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Thoracic Imaging |
1 From the Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Ave, Boston, MA 02215. Received February 16, 2001; revision requested March 27; revision received May 10; accepted June 7. Address correspondence to V.R. (e-mail: vraptopo@caregroup.harvard.edu).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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MATERIALS AND METHODS: Of 93 consecutive patients suspected of having pulmonary embolism, 48 underwent scanning with multi–detector row CT and 45 with single–detector row CT; scans were obtained in 9 seconds and 28 seconds with 2.5-mm and 3.0-mm collimation, respectively. The lungs were divided into three zones: central, middle, and peripheral. Two independent observers used five-point grading scales.
RESULTS: Conspicuity of pulmonary arteries in the central zone was ranked equal (median of 5), but in the middle and peripheral zones it was significantly higher at multi–detector row CT than at single–detector row CT (median 5 vs 4 and 4 vs 3, P < .001, respectively). In addition, multi–detector row CT improved the ability to connect peripheral arteries with their more centrally located pulmonary artery of origin in the peripheral but not the middle zone on transverse images and in both zones on multiplanar images. Viewing with a modified window setting (width, 1,000 HU; level, -100 HU) significantly increased pulmonary arterial conspicuity. Contrast material column in the pulmonary arteries was significantly more homogeneous at multi–detector row CT.
CONCLUSION: Use of multi–detector row CT significantly improves pulmonary arterial visualization in the middle and peripheral lung zones.
Index terms: Computed tomography (CT), angiography, 944.12916 • Computed tomography (CT), comparative studies • Computed tomography (CT), technology, 944.12912, 944.12915, 944.12916 • Embolism, pulmonary, 60.72, 944.77
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Results of two reports (6,8) indicate improvement in performing adequate single–detector row CT pulmonary angiographic studies and subsegmental vessel visualization by using thin (2.0-mm) collimation. The new multi–detector row CT scanners enable volumetric data acquisition without gaps in much shorter times than those achieved with single–detector row CT. Single breath-hold scanning can be performed over large body parts, and multivascular phase scans can be obtained without loss of resolution (9). The chest, for instance, can be scanned in 9 seconds with 2.5-mm collimation. Since multi–detector row CT can scan an area faster and with thinner collimation, its use should increase resolution and improve evaluation of peripheral pulmonary vessels. The purpose of this study was to compare vascular conspicuity and ability to connect pulmonary arterial branches on pulmonary angiograms obtained with multi–detector row CT and with those on pulmonary angiograms obtained with single–detector row CT.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Patients were selected according to geography. Our institution has two acute care hospitals serviced by the same clinical and radiology medical personnel with one single–detector row CT scanner (Somatom Plus 4; Siemens Medical Systems, Erlangen, Germany) at one site and one multi–detector row CT scanner (LightSpeed; GE Medical Systems, Milwaukee, Wis) at the other. At the time of this study, our institution was composed of two recently merged, previously independent, tertiary, acute-care, university-affiliated urban hospitals located across the street from each other and serving the same patient population. Although the medical personnel merged, the medical and surgical services remained separate, and the patients were admitted to either hospital on the basis of availability of hospital beds. At the hospital with multi–detector row CT, there were 195 acute medical or surgical beds, and at the hospital with single–detector row CT, there were 164 acute medical or surgical beds; the hospitals had 26 and 24 intensive care unit beds, respectively.
On the basis of these selection criteria, the two groups appeared similar. In addition, age, sex, frequency of pulmonary CT angiography performed, percentage of CT results positive for pulmonary embolism, and origin of patients (outpatients, inpatients, intensive care patients) were tabulated to assess for similarities or differences between the two groups. These results also showed no significant differences between the two groups (see Results).
In the 100 patients, two CT examinations performed with multi–detector row CT and five performed with single–detector row CT were excluded. These seven studies were excluded because of nonvascular enhancement at the bifurcation of the main pulmonary arteries. The remaining 93 studies (48 multi–detector row CT and 45 single–detector row CT) are included in this analysis.
