Items tagged “research”

The sensitivity of a test/investigation is defined as the ability of the test to identify true positive cases of the disease under question. Sensitive tests are useful for ruling out disease.  Calculation Sensitivity = true positives detected by test / total cases of the disease where total ca...

Specificity of a test/investigation is the ability of a test to be correctly negative (true negative) in persons without the disease in question. Calculation Specificity = true negatives detected by test / total cases without the disease where, total cases without the disease = true negative ...

Positive predictive value of a test/investigation is defined as the proportion of patients with positive results being truly diseased. Calculation Positive predictive value = true positives (TP) detected / total positive results (total positive results = true positive (TP) + false positive (F...

The p-value is defined as the probability in observing a value or effect equivalent to a value or effect observed when the null hypothesis is true. In other words, the p-value is based on the assumption that the null hypothesis is true By convention, p-value ≤0.05 is considered statistically si...

The nervus terminalis, also referred to as cranial nerve zero, cranial nerve XIII, zero nerve, nerve N or NT, is a previously unnumbered cranial nerve, most rostral of all cranial nerves. Gross anatomy It is a bilateral bundle of nerve fibers, which runs in the subarachnoid space from the medi...

ANOVA (ANalysis Of VAriance) is a statistical technique commonly seen in radiology research. ANOVA analyzes are conceptually similar to the student t-test, but involve comparison of multiple groups at once. The alternative to an ANOVA would be multiple head-to-head t-tests, but this would likel...

Case reports are a type of radiology research literature. They belong to the class of descriptive studies. Purpose The purpose of a radiology case report is to describe the patient history, clinical course, and imaging for a notable or unusual case. The case may be intended to aid other practi...

A case series is essentially a collection of case reports around a common theme. It belongs to the class of descriptive studies. Structure A case series typically contains: a short introduction the series of cases patient history, presentation, imaging, and clinical course are described in ...

The likelihood ratios (LR) can be useful to judge the probability of an event. They allow to calculate predictive values ​​independent of disease prevalence: LR+ = sensitivity / (1 - specificity) LR- = (1 - sensitivity) / specificity

The Pearson's chi-squared test is one of the most common statistical tests found in radiology research. It is a type of non-parametric test, used with two categorical variables (not continuous variables). Concept The heart of the chi-squared test is a 2 x 2 contingency table. We usually have ...

The paired t-test is the appropriate method when the researcher takes an experimental group, measures the baseline, subjects the members to an intervention, and then measures the results. Testing in a before-and-after manner like this ("matched data" or "repeated measures") requires a different...

Kappa is a nonparametric test that can be used to measure interobserver agreement on imaging studies. Cohen's kappa compares two observers, or in the case of machine learning can be used to compare a specific algorithm's output versus labels. Fleiss' kappa assesses interobserver agreement betwee...

Confusion matrices, a key tool to evaluate machine learning algorithm performance in classification, are a statistical tool. Contingency tables, a type of confusion matrix, are used in the evaluation of many diagnostic exams for sensitivity, specificity, positive and negative predictive values....

Retrospective studies are cohort or case-control studies that analyze existing data from before the time point at which the study began. These studies are more susceptible to bias and confounding than prospective studies.

Magnetic particle imaging (MPI) is an emerging cross-sectional imaging technique that in the future may be a new clinical imaging modality offering high resolution, dynamic functional imaging without utilizing ionizing radiation.  Physics Magnetic particle imaging is a tracer imaging technique...