ORIGINAL ARTICLE

Iterative reconstruction improves image quality and preservesdiagnostic accuracy in the setting of blunt solid organ injuries

Scott D. Steenburg & Scott Persohn & Changyu Shen &

Jeff W. Dunkle & Sean D. Gussick & Matthew J. Petersen &

Amy Wisnewski-Rhodes & Ryan T. Whitesell

Received: 15 April 2014 /Accepted: 28 May 2014# American Society of Emergency Radiology 2014

Abstract This study aims to investigate the effect of iterativereconstruction (IR) on MDCT image quality and radiologists’ability to diagnose and grade blunt solid organ injuries. Onehundred (100) patients without and 52 patients with solidorgan injuries were scanned on a 64-slice MDCT scannerusing reference 300 mAs, 120 kVp, and fixed 75 s delay.Raw data was reconstructed using filtered back projection(FBP) and three levels of iterative reconstruction (PhilipsiDose levels 2, 4, and 6). Four emergency radiologists, blindedto the reconstruction parameters and original interpretation,independently reviewed each case, assessed image quality,and assigned injury grades. Each reader was then asked todetermine if they thought that IR was used and, if so, whatlevel. There was no significant difference in diagnostic accu-racy between FBP and the various IR levels or effect on thedetection and grading of solid organ injuries (p>0.8). Imagesreconstructed using iDose level 2 were judged to have the bestoverall image quality (p<0.01). The radiologists had highsensitivity in detecting if IR was used (80 %, 95 % CI 76–

84 %). IR performed comparably to FBP with no effect onradiologist ability to accurately detect and grade blunt solidorgan injuries.

Keywords Iterative reconstruction . Solid organ injuries .

Blunt trauma .Multi-detector computed tomography . Imagequality

Introduction

Multi-detector computed tomography (MDCT) technologyhas evolved significantly over the past 20 years and can beused to generate high-resolution images of the entire body.MDCT has also been shown to decrease mortality; possesseshigh sensitivity, specificity, and negative predictive value; todecrease time to definitive therapy; and to increase survival oralter management when integrated into the comprehensiveevaluation of the acutely injured patient [1–5]. Thus, evalua-tion of hemodynamically stable blunt abdominal trauma pa-tients with MDCT is the currently accepted standard of eval-uation and has been shown to identify unexpected internalinjuries [6–10]. The value of MDCT in the comprehensiveevaluation of the acutely injured patient cannot be overstated.

There has been a shift towards the non-operative manage-ment (NOM) of patients with internal abdominal injuries withthe desire to avoid non-therapeutic surgery, with much of themanagement decisions guided by admission MDCT findings[10–18]. Therefore, image quality is of paramount importanceto ensure high diagnostic accuracy and confidence.

For decades, filtered back projection (FBP) has been theCT reconstruction algorithm of choice as the images generatedwell approximate true anatomic morphology and its relativelyrapid computer processing, though it is subject to imageartifact creation primarily in the form of image noise and beamhardening [19, 20]. Until recently, FBP was the only practical

S. D. Steenburg : J. W. Dunkle : S. D. Gussick :M. J. Petersen :A. Wisnewski-Rhodes : R. T. WhitesellDepartment of Radiology and Imaging Sciences, Division ofEmergency Radiology, Indiana University School of Medicine,Indianapolis, IN, USA

S. PersohnDepartment of Radiology and Imaging Sciences, Division ofRadiology Research, Indiana University School of Medicine,Indianapolis, IN, USA

C. ShenDepartment of Biostatistics, Indiana University School of Medicine,Indianapolis, IN, USA

S. D. Steenburg (*)Department of Radiology and Imaging Sciences, Indiana UniversityHealth Methodist Hospital, 1701 N. Senate Blvd, Room AG-176,Indianapolis, IN 46202, USAe-mail: ssteenbu@iuhealth.org

Emerg RadiolDOI 10.1007/s10140-014-1247-8

reconstruction algorithm that could be applied in the clinicalarena. Iterative reconstruction (IR), on the other hand, is anovel approach to improving image quality by reducing imagenoise [20–27]. The application of IR can therefore be used toimprove image quality for non-dose-reduced CT images aswell as those scans acquired with reduced dose by reducingoverall image noise. Iterative reconstruction, however, has notbeen utilized in the clinical setting until recently due to itsintensive computing power requirement [19, 20].

