In medicine we often want to compare two different methods of measuring some quantity, such as blood pressure, gestational age, or cardiac stroke volume. Sometimes we compare an approximate or simple method with a very precise one. This is a calibration problem, and we shall not discuss it further here. Frequently, however, we cannot regard either method as giving the true value of the quantity being measured. In this case we want to know whether the methods give answers which are, in some sense, comparable. For example, we may wish to see whether a new, cheap and quick method produces answers that agree with those from an established method sufficiently well for clinical purposes. Many such studies, using a variety of statistical techniques, have been reported. Yet few really answer the question “Do the two methods of measurement agree sufficiently closely?” In this paper we shall describe what is usually done, show why this is inappropriate, suggest a better approach, and ask why such studies are done so badly. We will restrict our consideration to the comparison of two methods of measuring a continuous variable, although similar problems can arise with categorical variables.

/pdf/measurement-in-medicine-the-analysis-of-method-comparison-2du2zwl4ni.pdf

Measurement in Medicine: The Analysis of Method Comparison Studies

https://www.gastrojournal.org/article/S0016-5085(02)00166-X/pdf

The utility of radiological imaging in nonalcoholic fatty liver disease

The aim of the study was to correlate the sonographic [ultrasound (US)] and color-Doppler (CFD) findings with the results of US-guided fine needle aspiration biopsy (FNA) and of pathologic staging of resected carcinomas to establish: 1) the relative importance of US features as risk factors of malignancy; and 2) a cost-effective management of nonpalpable thyroid nodules. Four hundred ninety-four consecutive patients with nonpalpable thyroid nodules (8–15 mm) were evaluated by US, CFD, and US-FNA. Ninety-two patients with inadequate cytology were excluded from the study. All patients with suspicious or malignant cytology underwent surgery, whereas subjects with benign cytology had clinical and US control 6 months later. Thyroid malignancies were observed in 18 of 195 (9.2%) solitary thyroid nodules and in 13 of 207 (6.3%) multinodular goiters. Cancer prevalence was similar in nodules greater or smaller than 10 mm (9.1 vs. 7.0%). Extracapsular growth (pT4) was present in 35.5%, and nodal involvement in 19.4...

/pdf/risk-of-malignancy-in-nonpalpable-thyroid-nodules-predictive-kh93bwpgur.pdf

Risk of malignancy in nonpalpable thyroid nodules: predictive value of ultrasound and color-Doppler features.

https://aasldpubs.onlinelibrary.wiley.com/doi/pdf/10.1002/hep.24452

Diagnostic accuracy and reliability of ultrasonography for the detection of fatty liver: A meta‐analysis

Background: The introduction of highly sensitive imaging techniques has made it possible to detect many nonpalpable nodules, or “incidentalomas,” in the thyroid. Discovery of these lesions raises c...

Thyroid Incidentalomas: Management Approaches to Nonpalpable Nodules Discovered Incidentally on Thyroid Imaging

/pdf/bronchiolitis-obliterans-roentgenologic-pathologic-2ltu1yw2z3.pdf

Bronchiolitis obliterans. Roentgenologic-pathologic correlation.

The effect of perfluoroctylbromide (PFOB) on liver and tumor echogenicity was evaluated in rabbits. The echogenicity of the kidney, which is not affected by PFOB, was used as the basis for comparison in the liver studies. For the liver echogenicity study, sonography was performed on four rabbits, two with PFOB and two without PFOB, and four rabbits prior to and following the intravenous administration of 5 ml/kg PFOB. All livers were equal to or less echogenic than kidney in the control animals. All livers became more echogenic than kidney two days after administration of PFOB. The effect of PFOB on tumor echogenicity was evaluated in 18 rabbits with VX2 tumor implanted in the liver. Ultrasound studies of all rabbits were performed by the same physician before and two days after half the rabbits had received PFOB (5 ml/kg intravenously). The reviewers correctly identified all rabbits that received PFOB by visualization of an echogenic rim around the hepatic tumors.

Perfluoroctylbromide: a liver/spleen-specific and tumor-imaging ultrasound contrast material.

