clinical study reducing radiation dose in...

Hindawi Publishing CorporationEmergency Medicine InternationalVolume 2013 Article ID 984645 7 pageshttpdxdoiorg1011552013984645

Clinical StudyReducing Radiation Dose in Emergency CT ScansWhile Maintaining Equal Image Quality Just a Promise orReality for Severely Injured Patients

Ulrich Grupp1 Max-Ludwig Schaumlfer1 Henning Meyer1

Alexander Lembcke1 Alexander Poumlllinger1 Gero Wieners1 Diane Renz1

Philipp Schwabe2 and Florian Streitparth1

1 Department of Radiology Charite Humboldt University Medical School Augustenburger Platz 1 13353 Berlin Germany2 Center for Musculoskeletal Surgery Charite Humboldt University Augustenburger Platz 1 13353 Berlin Germany

Correspondence should be addressed to Florian Streitparth florianstreitparthcharitede

Received 4 August 2013 Revised 26 September 2013 Accepted 27 September 2013

Academic Editor Stefan Puig

Copyright copy 2013 Ulrich Grupp et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Objective This study aims to assess the impact of adaptive statistical iterative reconstruction (ASIR) on CT imaging qualitydiagnostic interpretability and radiation dose reduction for a proven CT acquisition protocol for total body trauma Methods18 patients with multiple trauma (ISS ge 16) were examined either with a routine protocol (119899 = 6) 30 (119899 = 6) or 40 (119899 = 6)of iterative reconstruction (IR) modification in the raw data domain of the routine protocol (140 kV collimation 40 noise index15) Study groups were matched by scan range and maximal abdominal diameter Image noise was quantitatively measured Imagecontrast image noise and overall interpretability were evaluated by two experienced and blinded readersThe amount of radiationdose reductions was evaluated Results No statistically significant differences between routine and IR protocols regarding imagenoise contrast and interpretability were present Mean effective dose for the routine protocol was 253plusmn29mSv 197plusmn58mSv forthe IR 30 and 175plusmn 42mSv for the IR 40 protocol that is 221 effective dose reduction for IR 30 (119875 = 0093) and 308 effectivedose reduction for IR 40 (119875 = 00203) Conclusions IR does not reduce study interpretability in total body trauma protocols whileproviding a significant reduction in effective radiation dose

1 Introduction

The use of computed tomography (CT) brought enormousbenefits to modern medicine and diagnostic CT examina-tions are increasingly used in recent years because of theirspeed availability and diagnostical power In particularfor patients with polytrauma during the early resuscitationphase whole-body CT is recommended as the standard diag-nosticmodality [1]However the commonutilization ofCT isaccompanied by a steady increase in the populationrsquos cumula-tive exposure to ionizing radiation [2 3] As X-rays have beenclassified as ldquocarcinogenrdquo new efforts to minimize radiationexposurewere undertaken tomeet rising concerns of possiblelong-term cancer especially regarding pediatric and youngpatients as well as patients undergoing several follow-up CTexaminations [4] A plurality of approaches from ldquoAECrdquo

(automated exposure control) to ldquoX-ray beam collimationrdquoled to a significant reduction in radiation dose [5 6]With thefast advancement of computational power the technique ofiterative reconstruction (IR) well known from SPECT andPET imaging became the center of attention for CT adaptionin recent years [7ndash10]

The group of severely injured patients is of great concernfor dose reduction as these patients may be of a young ageand standard protocols for emergency settings use relativelyhigh radiation doses in order to detect subtle but possibly life-threatening lesions [11] As recently demonstrated IR algo-rithms do not significantly delayCT imaging time in an emer-gency setting [12] though the impact of IR on image qualityand dose reduction has not been investigated

The working hypothesis was that the use of IR algorithmswould reduce effective radiation doses without affecting

2 Emergency Medicine International

(a) (b) (c)