Collimation and pitch varied to accommodate scanning the chest during one breath hold. For single–detector row CT, collimation of 3.0 mm was used, with a pitch of 1.5 (4.5-mm table move per gantry rotation) and 0.75 second per gantry rotation (6-mm table move per second). With this regimen, the chest (17-cm span) can be scanned in 28 seconds. For longer coverage, in four patients, the pitch was increased to 2.0. With multi–detector row CT, collimation of 2.5 mm was used in fast mode, with a pitch of 6.0 (15-mm table move per gantry rotation) and 0.80 second per gantry rotation (18.75-mm table move per second). With this protocol, the chest (17-cm span) can be scanned in 9 seconds.
The patients were instructed to hold their breath for the duration of the study. If they were unable to do so, they were instructed to breathe as quietly as possible. If they could not hold their breath during scanning, they were instructed to resume quiet breathing. For such events, we scanned from the diaphragm to the apex to decrease respiratory motion.
A mechanical injector (Medrad, Pittsburgh, Pa) was used for intravenous injection of iodinated contrast material at a rate of 3.5 mL/sec. All patients received ioversal 68% (Optiray 320; Mallinckrodt Medical, St Louis, Mo), which contains 320 mg of iodine per milliliter. Patients undergoing single–detector row CT received 100 mL and those undergoing multi–detector row CT received 70 mL of contrast material. Start delay time was determined by using a test injection of 10 mL of contrast material at a rate of 3.5 mL/sec. Time-attenuation curves over the main pulmonary artery, just before the bifurcation, were produced from images obtained every 3 seconds. Start delay was determined by using the time-to-peak value plus 3 seconds.
Sequential transverse images were reconstructed in both groups (every 2.5 mm for multi–detector row CT and every 3 mm for single–detector row CT) and stored on a picture archiving and communication system (PACS; GE Medical Systems) for clinical interpretation. Coronal and sagittal reformations were also produced routinely. The studies were interpreted on PACS in the cine mode and static four-on-one viewing format. In our institution, review of all electronic patient data is monitored according to category. Our institutional review board approved our study but did not require patient informed consent for this retrospective study.
Two observers (V.R. and P.M.B.), working independently, retrospectively reviewed the scans without knowledge of the type of scanner that was used. Each observer was blinded to the other’s ratings. They both had clinical experience in interpreting pulmonary CT angiograms. The observations were made on PACS. The images were viewed without annotations to remove scanner identification, and each observer used a combined cine stack with static four-on-one viewing.
The lungs were divided into three zones: central, middle, and peripheral. The central zone occupied the main pulmonary artery and the right and left pulmonary arteries to their bifurcations. The middle zone extended superiorly to the aortic arch, inferiorly to the inferior pulmonary vein, and laterally to half the radius of the ipsilateral lung field. The peripheral zone occupied the remaining periphery of the lungs.
Two five-point scales were used—one to grade pulmonary arterial conspicuity and the other to grade ability to connect arteries in the peripheral and middle zones with their proximal pulmonary artery of origin. Conspicuity of pulmonary arteries in the central and middle zones was ranked as follows: 1, not depicted; 2, probably not depicted or faintly depicted; 3, partially depicted; 4, adequately depicted; 5, fully depicted. The grading was made as an overall assessment of vascular visualization throughout the zone evaluated, from lung base to apex and for both lungs. For example, grade 2 was given when few if any of the expected arteries were seen in a given region; grade 3, when many of the expected arteries were seen; and grade 4, when most of the expected vessels were seen. Vessel visualization in lung window settings served as reference. For the peripheral zone, the following criteria were used to aid consistent assessment: 1, not depicted (no pulmonary artery seen); 2, probably not depicted (one or two arteries possibly seen); 3, partially depicted (three to five arteries seen); 4, adequately depicted (five to seven arteries seen); 5, fully depicted (more than seven arteries seen).
An ability to connect arteries in the peripheral and middle zones with their proximal pulmonary artery of origin was ranked as follows: 1, not connected; 2, probably not connected; 3, possibly connected; 4, probably connected; 5, definitely connected. This was performed with both transverse and multiplanar images. In case of uncertainty in grading, half points were used between two grades. As with arterial conspicuity, the ability to connect peripheral to more medial arteries of origin was given a grade reflecting the reviewer’s overall assessment of vessel connectivity throughout a given zone.