The application of IR to CT images results in a changein image character that has been described by some as“smooth,” “blotchy,” “plastic appearing,” “unnatural,”and “artificial” [19, 20, 23, 26, 28], with the thought thatthe application of IR may reduce the ability to detectparenchymal lesions, though very little data are availableto support this claim [29]. Most of the body of literaturerelated to IR centers around image quality or lesion de-tection in phantoms [21, 22, 24–27, 30–38] though therehas been a recent flurry of studies dedicated to the detec-tion of pathology with IR [26–28, 39–43].

To our knowledge, there have been no studies investigatingthe effect of IR on the ability to diagnose and accurately gradesolid organ injuries. Thus, the purpose of this study is toinvestigate the effect of IR on subjective image quality andradiologists’ ability to diagnose and grade solid organ injuriesin the setting of blunt abdominal trauma. We hypothesize thatvarious levels of iterative reconstruction will have no signif-icant effect on radiologist diagnostic accuracy and ability tograde blunt solid organ injuries.

Methods

Our institutional IRB approved this study and waived require-ment for informed consent.

This study was compliant with the Health Insurance Por-tability and Accountability Act of 1996 (http://www.hhs.gov/ocr/privacy/hipaa/understanding/index.html).

Patient selection

One hundred (100) consecutive patients without and 52 con-secutive patients with solid organ injuries (liver, spleen, and/orkidney) as determined by the final attending radiologist reportand confirmed by the lead author constituted the study cohort.Finalized radiologist reports that described some uncertaintyas to the presence/absence of a solid organ injury or had severeimage quality degradation due to excessive motion artifact orbeam hardening artifact from external devices were excludedat the discretion of the lead author. Patient selection for imag-ing, and to what extent, was determined by the attendingtrauma surgeon based on their clinical assessment. Patientswho were <18 years of age, pregnant, hemodynamically

unstable as determined by the attending trauma surgeon, ex-hibited peritoneal signs on physical exam, who had otherindications for immediate surgery as determined by the at-tending trauma surgeon, received non-contrast enhancedexams (either due to lack of adequate IV access, documentedcontrast allergy, renal insufficiency), or exhibited severe mo-tion artifact significantly reducing diagnostic utility as deter-mined by the lead author were excluded.

Scan protocol

All scans were performed on a 64-slice MDCT scanner (Phil-lips Healthcare, Best, The Netherlands) within 2 hours ofadmission and were performed with reference 300 mAs and120 kVp from the domes of the diaphragm to the pubicsymphysis following the intravenous administration of130 mL of iodinated contrast (iopamidol 370 mg/mL, BraccoDiagnostic Inc, Princeton, NJ) using a power injector (BraccoDiagnostic Inc, Princeton, NJ) at a rate of 3.5 mL/s. No oralcontrast was administered to any of the patients per institu-tional trauma protocol. Images were acquired through theabdomen and pelvis (with or without the chest, as requestedby the trauma surgery service) using a fixed 35 second delay(arterial phase) followed by imaging of the abdomen from thedomes of the diaphragm to the iliac crests using a fixed75 second delay (portal venous phase).

Image reconstruction

The raw data from each portal venous phase scan of theabdomen were retrospectively reconstructed by one of theco-authors in the axial plane at 4 mm slice thickness and3 mm intervals, as per our institutional protocol, using FBPand three additional levels of IR (Philips iDose levels i2, i4,and i6), such that each patient scan resulted in four differentaxial series. The basic technical concept of Philips iDose hasbeen previously described [21, 44] though the precise com-putational model is proprietary. Patient identifiers were re-moved from the data sets and were subsequently labeled witha randomly generated unique three-digit identifier. These se-ries were loaded onto a dedicated research Picture Archivingand Communication System (PACS) (Synapse, FUJIFILMMedical Systems USA, Inc., Stamford, CT) database separatefrom the clinical PACS database.

Image assessment

Prior to image review, four American Board of Radiologyboard-certified emergency radiologists (with 2–6 years ofemergency radiology experience) first reviewed a trainingcase in which they reviewed a single clinical case that wasreconstructed using FBP and various levels of IR. Each serieswas labeled with the reconstruction parameters. This gave the

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radiologists a chance to see, side by side, the effect of IR onoverall image appearance and character (Fig. 1a–d). Imagetexture for FBP versus iDose level 6 focused on the spleen(Fig. 2a, b) in the same patient and slice level to show thedifference in overall image character.