Figure 1 25-year-old female patient with a heavy trauma falling from a roof with suicidal intention Image acquisition with the CT ASIR40 protocol (a) coronal orientationlung window showing bilateral pneumothoraces (arrow) with Bulau drains in situ heavy contusion inboth lungs and extensive thoracal and cervical soft tissue emphysema (b) coronal orientationsoft tissue window showing hypodensities interms of an acute liver haematoma in the right lobe (arrow) Also note a huge retroperitoneal haematoma in the lower abdomen (arrow) (c)another male 42-year-old patient after falling from a roof CT ASIR 40 protocol sagittal planebone window Vertebral body fracture in L3with consecutive spinal stenosis (arrow)

image quality and interpretability in comparisonwith routineCT imaging based on filtered back projection (FBP) There-fore this study aimed to prospectively evaluate different levelsof IR algorithms on imaging quality and dose reduction for aproven CT full body trauma protocol

2 Materials and Methods

21 Study Design The study was carried out prospectivelyThe study design was approved by the institutional ethicsboardThe need for informed consent was waived as patientswere not exposed to an additional radiation dose and patientdata was anonymized The study was conducted at a univer-sity teaching hospital

All examined patients were classified as severely injuredpatients (injury severity score (ISS) ge16) by the emergencydepartment and underwent CT scans within the scope of theroutine in-house algorithm for patients with severe and mul-tiple injuries in accordance with the currently valid guideline[13] At the time of study analysis 10 patients were examinedwith IR 30 and 16 patients with IR 40 protocol For matchingthe patients in all three patient groups (FBP IR 30 and IR40) these patients were compared by scan range andmaximalabdominal diameter Subsequently some patients had to beexcluded and 6 patients per group were enrolled in the finalstatistical analysis (age = 539 plusmn 199 years 5 females) Allgroups were matchedmanually as to scan range andmaximalabdominal cross-section area to attain a homogenous studycollective The authors regarded this approach to be a moreaccurate approximation for full body radiation exposure ofthe study group than traditional parameters that is BMI [14]The control group was examined with the routine filtered

back projection (FBP) protocol whereas the protocol forthe first study group performed on the same CT scannerconsisted in 30 adaptive statistical iterative reconstruction(ASIR) application in the raw data material After a prelimi-nary assessment of the newly acquired image quality and pos-itive results in terms of interpretability a stronger level of IR(40) was implemented on the standard protocol and per-formed on the second study group

22 CT Protocol All patients were examined using a 64-slicemultidetector CT scanner (Lightspeed VCT GE HealthcareUSA)The emergency protocol consists of two separate scansThe first is an axial scan of the cranium angulated between 0∘and 30∘ (depending on the positioning of the patient) withoutinjection of a contrast agent (CA) in order to detect possibleintracranial bleeding

Second after application of CA (see Section 23) a helicalscan of the whole body is performed in craniocaudal direc-tion ranging from above the frontal sinus (in order to picturethe cerebral arterial circle) to the bottom of the pelvis Imageacquisition is conducted with the following parameters tubevoltage 140 kV collimation 40 pitch 1375 and noise index15

The protocol of the axial cranium scan was not modifiedIf additional scans were performed due to individual injurypatterns these have not been considered and were excludedfrom the image quality and radiation dose analyses

23 Injection Table For the helical whole-body spiral 140mLof CA was administered in a split bolus technique

100mL CA (2mLs flow rate)

Emergency Medicine International 3

(a) (b)

(c)

Figure 2 Image acquisition with the routine CT protocol reconstructed by filtered back projection (FBP) without IR In (a) the whitearrow points to a small pneumothorax in the lingula segment In (b) a hepatic laceration in liver segments 2 and 4a is displayed Noticethe semicircular soft tissue emphysema on the right side In (c) the arrow points to the fracture of the left transverse process of L3 with nomajor dislocation and a corresponding haematoma of the psoas muscle

20mL saline (1mLs flow rate)60mL CA (4mLs flow rate)40mL saline (4mLs flow rate)

The CT scan starts with a delay of 85 seconds after firstinjection of the 100mL CA

Using this technique an additional scan and radiationdose can be avoided as arterial and venous contrasting isdepicted in the same scan The nonionic low osmolalitycontrast medium iobitridol (Xenetix 350 Guerbet GmbHGermany) was utilized as CA