By switching between lung and soft-tissue window settings on PACS, the observers distinguished between pulmonary arteries and veins by determining the consistent relationship of arteries to bronchi. Unlike arteries, which maintain a consistent relationship to the bronchi, veins flow independently. The ability to view the images on a PACS station in cine mode also aided distinction of arteries from veins by allowing the observers to follow peripheral arteries centrally to their origin in the main pulmonary artery and to follow peripheral veins centrally to the left atrium. In the lower lobes, veins were distinguished from arteries from their more horizontal course.
Transverse images were viewed in both a standard mediastinal window setting (width, 400 HU; level, 40 HU) and a lung window setting (width, 1,500 HU; level, -500 HU), as well as a modified window setting (width, 1,000 HU; level, -100 HU). These settings are slightly different from a window setting (width, 1,000 HU; level, 100 HU) described by Brink et al (10). In addition to transverse images, multiplanar views were ranked in all three window settings. These views were generated by the technologists at the time of the study and were included in the patients’ PACS folders. If not available (n = 11), they were generated retrospectively and transferred to the PACS. Standard multiplanar series included coronal and sagittal images that were 3 mm thick and obtained at 3-mm intervals covering the middle two-thirds of the lungs. In eight patients (one who underwent single–detector row CT and seven who underwent multi–detector row CT), multiplanar views were not considered adequate because of considerable respiratory motion.
Each observer ranked 21 points in each patient independently. These included assessment of vessel conspicuity in three zones viewed at three window settings (nine points) and assessment of the ability to connect pulmonary arterial segments (peripheral-to-middle and middle-to-central zones) viewed at three window settings in transverse (six points) and multiplanar (six points) images. A total of 1,905 points were graded ([93 transverse conspicuity x 9] + [93 transverse connection x 6] + [85 multiplanar connection x 6]). In case of disagreement, the average score for each point was used for statistical analysis.
The homogeneity of the pulmonary arterial contrast enhancement was assessed by means of measuring attenuation values in three locations. These locations included the origin of the common basilar trunk in the left lower lobe, the main pulmonary artery just before its bifurcation, and the origin of the right apical pulmonary artery. One reviewer (V.R.) made the measurements, and the area selected was equal to 75% of the cross-diameter of the vessel. The caudal-to-cranial direction of the attenuation sampling followed the temporal direction of scanning and covered a span of approximately 5.5 cm.
A commercially available statistical program (MINITAB; Minitab, State College, Pa) was used. For ordinal variables, the Kruskal-Wallis and Mann-Whitney tests were used. The Kruskal-Wallis test was used to evaluate for statistically significant differences in grading positions between the two groups (different scanners). The Mann-Whitney test was used to evaluate for statistically significant differences in grading positions within the groups (different window settings or planes). One-way analysis of variance was used to evaluate differences in interval values (eg, attenuation values), and the 
2 test was used for differences in nominal variables in the two groups. Agreement between the two observers was assessed with 
statistics. A P value less than .05 was considered to indicate statistical significance (11).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The percentage of cases assessed as positive for pulmonary embolism was also not significantly different: nine (20%) of 45 single–detector row CT studies and 12 (25%) of 48 multi–detector row CT studies (P = .24). In the multi–detector row CT group, 12 were outpatients, while six patients (one intubated) came from or were in intensive care units 2–6 days before CT angiography. In the single–detector row CT group, nine were outpatients, and seven patients (two intubated) came from or were in intensive care units 2–6 days before the test. These findings support the similarity of the two groups.
There was close agreement between the two observers. Of 1,905 observations performed by each reviewer, there was agreement within half of a grade in 78%, within one grade in 89%, and within two grades in 93% of the observations. The value was 0.67 (substantial agreement), and the weighted value was 0.77 (substantial to almost perfect agreement). The standard error was 0.015 (P < .001). In the central zone, there was perfect agreement ( = 1.00). In the middle zone, the value was 0.696 (substantial agreement), and the weighted value was 0.80 (substantial to almost perfect agreement). The standard error in the middle zone was 0.085 (P < .001). In the peripheral zone, the value was 0.431 (moderate agreement), and the weighted value was 0.58 (moderate to substantial agreement). The standard error in the middle zone was 0.052 (P < .001).
