Journal of Cardiovascular Computed Tomography (2011) 5, 325–332

Original Research Article

Prevalence and nature of excluded findings at reduced scanlength CT angiography for pulmonary embolism

Michael Kemal Atalay, MD, PhD*, Nicholas L. Walle, MD, Thomas K. Egglin, MD

Department of Diagnostic Imaging, Rhode Island Hospital, Warren Alpert School of Medicine, Brown University,593 Eddy Street, Providence, RI 02903, USA

KEYWORDS:Pulmonary embolism;CTPA;CT pulmonaryangiography;Scan length;Radiation dose;Chest pain;Shortness of breath;Emergency department

Conflict of interest: The authors re

* Corresponding author.

E-mail address: atalay_99@yahoo.c

Submitted April 1, 2011. Accepted

1934-5925/$ - see front matter � 2011

doi:10.1016/j.jcct.2011.08.001

BACKGROUND: Scan length reduction effectively decreases radiation dose at CT pulmonary angi-ography (CTPA) for pulmonary embolism (PE) but may exclude important incidental scan findings.

OBJECTIVE: We aimed to determine the prevalence and nature of excluded findings with the use ofreduced scan length CTPA.

METHODS: We reviewed 335 consecutive emergency department CTPA studies performed on 16- or64-detector row scanners with the use of a standard scan range. A scan length of 14.2 cm that was cen-tered 4.1 cm below the carina has been shown to be adequate for PE diagnosis. Boundary slices for thisscan range were determined. All pertinent and incidental findings within and outside the reduced scanrange were noted. To determine the significance of newly detected excluded findings, we reviewedmedical records and all relevant imaging studies before and 9–11 months after the reference CTPA.

RESULTS: We found 374 pertinent findings in 192 patients, including 28 (8%) cases of PE. All ex-cept 3 (0.8%) were adequately seen with the reduced scan range, among which only one finding alteredclinical management. There were a total of 230 incidental findings in 165 patients, 60 (26%) of whichwere excluded; 23 (10%) of the 60 were newly detected, including 10 thyroid nodules, 6 liver lesions,and an 8-mm pulmonary nodule. The reduced scan length decreased z-axis coverage by 49% 6 6%.

CONCLUSION: Substantial scan length reduction at CTPA may not compromise the diagnostic yieldfor pertinent alternative diagnoses.� 2011 Society of Cardiovascular Computed Tomography. All rights reserved.

Introduction

CT pulmonary angiography (CTPA) has become thepreferred method for diagnosing pulmonary embolism(PE).1,2 The need for rapid and accurate PE diagnosis com-bined with the widespread availability of multidetector CThave led to a significant increase in the number of patients

port no conflicts of interest.

om

for publication August 3, 2011.

Society of Cardiovascular Computed

being imaged for PE by CT both in emergency departmentand hospitalized patients.3,4 Unfortunately, the radiationdose associated with CTPA can be substantial, rangingfrom 2 to 20 mSv1,5,6; thus, efforts to reduce dose are war-ranted. Because scan length is linearly related to radiationdose,7 reduction of scan length has the potential to signifi-cantly decrease patient dose without altering the diagnosticaccuracy for PE detection provided that the z-axis coverageis adequate. Scan length reduction also leads to shorterbreath-hold durations and may in turn decrease or eliminatebreathing-related artifacts. It has been suggested that a scanlength from just above the aortic arch to just below theheart maintains diagnostic accuracy for PE while yielding

Tomography. All rights reserved.

326 Journal of Cardiovascular Computed Tomography, Vol 5, No 5, September/October 2011

an average scan length of 16.3 cm and decreasing z-axiscoverage by 37%.8 More recently, it has been shown thateven further reduction of scan length to a fixed value of14.2 cm is possible.9

With scan length reduction, however, important addi-tional or alternative diagnoses may be excluded from theimaging volume and therefore go undetected. These unde-tected findings may or may not be relevant to the clinicalpresentation. The purpose of this study was to determinethe prevalence and nature of excluded findings at reducedscan length CTPA.

Methods

Our hospital’s institutional review board approved thedesign of this retrospective study, and all data were handledin compliance with the Health Insurance Portability andAccountability Act. Informed consent was waived becausethis study was conducted on existing CTPA data sets.