Subsequently, each radiologist, blinded to the recon-struction parameters, surgical notes, clinical notes, andimaging follow-up, reviewed each study case on a PACSstation. The radiologists had the ability to alter the win-dow and level settings based on personal preference. Theradiologists reviewed only axial images and did not haveaccess to any other clinical information or imaging

exams for the subjects. The individual cases were allo-cated to each radiologist such that each radiologist onlyreviewed one reconstructed series from each patient toeliminate recall bias. Overall image quality was mea-sured on a five-point Likert scale (1=severely degraded;2=moderately degraded; 3=average; 4=better than aver-age; 5=excellent). The presence or absence of a solidorgan injury was determined by each reader (binary,“Yes” or “No”), and if present, were graded using theAmerican Association of Surgery in Trauma (AAST)Solid Organ Injury Scale [45]. Finally, the radiologistwas asked to determine if they felt that IR was used to

Fig. 2 Same patient as in Fig. 1focused on the uninjured spleenwith a side by side comparison ofFBP (a) versus iDose level 6 (b)

Fig. 1 Twenty-two-year-oldmale without solid organ injurystatus post blunt abdominaltrauma. Axial CT images throughthe upper abdomen acquiredduring the portal venous phaseand reconstructed with FBP (a)and various levels of iDose (biDose level 2, c iDose level 4, diDose level 6) show the differencein image character depending onreconstruction algorithm. There isprogressive decrease in imagenoise as the level of iDoseincreases

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generate the images (binary, “Yes” or “No”), and if so,what level of IR was employed.

Clinical follow-up and surgical findings

A vast majority of our patient cohort did not undergo surgicalconfirmation of their injuries, as non-operative management isthe currently accepted standard of care, and performing ex-ploratory laparotomy on clinically stable patients withoutevidence of injury on CT is no longer performed [10–18].As such, none of the 100 patients without solid organ injuryunderwent laparotomy during their hospital stay. Of the pa-tients with AAST 1 or 2 solid organ injuries diagnosed on CT,none underwent laparotomy during their hospital stay. Of thepatients with AAST ≥3 solid organ injuries, a total of fivepatients underwent exploratory laparotomy confirming theadmission CT findings and five different patients underwentangioembolization (grade 4 spleen ×3 and grade 3 spleen ×2).One of the angioembolization patients (with actively bleedinggrade 3 spleen injury on admission CT) subsequently deteri-orated requiring splenectomy on hospital day no. 2. Theremaining patients with AAST ≥3 solid organ injuries weresuccessfully managed non-operatively.

Statistical analysis

Categorical variables were summarized by count and percent-age. Linear mixed-effects models were used to analyze qualityof image and estimated iDose levels with true iDose levels asthe fixed effect and radiologists and patients treated as random

effects. Linear mixed-effects model was chosen as that (1) itcan account for the correlation of data points from the samepatient or same observer and (2) the between-observer andbetween-patient variability can be automatically estimated.Generalized linear mixed-effects models were used to analyzeiDose use (Yes/No) and injury (Yes/No) with intercept as theonly fixed effect and radiologists and patients treated as ran-dom effects. The sensitivity and specificity for iDose use andinjury were estimated by integrating out the random effects. Alinear mixed-effects model was used to analyze the estimatedgrade with the true grade as the fixed effect and radiologistsand patients treated as random effects. Patient-related variabil-ity in terms of image quality score was estimated by thestandard deviation of the random effect of patient. The inter-observer variability was estimated by the linear mixed-effectsmodel as the standard deviation of the random effect ofobserver. All analyses were performed using SAS 9.3 (SASInc., Cary, NC).

Results

There were a total of 61 solid organ injuries in the 52 patients,including 43 patients with one organ system injury (one ofwhich had bilateral grade 2 renal injuries) and nine patientswith two solid organ injuries. A total of six patients hadevidence of active bleeding on MDCT, including five spleeninjuries (three with AAST grade 4 and two with AAST grade

Table 4 Solid organ injury diagnostic accuracy

Endpoint Estimate (95 % CI)

Sensitivity Injury 83 % (72–90 %)

Bleed N/Aa

Liver 83 % (67–92 %)

Spleen 83 % (73–91 %)

Kidney 72 % (43–90 %)

Specificity Injury 88 % (83–92 %)

Bleed 92 % (88–95 %)