24 Data Reconstruction IR algorithms attempt to overcomeelevated image noise and artifacts resulting from reducedvoltage and current The adaptive statistical iterative recon-struction (ASIR) technique attempts to accurately rebuildimages by concentrating on noise reduction [15] It thereforeuses information obtained from the FBP algorithm as aninitial building block for image reconstruction The ASIRmodel then uses matrix algebra to transform the measuredvalue of each pixel (119910) to a new estimate of the pixel value (1199101015840)This pixel value is then compared with the ideal value that thenoise model predicts This process is repeated in successive

iterative steps until the final estimated (119883) and ideal pixel val-ues ultimately converge [16 17] Using this method IR algo-rithms are able to selectively identify and then subtract noisefrom an image

The image acquisition was modified by 30 (40) use ofIR in the raw data domain Due to computational limitationsthe raw data material is then first computed into slices of5mm thickness in order to deliver a fast summary of thepatient for diagnostical assessment and subsequently intoslices of 0625mm thicknessThe image reconstruction of the5mm slices used the same level of ASIR algorithms (3040)as those of the raw data whereas the thin slices were bothcomputed with 60 ASIR to further reduce image noise Nochange of radiation dose is linked to the reconstructionASIR

25 Data Analysis Quantitative analysis of image quality wasevaluated for noise that is the standard deviation (SD) ofattenuation value Therefore a region of interest (ROI) wasdrawn as large as possible in the supracarinal trachea withoutexceeding the lumen Qualitative analysis of the acquiredimages was performed by two experienced and blinded radi-ologists in consensusThe images were cleared of all technicalinformation in order to reduce expectation bias


(a) (b)

(c)

Figure 3 Image acquisition with the IR 30 protocol In (a) the arrow points to a major ventral pneumothorax of the right lung In the dorsalarea there is pleural effusion with adjacent dystelectasis In (b) a subtle laceration of the ventral splenic pole is marked by the arrow Similarto the FBP protocol in Figure 1 a fracture of a transverse process of L4 without major dislocation can be diagnosed on the right side

Image quality was evaluated in five categories noise con-trast artifacts detectability of small structures and overalldiagnosability Each category was evaluated by using a five-point Likert scale with 5 representing the best possible resultand 1 insufficient results for example for overall diagnosabil-ity (1) nondiagnostic image quality (2) severe blurring withuncertainty about the evaluation (3) moderate blurring withrestricted assessment (4) slight blurring with unrestricteddiagnostic image evaluation possible and (5) excellent imagequality no artifacts

26 Statistical Analysis The data were analyzed using SPSS180 (SPSS Inc Chicago Ill) Radiation doses and image qual-ity parameters were compared using the Mann-Whitney-119880test A 119875 value of less than 005 was considered a statisticalsignificance

3 Results

31 Image Quality Quantitative analysis for image noise(region of interest in the supracarinal trachea) yielded thefollowing results the standard deviations of attenuation valuemeasured in HU were 39 plusmn 07 34 plusmn 08 and 33 plusmn 06 for

the routine IR 30 and IR 40 protocol There were no sig-nificant differences between the three groups

Qualitative analysis yielded the following results all (119899 =18) CT examinations were estimated to be of excellent imagequality without artifacts compromising diagnosability (level5) in terms of image artifacts detectability of small structuresand overall diagnosability (Figures 1 2 3 and 4) Regardingimage noise and image contrast no statistically significantdifferences resulted with image noise estimated at 47 plusmn 055plusmn 0 and 48 plusmn 04 for the FBP IR 30 and IR 40 protocol Forimage contrast the results were 5 plusmn 0 48 plusmn 04 and 48 plusmn 04respectively There were no significant differences betweenthe three groups

32 Radiation Dose To estimate the effective radiation dosefirst the CT volume dose index (CTDIvol) and the dose-length product (DLP) were obtained from the electronicallystored dose report of each performed CT scan The effectiveradiation dose was then calculated by multiplying the DLPby a conversion coefficient 119896 of 0017mSvmGysdotcm [18] SeeTable 1 for an overview of the radiation doseThemean effec-tive dose for the standard FBP protocol was 253 plusmn 29mSvthe implementation of IR 3030 resulted in 197plusmn58mSv and


(a) (b)

(c)