Study participants

We reviewed all PE studies performed in our adultemergency department on different patients over a 2-monthperiod (February 1, 2010 to March 31, 2010), 335 studies intotal. All studies included chest pain, hypoxemia, tachy-cardia, and shortness of breath, or variations of these, asindications for the examination. This emergency depart-ment is part of an urban teaching hospital and is a busylevel 1 trauma center that averages .100,000 adult visitsper year.

CTPA scan and injection protocols

Two different CT scanners and injection protocols wereused. These are reviewed below. All studies were con-ducted with breast shields.

16-row CT

One hundred eighty-nine studies (56.3%) were con-ducted on a 16-row CT scanner (Sensation 16; SiemensMedical Solutions, Erlangen, Germany). With the use ofhelical acquisition, patients were scanned supine in acaudocranial direction with a scan range based on thescout view from 1 cm below the lowest costophrenic angleto 1 cm above the lung apex. This range was intended tocompletely cover the lungs and to accommodate any slightchanges in patient positioning or breathholding betweenthe scout view and the CTPA. Scan parameters were asfollows: in-plane field of view (FOV), 38 cm; matrix,512 ! 512; pitch, 1.25; collimation, 1.5 mm; rotation time,0.75 second; tube voltage, 120 kVp; and tube current timeproduct, 220 mAs. Images were reconstructed at 2-mmslice thickness with no overlap. For CTPA, 100 mL of

iopamidol 370 mg I/mL (Isovue; General Electric Health-care, Waukesha, WI) was injected intravenously at 4 mL/sfollowed by 20 mL of saline at the same rate with theuse of a dual-head power injector (Stellant D; Medrad,Indianola, PA) after a fixed scan delay of 22 seconds.

64-row CT

One hundred forty-seven studies (43.7%) were con-ducted on a 64-row CT scanner (Lightspeed VCT; GeneralElectric Healthcare). With the use of helical acquisition,patients were scanned supine in a caudocranial directionfrom 1 cm below the lowest costophrenic angle to 1 cmabove the lung apex. Scan parameters were as follows:FOV, 38 cm; matrix, 512 ! 512; pitch, 1.375; collimation,0.625 mm; rotation time, 0.8 second; tube voltage,100 kVp; and tube current, 100–750 mA, set to a noiseindex of 40.0. Images were reconstructed at 2.5-mm slicethickness with no overlap. For CTPA, 100 mL of iopamidol370 mg I/mL was injected intravenously at 4 mL/s followedby 20 mL of saline at the same rate with the use of a dual-head power injector after a fixed scan delay of 22 seconds.

Data analysis

All studies were reviewed at a picture archiving andcommunication system workstation (PACS; Centricity Ra-diology RA1000; General Electric Healthcare) by oneauthor (N.L.W.) to determine the scan length of the originalstudy and the boundary slices of the reduced scan range. Tomaximize the miss rate of excluded findings and toestablish a worst-case scenario we chose to study thesmallest scan length configuration that has been reported tomaintain diagnostic accuracy for PE, namely a scan range14.2 cm in length that is centered 4.1 cm below the carina(Fig. 1).9 By knowing the slice thickness of the study andthe slice position of the carina, the cephalad and caudadslice positions were readily found. Original scan lengthswere documented, and expected percentage of scan lengthreduction was determined for each study. In addition,dose length products (DLPs) were recorded, and effectiveradiation doses were calculated with a conversion factorof 0.017 mSv/mGy $ cm.7

All studies were subsequently reviewed by two boardcertified radiologists (M.K.A. and T.K.E.) both with emer-gency radiology and cardiovascular imaging expertise and aminimum of 10 years of experience. Each case was visuallyreviewed in lung, soft tissue, and bone windows (window/center HU: 1465/-498, 877/108, 3077/570, respectively) for16 pertinent findings that could explain the patients’presentation as well as an additional 15 incidental findingsthat may be important and warrant noting (Table 1).Reviewers determined whether each finding was inside oroutside the reduced scan range and documented this ac-cordingly. In the cases in which a finding straddled aboundary slice, it was considered inside the reduced scan

Figure 1 CTPA scout image. The horizontal white bars demar-cate the reduced scan range. The 14.2-cm scan range is centered4.1 cm below the carina. This is equivalent to having the superioredge 3.0 cm above the carina as shown. Distances are incentimeters.

Atalay et al Excluded findings at reduced scan length CTPA 327

range if the reviewer believed that (1) a substantial portionof the lesion was present within the reduced scan range and(2) it could be characterized in a manner similar to that us-ing the full scan range, and outside otherwise. The latter arereferred to as excluded findings.

