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Residents Can Be Trained to Detect Abdominal Aortic Aneurysms Using Personal Ultrasound Imagers: A Pilot Study
Residents Can Be Trained to Detect Abdominal Aortic Aneurysms Using Personal Ultrasound Imagers: A Pilot Study Douglas L. Riegert-Johnson, MD, Charles J. Bruce, MD, Victor M. Montori, MD, MSc, Rachel J. Cook, MD, and Peter C. Spittell, MD, Baltimore, Maryland, and Rochester, Minnesota
Our objective was to test the hypothesis that internal medicine residents can be trained to screen for abdominal aortic aneurysm (AAA) using personal ultrasound imagers. We trained 5 randomly chosen internal medicine residents to image the abdominal aorta for patients with risk factors for AAAs using personal ultrasound imagers. Residents were trained in 3 or 4 one-on-one sessions with an instructor. To be eligible, patients had to be older than 65 years and have hypertension. After training, each of the 5 residents studied
R
uptured abdominal aortic aneurysm (AAA) is an increasing cause of morbidity and mortality. 1 A consensus statement has recommended baseline AAA ultrasound screening for all men age 60 to 85 years and women age 60 to 85 years with cardiovascular risk factors.2 This recommendation was based on population studies that used expensive full-sized ultrasound instruments and costly dedicated sonographers. 3 Training internal medicine residents to use a personal ultrasound imager (PUI) to image the abdominal aorta and, therefore, to screen for AAA could potentially decrease morbidity and mortality from this frequently clinically occult disorder. A PUI is more portable and affordable than a full-sized ultrasound instrument. PUIs have a sensitivity and specificity for AAA similar to that of a standard echocardiography (S-ECHO) machine.4,5 Residents have been trained to detect AAAs using full-sized echocardiographic machines. 6 The objective of this study was to determine whether residents could be trained to image the abdominal aorta
From the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins Hospital, Baltimore; and the Division of Cardiovascular Disease and Internal Medicine (C.J.B., P.C.S.) and Department of Medicine (V.M.M., R.J.C.), Mayo Clinic College of Medicine, Rochester. Personal ultrasound imagers provided as an equipment grant from Philips Medical Systems. Reprint requests: Charles J. Bruce, MD, 200 First St SW, Rochester MN 55095 (E-mail: [email protected]). 0894-7317/$30.00 Copyright 2005 by the American Society of Echocardiography. doi:10.1016/j.echo.2004.12.019
394
3 patients independently. In 12 of the residents’ 15 unsupervised studies, their abdominal aorta measurements were within 5 mm of the instructor’s measurements with standard echocardiography (mean difference 3 mm, range 0-6 mm). Residents detected 3 previously unknown AAAs measuring 5.2, 4.2, and 3.9 cm in diameter. We conclude residents can be trained to image the abdominal aorta with personal ultrasound imagers and to identify AAAs in patients at risk. (J Am Soc Echocardiogr 2005;18:394-7.)
and effectively screen patients at risk for AAAs using PUIs.
METHODS Setting, Definitions, and Patient Enrollment The study setting was a large academic medical center with an Accreditation Council for Graduate Medical Educationaccredited internal medicine residency training program. The institutional review board of the Mayo Clinic, Rochester, Minn, approved this study. To enroll patients, we identified eligible patients from inpatients admitted to a cardiology ward. Eligible patients had to have systemic hypertension (defined as current therapy for hypertension or systolic blood pressure ⬎ 160 mm Hg), be older than 65 years, and able and willing to give informed verbal consent. We excluded patients with a documented AAA. We defined AAA as an abdominal aorta with a maximal diameter greater than 3.0 cm in either the transverse or long-axis plane. Resident Training Level III echocardiographers supervised the training of a random sample of internal medicine residents. Residents were selected from a list using a random number generator. The first 5 residents selected all agreed to participate in the study. Instructors and residents who participated in the study did so in addition to their other responsibilities with no protected time. Resident orientation to the study included an introduction to PUI, demonstration of a PUI examination of the abdominal aorta on one patient, and instruction in the
Journal of the American Society of Echocardiography Volume 18 Number 5