The pulmonary arterial conspicuity and the ability to connect peripheral arteries with the more proximal ones in the two groups are summarized in Tables 1–3. The pulmonary arterial conspicuity (Table 1) in the central zone was equal for both single–detector row CT and multi–detector row CT scanners (median of 5 in both). Arterial conspicuity in the middle zone was ranked higher with multi–detector row CT than with single–detector row CT when viewed with the standard mediastinal setting (median 5 vs 4, P < .001) but not when viewed at the modified window setting (median of 5 for both). In the peripheral zone, multi–detector row CT scans received a significantly higher pulmonary arterial conspicuity grade than did single–detector row CT scans when viewed both with standard and modified window settings (median of 4 vs 3, P < .001, with mediastinal window settings and median of 5 vs 4, P < .001, with modified window settings) (Figs 1, 2).
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As expected, as compared with the standard mediastinal window setting, the modified setting improved vessel conspicuity in the middle and peripheral zones in both scanners. This improvement was less pronounced in the middle zone, from a median in both groups of 4.5 to 5.0 (P = .03), than in the peripheral zone, from a median in both groups of 3.5 to 4.5 (P < .001). Vessel conspicuity was only slightly, but significantly, inferior with the modified window setting, as compared with the lung window setting (median 5.0 for lung vs 4.5 for modified, P < .001). However, the lung window setting cannot be used for detection of pulmonary arterial thrombus. There was no significant difference between modified and lung window settings in grading vessel conspicuity in the central and middle zones.
In both groups, multiplanar images, as compared with transverse images, significantly improved the ability to connect the more peripheral arteries with their central pulmonary artery of origin (Fig 1c). For multiplanar images, selection of window setting did not have any significant effect in the middle-to-central zone pulmonary arterial connections, with a median of 4 and 5 for each setting on transverse and multiplanar images, respectively. However, in the peripheral zone, as compared with the standard mediastinal window setting, the modified setting significantly improved the ability to connect vessels in both transverse and multiplanar views (median of 3.0 vs 2.5, P < .001 and 4 vs 5, P < .001, respectively). In the same (peripheral) zone, as compared with the modified window setting, the lung setting improved the ability to connect vessels on transverse (median 3.0 vs 3.5, P < .001) but not on multiplanar views.
The main pulmonary arterial attenuation was not significantly different in the two groups (mean attenuation, 243 HU ± 79 for single–detector row CT; mean attenuation, 236 HU ± 42 for multi–detector row CT, P = .59). However, there was a significant and substantial difference in pulmonary arterial attenuation decrease from the lower to the upper lobe in scans obtained with single–detector row CT, as compared with scans obtained with multi–detector row CT (an average decrease of 100 HU ± 25, as compared with an average decrease of 38 HU ± 29, P < .001).
Filling defects, presumed pulmonary emboli, were identified in 64 zones in 21 patients. There was no significant difference in the detection of the number of presumed pulmonary emboli in the central and middle zones between the multi–detector row CT and single–detector row CT scanners (11 vs 13 in the central zone and 15 vs 12 in the middle zone, respectively). However, there was a significantly higher number of peripheral filling defects detected in patients who underwent multi–detector row CT than in patients who underwent single–detector row CT (12 vs 1, P < .001). With the exception of five such isolated peripheral defects in two patients who underwent multi–detector row CT, all others were associated with more centrally located ones. Although these defects were presumed to be pulmonary emboli, their presence was not confirmed by using another independent test, such as catheterization and pulmonary angiography.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Remy-Jardin et al (6,8) found that faster single–detector row CT scanning improves the number of studies that are technically adequate for interpretation. This may be related to gantry rotation speed. Although multi–detector row CT can scan over the same volume much faster than single–detector row CT can, the speed of gantry rotation is not different (0.80 second per rotation, as compared with 0.75 second). Thus, we did not observe any significant difference in the number of studies deemed uninterpretable in our two groups of patients. In contrast, multi–detector row CT improved the quality of the images obtained, as seen in the improved conspicuity of arteries in the middle and peripheral zones, as well as in the significantly larger number of peripheral filling defects identified. This improvement may be related to the speed of volumetric scanning over the chest (9 vs 28 seconds for multi–detector row CT vs single–detector row CT).