For both pertinent and incidental findings we evaluatedthe prevalence of each finding, the number of patients withR1 such finding, the number of excluded findings, and thenumber of patients withR1 excluded finding. To determinethe clinical significance of newly detected excluded find-ings we reviewed our hospital’s electronic medical recordand all relevant imaging studies before and after the

Table 1 Pertinent and incidental findings

Pertinent findings

Acute aortic injury: intramural hematoma, dissectionAir-space disease/opacityChronic obstructive pulmonary disease (COPD)Congestive heart failure (CHF)Coronary artery calcification (CAC)Esophageal disease: thickening, hiatal hernia, diverticulumLarge airways disease: bronchitis, obstruction, tracheomalacia (LAD)Pericardial effusionPleural effusionPneumomediastinumPneumothoraxPulmonary artery hypertension (PAH; MPA . 3 cm)Pulmonary embolism (PE)Pulmonary or chest wall mass (.3 cm)Rib fracture (acute)Right heart dysfunction (RHD)

MPA, main pulmonary artery.

RHD is suggested when the right heart chambers are clearly dilated re

Tracheomalacia is diagnosed when a segment of trachea is ,50% of its expec

reference CTPA on PACS through December 31, 2010.(We did not evaluate the significance of newly detectedfindings within the reduced scan range because scan lengthreduction would not alter their detection.) Data were ana-lyzed for the overall population, for each sex, and for each of3 age groups: ,40 years, 40–59 years, and R60 years.

Statistics

Continuous data are presented as mean 6 SD. Tocompare scan lengths, we used paired t test. Percentageswere compared with the chi-square test. Statistical signifi-cance was defined as a P value , 0.05.

Results

A total of 341 CTPA studies were conducted during thereview period of which 6 were repeat studies that were notincluded in the analysis. Therefore, 335 studies werereviewed (200 women (60%); age, 56 6 18 years). Ofthese 28 (8%) were positive for PE. The average scanlength of the original studies was 28.0 6 3.4 cm, and thereduced scan range would have decreased z-axis coverageby 49%6 6%. The average DLP was 4766 210 mGy $ cm,and the average effective dose was 8.1 6 3.6 mSv.

Therewere a total of 374 pertinent findings, for an averageof 1.1 findings per patient. Men were significantly morelikely to have R1 pertinent finding (P 5 0.005; Table 2).Younger patients (,40 years) were significantly less likelyto have R1 pertinent finding than the middle-aged group(40–59 years; P 5 0.004) who in turn were significantlyless likely to have such a finding than the older group(P , 1 ! 10211). Overall, 192 patients (57%) had

Incidental findings

AdenopathyAdrenal adenomaAdrenal mass (indeterminate)Aortic dilation (.3.8 cm)AscitesCardiomegalyGallstonesLiver disease (diffuse)Liver lesionOsseous lesion (non-acute)Pulmonary nodule (.5 mm, ,3 cm)Pulmonary nodule (%5 mm)Renal massSplenic lesionSplenomegalyThyroid nodule

lative to the left and contrast refluxes into the inferior vena cava.

ted diameter.

Table 2 Total and excluded number of pertinent and incidental findings and of patients with such findings overall and for age and sex

All patients(n 5 335)

Age ,40 y(n 5 64)

Age 40–59 y(n 5 130)

Age .60 y(n 5 141) M (n 5 135) F (n 5 200)

Pertinent findingsTotal, n 374 22 101 251 169 205Excluded, n (%) 3 (0.8) 0 (0) 1 (1.0) 2 (0.8) 1 (0.6) 2 (1.0)

Incidental findingsTotal, n 230 21 75 134 84 146Excluded, n (%) 60 (26) 2 (10) 18 (24) 40 (30) 18 (21) 42 (29)

No. of patients withPertinent. findings, n (%) 192 (57) 15 (23) 58 (45) 119 (84) 90 (67) 102 (51)Excluded, n (%) 3 (0.9) 0 (0) 1 (0.8) 2 (3) 1 (0.7) 2 (1.0)Incidental findings, n (%) 165 (49) 21 (33) 55 (42) 89 (63) 61 (45) 104 (52)Excluded, n (%) 52 (16) 2 (3) 18 (14) 32 (23) 17 (13) 35 (18)

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R1 pertinent finding (Table 2), the most common of whichwas coronary artery calcification (31% of patients), followedby air-space disease (16%), esophageal disease (13%), andchronic obstructive pulmonary disease (12%) (Table 3).