physical examination of this vessel using the technique of Lerderle and Simel.7 The instructors trained and evaluated residents in one-on-one sessions. The length of each training and evaluation session was dictated by available time and patients. Each resident performed 7 training studies followed by 3 evaluation studies. Before every study with the PUI, residents palpated the aorta and classified it as enlarged or not enlarged. In the training sessions, after measuring the maximal diameter of the abdominal aorta by PUI, residents received feedback and their measurement of the aortic diameter was compared with the instructor’s findings using S-ECHO. During the evaluation studies, residents assessed the abdominal aorta using physical examination and the PUI. Contrary to the training studies, residents received no feedback. The instructor independently performed a physical examination and S-ECHO study of the abdominal aorta unaware of the residents’ findings. Equipment We used an imager with a 2.5-MHz phased-array transducer (Optigo, Phillips Medical Sytems, Andover, Mass) to perform PUI studies. Powered from a rechargeable lithium battery, the imager weighs 3.5 kg, measures 34.3 ⫻ 24.1 ⫻ 8.1 cm, and offers high-resolution real-time 2-dimensional imaging with color flow Doppler. The imager is not capable of M-mode imaging, pulsed wave Doppler, or continuous wave Doppler. Operators could “freeze” the images, take measurements of the still frames using online calipers, and then save single images on a flashcard. We used echocardiographic instruments (Sequoia C512, C256, and 128XP10, Acuson, Mountain View, Calif; and Sonos 2000 and 5500, Hewlett-Packard, Andover, Mass) for the S-ECHO examinations. Both systems were equipped with standard multifrequency transducers (2.0-3.5 MHz) and harmonic imaging. Imaging Techniques and Measurements for PUI and S-ECHO There was no fasting or other preparation of patients before imaging for this study. Many of the patients were fasting in preparation for other tests or procedures. Residents and instructors used the same imaging technique to complete PUI and S-ECHO studies. With the patient in the supine position and using the subcostal and abdominal imaging windows, the abdominal aorta was visualized from the upper abdomen to the level of the aortic bifurcation. Using still frames and online calipers, the maximal diameter of the abdominal aorta was measured in both the transverse and longitudinal views.
RESULTS Of 226 patients evaluated for study eligibility, 74 met inclusion criteria. Of these, 21 were not available (eg, undergoing other testing), 9 declined to
Riegert-Johnson et al 395
participate, and 44 enrolled in the study. Table shows the characteristics of enrolled patients. Each of the 2 first-year residents and 3 second-year residents received 3 to 4 training sessions during a mean of 61 days (range 31-104). During training of the residents, problems encountered included difficulty distinguishing the inferior vena cava and the abdominal aorta (some patients had a severely distended inferior vena cava), failure to apply enough pressure with the transducer to the abdomen to obtain an adequate image of the abdominal aorta, and failure to use image depth and contrast optimally. Mean instructor time per resident was 9.6 hours. Each resident took a mean of 11 minutes to complete each PUI evaluation study (range 6-23 minutes). Three previously unknown AAAs were identified during the study (maximum diameter 5.2, 4.2, and 3.9 cm) (Figure 1). One AAA was detected during a demonstration of PUI technique, another during a training study, and the last during an evaluation study; in all cases a resident using the PUI detected the aneurysm. In 13 of the residents’ 15 evaluation studies, their measurements of the diameter of the abdominal aorta were within 5 mm of the instructor’s measurements with S-ECHO (mean difference 3 mm, range 0-6 mm). A Bland-Altman plot shows no correlation of the difference of resident and instructor measurements and aortic size (Figure 2). The instructor was able to visualize the AAA to the bifurcation in all enrolled patients. Residents were able to visualize the aorta in all patients; however, in 5 of 44 patients they were unable to visualize the aortic bifurcation. The ultrasonographic classification of the aorta by S-ECHO as enlarged or not enlarged differed from the classification by physical examination in 12% of patients (ie, the physical examination accurately classified the aorta as enlarged or not enlarged in 88% of patients). Residents rated their confidence in their physical findings from 1 (no confidence) to 5 (completely confident). Resident mean confidence scores were 2.7 and 2.6 in the PUI training and evaluation examinations, respectively. They were not confident with 10 examinations, somewhat confident with 8, confident with 10, more confident with 12, and very confident with 1 examination. Residents completed an anonymous survey at the end of the study. All residents agreed or strongly agreed with the statements: “At the end of the study, I could use PUI to detect AAAs” and “If I was provided access to a PUI I would use it clinically to evaluate the abdominal aorta of my patients.” Residents identified lack of time in their schedule and the difficulty in visualizing the abdominal aorta in obese patients with PUI as barriers to this practice.