Liver 93 % (88–96 %)

Spleen 93 % (89–95 %)

Kidney 93 % (89–96 %)

a Too few for statistical analysis

Table 3 Subjective iDose assessment versus true iDose level

True iDose level Subjective iDose level (Ave) p value

2 2.67 NA

4 2.62 0.8

6 3.66 <0.001

Table 2 Subjective image quality (on a five-point scale)

Livera Spleena Kidneya

Filtered back projection 3.16 3.22 3.3

iDose 2 3.39, p=0.002 3.41, p=0.01 3.45, p=0.05

iDose 4 3.20, p=0.01 3.28, p=0.08 3.28, p=0.03

iDose 6 3.01, p=0.01 3.10, p=0.01 3.07, p=0.006

Radiologistinter-observervariabilityb

0.46 0.36 0.36

Patient-relatedvariabilityb

0.62 0.63 0.60

aMean Score, p value compared to immediate lower iDose levelb Standard deviation

Table 1 Solid organ injury distribution

Organ Grade 1 Grade 2 Grade 3 Grade 4 Grade 5 Total

Liver 1 4 14 0 1 20

Spleen 7 9 12 5 0 33

Kidney 3 2 2 1 0 8

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3) and one grade 3 renal injury. No patient with liver injuryexhibited evidence of active bleeding. The proportion of pa-tients with solid organ injuries to those without is artificiallyelevated as the 100 patients without solid organ injuries werecollected at a faster rate than those with solid organ injuries.The distribution of solid organ injuries with AAST grade canbe seen in Table 1.

Subjective image quality

For the four radiologists, the average quality score for theliver, spleen, and kidney was best for iDose level 2 (averagequality score=3.39, i.e., “average” to “better than average,”see Table 2). There was a relatively high degree of radiologistimage quality inter-observer variability, highlighting the sub-jective nature of image quality assessment. See Table 2 forsummary of image quality scores and p values.

Radiologists determination if iDose was used in imagereconstruction

The sensitivity of the radiologists to determine if iDose wasused in image reconstruction was 80 % (95 % CI 76–84 %).However, the specificity for determining the precise iDoselevel was intermediate at 39 % (95 % CI 26–54 %).

Radiologists’ estimate of iDose level and diagnostic accuracy

The radiologists’ estimates of iDose levels 2 and 4 weresimilar with no statistically significant difference (p=0.8).There was, however, a statistically significant difference be-tween the radiologists’ estimate of iDose level 4 versus iDoselevel 6 (p<0.001). The radiologists overestimated the level ofiterations for cases reconstructed with iDose level 2 andunderestimated the level of iterations reconstructed with iDoselevels 4 and 6 (Table 3). The radiologists had good accuracy indiagnosing solid organ injuries across all iDose levels(Table 4).

AAST grade assignment

The various levels of IR levels did not alter the ability of theradiologists to detect solid organ injury grade (p=0.8 forspleen, liver, and renal injuries). The average AAST gradeassigned by the radiologists can be seen in Table 5.

There was very low radiologist inter-observer vari-ability with respect to solid organ injury grading. Ex-amples of grade 3 liver (Fig. 3), grade 2 renal (Fig. 4),grade 4 spleen with active bleeding (Fig. 5), and grade1 spleen (Fig. 6) images reconstructed with FBP versusiDose level 6.

Fig. 3 Thirty-year-old femalewith AAST grade 3 liverlaceration following motorvehicle collision. Axial CTimages acquired during the portalvenous phase reconstructed usingFBP (a) and iDose level 6 (b)demonstrate right hepatic lobelacerations (arrows) between theright and left portal veins

Table 5 AAST grade assignment

a Standard deviationb Based on original radiologistreportc For statistical analysis purposes,a single grade 5 liver injury wasincluded in this category

Radiologist AAST meangrade, p value

True AAST gradeb Liver Spleen Kidney

Grade 1 0.99 1.27 1.77

Grade 2 2.12, p=0.19 1.67, p=0.13 1.98, p=0.82

Grade 3 2.86, p=0.08 3.23, p<0.001 3.22, p=0.30

Grade 4c 4.25, p=0.07 3.90, p=0.01 3.25, p=0.98

Radiologist inter-observer variabilitya 0.055 0.173 0

Patient-related variabilitya 0.671 0.4 0.854

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Discussion

Solid organ injuries in the setting of blunt abdominal traumaare common and may be clinically unsuspected, particularlylow-grade injuries in hemodynamically stable patients [6–10].Multi-detector CT has become the standard examination forthe imaging evaluation of blunt abdominal trauma [10–18],with much of the clinical decision-making is determined ad-mission MDCT findings. Thus, accurate detection and grad-ing are essential for proper patient management and triage.