There were 3 pertinent findings in different patients(0.9%) that were outside the reduced scan range. Thesewere (1) a known 6-cm bronchogenic carcinoma in theright apex of a 50-year-old man (Fig. 2), (2) a newly diag-nosed Zenker diverticulum in an 89-year-old woman thatdid not alter the patient’s subsequent management(Fig. 3), and (3) a dilated, fluid-filled upper esophagus sec-ondary to a radiation-related stricture in an 81-year-oldwoman with known lung cancer (Fig. 4). This was a newlydetected finding, and the patient had endoscopic esophagealdilatation 2 days after the CTPA.

Table 3 Prevalence of pertinent findings overall and for age and se

All patients(n 5 335)

Age ,40 y(n 5 64)

A(

Acute aortic injury, n (%) 1 (0.3) 0 (0)Air-space disease, n (%) 55 (16) 6 (9) 1CAC, n (%) 103 (31) 0 (0) 2CHF, n (%) 10 (3) 0 (0)COPD, n (%) 41 (12) 0 (0)Esophageal disease, n (%) 44 (13) 4 (6) 1LAD, n (%) 16 (5) 2 (3)PAH, n (%) 12 (4) 4 (6)PE, n (%) 28 (8) 4 (6)Pericardial effusion, n (%) 5 (1) 0 (0)Pleural effusion, n (%) 35 (10) 1 (2) 1Pneumomediastinum, n (%) 1 (0.3) 0 (0)Pneumothorax, n (%) 1 (0.3) 0 (0)Pulmonary/chest mass, n (%) 7 (2) 0 (0)Rib fracture, n (%) 5 (1) 0 (0)RHD, n (%) 10 (3) 1 (2)Total, n 374 22 1

CAC, coronary artery calcification; CHF, congestive heart failure; COPD, chron

obstruction, tracheomalacia; MPA, main pulmonary artery; PAH, pulmonary arte

There were a total of 230 incidental findings, for anaverage of 0.7 findings per patient. There was no significantdifference in the percentage of men and women having R1incidental finding (P 5 0.22). Although no significant dif-ference was observed between middle- and younger-agedgroups for having R1 incidental finding (P 5 0.20), bothgroups were significantly less likely to have R1 such find-ing than older patients (P , 0.001). Overall, 165 patients(49%) had R1 incidental finding (Table 2), the most com-mon of which was cardiomegaly (17%), followed by lungnodules (16%) and adenopathy (10%) (Table 4).

Therewere 60 incidental findings (26% of such findings) in52 patients (16%) that were outside the reduced scan range(Table 2). These included 20 of 21 thyroid nodules, 11 of 22liver lesions, and 3 of 54 pulmonary nodules (all 3 were

x

ge 40–59 yn 5 130)

Age .60 y(n 5 141) M (n 5 135) F (n 5 200)

1 (0.8) 0 (0) 0 (0) 1 (0.5)7 (13) 32 (23) 30 (22) 25 (12)0 (15) 83 (59) 54 (40) 49 (25)5 (4) 5 (4) 4 (3) 6 (3)8 (6) 33 (23) 21 (16) 20 (10)4 (11) 26 (18) 19 (14) 25 (12)4 (3) 10 (7) 9 (7) 7 (3)1 (1) 7 (5) 2 (1) 10 (5)8 (6) 16 (11) 8 (6) 20 (10)3 (2) 2 (1) 3 (2) 2 (1)3 (10) 21 (15) 12 (9) 23 (11)1 (1) 0 (0) 0 (0) 1 (0.5)0 (0) 1 (1) 1 (1) 0 (0)1 (1) 6 (4) 2 (1) 5 (2)3 (2) 2 (1) 1 (1) 4 (2)2 (2) 7 (5) 3 (2) 7 (3)01 251 169 205

ic obstructive pulmonary disease; LAD, large airways disease: bronchitis,

ry hypertension; PE, pulmonary embolism; RHD, right heart dysfunction.

Figure 2 A 50-year-old man with known right apical bronchogenic carcinoma and worsening shortness of breath. (A) Coronal and (B)axial CTPA images show the neoplasm (arrows). (C) Axial image shows bilateral lower lobe pulmonary air space consolidations.