The improved vessel conspicuity of the peripheral arteries is largely due to the decreased partial volume effect achieved with multi–detector row CT. Several mechanisms may play a role, including thinner collimation, faster volumetric scanning, and more homogeneous contrast material column. Because of the large difference in attenuation between pulmonary vessels and air, small variations in these variables may have considerable effect on the partial volume, especially of small structures, such as peripheral pulmonary arteries. Although a decrease in collimation from 3.0 to 2.5 mm is important, it cannot solely explain the improved performance of multi–detector row CT. Furthermore, the difference in section thickness is less if one considers the effect that spiral CT has on section thickness.
According to the manufacturers, at single–detector row CT, 3.0-mm collimation with a pitch of 1.5 results in an effective section thickness of 3.45 mm, while 2.5-mm collimation at high-speed multi–detector row CT with a pitch of 6.0 results in an effective section thickness of 3.20 mm, which results in an effective section thickness difference of 0.25 mm. Faster volumetric scanning, from 28 to 9 seconds for the total acquisition, improves image quality because overall it decreases misregistration due to respiratory (often involuntary) and biologic motion. The improved homogeneity of the pulmonary arterial contrast material column achieved with multi–detector row CT contributes to improved peripheral visualization.
In our study, there was a substantial temporal decrease in pulmonary arterial attenuation of an average of 100 HU on single–detector row CT scans at measurements performed in the lower and upper lobe arteries 5.5 cm apart (3 seconds with multi–detector row CT and 9 seconds with single–detector row CT). This was statistically significantly larger, as compared with 38 HU noted on multi–detector row CT scans. Peripheral arteries are located further out than the central ones, therefore they fill with contrast material later. Inhomogeneous contrast material column will result in inconsistent, frequently lower, attenuation of the more peripheral vessels. The effect of temporal differences in delivery of contrast material to peripheral vessel attenuation is exacerbated by the small caliber of the peripheral vessels. This increases partial volume effect and results in a considerable decrease in vessel-lung average attenuation and poorer visualization with clinically useful window settings.
On the basis of our results, we have recently increased the volume of contrast material administered intravenously for pulmonary angiograms obtained with the SCDT scanner from 100 to 150 mL, and we have increased the start delay from peak plus 3 seconds to peak plus 5 seconds to increase the useful enhancement time of the peripheral arteries. Newer single–detector row CT scanners allow for faster scanning with 0.50 second per gantry rotation. If available, use of 2.0-mm collimation would improve image quality and allow for faster data acquisition, with a pitch of 2.0. This protocol could be used to scan over the chest (eg, 17 cm) in 18.5 seconds, which is considerably less than the 28 seconds needed with 3.0-mm collimation, pitch of 1.5, and 0.75 second per gantry rotation. Conversely, in the same time (<20 seconds) multi–detector row CT could scan the chest with 1.25-mm collimation. However, ever decreasing section thickness results in an increased number of images and adversely affects the reconstruction time, while its clinical usefulness in pulmonary angiography has not yet been determined.
The purpose of this study was to compare vascular conspicuity and ability to connect pulmonary arterial branches at multi–detector row CT with those at single–detector row CT. Toward this goal, we used a conventional lung window setting as an internal control. This setting, however, does not allow for arterial lumen assessment, and therefore evaluation for pulmonary embolism is impossible. As compared with a lung window setting, however, a conventional mediastinal window setting significantly decreases visualization of vessels in the middle and peripheral lung zones. In an experimental porcine model, Brink et al (10) identified a modified window setting (width, 1,000 HU; level, 100 HU) optimal for detection of pulmonary embolism. In our study, we used a slightly different setting (width, 1,000 HU; level, -100 HU), as we found it more appropriate for use in the patients in our study. The modified window setting significantly improved vessel visualization in the peripheral zone for both scanners and visualization in the middle zone at single–detector row CT, while allowing for adequate assessment of arterial lumen.