Journal of the American Society of Echocardiography May 2005
396 Riegert-Johnson et al
Table Characteristics of enrolled patients Age, y Sex BMI History of tobacco use
78.8 ⫾ 8 23 female, 21 male 29 ⫾ 8 kg/m2 24 (55%)
BMI, Body mass index.
Figure 1 Transverse view of previously undetected abdominal aortic aneurysm with adherent mural thrombus in 69-year-old white man with ischemic cardiomyopathy, hypertension, and history of tobacco use. Image was obtained by trainee using personal ultrasound imager.
Figure 2 Bland-Altman plot. On x-axis is difference of personal ultrasound imager (PUI) measurements by residents and standard echocardiography (S-ECHO) using full-sized machine measurements by instructors. Y-axis shows average of PUI measurements by residents and SECHO measurements by instructors for given aorta. Data from residents’ last 15 studies is shown.
DISCUSSION Residents can be trained to image the abdominal aorta using PUIs and to detect AAA for patients at risk. To our knowledge, this is the first study assessing the training of residents or other nontraditional
sonographers using PUI to detect AAA. The variation in measurement between residents using PUI and instructors with S-ECHO was similar to the reported variation between trained sonographers and radiologists using full-sized ultrasound machines.8 The strengths of our study are the random selection of residents to limit volunteer bias, the independent and blinded assessment of resident performance by reference standard procedures, and the participation of patients who are, in turn, adequate candidates for AAA screening. Random selection of residents is reflected in their varied career plans (one each in cardiology, general medicine, infectious disease, oncology, and gastroenterology). Although the small number of residents trained and the fact that we conducted the study within a single hospital and training program limit the generalizability of our findings, this study is applicable to the usual environment in which residents receive onthe-job training. The retail price for the PUIs used is in this study is far less that that of the full-sized echocardiographic instruments used (⬍$15,000 vs ⬎$100,000). Although not calculated, training costs for residents in this study were high. Scaling up our study to train each of the more than 170 residents in the internal medicine residency program would be cost prohibitive. A possible solution would be to use ultrasonographers as instructors. As debate continues as to whether residents and other nontraditional sonographers should conduct ultrasound examinations using a PUI ,9,10 limited access to ultrasound screening programs for AAA remains a problem. Expanding the number of physicians trained in screening for AAA through appropriate training during medical school and residency as part of an extended physical examination could be the solution. Our study demonstrates that physicians in training can be instructed in how to conduct an accurate PUI examination of the abdominal aorta and are able to detect AAA for patients at risk. Our study further demonstrates that this training can occur during usual hospital rotations. In conclusion, this pilot study demonstrates that internal medicine residents can be trained to image the abdominal aorta to detect AAA with a PUI.
REFERENCES 1. Bengtsson H, Bergqvist D, Sternby NH. Increasing prevalence of abdominal aortic aneurysms: a necropsy study. Eur J Surg 1992;158:19-23. 2. Kent KC, Zwolak RM, Jaff MR, Hollenbeck ST, Thompson RW, Schermerhorn ML, et al. Screening for abdominal aortic aneurysm: a consensus statement. J Vasc Surg 2004;39:267-9. 3. Scott RA, Wilson NM, Ashton HA, Kay DN. Influence of screening on the incidence of ruptured abdominal aortic aneurysm: 5-year results of a randomized control study. Br J Surg 1995;82:1066-70.
Journal of the American Society of Echocardiography Volume 18 Number 5
4. Bruce CJ, Spittell PC, Montgomery SC, Bailey KR, Tajik AJ, Seward JB. Personal ultrasound imager: abdominal aortic aneurysm screening. J Am Soc Echocardiogr 2000;13:674-9. 5. Spittell PC, Ehrsam JE, Anderson L, Seward JB. Screening for abdominal aortic aneurysm during transthoracic echocardiography in a hypertensive patient population. J Am Soc Echocardiogr 1997;10:722-7. 6. Bailey RP, Ault M, Greengold NL, Rosendahl T, Cossman D. Ultrasonography performed by primary care residents for abdominal aortic aneurysm screening. J Gen Intern Med 2001;16:845-9.
Riegert-Johnson et al 397
7. Lederle FA, Simel DL. Does this patient have abdominal aortic aneurysm? JAMA 1999;281:77-82. 8. Singh K, Bonaa KH, Solberg S, Sorlie DG, Bjork L. Intra- and interobserver variability in ultrasound measurements of abdominal aortic diameter: the Tromso study. Eur J Vasc Endovasc Surg 1998;15:497-504. 9. Filly RA. Is it time for the sonoscope? If so, then let’s do it right! J Ultrasound Med 2003;22:323-5. 10. Greenbaum LD. It is time for the sonoscope. J Ultrasound Med 2003;22:321-2.