Atalay et al Excluded findings at reduced scan length CTPA 329

%8 mm). Of these 60 incidental findings there were 11 casesof cholelithiasis and 4 diagnostic cases of adrenal adenoma.Ofthe remaining 45 incidental findings, 22 in 21 patients werepreviously known, leaving 23 indeterminate findings (10%)in 19 patients (6%) that were newly detected. These newexcluded incidental findings and their subsequent imagingfollow-up, clinical management, and diagnoses where avail-able are in Table 5. Of note, 1 patient had a newly detectedthyroid nodule that was subsequently found at biopsy to besuspicious for papillary carcinoma. A second had newly diag-nosed cholangiocarcinoma. However, this patient had abdom-inal symptoms at the time of the reference CTPA and had aconcurrent abdominal CT that also showed the liver lesion.

Two of the 21 (10%) incidental findings in the ,40-yearage group were excluded, 18 of 75 (24%) such findings inthe 40–59-y age group were excluded, and 40 of 134 (31%)such findings in the .59-y age group were excluded. Selectadditional incidental findings are shown in Figures 5 and 6.

Discussion

Scan length is an important determinant of radiationdose at CTPA and 3 recent studies have reported that scan

Figure 3 An 89-year-old woman with shortness of breath and a historyingested material in a Zenker diverticulum (arrow). (D) Lung window

length can be reduced substantially while maintainingdiagnostic accuracy for PE.8–10 A scan length extendingfrom just above the aortic arch to just below the heart(w16.3 cm) reduces mean scan length by %38% comparedwith standard z-axis coverage. This scan range is appealingbecause it permits comprehensive simultaneous evaluationof the thoracic aorta, the pulmonary arteries, and the coro-nary arteries and can be used to exclude acute pathologyrelated to these structures. Even further reduction of scanlength is possible. A recent study of 100 consecutive pa-tients with positive PE showed that a correct positive diag-nosis could be rendered with an appropriately positionedscan length of 14.2 cm, reducing scan length by 44%.9

In principle, effective radiation dose is linearly related toscan length,7 and a reduction in scan length therefore leadsto a proportional decrease in dose. However, the use of tubecurrent modulation (automatic exposure control) alters thisrelation by varying the CT volume dose index along thez-axis. The reduced scan lengths proposed in these recentstudies are centered near the middle of the thorax. This re-gion has a lower attenuation relative to both the lower tho-rax/upper abdomen and upper chest (at the shoulder level)and would normally be subjected to lower radiation doses.Estimates of percentage scan length reduction are therefore

of CHF. (A–C) Serial transaxial CTPA images show high-densitysettings confirm congestive heart failure.

Figure 4 An 81-year-old woman with known left lower lobe lung cancer and right-sided chest pain. (A) Coronal and (B) axial CTPAimages show a dilated, debris-laden upper esophagus. A radiation-related stricture was dilated at endoscopy 2 days later. The patientalso had osseous metastatic disease. A left posterior third rib metastasis is noted (arrowhead). Although this lesion was excluded fromthe reduced scan range, other osseous lesions were seen.

330 Journal of Cardiovascular Computed Tomography, Vol 5, No 5, September/October 2011

likely to underestimate the real radiation benefits. The 49%scan length reduction seen in our study, for example, shouldresult in a radiation dose savings of .49% in an actualCTPA examination.

Our study compliments the earlier research by showingthat few pertinent findings are excluded at CTPA when areduced scan length of 14.2 cm is used. In our study only 3 of375 pertinent findings (0.8%) were excluded, one of whichdirectly changed clinical management (esophageal stricture).Therefore, substantial scan length reduction can be achievedon CTPA without compromising the diagnostic yield for PEor pertinent alternative diagnoses, with a commensuratereduction in radiation dose. This is particularly true forpatients ,40 years of age, because no pertinent findings

Table 4 Prevalence of incidental findings overall and for age and s

All patients(n 5 335)

Age ,40 y(n 5 64)

Adenopathy, n (%) 33 (10) 5 (8)Adrenal adenoma, n (%) 4 (1) 0 (0)Adrenal mass, n (%) 3 (1) 0 (0)Aortic dilation, n (%) 7 (2) 0 (0)Ascites, n (%) 5 (1) 0 (0)Cardiomegaly, n (%) 56 (17) 6 (9)Gallstones, n (%) 11 (3) 0 (0)Liver disease, n (%) 7 (2) 1 (2)Liver lesion, n (%) 22 (7) 0 (0)Pulmonary nodule . 5 mm, n (%) 26 (8) 3 (5)Pulmonary nodule % 5 mm, n (%) 28 (8) 4 (6)Renal mass, n (%) 2 (1) 0 (0)Spine lesion, n (%) 2 (1) 0 (0)Splenic lesion, n (%) 2 (1) 0 (0)Splenomegaly, n (%) 1 (0) 1 (2)Thyroid nodule, n (%) 21 (6) 1 (2)Total, n 230 21

were excluded in this population and these patients stand tobenefit most from radiation reduction.