Figure 4 Image acquisition with the IR 40 protocol In (a) the white arrows mark the bipulmonary contusions The black arrow tags themediastinal emphysema In (b) the white arrowmarks a subtle splenic laceration in the dorsal pole similar to the splenic lesion in Figure 3(b)Finding of a vertebral body fracture in (c) after a motorcycle accident No accompanying lesion of the pancreas could be found

Table 1 Radiation dose

Parameters Standard140 kV

IR 30140 kV

IR 40140 kV

Scan range (cm) 901 plusmn 32 909 plusmn 49 908 plusmn 34Max abdominalcross-section

Coronal (cm) 352 plusmn 37 372 plusmn 31 363 plusmn 33Sagittal (cm) 275 plusmn 33 272 plusmn 47 268 plusmn 44

CDTIvol (mGysdotcm) 155 plusmn 18 121 plusmn 35 107 plusmn 25DLP (mGycm) 14914 plusmn 1601 11791 plusmn 3546 10354 plusmn 2291Effective radiationdose (mSv) 253plusmn 29 197plusmn 58 175plusmn 42

Parameters of the routine FBP protocol IR 30 protocol and IR 40 protocolData are presented as mean plusmn standard deviation CTDIvol CT volume doseindex DLP dose-length product

in 175plusmn42mSv for IR 4040 protocol that is 221 effectivedose reduction for IR 30 (119875 = 0093) and 308 effective dosereduction for IR 40 (119875 = 00203) See Figure 5 for an overviewof the dose reduction

4 Discussion

After its introduction in 1973 computed tomography (CT)was fast accepted by the medical community In particularin the treatment of severely injured patients its diagnosticaccuracy brought immense benefits and whole-body CTscans have become an integral part of the Advanced TraumaLife Support (ATLS) in multiple trauma centers As severalmulticenter studies showedwhole-bodyCT scans in the earlyphase of treatment resulted in a significant increase of sur-vival [1 18 19] Hence benefits of CT in an emergency settingoutweigh by far the downsides with exposure to ionizingradiation being themost critical disadvantageWith amediancumulative effective dose as high as 402mSv for CT scans ofblunt trauma patients [11] efforts to reduce effective radiationdoses still constitute a primary objective Since the first intro-duction of IR algorithms into CT imaging there have beennumerous studies regarding image quality noise and radia-tion dose reduction [20ndash22] The overall findings dependingon the study design proved either a significant dose reduc-tion a better image quality or both However the applicabil-ity of these algorithms to an emergency setting has not yet


FBP 30 ASIR 40 ASIR0

5

10

15

20

25

30

35

Effec

tive r

adia

tion

dose

(mSv

)

P = 0093 P = 00203

Figure 5 Dose reduction comparison of three different CT proto-cols The mean effective dose for the standard (FBP) protocol was253plusmn29mSv for IR 30 197plusmn58mSv and 175plusmn42mSv for IR 40protocol that is 221 effective dose reduction for IR 30 (119875 = 0093)and 308 effective dose reduction for ASIR 40 (119875 = 00203) A 119875value of less than 005 was considered a statistical significance

been examined as image quality is of the highest priority inthese circumstances

With our findings being a first evaluation of the impactof IR algorithms in an emergency setting a number of issueshave to be addressed in the future

It has been shown in the literature that the mean effectivedose for full body CT examinations ranges between 14 and21mGy whereas the mean effective dose in the control groupof our study was 25mGy [23] The effective radiation doseis slightly above average as we used 140 kV for the routinetrauma protocol This is based on the fact that as a nationalcenter of maximum care we are confronted by a tendencyto receive more complex severely injured patients than otherinstitutions and image quality is paramount After carefulconsiderations of advantages and disadvantages our insti-tution decided to apply 140 kV for the routine whole-bodytrauma protocol as this protocol is more robust concerningartifacts from foreign bodies (eg equipment from anestheticintensive care) Of course the use of a protocol with 120 kV isalso appropriate It can be assumed that the implementationof 120 kV for whole-body protocols instead of 140 kVwill leadto a further reduction in radiation dose The impact of IR ona 120 kV protocol has to be addressed in future studies

As mentioned earlier we first implemented an IR levelof 30 in the routine protocol to ensure an excellent imagequality and only afterwards modified the protocol to ASIR40 As our study demonstrates there is no compromise to thediagnosability and it seems justifiable to investigate the imple-mentation of ASIR 50 (representing the highest level of ASIR)to whole-body protocols in an emergency setting

