the measurement of the common carotid artery intima and media combined layers as determined by high - resolution b - mode ultrasonography is now widely recognized as a useful tool for early identification for systemic atherosclerosis .
intima - media thickness ( imt ) evaluation can identify individuals at risk for future cardiovascular events,17 and also evaluate the effectiveness of different therapy modalities for controlling morbidities that lead to the development of atherosclerotic - based diseases by identifying regression in imt values after such interventions.813 imt measurement methods have become more complex since the initial reports .
the necessity of same - patient serial measurements in prospective cohort studies demanded a homogenization of the technique in order to avoid differences between repeated exams due to technical reproducibility difficulties as opposed to real imt changes .
however , complex models require longer examination periods , are more expensive , and require auxiliary devices and additional human resources . the objective of this study was to test and describe a practical protocol to measure common carotid imt that uses the combined values of two longitudinal examination angles to increase its sensitivity .
between february and september 2005 , 210 patients underwent duplex scan examination of carotid vessels at our institution . generally , the indication for carotid investigation was the occurrence of a neurological event ( stroke , tia , or both ) , assessment of cardiovascular status in patients with risk factors for atherosclerosis , and preoperative evaluation for vascular surgeries .
the remaining 206 patients were evaluated in a cross - sectional study where conventional carotid and vertebral duplex investigation was complimented by imt measurements taken from both common carotid arteries ( cca ) , except in five cases due to unilateral cca occlusion .
all examinations were performed by a single physician with certified skills in duplex scan diagnostic procedures .
the exams were initially performed with an atl hdi 1500 ultrasound system ( phillips medical systems , bothel , wa , usa ) using a 1012 mhz linear transducer . in the latter included patients ,
a logiq 5 ultrasound system ( ge healthcare , milwaukee , wi , usa ) and a 710 mhz linear transducer were used .
imt measurements were obtained with the patient lying in the supine position and with the neck rotated to the opposite side of examination .
cca images were obtained to measure imt by using three different angle views for each vessel ( figure 1 ) .
initially , a transversal scanning view of the acc was performed in the longest extension possible from the base of the neck to the carotid bulb .
at least three imt points were measured in the near and far walls in the most thickened area of each vessel .
also , lateral wall measurements were taken when both thickening was evident and accurate images were possible .
subsequently , the vessel was scanned by two longitudinal views : posterolateral ( pl ) , with the transducer positioned parallel to the posterior border of the sternocleidomastoid muscle , and anterolateral ( al ) , with the transducer positioned parallel to the anterior border of the sternocleidomastoid muscle ; at least three imt measurements were obtained for each near and far wall .
optimal b - mode settings of gain , depth , focal zone placement , and compression were individually adjusted for each vessel to enhance arterial wall structures and image quality .
imt was measured by manual technique using electronic calipers , similar to the method of sidhu and desai.14 the maximum imt value was selected for each angle .
an imt superior to 1.0 mm was considered to be an abnormal finding.15 quantitative imt measurement differences between the different angles were calculated by anova with the lsd post - hoc test .
imt measurements were obtained with the patient lying in the supine position and with the neck rotated to the opposite side of examination .
cca images were obtained to measure imt by using three different angle views for each vessel ( figure 1 ) .
initially , a transversal scanning view of the acc was performed in the longest extension possible from the base of the neck to the carotid bulb .
at least three imt points were measured in the near and far walls in the most thickened area of each vessel .
also , lateral wall measurements were taken when both thickening was evident and accurate images were possible .
subsequently , the vessel was scanned by two longitudinal views : posterolateral ( pl ) , with the transducer positioned parallel to the posterior border of the sternocleidomastoid muscle , and anterolateral ( al ) , with the transducer positioned parallel to the anterior border of the sternocleidomastoid muscle ; at least three imt measurements were obtained for each near and far wall .
optimal b - mode settings of gain , depth , focal zone placement , and compression were individually adjusted for each vessel to enhance arterial wall structures and image quality .