We have found that 60 of 230 (26%) incidental findingswere excluded with the reduced scan range. These findingswere of variable clinical significance. Indeed, the manage-ment of incidental findings on imaging studies is vexing andcontroversial.11 Several prior studies have addressed theprevalence and significance of incidental findings on chestCT examination.12–21 Those prior studies specifically ad-dressed unexpected findings observed within the scan rangeduring coronary calcium scoring, cardiac CTA, or lung can-cer screening. Hall et al22 recently reviewed 589 CTPAs per-formed in a tertiary care hospital emergency department inan effort to evaluate the clinical relevance of unexpected

ex

Age 40–59 y(n 5 130)

Age .60 y(n 5 141) M (n 5 135) F (n 5 200)

13 (10) 15 (11) 14 (10) 19 (9)2 (2) 2 (1) 1 (1) 3 (2)1 (1) 2 (1) 0 (0) 3 (1)1 (1) 6 (4) 6 (4) 1 (0)2 (2) 3 (2) 1 (1) 4 (2)

14 (11) 36 (26) 17 (13) 39 (19)2 (2) 9 (6) 5 (4) 6 (3)5 (4) 1 (1) 3 (2) 4 (2)8 (6) 14 (10) 10 (7) 12 (6)7 (5) 16 (11) 9 (7) 17 (8)

11 (8) 13 (9) 12 (9) 16 (8)0 (0) 2 (1) 0 (0) 2 (1)1 (1) 1 (1) 2 (1) 0 (0)0 (0) 2 (1) 0 (0) 2 (1)0 (0) 0 (0) 1 (1) 0 (0)8 (6) 12 (9) 3 (2) 18 (9)

75 134 84 146

Table 5 Correlative imaging findings and/or clinical follow-up of new incidental findings outside the reduced scan field of view

Sex Age, y Finding Correlative imaging findings/diagnosis

1 F 44 Pulmonary nodule (8 mm) CT Ch (7 m): stable; 1–y follow-up recommended2 F 46 Thyroid nodule CT Ch (6 m): Stable3 F 48 Thyroid nodule US Bx (1 m): Benign4 F 50 Thyroid nodule No follow-up to date5 F 56 Liver lesion No follow-up to date6 F 58 Thyroid nodule NM (1 m): Subacute thyroiditis7 M 60 Spine lesion (lytic T4) MRI spine (1 m): Metastasis from known bladder cancer; pulmonary

nodule and hilar adenopathy present on CTPA8 M 65 Thyroid nodule US Bx (3 d): Suspicious for papillary carcinoma9 M 66 Liver lesion CT Abd (1 m): Liver cyst10 F 67 Liver lesion MRI Abd (1 d): Limited; US Abd (13 d): Hypoechoic;

follow-up recommended11 F 67 Renal mass US Abd (2 d): Renal cyst12 M 70 Liver lesion; liver disease CT Abd (0 d): shows liver lesion; subsequent Bx: cholangiocarcinoma13 F 71 Thyroid nodule No follow-up to date14 F 77 Thyroid nodule CT Neck (3 m): Stable15 M 80 Liver lesion No follow-up to date16 F 80 Thyroid nodule, spleen

and renal lesionsCT Ch (2 m): All lesions stable; known metastatic spindle cell sarcoma

17 F 82 Thyroid nodule No follow-up to date; known spindle cell sarcoma18 F 91 Liver lesion No follow-up to date19 F 91 Thyroid nodule,

adrenal massUS Thyroid (2 d): Nodule confirmed. No Bx recommended;no follow-up to date for adrenal

Abd, abdomen; Bx, biopsy; Ch, chest; Dx, diagnosis; MRI, magnetic resonance imaging; NM: nuclear medicine iodine-131; US, ultrasound.

Comparison imaging study dates are shown parenthetically in days (d) and months (m) relative to the reference CTA study.

