Accuracy Of Ultrasound Measurements Research Articles

Assessing the accuracy of ultrasound measurements of tracheal diameter: an in vitro experimental study

BackgroundRecent studies indicate that ultrasound can detect changes in tracheal diameter during endotracheal tube (ETT) cuff inflation. We sought to assess the accuracy of ultrasound measurement of tracheal diameter, and to determine the relationship between tracheal wall pressure (TWP), cuff inflation volume (CIV), and the degree of tracheal deformation.MethodsOur study comprised two parts: the first included 45 porcine tracheas, the second 41 porcine tracheas. Each trachea was intubated with a cuffed ETT, which was connected to an injector and the manometer via a three-way tap. The cuff was inflated and the cuff pressure recorded before and after intubation. The tracheal diameter was measured using ultrasound. This included three separate measurements: outer transverse diameter (OTD), internal transverse diameter (ITD), and anterior tracheal wall thicknesses (ATWT). A precision electronic Vernier caliper was also used to measure tracheal diameter. We calculated TWP and the percentage change of tracheal diameter. The Bland–Altman method, linear regression, and locally weighted regression (LOESS) were used to analyze the data.ResultsThere were strong correlation and agreement for OTD (r = 0.97, P < 0.001) and ITD (r = 0.90, P < 0.001) as measured by ultrasound and by precision electronic Vernier caliper, but a poor correlation for ATWT (r = 0.58, P < 0.001). There was a strong correlation between the percentage change of OTD (OTD%, r = 0.75, P < 0.001) and CIV, the percentage change of ITD (ITD%, r = 0.77, P < 0.001) and CIV, TWP (r = 0.75, P < 0.001) and CIV. And a strong correlation was also found between TWP and OTD% (r = 0.84, P < 0.001), TWP and ITD% (r = 0.84, P < 0.001).ConclusionsUse of ultrasound to measure OTD and ITD is accurate, but is less accurate for ATWT. There is a close correlation between OTD%, ITD%, CIV and TWP.

Optic Nerve Sheath Diameter Measured by Point-of-Care Ultrasound and MRI.

Ultrasound (US) measurement of the optic nerve sheath diameter (ONSD) and optic nerve diameter (OND) is a method frequently used to screen for an increased intracranial pressure. The aim of this study was to assess the accuracy of US measurements of ONSD and OND, when compared to magnetic resonance imaging (MRI) measurements as the criterion standard. In this prospective, single-institution study, orbital US was performed for those patients requiring an emergent brain MRI. ONSD and OND of both eyes were measured in the axial and coronal planes in straight gaze by US. ONSD and OND from brain and orbital MRI were measured by two neuroradiologists. Correlation and agreement between readings were assessed using Pearson's correlations. Eighty-two patients met inclusion criteria. The mean axial and coronal ONSD in the MRI examinations was 5.6 and 5.7 mm at 3-5.9 mm behind the globe, respectively. The mean ONSD from the US measurements was 6.22 and 5.52 mm in the axial and coronal planes, respectively. The mean OND in US examinations was 4.31 mm (axial) and 3.68 mm (coronal). Axial versus coronal measurements of ONSD had a modest correlation in US assessment with an r2 of .385 (P < .001) but there were no correlations between any of the US and MRI measurements. In measuring ONSD and OND, US measurements showed a modest correlation between axial and coronal measurements, but no concordance was found between US and MRI in our setting.

Ultrasound Measurement Error and Its Implications for Carpal Tunnel Syndrome Diagnosis.

Background: Ultrasound (US) measurement of the cross-sectional area (CSA) of peripheral nerves has been validated as a method for diagnosing peripheral nerve compression; however, the accuracy of US measurements and variation among examiners have not been well established. The purpose of this study was to determine the percent error from a known measurement among multiple US examiners using a gel phantom model. Methods: A US phantom gel, with 2 embedded, premeasured cylindrical objects, was constructed, and 9 residents, fellows, and attending physicians with upper-extremity US experience were recruited to use US to measure the CSA of each object. Percent error was calculated based on the premeasured value of each object, which was measured using digital calipers, and was calculated using the formula for CSA of a cylinder (A = pi × r2) prior to insertion into the gel phantom. Results: The mean percent error for examiners' CSA measurements was 9.0% ± 4.7% (range, 1.6%-17.0%). There was a greater mean percent error for the smaller measured object compared with the larger one. There was a very minimal decline in percent error with increase in years of training experience (slope = -0.029, R2 = 0.0002). Conclusion: This study demonstrates that US examiners were able to measure CSAs of premeasured objects with approximately 10% error. When considering the use of US for the diagnosis of carpal tunnel syndrome, a cutoff value of 10 mm2 is often used, and therefore in cases where measurements are within 10% of the diagnostic threshold, caution should be exercised in interpreting the results.