Our objective was to test the hypothesis that internal medicine residents can be trained to screen for abdominal aortic aneurysm (AAA) using personal ultrasound imagers. We trained 5 randomly chosen internal medicine residents to image the abdominal aorta for patients with risk factors for AAAs using personal ultrasound imagers. Residents were trained in 3 or 4 one-on-one sessions with an instructor. To be eligible, patients had to be older than 65 years and have hypertension. After training, each of the 5 residents studied
R
uptured abdominal aortic aneurysm (AAA) is an increasing cause of morbidity and mortality. 1 A consensus statement has recommended baseline AAA ultrasound screening for all men age 60 to 85 years and women age 60 to 85 years with cardiovascular risk factors.2 This recommendation was based on population studies that used expensive full-sized ultrasound instruments and costly dedicated sonographers. 3 Training internal medicine residents to use a personal ultrasound imager (PUI) to image the abdominal aorta and, therefore, to screen for AAA could potentially decrease morbidity and mortality from this frequently clinically occult disorder. A PUI is more portable and affordable than a full-sized ultrasound instrument. PUIs have a sensitivity and specificity for AAA similar to that of a standard echocardiography (S-ECHO) machine.4,5 Residents have been trained to detect AAAs using full-sized echocardiographic machines. 6 The objective of this study was to determine whether residents could be trained to image the abdominal aorta
From the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins Hospital, Baltimore; and the Division of Cardiovascular Disease and Internal Medicine (C.J.B., P.C.S.) and Department of Medicine (V.M.M., R.J.C.), Mayo Clinic College of Medicine, Rochester. Personal ultrasound imagers provided as an equipment grant from Philips Medical Systems. Reprint requests: Charles J. Bruce, MD, 200 First St SW, Rochester MN 55095 (E-mail: [email protected]). 0894-7317/$30.00 Copyright 2005 by the American Society of Echocardiography. doi:10.1016/j.echo.2004.12.019
394
3 patients independently. In 12 of the residents’ 15 unsupervised studies, their abdominal aorta measurements were within 5 mm of the instructor’s measurements with standard echocardiography (mean difference 3 mm, range 0-6 mm). Residents detected 3 previously unknown AAAs measuring 5.2, 4.2, and 3.9 cm in diameter. We conclude residents can be trained to image the abdominal aorta with personal ultrasound imagers and to identify AAAs in patients at risk. (J Am Soc Echocardiogr 2005;18:394-7.)
and effectively screen patients at risk for AAAs using PUIs.
METHODS Setting, Definitions, and Patient Enrollment The study setting was a large academic medical center with an Accreditation Council for Graduate Medical Educationaccredited internal medicine residency training program. The institutional review board of the Mayo Clinic, Rochester, Minn, approved this study. To enroll patients, we identified eligible patients from inpatients admitted to a cardiology ward. Eligible patients had to have systemic hypertension (defined as current therapy for hypertension or systolic blood pressure ⬎ 160 mm Hg), be older than 65 years, and able and willing to give informed verbal consent. We excluded patients with a documented AAA. We defined AAA as an abdominal aorta with a maximal diameter greater than 3.0 cm in either the transverse or long-axis plane. Resident Training Level III echocardiographers supervised the training of a random sample of internal medicine residents. Residents were selected from a list using a random number generator. The first 5 residents selected all agreed to participate in the study. Instructors and residents who participated in the study did so in addition to their other responsibilities with no protected time. Resident orientation to the study included an introduction to PUI, demonstration of a PUI examination of the abdominal aorta on one patient, and instruction in the
Journal of the American Society of Echocardiography Volume 18 Number 5
physical examination of this vessel using the technique of Lerderle and Simel.7 The instructors trained and evaluated residents in one-on-one sessions. The length of each training and evaluation session was dictated by available time and patients. Each resident performed 7 training studies followed by 3 evaluation studies. Before every study with the PUI, residents palpated the aorta and classified it as enlarged or not enlarged. In the training sessions, after measuring the maximal diameter of the abdominal aorta by PUI, residents received feedback and their measurement of the aortic diameter was compared with the instructor’s findings using S-ECHO. During the evaluation studies, residents assessed the abdominal aorta using physical examination and the