Atalay et al Excluded findings at reduced scan length CTPA 331

findings. They found a similar percentage of positive PEstudies as in our study (9% vs 8%). With the use of a lesscomprehensive list of pertinent and incidental findings,they found that 33% of studies supported alternative diagno-ses and that 24% of patients had a new incidental findingthat required diagnostic follow-up. Overall, 13% of patientshad a new pulmonary nodule and 9% had new adenopathy.

Our interest in the present study was chiefly aimed atevaluating the significance of all new pertinent or incidentalfindings that were outside the reduced scan range. As suchour results cannot be directly compared with that earlier

Figure 5 A 59-year-old man with metastatic transitional cell carcinomaa right lower lobe pulmonary nodule (arrow) and adjacent hilar adenopathyimage with bone window settings shows a 1.6-cm lytic vertebral metastas

study. However, we did find that 10% of newly detected,indeterminate, incidental findings were excluded. Becauseincidental findings do not pertain to the clinical indicationfor the CTPA study and may lead to additional, potentiallyunnecessary workup, a smaller scan range aimed ataddressing the specific clinical concern is justified, beyondthe benefits associated with radiation dose. Although notinvestigated in this study, a detailed review of the CTPAscout images or of a concomitant chest radiograph mayprovide some measure of additional assurance that perti-nent findings are not missed.

of the bladder. (A) Axial CT image with lung window settings shows. These findings were within the reduced scan range. (B) Coronal CTis (arrowhead) that was excluded by the reduced scan range.

Figure 6 A 48-year-old woman with cough, shortness of breath,tachycardia, and a history of right breast cancer and nonischemiccardiomyopathy associated with Adriamycin. The axial CT imageshows right axillary adenopathy (arrow) that was excluded by thereduced scan range but that was known from physical examinationand prior surveillance imaging.

332 Journal of Cardiovascular Computed Tomography, Vol 5, No 5, September/October 2011

This study has limitations. It is a retrospective review ofa moderate sized patient population in which outcomeswere only considered for newly detected excluded findings.In an effort to be comprehensive and to maintain a worst-case scenario, we considered a broad range of possiblediagnoses. Yet some potential diagnoses may have beenexcluded. Reviewers were not blinded to the scannedvolume outside the reduced scan range. This may bias thedetermination of whether a finding is considered to beinside or outside the reduced scan region when it straddleda boundary. However, we believe that the criteria estab-lished for ultimately making this determination were ade-quately sound and objective. Finally, we did not conductanalyses of interreader and intrareader variability.

In conclusion, substantial scan length reduction can beachieved on CTPA in the emergency department and maynot alter the diagnostic yield for PE or pertinent alternativediagnoses.

References

1. Remy-Jardin M, Pistolesi M, Goodman LR, Gefter WB, Gottschalk A,

Mayo JR, Sostman HD: Management of suspected acute pulmonary

embolism in the era of CTangiography: a statement from the Fleischner

Society. Radiology. 2007;245:315–29.

2. Weiss CR, Scatarige JC, Diette GB, Haponik EF, Merriman B,

Fishman EK: CT pulmonary angiography is the first-line imaging

test for acute pulmonary embolism: a survey of US clinicians. Acad

Radiol. 2006;13:434–46.

3. Donohoo JH, Mayo-Smith WW, Pezzullo JA, Egglin TK: Utilization

patterns and diagnostic yield of 3421 consecutive multidetector row

computed tomography pulmonary angiograms in a busy emergency

department. J Comput Assist Tomogr. 2008;32:421–5.

4. Prologo JD, Gilkeson RC, Diaz M, Asaad J: CT pulmonary angiogra-

phy: a comparative analysis of the utilization patterns in emergency

department and hospitalized patients between 1998 and 2003. AJR

Am J Roentgenol. 2004;183:1093–6.

5. Kuiper JW, Geleijns J, Matheijssen NA, Teeuwisse W, Pattynama PM:

Radiation exposure of multi-row detector spiral computed tomography

of the pulmonary arteries: comparison with digital subtraction pulmo-

nary angiography. Eur Radiol. 2003;13:1496–500.

6. Pahade JK, Litmanovich D, Pedrosa I, Romero J, Bankier AA,

Boiselle PM: Quality initiatives: imaging pregnant patients with sus-

pected pulmonary embolism: what the radiologist needs to know. Ra-

diographics. 2009;29:639–54.