Iterative reconstruction is a novel reconstruction algorithmthat can be used to decrease CT image noise [20–27] and thuscan be used in conjunction with radiation dose reduction or toreduce image noise of non-radiation reduced images. Thedecreased image noise with IR however can results in imagecharacter that is distinct from FBP, described by some as“smooth” and “unnatural” [19, 20, 23, 26, 28] with the poten-tial for the alteration of diagnostic accuracy.

There have been several recent studies evaluating the clin-ical utility of IR for the detection and classification of pathol-ogy with IR, with much of the data indicating that the appli-cation of IR has no significant negative impact on diagnostic

accuracy or confidence compared to FBP [26–28, 39–43]. The“smoothness” of the image character may raise the possibilitythat subtle anatomy or pathology may be masked; however,there is a paucity of data to support this claim. Yanagawa et al.[29] showed that image quality could be increased by decreas-ing image noise, however, with some obscuration ofintraloblar reticular opacities and peripheral vessels. To ourknowledge, there have been no studies performed to evaluatethe effect of IR on image quality and diagnostic accuracy inthe setting of blunt solid organ injuries.

Our research demonstrates that there is no difference in thediagnostic accuracy for the detection and grading solid organinjuries, regardless of the reconstruction algorithm and levelof iDose, which supports the existing literature that there is nosignificant difference in diagnostic accuracy of IR comparedto FBP. Overall diagnostic accuracy remained high with verylittle inter-observer variability. However, it appears that theradiologists, in general, tended to over grade AAST grade 1renal injuries (average 1.77) and under grade AAST grade 4renal injuries (average 3.25, Table 5). Interestingly, thepatient-related variability standard deviation of image qualityscores was much higher than the radiologist inter-observer

Fig. 5 Twenty-year-old male with AAST grade 4 spleen laceration andactive bleeding following driver’s side T-bone motor vehicle collision.Axial CT images acquired during the portal venous phase reconstructedusing FBP (a) and iDose level 6 (b) demonstrate extensive splenic

parenchymal lacerations (arrows) with multiple foci of active bleedinginto the peri-splenic space (arrow heads) which was successfully treatedwith coil embolization (not shown)

Fig. 4 Fifty-four-year-old femalewith AAST grade 2 renallaceration following a motorvehicle collision. Axial CTimages acquired during the portalvenous phase reconstructed usingFBP (a) and iDose level 6 (b)demonstrate a 1 cm corticallaceration (arrows) with adjacentperinephric hematoma. Thepatient also had a right adrenalcontusion (not shown)

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variability, indicating that variation in estimated solid organinjury grade is primarily driven by patient-related variability,with the radiologists grading solid organ injuries veryconsistently.

Overall image quality scores were similar across the spec-trum of FBP to iDose level 6 (3.01–3.45, i.e., “average” to“better than average” for the three organ systems), thoughimages deemed to have the best overall image quality werethose reconstructed with iDose level 2. Interestingly, as withthe organ injury grading assessment, the patient-related vari-ability standard deviation of image quality scores was higherthan the radiologist inter-observer variability, indicating thatcertain variation among patients has more contribution to thevariation of image quality assessed by radiologists than thedifference among radiologists.

The radiologists were able to determine that IR was used toa high degree of reliability (80 % sensitivity, 95 % CI 76–84 %), suggesting that the radiologists had a low threshold toclaim the use of iDose based on the perceived image character.However, the radiologists had only modest specificity (39 %,95% CI 26–54%) in determining which level of IR was used.The radiologists were unable to differentiate between iDoselevels 2 and 4 (p=0.8) but were able to differentiate betweeniDose levels 4 and 6 (p<0.001), felt to be due to the acceler-ated increase in image “smoothness” at the higher iterationlevels. Despite the radiologists’ ability to detect a differencebetween iDose levels 4 and 6, they still underestimated trueiDose level 6 to be, on average, level 3.66 (i.e., “average” to“better than average”).