PUI. Contrary to the training studies, residents received no feedback. The instructor independently performed a physical examination and S-ECHO study of the abdominal aorta unaware of the residents’ findings. Equipment We used an imager with a 2.5-MHz phased-array transducer (Optigo, Phillips Medical Sytems, Andover, Mass) to perform PUI studies. Powered from a rechargeable lithium battery, the imager weighs 3.5 kg, measures 34.3 ⫻ 24.1 ⫻ 8.1 cm, and offers high-resolution real-time 2-dimensional imaging with color flow Doppler. The imager is not capable of M-mode imaging, pulsed wave Doppler, or continuous wave Doppler. Operators could “freeze” the images, take measurements of the still frames using online calipers, and then save single images on a flashcard. We used echocardiographic instruments (Sequoia C512, C256, and 128XP10, Acuson, Mountain View, Calif; and Sonos 2000 and 5500, Hewlett-Packard, Andover, Mass) for the S-ECHO examinations. Both systems were equipped with standard multifrequency transducers (2.0-3.5 MHz) and harmonic imaging. Imaging Techniques and Measurements for PUI and S-ECHO There was no fasting or other preparation of patients before imaging for this study. Many of the patients were fasting in preparation for other tests or procedures. Residents and instructors used the same imaging technique to complete PUI and S-ECHO studies. With the patient in the supine position and using the subcostal and abdominal imaging windows, the abdominal aorta was visualized from the upper abdomen to the level of the aortic bifurcation. Using still frames and online calipers, the maximal diameter of the abdominal aorta was measured in both the transverse and longitudinal views.
RESULTS Of 226 patients evaluated for study eligibility, 74 met inclusion criteria. Of these, 21 were not available (eg, undergoing other testing), 9 declined to
Riegert-Johnson et al 395
participate, and 44 enrolled in the study. Table shows the characteristics of enrolled patients. Each of the 2 first-year residents and 3 second-year residents received 3 to 4 training sessions during a mean of 61 days (range 31-104). During training of the residents, problems encountered included difficulty distinguishing the inferior vena cava and the abdominal aorta (some patients had a severely distended inferior vena cava), failure to apply enough pressure with the transducer to the abdomen to obtain an adequate image of the abdominal aorta, and failure to use image depth and contrast optimally. Mean instructor time per resident was 9.6 hours. Each resident took a mean of 11 minutes to complete each PUI evaluation study (range 6-23 minutes). Three previously unknown AAAs were identified during the study (maximum diameter 5.2, 4.2, and 3.9 cm) (Figure 1). One AAA was detected during a demonstration of PUI technique, another during a training study, and the last during an evaluation study; in all cases a resident using the PUI detected the aneurysm. In 13 of the residents’ 15 evaluation studies, their measurements of the diameter of the abdominal aorta were within 5 mm of the instructor’s measurements with S-ECHO (mean difference 3 mm, range 0-6 mm). A Bland-Altman plot shows no correlation of the difference of resident and instructor measurements and aortic size (Figure 2). The instructor was able to visualize the AAA to the bifurcation in all enrolled patients. Residents were able to visualize the aorta in all patients; however, in 5 of 44 patients they were unable to visualize the aortic bifurcation. The ultrasonographic classification of the aorta by S-ECHO as enlarged or not enlarged differed from the classification by physical examination in 12% of patients (ie, the physical examination accurately classified the aorta as enlarged or not enlarged in 88% of patients). Residents rated their confidence in their physical findings from 1 (no confidence) to 5 (completely confident). Resident mean confidence scores were 2.7 and 2.6 in the PUI training and evaluation examinations, respectively. They were not confident with 10 examinations, somewhat confident with 8, confident with 10, more confident with 12, and very confident with 1 examination. Residents completed an anonymous survey at the end of the study. All residents agreed or strongly agreed with the statements: “At the end of the study, I could use PUI to detect AAAs” and “If I was provided access to a PUI I would use it clinically to evaluate the abdominal aorta of my patients.” Residents identified lack of time in their schedule and the difficulty in visualizing the abdominal aorta in obese patients with PUI as barriers to this practice.
Journal of the American Society of Echocardiography May 2005
396 Riegert-Johnson et al
Table Characteristics of enrolled patients Age, y Sex BMI History of tobacco use
78.8 ⫾ 8 23 female, 21 male 29 ⫾ 8 kg/m2 24 (55%)
BMI, Body mass index.