7. Huda W, Ogden KM, Khorasani MR: Converting dose-length product

to effective dose at CT. Radiology. 2008;248:995–1003.

8. Kallen JA, Coughlin BF, O’Loughlin MT, Stein B: Reduced Z-axis

coverage multidetector CT angiography for suspected acute pulmo-

nary embolism could decrease dose and maintain diagnostic accuracy.

Emerg Radiol. 2010;17:31–5.

9. Atalay MK, Walle NL, Grand DJ, Mayo-Smith WW, Cronan JJ,

Egglin TK: Scan length optimization for pulmonary embolism at CT

angiography: analysis based on the three-dimensional spatial distribu-

tion of 370 emboli in 100 patients. Clin Radiol. 2011;66:405–11.

10. Uehara M, Tanabe N, Funabashi N, Takaoka H, Ikari J, Toyama S,

Shimizu H, Hoshino S, Sugiura T, Saito M, Kawata N, Matsuura Y,

Kuriyama T, Tatsumi K, Komuro I: Detailed distribution of acute pul-

monary thromboemboli: direct evidence for reduction of acquisition

length and radiation dose for triple rule-out CT angiography. Int J Car-

diol. 2011;147:234–8.

11. Berland LL, Silverman SG, Gore RM, Mayo-Smith WW, Megibow AJ,

Yee J, Brink JA, Baker ME, Federle MP, Foley WD, Francis IR,

Herts BR, Israel GM, Krinsky G, Platt JF, Shuman WP, Taylor AJ:

Managing incidental findings on abdominal CT: white paper of the

ACR incidental findings committee. J Am Coll Radiol. 2010;7:754–73.

12. Dewey M, Schnapauff D, Teige F, Hamm B: Non-cardiac findings on

coronary computed tomography and magnetic resonance imaging. Eur

Radiol. 2007;17:2038–43.

13. Horton KM, PostWS, Blumenthal RS, Fishman EK: Prevalence of signif-

icant noncardiac findings on electron-beam computed tomography coro-

nary artery calciumscreening examinations.Circulation. 2002;106:532–4.

14. Hunold P, Schmermund A, Seibel RM, Gronemeyer DH, Erbel R:

Prevalence and clinical significance of accidental findings in

electron-beam tomographic scans for coronary artery calcification.

Eur Heart J. 2001;22:1748–58.

15. Kirsch J, Araoz PA, Steinberg FB, Fletcher JG, McCollough CH,

Williamson EE: Prevalence and significance of incidental extracardiac

findings at 64-multidetector coronary CTPA. J Thorac Imaging. 2007;

22:330–4.

16. Koonce J, Schoepf JU, Nguyen SA, Northam MC, Ravenel JG:

Extra-cardiac findings at cardiac CT: experience with 1,764 patients.

Eur Radiol. 2009;19:570–6.

17. Law YM, Huang J, Chen K, Cheah FK, Chua T: Prevalence of signif-

icant extracoronary findings on multislice CT coronary angiography

examinations and coronary artery calcium scoring examinations.

J Med Imaging Radiat Oncol. 2008;52:49–56.

18. Lehman SJ, Abbara S, Cury RC, Nagurney JT, Hsu J, Goela A,

Schlett CL, Dodd JD, Brady TJ, Bamberg F, Hoffmann U: Signifi-

cance of cardiac computed tomography incidental findings in acute

chest pain. Am J Med. 2009;122:543–9.

19. Onuma Y, Tanabe K, Nakazawa G, Aoki J, Nakajima H, Ibukuro K,

Hara K: Noncardiac findings in cardiac imaging with multidetector

computed tomography. J Am Coll Cardiol. 2006;48:402–6.

20. Schragin JG, Weissfeld JL, Edmundowicz D, Strollo DC,

Fuhrman CR: Non-cardiac findings on coronary electron beam com-

puted tomography scanning. J Thorac Imaging. 2004;19:82–6.

21. Jacobs PC, Mali WP, Grobbee DE, van der Graaf Y: Prevalence

of incidental findings in computed tomographic screening of the chest:

a systematic review. J Comput Assist Tomogr. 2008;32:214–21.

22. Hall WB, Truitt SG, Scheunemann LP, Shah SA, Rivera MP,

Parker LA, Carson SS: The prevalence of clinically relevant incidental

findings on chest computed tomographic angiograms ordered to diag-

nose pulmonary embolism. Arch Intern Med. 2009;169:1961–5.