There are several limitations to this study. First, this is asingle center study with an artificially elevated proportion ofpositive to negative exams. Secondly, this study depends onthe radiologists maintaining consistency with respect to sub-jective image quality assessment. Despite this, there was highaccuracy and low inter-observer variability suggesting that thesubjective nature of image quality assessment was kept as lowas possible. Thirdly, only axial plane portal venous phaseimages were reconstructed and available to the radiologists;prior studies have shown that additional MPRs can improve

diagnostic accuracy and confidence for both traumatic andnon-traumatic acute abdominal pathology [46–50]. Lastly,there is a lack of a uniform reference standard (i.e., surgicalconfirmation) for both the positive and negative solid organinjury cases, with the original radiologist report serving as thereference standard. Only six patients out of the 152-patientcohort underwent laparotomy.

Conclusions

In conclusion, the use of iterative reconstruction in the settingof blunt abdominal trauma has no effect on the detection oraccurate solid organ injury grading. This data is consistentwith recently published data supporting the similar diagnosticaccuracy and confidence of IR compared to FBP and lays thegroundwork for MDCT dose reduction in the setting of bluntabdominal trauma.

Conflict of interest The authors declare that they have no conflict ofinterest.

References

1. Huber-Wagner S, Lefering R, Qvick LM, Korner M, Kay M et al(2009) Effect of whole-body CT during trauma resuscitation onsurvival: a retrospective, multicentre study. Lancet 373:1455–1461

2. Huber-Wagner S, Biberthaler P, Haberle S,Wierer M, Dobritz M et al(2013) Whole-body CT in haemodynamically unstable severely in-jured patients—a retrospective, multicentre study. PLoS One 8:e68880

3. van Vugt R, Kool DR, Deunk J, Edwards MJ (2012) Effects onmortality, treatment, and time management as a result of routine useof total body computed tomography in blunt high-energy traumapatients. J Trauma Acute Care Surg 72(3):553–559

4. Wurmb TE, Fruhwald P, Hopfner W, Keil T, Kredel M et al (2009)Whole-body multislice computed tomography as the first line diag-nostic tool in patients with multiple injuries: the focus on time. JTrauma 66:658–665

Fig. 6 Twenty-two-year-oldmale with AAST grade 1 spleenlaceration status post motorvehicle versus tree. Axial CTimages acquired during the portalvenous phase reconstructed usingFBP (a) and iDose level 6 (b)demonstrate a tiny <1 cmlaceration of the postero-medialspleen (arrows) which wassuccessfully managed non-operatively

Emerg Radiol

5. Rieger M, Czermak B, El Attal R, Sumann G, Jaschke W, Freund M(2009) Initial clinical experience with a 64-MDCTwhole-body scan-ner in an emergency department: better time management and diag-nostic quality? J Trauma 66:648–657

6. Salim A, Sangthong B, Martin M, Brown C, Plurad D, DemetriadesD (2006) Whole body imaging in blunt multisystem trauma patientswithout obvious signs of injury: results of a prospective study. ArchSurg 141:468–473, discussion 473–465

7. Brown CK, Dunn KA, Wilson K (2000) Diagnostic evaluation ofpatients with blunt abdominal trauma: a decision analysis. AcadEmerg Med 7:385–396

8. Schurink GW, Bode PJ, van Luijt PA, van Vugt AB (1997) The valueof physical examination in the diagnosis of patients with bluntabdominal trauma: a retrospective study. Injury 28:261–265

9. Ferrera PC, Verdile VP, Bartfield JM, Snyder HS, Salluzzo RF (1998)Injuries distracting from intraabdominal injuries after blunt trauma.Am J Emerg Med 16:145–149

10. Livingston DH, Lavery RF, Passannante MR, Skurnick JH, FabianTC et al (1998) Admission or observation is not necessary after anegative abdominal computed tomographic scan in patients withsuspected blunt abdominal trauma: results of a prospective, multi-institutional trial. J Trauma 44:273–280, discussion 280–272

11. Rutledge R, Hunt JP, Lentz CW, Fakhry SM, Meyer AA et al (1995)A statewide, population-based time-series analysis of the increasingfrequency of nonoperative management of abdominal solid organinjury. Ann Surg 222:311–322, discussion 322–316

12. Hunt JP, Lentz CW, Cairns BA, Ramadan FM, Smith DL et al (1996)Management and outcome of splenic injury: the results of a five-yearstatewide population-based study. Am Surg 62:911–917