imt was measured by manual technique using electronic calipers , similar to the method of sidhu and desai.14 the maximum imt value was selected for each angle .
an imt superior to 1.0 mm was considered to be an abnormal finding.15 quantitative imt measurement differences between the different angles were calculated by anova with the lsd post - hoc test .
the population studied had a mean age of 60.812.9 years , and 106 ( 51.5% ) of the individuals were male .
reliable measurement images could be achieved in 406 vessels in the transversal angle view , 404 in the longitudinal posterior view , and 398 in the longitudinal anterior angle view .
the mean time necessary to take measurements was 8.11.24 minutes . comparing the thickest measurement obtained from all views , 270 ( 66.3% ) carotid arteries had an imt greater than 1 mm .
the mean imt values achieved with the different incidences were 1.260.6 mm ( transversal ) , 1.170.54 mm ( longitudinal al ) , and 1.180.58 mm ( longitudinal pl ) .
detailed data of mean imt for each angle view are presented in table 1 . a significant difference in imt measurement values
was observed when the three angles of examination plus the combined positive results of both longitudinal angles were compared by anova ( p=0.005 ) .
the lsd post - hoc test identified that the combined results of longitudinal views had similar results to transversal views ( p=0.28 ) and higher imt means than isolated al or pl longitudinal views ( p=0.02 and 0.05 , respectively ) .
a direct comparison of the different angles of measurement was obtained with mcnemar s test .
no statistical difference was observed in comparison between al and pl longitudinal angles ( p=0.63 ) .
the transversal view identified a greater number of arteries with increased imt in comparison to the anterior or posterior longitudinal examination angles ( p<0.001 for both ) .
the combined results of the two longitudinal angles show superior results over isolated longitudinal views ( p<0.001 for both ) and similar results to transversal measurements ( p=0.52 ) .
imt measurement is a simple , feasible , and cost - effective method for assessing systemic atherosclerosis and cardiovascular risk in adults.1 also , is somewhat easy to provide specific training for professionals with previous vascular ultrasound experience to take imt measurements that meet good quality standards after a short period of practice.14 in this study , we proposed an objective and practical method to evaluate imt with the intention of improving the measurement quality by a short increase in the time required for carotid examination while maintaining its characteristic simplicity .
specific software1620 has been developed for automatic imt evaluation that minimizes the subjectivity of direct eye observation .
computer - assisted imt measurements are widely used in other countries for longitudinal cohort studies and are encouraged by latest consensus.2122 however , such an option demands complex human and material resources . although software can perform more than a hundred measurements from each segment in a short time , the results obtained were not proven to be more accurate than manual measurements.23 another improvement is the concomitant use of ecg24 during examination , which allows the observer to take measurements only during systolic activity , preventing small differences that could appear during the diastolic period when the inner arterial layers are less compressed .
also , external devices that measure head rotation and transducer position in degrees , such as the meijer arc , make it possible to reproduce the same positions in repeated examinations .
these improvements bring many advantages and raise the quality of the data obtained , but such procedures also require more time24 and are more expensive .
the application of such protocols should be preceded by a careful cost - benefit analysis that depends on the objectives of each investigation .
only the sternocleidomastoid and the carotid bulb were used , which represent simple anatomical references that remain virtually unchanged over time .
the transversal angle view provided a panoramic observation of the cca , thus allowing the observer to identify and measure the thickest imt points , even of the side walls .
however , measurements taken from the transversal view may result in poor quality images , which are subject to many artifacts that are mainly the result of refraction from the side walls . rather than being a proper measurement angle ,
previous authors have performed imt measurements from a single longitudinal view,14,2526 which can provide limited observation of the vessel walls , leading to the underestimation of early atherosclerotic processes .
we avoided directly comparing our findings with these reports due to the methodological differences of each study .
instead , we used the numbers obtained in our investigation to compare the combined results of imt measured from the two longitudinal views with results from each single longitudinal view .