Factors influencing spinal curvature measurements on ultrasound images for children with adolescent idiopathic scoliosis (AIS).

The measurements of spinal curvatures using the ultrasound (US) imaging method on children with scoliosis have been comparable with radiography. However, factors influencing the reliability and accuracy of US measurement have not been studied. The purpose of this study is to investigate the effects of curve features and patients’ demographics on US measurements and to determine which factors influence the reliability and accuracy. Two hundred children with scoliosis were recruited and scanned with US by one experienced operator and three trainees. One experienced rater measured the proxy Cobb angles from US images twice one week apart and compared the results with clinical radiographic records. The correlation and accuracy between the US and radiographic measurements were subdivided by different curve severities, curve types, subjects’ weight status and US acquisition experiences. A total of 326 and 313 curves were recognized from radiographs and US images, respectively. The mean Cobb angles of the 13 missing curves were 17.4±7.4° and 11 at the thoracic region. Among the 16 curves showing large discrepancy (≥6°) between US and radiographic measurements, 7 were main thoracic and 6 were lumbar curves. Twelve had axial vertebral rotation (AVR) greater than 8°. The US scans performed by the experienced operator showed fewer large discrepancy curves, smaller difference and higher correlation than the scans from the trainees (3%, 1.7±1.5°, 0.95 vs 6%, 2.4±1.8°, 0.90). Only 4% missing and 5% large discrepancy curves were demonstrated for US measurements in comparison to radiography. The missing curves were mainly caused by small severity and in the upper spinal region. There was a higher chance of the large discrepancy curves in the main thoracic and lumbar regions with AVR>8°. A skilled operator acquired better US images and led to more accurate measurements especially for those subjects with larger curvatures, AVR and body mass index (BMI).

Reliability and accuracy of ultrasound measurements with and without the aid of previous radiographs in adolescent idiopathic scoliosis (AIS).

The objectives of this preliminary study were to assess the reliability and accuracy of ultrasound (US) for measuring coronal curvature with and without the aid of a previous radiograph, and to evaluate the ability of US to detect curve progression in adolescent idiopathic scoliosis (AIS) patients. Four raters measured 20 AIS US images twice at one-week intervals. Intra-rater reliability and correlation with radiograph were investigated with (rater 1) and without (raters 2-4) the aid of a previous radiograph. The center of lamina (COL) method was used to approximate the Cobb angle. Thirty-six curves were identified. All raters showed high intra-rater reliability (ICC[2,1] >0.80). With the aid of a previous radiograph, rater 1 showed higher correlation with radiograph (ICC[2,1]=0.86), better standard error of measurement (SEM=2.2°), and improved error index of selecting end-vertebrae (EI=1.34), but no statistical improvement of intra-rater reliability (p>0.05). For rater 2-4, the range of the ICC[2,1] values between US and radiograph measurements, the SEM value, and the range of the EI values were 0.70°-0.72°, 3.3°, and 1.65°-2.36°, respectively. Specificity and sensitivity of US for detecting curve progression were 0.91 and 0.83, respectively. Using a previous radiograph as a measurement aid helped the user to measure coronal curvature from US images, and improved the accuracy of end-vertebrae selection. US showed high sensitivity and specificity for detecting curve progression, indicating that US may be a suitable, radiation-free alternative for monitoring patients with AIS who have mild or moderate curves.

Accuracy of Ultrasound Measurements by Novices: Pixels or Voxels

ABSTRACT During the last two decades three-dimensional (3D) ultrasound has become increasingly popular around the world. There have been a great number of research papers studying its feasibility as well as reliability and accuracy. Compared to two-dimensional (2D), 3D ultrasound produces better visualization with minimal probe manipulation. The sonographer performing 2D ultrasound has to mentally assemble crosssectional images of a structure and/or object into a 3D image. In cases with uncertain anatomic orientation less experienced examiners may experience difficulties in envisioning three dimensions of the visualized structure, lesion or organ. Patients and parents are often faced with similar problems. A number of studies have shown that novice operators can efficiently store and interpret the volume data by 3D ultrasound, which may have many positive implications in the practice.