13. Soto JA, Anderson SW (2012) Multidetector CT of blunt abdominaltrauma. Radiology 265:678–693

14. Boscak A, Shanmuganathan K (2012) Splenic trauma: What is new?Radiol Clin North Am 50:105–122

15. Sclafani SJ, Weisberg A, Scalea TM, Phillips TF, Duncan AO (1991)Blunt splenic injuries: nonsurgical treatment with ct, arteriography,and transcatheter arterial embolization of the splenic artery.Radiology 181:189–196

16. Shanmuganathan K, Mirvis SE (1998) CT scan evaluation of blunthepatic trauma. Radiol Clin North Am 36:399–411

17. Velmahos GC, Toutouzas K, Radin R, Chan L, Rhee P et al (2003)High success with nonoperative management of blunt hepatic trauma:the liver is a sturdy organ. Arch Surg 138:475–480, discussion 480–471

18. Miller LA, Shanmuganathan K (2005) Multidetector CT evaluationof abdominal trauma. Radiol Clin North Am 43:1079–1095

19. Fleischmann D, Boas FE (2011) Computed tomography—old ideasand new technology. Eur Radiol 21:510–517

20. Willemink MJ, de Jong PA, Leiner T, de Heer LM, Nievelstein RAet al (2013) Iterative reconstruction techniques for computed tomog-raphy part 1: technical principles. Eur Radiol 23:1623–1631

21. Noel PB, Fingerle AA, Renger B, Munzel D, Rummeny EJ, DobritzM (2011) Initial performance characterization of a clinical noise-suppressing reconstruction algorithm for MDCT. AJR 197:1404–1409

22. Funama Y, Taguchi K, Utsunomiya D, Oda S, Yanaga Yet al (2011)Combination of a low-tube-voltage technique with hybrid iterativereconstruction (iDose) algorithm at coronary computed tomographicangiography. J Comput Assist Tomogr 35:480–485

23. Prakash P, KalraMK, KambadakoneAK, Pien H, Hsieh J et al (2010)Reducing abdominal CT radiation dose with adaptive statistical iter-ative reconstruction technique. Invest Radiol 45:202–210

24. Winklehner A, Karlo C, Puippe G, Schmidt B, Flohr T et al (2011)Raw data-based iterative reconstruction in body CTA: evaluation ofradiation dose saving potential. Eur Radiol 21:2521–2526

25. Sato J, Akahane M, Inano S, Terasaki M, Akai H et al (2012) Effectof radiation dose and adaptive statistical iterative reconstruction on

image quality of pulmonary computed tomography. Jap J Radiol 30:146–153

26. Singh S, Kalra MK, Gilman MD, Hsieh J, Pien HH et al (2011)Adaptive statistical iterative reconstruction technique for radiationdose reduction in chest CT: a pilot study. Radiology 259:565–573

27. Pontana F, Pagniez J, Flohr T, Faivre JB, Duhamel A et al (2011)Chest computed tomography using iterative reconstruction vs filteredback projection (part 1): evaluation of image noise reduction in 32patients. Eur Radiol 21:627–635

28. Prakash P, Kalra MK, Ackman JB, Digumarthy SR, Hsieh J et al(2010) Diffuse lung disease: CT of the chest with adaptive statisticaliterative reconstruction technique. Radiology 256:261–269

29. Yanagawa M, Honda O, Yoshida S, Kikuyama A, Inoue A et al(2010) Adaptive statistical iterative reconstruction technique for pul-monary CT: image quality of the cadaveric lung on standard- andreduced-dose CT. Acad Radiol 17:1259–1266

30. Willemink MJ, Leiner T, de Jong PA, de Heer LM, Nievelstein RAet al (2013) Iterative reconstruction techniques for computed tomog-raphy part 2: initial results in dose reduction and image quality. EurRadiol 23:1632–1642

31. Mitsumori LM, Shuman WP, Busey JM, Kolokythas O, KoprowiczKM (2012) Adaptive statistical iterative reconstruction versus filteredback projection in the same patient: 64 channel liver CT imagequality and patient radiation dose. Eur Radiol 22:138–143

32. Ren Q, Dewan SK, Li M, Li J, Mao D et al (2012) Comparison ofadaptive statistical iterative and filtered back projection reconstruc-tion techniques in brain CT. Eur J Radiol 81:2597–2601