As stated above the full body trauma protocol consists oftwo scans an axial cranium scan and a helical body spiral Inthis study only the latter was modified with IR algorithms asto our knowledge the impact of IR algorithms on the imagequality for the neurocranium has not yet been evaluatedoutside an emergency setting Nonetheless mean DLP forroutine protocolswas 22730mGysdotcmwhereasmeanDLP forthe helical spiral was 14914mGysdotcm thus accounting only for

about 66 of total radiation dose that is axial cranium scansaccount for about one-third of radiation doseWhether or notIR algorithms are applicable for cranium scans has to beinvestigated by future studies

41 Limitations With this study designed to be a feasibilityevaluation of IR algorithms in an emergency setting themajor limitation naturally consists in the small numberof patients examined Secondly there is no possibility ofintraindividual comparison of image quality and radiationdose This obstacle could be limited with a manually selectedstudy group with respect to scan range and abdominal cross-section diameter Nonetheless a series of validity impair-ments that is limitations in the positioning of patientsforeign bodies in the FOV et cetera may have resulted inincreased radiation doses due to beam-hardening artifacts

Thirdly the small study group did not allow for evaluationof similar injury patterns Fourthly as the sole parameter forobjective image quality we only assessed the image noiseFurther studies have to be performed in a larger patientcollective investigating different contrast-to-noise ratios

5 Conclusions

In these preliminary results the use of IR algorithms is apromising application to reduce radiation exposure withoutcompromise to the radiological interpretability even in anemergency setting where image quality is paramount

Conflict of Interests

The authors declare that they have no relevant conflict ofinterests to disclose

Acknowledgments

The authors acknowledge Mr Klaus Helmig expert CTradiographer ChariteMr Dipl-Phys Ralf Juran Head of theMedical Physics Department Charite and Ms Lea-HeleenHuizing medical student Humboldt University of Berlin fortheir help in conducting this study as well as their contribu-tion to the paper

References

[1] S Huber-Wagner R Lefering L Qvick et al ldquoEffect of whole-body CT during trauma resuscitation on survival a retrospec-tive multicentre studyrdquoThe Lancet vol 373 no 9673 pp 1455ndash1461 2009

[2] A B de Gonzalez M Mahesh K Kim et al ldquoProjected cancerrisks from computed tomographic scans performed in theUnited States in 2007rdquoArchives of InternalMedicine vol 169 no22 pp 2071ndash2077 2009

[3] E J Hall and D J Brenner ldquoCancer risks from diagnostic radi-ologyrdquoTheBritish Journal of Radiology vol 81 no 965 pp 362ndash378 2008

[4] World Health Organization ldquoOverall evaluations of carcino-genicity to humans list of all agents evaluated to daterdquo WorldHealth Organization International Agency for Research on


Cancer httpmonographsiarcfrENGClassificationClassifi-cationsAlphaOrderpdf

[5] W A Kalender H Wolf and C Suess ldquoDose reduction in CTby anatomically adapted tube current modulation II Phantommeasurementsrdquo Medical Physics vol 26 no 11 pp 2248ndash22531999

[6] C H McCollough M R Bruesewitz and J M Kofler Jr ldquoCTdose reduction and dose management tools overview of avail-able optionsrdquo Radiographics vol 26 no 2 pp 503ndash512 2006

[7] D Fleischmann and F E Boas ldquoComputed tomographymdasholdideas and new technologyrdquo European Radiology vol 21 no 3pp 510ndash517 2011

[8] J E Wilting A Zwartkruis M S van Leeuven J Timmer AG A Kamphuis andM Feldberg ldquoA rational approach to dosereduction inCT individualized scan protocolsrdquoEuropean Radi-ology vol 11 no 12 pp 2627ndash2632 2001

[9] M J Willemink P A de Jong T Leiner et al ldquoIterative recon-struction techniques for computed tomography part 1 techni-cal principlesrdquo European Radiology vol 23 no 6 pp 1623ndash16312013