Evaluation of imaging technologies to correct for photon attenuation in the overlying tissue for in vivo bone strontium measurements

The interpretation of measurements of bone strontium in vivo using energy dispersive x-ray fluorescence spectroscopy is presently hindered by overlying skin and soft-tissue absorption of the strontium x-rays. The use of imaging technologies to measure the overlying soft-tissue thickness at the index finger measuring site might allow correction of the strontium reading to estimate its concentration in bone. An examination of magnetic resonance (MR), computed tomography (CT) and high-frequency ultrasound (US) imaging technologies revealed that 55 MHz US had the smallest range of measurement uncertainty at 3.2% followed by 1 Tesla MR, 25 MHz US, 8 MHz US and CT at 4.3, 5.4, 6.6 and 7.1% uncertainty, respectively. Of these, only CT imaging appeared to underestimate total thickness (p < 0.05). Furthermore, an inter-study comparison on the accuracy of US measurements of the overlying tissue thickness at finger and ankle in nine subjects was investigated. The 8 MHz US system used in prior in vivo experiments was found to perform satisfactorily in a repeat study of ankle measurements, but indicated that finger thickness measurements may have been misread in previous studies by up to 17.7% (p < 0.025). Repeat ankle measurements were not significantly different from initial measurements at 2.2% difference.

In vivo quantification of embryonic and placental growth during gestation in mice using micro-ultrasound

BackgroundNon-invasive micro-ultrasound was evaluated as a method to quantify intrauterine growth phenotypes in mice. Improved methods are required to accelerate research using genetically-altered mice to investigate the interactive roles of genes and environments on embryonic and placental growth. We determined (1) feasible age ranges for measuring specific variables, (2) normative growth curves, (3) accuracy of ultrasound measurements in comparison with light microscopy, and (4) weight prediction equations using regression analysis for CD-1 mice and evaluated their accuracy when applied to other mouse strains.MethodsWe used 30–40 MHz ultrasound to quantify embryonic and placental morphometry in isoflurane-anesthetized pregnant CD-1 mice from embryonic day 7.5 (E7.5) to E18.5 (full-term), and for C57Bl/6J, B6CBAF1, and hIGFBP1 pregnant transgenic mice at E17.5.ResultsGestational sac dimension provided the earliest measure of conceptus size. Sac dimension derived using regression analysis increased from 0.84 mm at E7.5 to 6.44 mm at E11.5 when it was discontinued. The earliest measurement of embryo size was crown-rump length (CRL) which increased from 1.88 mm at E8.5 to 16.22 mm at E16.5 after which it exceeded the field of view. From E10.5 to E18.5 (full term), progressive increases were observed in embryonic biparietal diameter (BPD) (0.79 mm to 7.55 mm at E18.5), abdominal circumference (AC) (4.91 mm to 26.56 mm), and eye lens diameter (0.20 mm to 0.93 mm). Ossified femur length was measureable from E15.5 (1.06 mm) and increased linearly to 2.23 mm at E18.5. In contrast, placental diameter (PD) and placental thickness (PT) increased from E10.5 to E14.5 then remained constant to term in accord with placental weight. Ultrasound and light microscopy measurements agreed with no significant bias and a discrepancy of less than 25%. Regression equations predicting gestational age from individual variables, and embryonic weight (BW) from CRL, BPD, and AC were obtained. The prediction equation BW = -0.757 + 0.0453 (CRL) + 0.0334 (AC) derived from CD-1 data predicted embryonic weights at E17.5 in three other strains of mice with a mean discrepancy of less than 16%.ConclusionMicro-ultrasound provides a feasible tool for in vivo morphometric quantification of embryonic and placental growth parameters in mice and for estimation of embryonic gestational age and/or body weight in utero.

SU-GG-I-155: A QA Program for US Preclinical Tumor Drug Response Testing

Purpose: Growing concern with rising costs of preclinical testing of anti‐tumor drugs in animalmodels creates demand for improvements in measurement accuracy. Caliper tumor volume measurements are the most commonly accepted parameter in tumor response studies. High frequency ultrasound (∼35 MHz) is more accurate and the least expensive imaging measurement device for rodent tumors. The accuracy of US measurements is unfortunately highly dependent on operator performance and training. Although commercial phantoms for quality assurance (QA) in clinical ultrasound are common no source of QA phantoms was available to validate the accuracy of tumor response to chemotherapeutic agents in rodent models.Method and Materials: For these studies a special purpose ultrasound(US) phantom was designed using Gammex ultrasound materials and manufacturing expertise from clinical radiology. The prototype phantom is composed of four parts; A) high contrast uniformly spaced wire tool to measure vertical (depth) accuracy, horizontal accuracy and linearity, B) low contrast variable diameter cylinder accuracy tool at uniform depth, C) low contrast cylinder 2mm‐diameter accuracy at variable depth tool and D) low contrast hyperechoic spheres to measure tumor volume accuracy. USimages of the phantom were acquired and tumor volume measurements made with a 35MHz ultrasound Vevo 707 Visualsonics Rodent Imager.Results: The measurements showed that the errors are generally less than ±5%. Large inter‐operator errors approaching 50%, however, were observed due to 1. insufficient training, 2. undeveloped measurement protocols and 3. simple operator errors. Conclusion: The materials and manufacturing procedures for Gammex US phantoms for human studies can be used with smaller imaging objects suitable for mouse models. Preliminary experience shows potential for improved inter‐institutional variability by improving measurement protocols and operator training. These phantoms are expected to improve small animaltumor response measurements, and reduce the cost of cancer drug testing by improving confidence levels of outcomes.