33. Hansmann J, Schoenberg GM, Brix G, Henzler T, Meyer M et al(2013) CTof urolithiasis: comparison of image quality and diagnosticconfidence using filtered back projection and iterative reconstructiontechniques. Acad Radiol 20:1162–1167

34. Korn A, Fenchel M, Bender B, Danz S, Hauser TK et al (2012)Iterative reconstruction in head CT: image quality of routine and low-dose protocols in comparison with standard filtered back-projection.AJNR 33:218–224

35. Singh S, Kalra MK, Hsieh J, Licato PE, Do S et al (2010) AbdominalCT: comparison of adaptive statistical iterative and filtered backprojection reconstruction techniques. Radiology 257:373–383

36. Deak Z, Grimm JM, Treitl M, Geyer LL, Linsenmaier U et al(2013) Filtered back projection, adaptive statistical iterativereconstruction, and a model-based iterative reconstruction inabdominal CT: an experimental clinical study. Radiology 266:197–206

37. Martinsen AC, Saether HK, Hol PK, Olsen DR, Skaane P (2012)Iterative reconstruction reduces abdominal CT dose. Eur J Radiol 81:1483–1487

38. Schindera ST, Diedrichsen L, Muller HC, Rusch O, Marin D et al(2011) Iterative reconstruction algorithm for abdominal multidetectorCT at different tube voltages: assessment of diagnostic accuracy,image quality, and radiation dose in a phantom study. Radiology260:454–462

39. Vardhanabhuti V, Ilyas S, Gutteridge C, Freeman SJ, Roobottom CA(2013) Comparison of image quality between filtered back-projectionand the adaptive statistical and novel model-based iterative recon-struction techniques in abdominal CT for renal calculi. InsightsImaging 4:661–669

40. O'Neill SB, Mc Laughlin PD, Crush L, O’Connor OJ, McWilliamsSR et al (2013) A prospective feasibility study of sub-millisievertabdominopelvic CT using iterative reconstruction in Crohn's disease.Eur Radiol 23:2503–2512

41. Marin D, Choudhury KR, Gupta RT, Ho LM, Allen BC et al (2013)Clinical impact of an adaptive statistical iterative reconstructionalgorithm for detection of hypervascular liver tumours using a lowtube voltage, high tube current MDCT technique. Eur Radiol 23(12):3325–3335

Emerg Radiol

42. Becce F, Ben Salah Y, Verdun FR, Vande Berg BC, Lecouvet FE et al(2013) Computed tomography of the cervical spine: comparison ofimage quality between a standard-dose and a low-dose protocol usingfiltered back-projection and iterative reconstruction. Skeletal Radiol42:937–945

43. Kulkarni NM, Uppot RN, Eisner BH, Sahani DV (2012) Radiationdose reduction at multidetector CT with adaptive statistical iterativereconstruction for evaluation of urolithiasis: How low can we go?Radiology 265:158–166

44. Scibelli A. IDose4 iterative reconstruction technique. PhilipsHealthcare Website http://www.healthcare.philips.com/pwc_hc/main/shared/Assets /Documents/ct / idose_white_paper_452296267841.pdf. Published online March 11, 2011

45. Moore EE, Cogbill TH, Malangoni MA, Jurkovich GJ, ShackfordSR, Champion HR,McAninch JW (1995) Organ injury scaling. SurgClin North Am 75:293–303

46. Zangos S, Steenburg SD, Phillips KD, Kerl JM, Nguyen SA et al(2007) Acute abdomen: added diagnostic value of coronal reforma-tions with 64-slice multidetector row computed tomography. AcadRadiol 14:19–27

47. Neville AM, Paulson EK (2009) MDCT of acute appendicitis: valueof coronal reformations. Abdom Imaging 34:42–48

48. Itri JN, Boonn WW (2011) Use of a dedicated server to performcoronal and sagittal reformations in trauma examinations. J DigitImaging 24:494–499

49. Hodel J, Zins M, Desmottes L, Boulay-Coletta I, Julles MC et al(2009) Location of the transition zone in CTof small-bowel obstruc-tion: added value of multiplanar reformations. Abdomin Imaging 34:35–41

50. KimHC, Yang DM, JinW, Park SJ (2008) Added diagnostic value ofmultiplanar reformation of multidetector CT data in patients withsuspected appendicitis. Radiographics 28:393–405

Emerg Radiol