[10] M J Willemink T Leiner P A de Jong et al ldquoIterative recon-struction techniques for computed tomography part 2 initialresults in dose reduction and image qualityrdquo European Radiol-ogy vol 23 no 6 pp 1632ndash1642 2013

[11] J E Winslow J W Hinshaw M J Hughes R C Williams andW P Bozeman ldquoQuantitative assessment of diagnostic radia-tion doses in adult blunt trauma patientsrdquo Annals of EmergencyMedicine vol 52 no 2 pp 93ndash97 2008

[12] M J Willemink A M R Schilham T Leiner et al ldquoIterativereconstruction does not substantially delay CT imaging in anemergency settingrdquo Insights into Imaging vol 4 no 3 pp 391ndash397 2013

[13] ldquoS3-Guideline on Treatment of Patients with Severe and Multi-ple Injuriesrdquo Arbeitsgemeinschaft derWissenschaftlichenMed-izinischen Fachgesellschaften eV German Trauma Society(DGU) httpwwwdgu-onlinedefileadminpublished con-tent5Qualitaet und SicherheitPDF20110720 S3 LL Poly-trauma DGU eng fpdf

[14] J Reid J Gamberoni F Dong andWDavros ldquoOptimization ofkVp and mAs for pediatric low-dose simulated abdominal CTis it best to base parameter selection on object circumferencerdquoAmerican Journal of Roentgenology vol 195 no 4 pp 1015ndash1020 2010

[15] A K Hara R G Paden A C Silva et al ldquoIterative reconstruc-tion technique for reducing body radiation dose at CT feasibil-ity studyrdquoAmerican Journal of Roentgenology vol 193 no 3 pp764ndash771 2009

[16] L P Qi Y Li L Tang et al ldquoEvaluation of dose reductionand image quality in chest CT using adaptive statistical iterativereconstruction with the same group of patientsrdquo British Journalof Radiology vol 85 no 1018 pp e906ndashe911 2012

[17] TheAmerican Association of Physicists inMedicine ldquoThemea-surement reporting andmanagement of radiation dose in CTrdquoTech Rep 96 The American Association of Physicists in Med-icine 2008

[18] J M Yeguiayan A Yap M Freysz et al ldquoImpact of whole-bodycomputed tomography on mortality and surgical managementof severe blunt traumardquo Critical Care vol 16 no 3 article R1012012

[19] J C Sierink T P Saltzherr L FM Beenen et al ldquoAmulticenterrandomized controlled trial of immediate total-body CT scan-ning in traumapatients (REACT-2)rdquoBMCEmergencyMedicinevol 12 article 4 2012

[20] J Leipsic G Nguyen J Brown D Sin and J R Mayo ldquoAprospective evaluation of dose reduction and image qualityin chest CT using adaptive statistical iterative reconstructionrdquoAmerican Journal of Roentgenology vol 195 no 5 pp 1095ndash1099 2010

[21] A C Martinsen H K Saether P K Hol et al ldquoIterative recon-struction reduces abdominal CT doserdquo European Journal ofRadiology vol 81 no 7 pp 1483ndash1487 2012

[22] S Baumueller A Winklehner C Karlo C et al ldquoLow-dose CTof the lung potential value of iterative reconstructionsrdquo Euro-pean Radiology vol 22 no 12 pp 2597ndash2606 2012

[23] D J Brenner and C D Elliston ldquoEstimated radiation on riskspotentially associated with full-body CT screeningrdquo Radiologyvol 232 no 3 pp 735ndash738 2004

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


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Research and TreatmentAIDS


Gastroenterology Research and Practice


Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


(a) (b) (c)

Figure 1 25-year-old female patient with a heavy trauma falling from a roof with suicidal intention Image acquisition with the CT ASIR40 protocol (a) coronal orientationlung window showing bilateral pneumothoraces (arrow) with Bulau drains in situ heavy contusion inboth lungs and extensive thoracal and cervical soft tissue emphysema (b) coronal orientationsoft tissue window showing hypodensities interms of an acute liver haematoma in the right lobe (arrow) Also note a huge retroperitoneal haematoma in the lower abdomen (arrow) (c)another male 42-year-old patient after falling from a roof CT ASIR 40 protocol sagittal planebone window Vertebral body fracture in L3with consecutive spinal stenosis (arrow)

image quality and interpretability in comparisonwith routineCT imaging based on filtered back projection (FBP) There-fore this study aimed to prospectively evaluate different levelsof IR algorithms on imaging quality and dose reduction for aproven CT full body trauma protocol