as shown in the results , isolated longitudinal views had poorer sensitivity on identifying areas of increased imt .
the longitudinal views obtained in this investigation provided at least 12 different measurement points ( three from each wall ) , covering the whole extension of the cca in perpendicular angles to generate virtual tri - dimensional information about carotid wall thickness .
although some authors believe that the near wall images are not accurate enough for imt measurements,2728 we decided to consider these values . in many cases , the near wall presents layers that are far thicker than those in the far wall , which may even have normal values .
thus , ignoring these findings would underestimate the real state of the carotid artery atherosclerotic process.2930 recent studies revealed a tendency to use the mean maximum thickness of the cca , carotid bulbs , and internal carotid artery ( ica).31 in this investigation , we avoided taking measurements from the carotid bulb or ica for the following reasons : first , even though bulb and ica measurements may be worthwhile , they present limitations : as opposed to cca , they can be measured only in limited angles that may not reflect the thickest portions of vessel wall.3233 also , up to 52% of images can fail to obtain accurate bulb and ica measurements.34 the variance of results of bulb and ica imt amongst repeated examinations and different physicians is higher than cca measurements , making longitudinal comparisons more unreliable.3537 finally , cca , bulb , and ica have morphological differences that make direct imt comparison among them inaccurate.21 yet , cca / bulb / ica measurements do not appear to be superior to cca imt alone.38 we believe that the suggested protocol is an inexpensive method to measure imt .
we avoided expressing costs in numbers because values may vary from country to country and from private to public healthcare models .
thus , the eventual cost calculation in our institution may not reflect the reality for many readers .
although we did not show numbers to confirm our impression , we judged that the presented technique is less expensive because it does not uses complimentary devices and does not depend on external software to analyze the obtained images .
the acquisition and maintenance of the necessary devices would certainly impact the final costs of examinations .
the mean time expended in taking all measurements was about 8 minutes . this value is shorter than other models suggested,24 thus representing less of an impact in terms of physician human resources than more complex models .
the protocol presented is a fast and practical method for obtaining common carotid artery intima - media thickness measurements .
the combined values of anterolateral and posterolateral longitudinal views provide a more sensitive evaluation of the inner layers of the carotid walls than isolated longitudinal views .
 objectiveto describe and test a practical protocol to measure common carotid intima - media thickness that uses the combined values of two longitudinal examination angles to increase sensitivity.methodbetween february and september 2005 , 206 patients underwent duplex scan examination of carotid vessels , and the intima - media thickness of 407 common carotids were measured in three angles : transversal , longitudinal posterolateral , and anterolateral , with three intima - media thickness measurements for each near and far wall . 
 in addition to numbers obtained from the three angles of measurement , a fourth visual perspective was obtained by combining the intima - media thickness results of posterolateral and anterolateral longitudinal views and considering the thickest wall measurement.resultstwo hundred seventy ( 66.3% ) carotid arteries had an intima - media thickness thicker than 1 mm . 
 the mean intima - media thickness values achieved by the different incidences were 1.260.6 mm ( transversal ) , 1.170.54 mm ( longitudinal anterolateral ) , and 1.180.58 mm ( longitudinal posterolateral ) . 
 a significant difference in intima - media thickness measurement values was observed when the three angles of examination plus the combined positive results of both longitudinal angles were compared by anova ( p=0.005 ) . 
 the lsd post - hoc test determined that the combined longitudinal view results were similar to the transversal views ( p=0.28 ) and had greater intima - media thickness means than isolated anterolateral or posterolateral longitudinal views ( p=0.02 and 0.05 , respectively).conclusionsthe protocol presented is a practical method for obtaining common carotid artery intima - media thickness measurements . 
 the combined longitudinal posterolateral and anterolateral longitudinal views provide a more sensitive evaluation of the inner layers of the carotid walls than isolated longitudinal views . 
INTRODUCTION
METHOD
Technique Description
RESULTS
DISCUSSION
CONCLUSION