From a practical standpoint, the potential effect of analyzing pulmonary arteries on multiplanar images in the clinical context of pulmonary embolism is threefold. One is familiarity of the images resulting from conventional pulmonary angiogram-like images. The second is potential for economy in the number of images required for interpretation. Third, viewing an abnormality in more than one view could increase the interpreter’s confidence. Use of multiplanar views significantly reduced fragmentation of the arteries by improving the ability to connect peripheral vessels with their central arteries of origin. Multiplanar views provided better anatomic depiction and viewing of longer segments of pulmonary arteries, but whether they also improve detection of pulmonary embolism needs further investigation.
Because pulmonary arteries must be seen before they can be assessed (7), it makes intuitive sense that with an appropriate window setting, improved conspicuity of peripheral pulmonary vessels will aid in the detection of peripheral pulmonary emboli. The increased detection rates of peripheral pulmonary filling defects in the multi–detector row CT group, as compared with those in the single–detector row CT group in our study, suggest that increased peripheral pulmonary arterial conspicuity may improve detection of peripheral pulmonary emboli.
This position, however, needs to be proved because better vessel conspicuity does not necessarily mean that filling defects can be seen more accurately. An inappropriate window setting may mask thrombi by being either too narrow or too wide. Even with an appropriate window setting, apparent filling defects may be due to contrast material flow inhomogeneity rather than actual space-occupying thrombi. Thus, because of a lack of a reference standard for pulmonary embolism in this study, the true significance of peripheral filling defects in the study populations is uncertain.
To complicate matters, given the high sensitivity and specificity of CT for pulmonary embolism in recent studies (4–6), and the known high interobserver variability for diagnosing subsegmental pulmonary embolism with conventional angiography (12), the ideal reference standard test for peripheral pulmonary embolism, other than autopsy, is uncertain. Future animal studies may be helpful for clarifying the precise sensitivity and specificity of multi–detector row CT for peripheral pulmonary embolism.
Our results suggest the need for further studies with multi–detector row scanners in evaluating peripheral pulmonary embolism, especially to assess whether such detection has clinical importance. In our preliminary study, of the 13 presumed peripheral pulmonary emboli identified, eight filling defects in peripheral vessels were connected to defects in segmental vessels, and the other five were isolated to the peripheral arteries. Since there was no other confirmatory test, it is possible that some or all these findings were false and that unnecessary treatment was instituted. On the other hand, it is possible that we missed a number of additional peripheral pulmonary emboli with the multi–detector row scanner.
The improved sensitivity of multi–detector row CT to depict peripheral arteries along with the rare occurrence of pulmonary embolism after negative pulmonary CT angiograms (13,14) strengthens the clinical usefulness of the test. The test is further strengthened by the low interobserver variability observed in our study and that of others (1,15). These observations further support the evolution of CT from a problem-solving technique (16,17) to a first-line diagnostic tool in patients suspected of having acute pulmonary embolism (4,5,18).
In conclusion, as compared with single–detector row scanning, pulmonary angiography with multi–detector row CT significantly improves vessel visualization in the middle and peripheral lung zones. Multiplanar reconstructions improve the ability to identify the origin of middle and peripheral vessels and connect them with their central arteries of origin. Narrower collimation improves the quality of the transverse and multiplanar images, and faster acquisition times make the examination better tolerated and improve contrast and spatial resolution, which may improve detection of peripheral pulmonary emboli. The improved visualization of peripheral vessels is attributed to the faster speed of multi–detector row CT, which allows scanning during a more uniform contrast material column in the pulmonary arteries.
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FOOTNOTES |
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Author contributions: Guarantors of integrity of entire study, V.R., P.M.B.; study concepts and design, V.R., P.M.B.; literature research, V.R., P.M.B.; clinical studies, V.R., P.M.B.; data acquisition and analysis/interpretation, V.R., P.M.B.; statistical analysis, V.R.; manuscript preparation, V.R.; manuscript definition of intellectual content, editing, revision/review, and final version approval, V.R., P.M.B.