Estimating organ size in small migrating shorebirds with ultrasonography: An intercalibration exercise.

Organs, even of fully grown adult birds, mammals, and reptiles, may show substantial size changes in relation to specific performances. These changes are difficult to study, because measurements usually can only be obtained following the death of the animal. We explored the use of ultrasonographic imaging, a relatively simple noninvasive technique, to measure size of pectoral muscles and stomach in two small shorebird species (red knots Calidris canutus and golden plovers Pluvialis apricaria). Accuracy of ultrasound measurements in estimating organ mass in red knots was reasonably high. Depending on the equipment used, the error of individual measurements was 20%-25% for the pectoral muscles and 26%-44% for the stomach. In plovers the technique was less accurate, probably because of the low variability of the organs involved. Ultrasound scanning is particularly suited to measure rapidly changing organ sizes over short time intervals. We demonstrate this with an example in which changes in individuals in size of pectoral muscle and stomach were monitored in captive red knots following a change in diet. Ultrasound measures will enable studies on the links between body composition and future behavior and physiology.

Prediction of lean yield in yearling bulls using real-time ultrasound

A study was undertaken to determine the repeatability and accuracy of ultrasound measurements taken on yearling bulls and to assess the value of these live measurements to predict lean yield. Ultrasonic fat depth and 1. dorsi area were measured on 616 yearling bulls prior to slaughter. Corresponding carcass measurements were obtained through the Agriculture Canada Blue Tag Program. Carcass side lean (LEANYIELD) was extrapolated from the lean content of the seven-bone rib section from the carcasses of 41 Angus and 41 Charolais bulls. Stepwise multiple regression used live (USFAT and USREA) measurements to predict LEANYIELD. Repeatability (SER) and accuracy (SEP) statistics for USFAT were 0.8 mm and 1.6 mm, respectively. The corresponding results for USREA were SER = 4.3 cm2 and SEP = 7.8 cm2. The ultrasound lean yield (USLEAN) prediction equation was: USLEAN = 599.2 − (9.5 × USFAT) + (1.1 × USREA); R2 = 0.73, RSD = 17.9 g kg−1. Results indicated that LEANYIELD was predicted better by USLEAN (SEP = 18.0 g kg−1) than by BTLEAN (SEP = 22.6 g kg−1). Results from a second group of dissected bulls (n = 110) confirmed that ultrasound can predict LEANYIELD as effectively as carcass measurements (SEP = 22.8 and 22.6 g kg−1 for USLEAN AND BTLEAN) in young breeding bulls in this study. Key words: real-time ultrasound, performance testing, beef bulls, carcass traits

The influence of primary non-function on the accuracy of ultrasound measurements in the diagnosis of renal allograft rejection

Abstract Daily ultrasonographic measurements of transplant cross-sectional area were used to quantify allograft swelling as a diagnostic test for acute rejection in a series of 120 renal transplants. Initial graft function (IF) occurred in 86 patients (72 %) and primary non-function (PNF) occurred in the remaining 34 (28 %). An increase in allograft cross-sectional area greater than or equal to 10 % was defined as a positive ultrasound scan suggesting an acute rejection episode and was investigated by needle core biopsy. During periods of PNF, allografts with consistently negative ultrasound scans were submitted to needle core biopsy on a weekly basis. The diagnosis of rejection was based exclusively on the histological findings. In the IF group, agreement between ultrasound and histological diagnosis was good (k = 0.63, sensitivity 81 %, specificity 83 %, positive predictive value 76 %, negative predictive value 86 % and overall accuracy 82 %). In the PNF group, agreement between ultrasound and histology was only fair (k = 0.46, sensitivity 77 %, specificity 70 %, positive predictive value 69 %, negative predictive value 78 % and overall accuracy 73 %). It it concluded that a degree of allograft swelling is sometimes associated with acute tubular necrosis, and this makes ultrasound measurements of transplant size a less useful technique of monitoring kidneys with PNF.