Cross-sectional echocardiography is a new noninvasive technique for imaging the heart. We developed a method for using mechanical cross-sectional echocardiograms (sector scans) to determine left ventricular volumes and ejection fraction. Using left ventricular cineangiography as a standard, sector scan ejection fraction correlated better (r = 0.93) than M-mode echocardiography by any of three established methods, and the sector scan regression line did not differ from the line of identity (p greater than 0.33). Interobserver variability for sector scan ejection fraction was 2.3 +/- 1.2% (mean +/- SD). Variation between two studies performed within 24 hours and analyzed by the same observer was 1.4 +/- 1.5%. However, the sector scans consistently underestimated left ventricular end-diastolic volume. We conclude that sector scan echocardiography is more reliable than conventional M-mode technique for estimating left ventricular ejection fraction, but estimation of left ventricular end-diastolic volume is unreliable with the methods currently available.

Measurement of left ventricular ejection fraction by mechanical cross-sectional echocardiography.

Objective : The purpose of this study is to evaluate the utility and feasibility of abdominal ultrasound (US) in blunt trauma patients. Design : This prospective study examined the operational issues and the diagnostic accuracy of US in selected blunt trauma patients triaged to a Level 1 trauma center. Materials and Methods : All patients were evaluated by an attending trauma surgeon and our usual criteria for objective evaluation of the abdomen were applied. US was performed by US technicians and interpreted by the trauma surgeon. We prospectively evaluated the availability (time to arrival), the ease with which the US could be integrated into the resuscitation (minutes to start after arrival), and the time required to perform the study. The US results were compared to diagnostic peritoneal lavage and computed tomography findings, clinical course, operative findings, and to repeat US examinations to determine sensitivity, specificity, and usefulness. Measurements and Main Results : A total of 800 US studies were performed over IS months. In four cases (0.5%), the US was incomplete for technical reasons. The results in the remaining 796 studies were as follows : True negative 728 Sensitivity 88.2% True positive 45 Specificity 97.7% False positive 17 Positive predictive index 72.3% False negative 6 Negative predictive index 99.2% Overall accuracy = 97.1% The average time to arrival of the US was 17.3 minutes (range 0-120) and the average minutes to start after arrival was 7.0 (range 1-49). The average time required to perform the study was 10.6 minutes (range 2-26). Conclusions : This study demonstrates that US can be obtained rapidly, integrated into the resuscitation, and completed quickly. US provides a highly accurate, noninvasive method to evaluate the abdomen in the blunt trauma patient, and has supplanted the previously used methods at this institution.

A prospective evaluation of abdominal ultrasound in blunt trauma: is it useful?

Retrospective evaluations were made of abdominal echograms in 61 patients who underwent liver biopsy within 3 weeks after ultrasound study Without knowledge of clinical or biopsy data, determinations were made by two independent observers of: (1) liver size, (2) beam penetration, (3) echogenicity, (4) vascularity, (5) ancillary abnormality, and (6) diagnostic impression Using these parameters, the presence of generalized parenchymal disease was identified in 81% of reviews of patients with cirrhosis Thus, in patients with known cirrhosis, there was a 19% false negative rate In normal patients, 76% were correctly called normal by the reviewers However, in 24% generalized parenchymal disease was suggested (24% false positive) Patients with fatty liver could not be reliably distinguished from patients with cirrhosis, nor could patients with hepatitis be easily separated from those with normal livers In all of these determinations, the combination of several features provided more diagnostic accuracy than any single echographic finding

https://www.ajronline.org/doi/pdfplus/10.2214/ajr.133.1.19

Barbara B. Gosink

Papers

Bronchiolitis obliterans. Roentgenologic-pathologic correlation.

Perfluoroctylbromide: a liver/spleen-specific and tumor-imaging ultrasound contrast material.

Measurement of left ventricular ejection fraction by mechanical cross-sectional echocardiography.

A prospective evaluation of abdominal ultrasound in blunt trauma: is it useful?

Accuracy of ultrasonography in diagnosis of hepatocellular disease.