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REFERENCES |
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M. L. Storto, A. Di Credico, F. Guido, A. R. Larici, and L. Bonomo Incidental Detection of Pulmonary Emboli on Routine MDCT of the Chest Am. J. Roentgenol., January 1, 2005; 184(1): 264 - 267. [Abstract] [Full Text] [PDF]
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M. P. Revel, D. Petrover, A. Hernigou, C. Lefort, G. Meyer, and G. Frija Diagnosing Pulmonary Embolism with Four-Detector Row Helical CT: Prospective Evaluation of 216 Outpatients and Inpatients Radiology, January 1, 2005; 234(1): 265 - 273. [Abstract] [Full Text] [PDF]
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 J H Reid Multislice CT pulmonary angiography and CT venography Br. J. Radiol., December 1, 2004; 77(suppl_1): S39 - S45. [Abstract] [Full Text] [PDF]
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J. D. Prologo, R. C. Gilkeson, M. Diaz, and J. Asaad CT Pulmonary Angiography: A Comparative Analysis of the Utilization Patterns in Emergency Department and Hospitalized Patients Between 1998 and 2003 Am. J. Roentgenol., October 1, 2004; 183(4): 1093 - 1096. [Abstract] [Full Text] [PDF]
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 P. Reinartz, J. E. Wildberger, W. Schaefer, B. Nowak, A. H. Mahnken, and U. Buell Tomographic Imaging in the Diagnosis of Pulmonary Embolism: A Comparison Between V/Q Lung Scintigraphy in SPECT Technique and Multislice Spiral CT J. Nucl. Med., September 1, 2004; 45(9): 1501 - 1508. [Abstract] [Full Text] [PDF]
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A. S. Wu, J. A. Pezzullo, J. J. Cronan, D. D. Hou, and W. W. Mayo-Smith CT Pulmonary Angiography: Quantification of Pulmonary Embolus as a Predictor of Patient Outcome--Initial Experience Radiology, March 1, 2004; 230(3): 831 - 835. [Abstract] [Full Text] [PDF]
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E. Coche, F. Verschuren, A. Keyeux, P. Goffette, L. Goncette, P. Hainaut, F. Hammer, E. Lavenne, F. Zech, P. Meert, et al. Diagnosis of Acute Pulmonary Embolism in Outpatients: Comparison of Thin-Collimation Multi-Detector Row Spiral CT and Planar Ventilation-Perfusion Scintigraphy Radiology, December 1, 2003; 229(3): 757 - 765. [Abstract] [Full Text] [PDF]
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I. Hasegawa, P. M. Boiselle, V. Raptopoulos, and H. Hatabu Tracheomalacia Incidentally Detected on CT Pulmonary Angiography of Patients with Suspected Pulmonary Embolism Am. J. Roentgenol., December 1, 2003; 181(6): 1505 - 1509. [Abstract] [Full Text] [PDF]
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E. E. Chiang, P. M. Boiselle, V. Raptopoulos, K. F. Reynolds, M. P. Rosen, and M. Simon Detection of Pulmonary Embolism: Comparison of Paddlewheel and Coronal CT Reformations--Initial Experience Radiology, August 1, 2003; 228(2): 577 - 582. [Abstract] [Full Text] [PDF]
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British Thoracic Society guidelines for the management of suspected acute pulmonary embolism Thorax, June 1, 2003; 58(6): 470 - 483. [Full Text] [PDF]
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 S.-i. Watanabe, K. Arai, T. Watanabe, W. Koda, and H. Urayama Use of three-dimensional computed tomographic angiography of pulmonary vessels for lung resections Ann. Thorac. Surg., February 1, 2003; 75(2): 388 - 392. [Abstract] [Full Text] [PDF]
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 I. D.C. Kirkpatrick Images of a pulmonary embolus: classic and contemporary Can. Med. Assoc. J., September 1, 2002; 167(5): 511 - 512. [Full Text]
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 J. W. T. Leung, P. J. Kornguth, and M. B. Gotway Utility of Targeted Sonography in the Evaluation of Focal Breast Pain J. Ultrasound Med., May 1, 2002; 21(5): 521 - 526. [Abstract] [Full Text] [PDF]
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