The influence of primary non-function on the accuracy of ultrasound measurements in the diagnosis of renal allograft rejection.

Daily ultrasonographic measurements of transplant cross-sectional area were used to quantify allograft swelling as a diagnostic test for acute rejection in a series of 120 renal transplants. Initial graft function (IF) occurred in 86 patients (72%) and primary non-function (PNF) occurred in the remaining 34 (28%). An increase in allograft cross-sectional area greater than or equal to 10% was defined as a positive ultrasound scan suggesting an acute rejection episode and was investigated by needle core biopsy. During periods of PNF, allografts with consistently negative ultrasound scans were submitted to needle core biopsy on a weekly basis. The diagnosis of rejection was based exclusively on the histological findings. In the IF group, agreement between ultrasound and histological diagnosis was good (k = 0.63, sensitivity 81%, specificity 83%, positive predictive value 76%, negative predictive value 86% and overall accuracy 82%). In the PNF group, agreement between ultrasound and histology was only fair (k = 0.46, sensitivity 77%, specificity 70%, positive predictive value 69%, negative predictive value 78% and overall accuracy 73%). It is concluded that a degree of allograft swelling is sometimes associated with acute tubular necrosis, and this makes ultrasound measurements of transplant size a less useful technique of monitoring kidneys with PNF.

Comparison of two mechanical ultrasound devices with and without echogenic contrast dye

To evaluate the impact and limitations of intracoronary ultrasound, 64 segments of 13 isolated coronary arteries were examined and 2 mechanical devices (device A, 30 MHz 5Fr [CVIS] and device B, 20 MHz 4.8Fr [Diasonics/Boston Scientific] were compared with the corresponding histologic specimens. Luminal dimensions were assessed with and without echogenic contrast dye (Laevovist®, Schering AG, Germany). After application of contrast dye, correlation of luminal area between histology and ultrasound was improved from r = 0.62 to r = 0.77 (device B; p < 0.05) and from r = 0.82 to r = 0.88 (device A; p = NS). Low accuracy of lumen measurements in segments <2.5 mm could be improved by application of contrast dye. The number of quadrants in which wall thickness measurements were impossible was significantly higher for device B (n = 56; 22%) than for device A (n = 28; 11%); p < 0.01. This may be due to the different ringdown diameters of both systems (B, 2.6 mm; A, 2.0 mm; p < 0.0001). In assessing wall thickness only in segments of >2.5 mm, a reliable correlation between ultrasound and histology was found (A, r = 0.80; B, r = 0.60). Sensitivity of plaque (n = 51) detection was lower for device B (63%) than for device A (82%, p < 0.05), and measurements correlated with histology only for device A. There are considerable differences in the accuracy of ultrasound measurements between mechanical systems. Nevertheless, additional application of contrast dye can improve accuracy of luminal measurements, especially in smaller vessels.

Evaluation of ultrasound for prediction of carcass fat thickness and longissimus muscle area in feedlot steers.

Four hundred fifty-two yearling steers from two experiments were measured for subcutaneous fat thickness and longissimus muscle area between the 12th and 13th ribs using real-time linear array ultrasound equipment. Ultrasonic predictions were compared to corresponding carcass measurements to determine accuracy of ultrasound measurements. In Exp. 1, 74% of the ultrasonic estimates of fat thickness were within 2.54 mm of carcass values (r = .81) and muscle area was predicted within 6.45 cm2 for 47% of all carcasses (r = .43). Although similar correlation coefficients between ultrasonic and carcass fat thickness were obtained in Exp. 2 (r = .82), estimates were more biased; only 62% of ultrasound estimates were within 2.54 mm of carcass measurements. Improvement in longissimus muscle area estimates was noted in Exp. 2, in which 54% of ultrasonic estimates were within 6.45 cm2 of carcass values (r = .63). The extremes for each trait proved most difficult to predict; fat thickness was underestimated on fatter cattle and muscle area was underpredicted on more heavily muscled steers. Ultrasonic measurements of fat thickness are precise and accurate in determining carcass fat thickness, but muscle area estimates are inconsistent and warrant further investigation.

Comparison of pregnancy‐specific β1‐glycoprotein (SP1) and ultrasound in predicting the date of delivery

The accuracy of ultrasound measurements (crown-rump length and gestational sac diameter) and the serum concentration of pregnancy-specific beta 1-glycoprotein (SP1) in the prediction of the date of birth was analysed in a study population of 94 patients. When measured before 8 weeks after the last menstrual period (LMP) the serum concentration of SP1 was found to be a good predictor of the expected date of delivery and a good alternative to ultrasound, but it was of limited use when determined at a later gestation.