauteren
MScMedical Imaging and Physical Sciences
1
Multislice CT and clinical outcome
DoseWorkflow
accuracyefficiency
function
Characterizationperfusion
Spatial ResolutionTemporalCoverageWhat makes a good CT?
2
Low Dose CT = quality ?1980 2007: Dose optimalisation
More imagesHigher resolution
2008 - : Dose optimalisation
Less dose???Functional???Iterative reconDual energy
3
Noise suppression The straightforward way increase # photons,
increase patient dose (mAs)
120 mAs60 mAs
10 mAs
CTDIv = 0,8 mGyCTDIv = 5 mGyCTDIv = 10 mGy
4Erratic information
Effective doses for CT procedures(review over 20 published
articles)
Does the age of the patient at time ofexposure affect the
patient risk?
Children are 2-10 x more sensitive!Hall Pediatric Radiology Apr
2002 pg 226
source
Iterative reconstruction
sImage acquisitionsinogramdetector
source
Goal:reconstruction
Adaptive Statistical Iterative Reconstruction (0%.....100%) and
noise0.8 mGy16.8 mGy
10 mAs30 mAs60 mAs120 mAsGE CT750 HD, 100 kVp, p = 0.9, r = 1, t
= 2.5 mm, FOV = 230 mm
8Asir strength depends on initial noise levelCan not make a
60mAs like image from a 10mAs image
ASIR (60%) and Spatial resolution
ASIRFBP
Female 45Acute dyspnea, suspicion pulmonary embolism
Scan ParametersRange 26 cmNi: 30120KVASiR: 40% CTDIv 7.44 (mGy)E
2.7 (mSv)
0.625 mm
1.25 mm1.25 mm
Body PackersBody packers: low dose CT / GSI
ECR EPPOS: C-2068 ECR 2011 K. H. Nieboer, N. Buls, J. de Mey, G.
Van Gompel; Brussels/BE, The use of iterative reconstruction in
ultra low dose computed tomography for bodypacker screening
VeoTM future in dose reduction= Model Based Iterative
Reconstruction
SYSTEM NOISE STATISTICSREAL 3D SYSTEM OPTICS
FBPVEOASIR
Iterative impact on image noise
Tube currentNoise
FBPASIR 50%VEOCTDIvol = 12.5 mGyResolution at standard dose
Performance at 6 lp/cm and 8 lp/cm
Catphan 504 phantom
Ultra low dose Chest follow-up with VEO4mAs,
0.06mSv*FBPVeoASiRTypical CXR effective dose is about 0.06 mSv.
Source: Health Physics
Society.http://www.hps.org/publicinformation/ate/q2372.html
* Determined by internal organ dosimetry on a humanoid
phantom
Chest CT with Veo Cystic Fibrosis 26y * Obtained by EUR-16262
EN, using a chest factor of 0.017*DLPConversions of CTDI or DLP to
effective dose are only rough estimations for children
CDTIvol = 0.10 mGy Effective dose = 0.05 mSv*
Chest CT with Veo Cystic Fibrosis 15y
FBP-images 2011Ultra low dose
Veo-images 2011Ultra low dose
FBP- Images 2010Low dose DLP = 2.51 mGy.cm CTDIvol:0,09 mGyDLP =
54,3 mGy.cm CTDIvol: 1,65 mGy
Scan protocol: 4 mAs, 80 kVSlice thickness: 0.625mm
95 % dose reductionVEO reconstruction 2011FBP reconstruction
2010Chest CT with Veo Cystic Fibrosis 15y
Chest CT with Veo Cystic Fibrosis 15y Veo-images: Ray Sum
CTPrevious Chest X-ray
PATIENT 1 (2010)3Y Old, empyemaFBP-imagesCTDi 2.1
PATIENT 2 (2011)3 y old, empyemaVeo-imagesCTDi 1.25
40% dose reduction
Pediatric maxilo-facial CT with Veo 95% dose reductionCT at
plain film dose+/- 0.06 mSv
70% dose reductionNo quality loss
50% dose and low KVpNo quality loss + 50 % contrast
reduction
40% dose reductionBetter image, less artifacts
Equal dose and low KVpUp to 60% contrast reduction
Dual energyspectral imaging:Need for at least two datasets on
different energy level
Dual tubeMaking two scansDual layer detectorPhoton counting
Discovery CT750 HD
Fast switching tube
Dual energyspectral imaging:Need for at least two datasets on
different energy level
Dual tubeFOV max 33 cmSpectral filter on 140Making two scansTime
DifferenceDual layer detectorResearchPhoton countingFutureFOV 50
cmReal Time
?