2 Materials and Methods

21 Study Design The study was carried out prospectivelyThe study design was approved by the institutional ethicsboardThe need for informed consent was waived as patientswere not exposed to an additional radiation dose and patientdata was anonymized The study was conducted at a univer-sity teaching hospital

All examined patients were classified as severely injuredpatients (injury severity score (ISS) ge16) by the emergencydepartment and underwent CT scans within the scope of theroutine in-house algorithm for patients with severe and mul-tiple injuries in accordance with the currently valid guideline[13] At the time of study analysis 10 patients were examinedwith IR 30 and 16 patients with IR 40 protocol For matchingthe patients in all three patient groups (FBP IR 30 and IR40) these patients were compared by scan range andmaximalabdominal diameter Subsequently some patients had to beexcluded and 6 patients per group were enrolled in the finalstatistical analysis (age = 539 plusmn 199 years 5 females) Allgroups were matchedmanually as to scan range andmaximalabdominal cross-section area to attain a homogenous studycollective The authors regarded this approach to be a moreaccurate approximation for full body radiation exposure ofthe study group than traditional parameters that is BMI [14]The control group was examined with the routine filtered

back projection (FBP) protocol whereas the protocol forthe first study group performed on the same CT scannerconsisted in 30 adaptive statistical iterative reconstruction(ASIR) application in the raw data material After a prelimi-nary assessment of the newly acquired image quality and pos-itive results in terms of interpretability a stronger level of IR(40) was implemented on the standard protocol and per-formed on the second study group

22 CT Protocol All patients were examined using a 64-slicemultidetector CT scanner (Lightspeed VCT GE HealthcareUSA)The emergency protocol consists of two separate scansThe first is an axial scan of the cranium angulated between 0∘and 30∘ (depending on the positioning of the patient) withoutinjection of a contrast agent (CA) in order to detect possibleintracranial bleeding

Second after application of CA (see Section 23) a helicalscan of the whole body is performed in craniocaudal direc-tion ranging from above the frontal sinus (in order to picturethe cerebral arterial circle) to the bottom of the pelvis Imageacquisition is conducted with the following parameters tubevoltage 140 kV collimation 40 pitch 1375 and noise index15

The protocol of the axial cranium scan was not modifiedIf additional scans were performed due to individual injurypatterns these have not been considered and were excludedfrom the image quality and radiation dose analyses

23 Injection Table For the helical whole-body spiral 140mLof CA was administered in a split bolus technique

100mL CA (2mLs flow rate)


(a) (b)

(c)










(a) (b)

(c)




3 Results






(a) (b)

(c)




IR 30140 kV

IR 40140 kV






4 Discussion




5

10

15

20

25

30

35

Effec

tive r

adia

tion

dose

(mSv

)

P = 0093 P = 00203










5 Conclusions




Acknowledgments


References































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















(a) (b)

(c)










(a) (b)

(c)




3 Results






(a) (b)

(c)




IR 30140 kV

IR 40140 kV






4 Discussion




5

10

15

20

25

30

35

Effec

tive r

adia

tion

dose

(mSv

)

P = 0093 P = 00203










5 Conclusions




Acknowledgments


References































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















(a) (b)

(c)




3 Results






(a) (b)

(c)




IR 30140 kV

IR 40140 kV






4 Discussion




5

10

15

20

25

30

35

Effec

tive r

adia

tion

dose

(mSv

)

P = 0093 P = 00203










5 Conclusions




Acknowledgments


References































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















(a) (b)

(c)




IR 30140 kV

IR 40140 kV






4 Discussion




5

10

15

20

25

30

35

Effec

tive r

adia

tion

dose

(mSv

)

P = 0093 P = 00203










5 Conclusions




Acknowledgments


References































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


















5

10

15

20

25

30

35

Effec

tive r

adia

tion

dose

(mSv

)

P = 0093 P = 00203










5 Conclusions




Acknowledgments


References































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of










































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















clinical study reducing radiation dose in...

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