Figure 1 Transverse view of previously undetected abdominal aortic aneurysm with adherent mural thrombus in 69-year-old white man with ischemic cardiomyopathy, hypertension, and history of tobacco use. Image was obtained by trainee using personal ultrasound imager.
Figure 2 Bland-Altman plot. On x-axis is difference of personal ultrasound imager (PUI) measurements by residents and standard echocardiography (S-ECHO) using full-sized machine measurements by instructors. Y-axis shows average of PUI measurements by residents and SECHO measurements by instructors for given aorta. Data from residents’ last 15 studies is shown.
DISCUSSION Residents can be trained to image the abdominal aorta using PUIs and to detect AAA for patients at risk. To our knowledge, this is the first study assessing the training of residents or other nontraditional
sonographers using PUI to detect AAA. The variation in measurement between residents using PUI and instructors with S-ECHO was similar to the reported variation between trained sonographers and radiologists using full-sized ultrasound machines.8 The strengths of our study are the random selection of residents to limit volunteer bias, the independent and blinded assessment of resident performance by reference standard procedures, and the participation of patients who are, in turn, adequate candidates for AAA screening. Random selection of residents is reflected in their varied career plans (one each in cardiology, general medicine, infectious disease, oncology, and gastroenterology). Although the small number of residents trained and the fact that we conducted the study within a single hospital and training program limit the generalizability of our findings, this study is applicable to the usual environment in which residents receive onthe-job training. The retail price for the PUIs used is in this study is far less that that of the full-sized echocardiographic instruments used (⬍$15,000 vs ⬎$100,000). Although not calculated, training costs for residents in this study were high. Scaling up our study to train each of the more than 170 residents in the internal medicine residency program would be cost prohibitive. A possible solution would be to use ultrasonographers as instructors. As debate continues as to whether residents and other nontraditional sonographers should conduct ultrasound examinations using a PUI ,9,10 limited access to ultrasound screening programs for AAA remains a problem. Expanding the number of physicians trained in screening for AAA through appropriate training during medical school and residency as part of an extended physical examination could be the solution. Our study demonstrates that physicians in training can be instructed in how to conduct an accurate PUI examination of the abdominal aorta and are able to detect AAA for patients at risk. Our study further demonstrates that this training can occur during usual hospital rotations. In conclusion, this pilot study demonstrates that internal medicine residents can be trained to image the abdominal aorta to detect AAA with a PUI.
REFERENCES 1. Bengtsson H, Bergqvist D, Sternby NH. Increasing prevalence of abdominal aortic aneurysms: a necropsy study. Eur J Surg 1992;158:19-23. 2. Kent KC, Zwolak RM, Jaff MR, Hollenbeck ST, Thompson RW, Schermerhorn ML, et al. Screening for abdominal aortic aneurysm: a consensus statement. J Vasc Surg 2004;39:267-9. 3. Scott RA, Wilson NM, Ashton HA, Kay DN. Influence of screening on the incidence of ruptured abdominal aortic aneurysm: 5-year results of a randomized control study. Br J Surg 1995;82:1066-70.
Journal of the American Society of Echocardiography Volume 18 Number 5
4. Bruce CJ, Spittell PC, Montgomery SC, Bailey KR, Tajik AJ, Seward JB. Personal ultrasound imager: abdominal aortic aneurysm screening. J Am Soc Echocardiogr 2000;13:674-9. 5. Spittell PC, Ehrsam JE, Anderson L, Seward JB. Screening for abdominal aortic aneurysm during transthoracic echocardiography in a hypertensive patient population. J Am Soc Echocardiogr 1997;10:722-7. 6. Bailey RP, Ault M, Greengold NL, Rosendahl T, Cossman D. Ultrasonography performed by primary care residents for abdominal aortic aneurysm screening. J Gen Intern Med 2001;16:845-9.
Riegert-Johnson et al 397
7. Lederle FA, Simel DL. Does this patient have abdominal aortic aneurysm? JAMA 1999;281:77-82. 8. Singh K, Bonaa KH, Solberg S, Sorlie DG, Bjork L. Intra- and interobserver variability in ultrasound measurements of abdominal aortic diameter: the Tromso study. Eur J Vasc Endovasc Surg 1998;15:497-504. 9. Filly RA. Is it time for the sonoscope? If so, then let’s do it right! J Ultrasound Med 2003;22:323-5. 10. Greenbaum LD. It is time for the sonoscope. J Ultrasound Med 2003;22:321-2.