Discovery CT750 HD
Photon energy with Tungsten? What is dual energy?
Mean 61.1 KeV120 KV scanMean 49.9 KeV80 KV scanMean 66.1 KeV140
KV scan
Spectral material differentiation
34
From 2 datasets to 101 datasets? Is this real?
Phantom dataQualitative comparison DECT literature (NIST)ECR:
B-851 Monday 14.00G. Van Gompel, N.Buls, K. Nieboer, J. de
MeyAccuracy estimation of spectral attenuation curves obtained by
dual energy
Cadaver blood vesselsFilled with CM concentration, GSI scan
ROI2: water + CMROI3: soft plaqueROI4: calcified plaqueClinical
use?
Relative dose reduction? (No need for non-CE scans) Contrast
reduction? (Higher contrast in image)
WaterIodine
Pleural effusion: Exudate >< transudate?ECR EPOS: C-1996
Y. De Brucker, N. Buls, G. Van Gompel, F. Vandenbroucke, H.
Nieboer, T. De Keukeleire, J. de Mey; Brussels/BE Characterization
of pleural effusion using dual energy CT: feasibility study.
Phantom size on quantitative iodine measurement: dual energy CT
>< standard CT.
23 cm120 keVGSI 70 keV 17 cm2919310631893145 17 cm +
t32553158range345Obtained CT-values (HU)
VAR10.9%1.6%
39
StandardPhantom size on quantitative iodine measurement:
spectral CT >< standard CT. 120 kV
DECT at 70 keVStandardSpectral
40
Male 77Acute dyspnea, suspicion pulmonary embolism
Iodine image
Water imageMonochromatic 40 140 KeVAxial recon image
Water imageIodine imageScatterplot
42
S
GSI: spectral imagingSubsegmental pulmonary embolismClinical
value
Pulmonary embolism was not depicted during 1st reading on
standard images
MD Iodine shows clearly a hypo perfusion on the left.
2nd reading confirms pulmonary embolism resulting from a small
thrombus in a small pulmonary vessel
GSI allows physicians to detect pulmonary embolism by showing
subtle lung perfusion defect
Embolism
70 keV images with lung window Iodine Based Images70 keV
Monochromatic Images70 keV Monochromatic Images
Images Courtesy of Dr. Jean Louis Sablayrolles; Centre
Cardiologique du NordPulmonary EmbolismClinical value
Pulmonary embolism was not depicted during 1st reading on
standard images
MD Iodine shows clearly a hypo perfusion in left lung resulting
from a pulmonary embolism. Hypo perfusion could not be seen on
standard CT image
2nd reading confirms pulmonary embolism resulting from a small
thrombus in a small pulmonary vessel
GSI allows physicians to detect pulmonary embolism by showing
subtle lung perfusion defect
Standard 120 kV acquisitionMonochromatic with MARsGSI: Artefact
reduction
MD Water (Iodine)80 keVMD Iodine (Water)55 keV
Images Courtesy of Pr Dacher, CHU de RouenIliac Stent
BleedingClinical value
Endoleak is better visualized on low energy (55 keV) images
(green Arrows)
MD Iodine suggests Iodine leak
GSI allows physicians to better visualize bleeding vs.
conventional CT
70 keV image 110 keV images
Metal Artifact Reduction: Spine
GSI acquisition allows to create a spectrum of monochromatic
images where beam hardening is highly reduced
In this case the radiologist could recover information
previously hidden by the beam hardening
Images Courtesy of Dr. Sablayrolles, CCN, France
Thank you for your attentionStatistical iterative
reconstruction: important dose reductionDose reduction up to 50%
and same qualityScanning at low KVp and contrast reductionIn some
cases alternative for plain film
Spectral imaging and real iterative rec.: a new dimension in
CTUltra low dose at diagnostic quality up to 95% reductionArtifact
reduction and high quality imagesCharacterization and
differentiationContrast amount and concentration reduction
Conclusion: New dimensions in CT