# Items tagged “research”

Article

#### Sensitivity

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...

Article

#### Specificity

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 ...

Article

#### Positive predictive value

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...

Article

#### p-value

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...

Article

#### Nervus terminalis

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...

Article

#### ANOVA

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...

Article

#### Case report

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...

Article

#### Case series

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 ...

Article

#### Likelihood ratios

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

Article

#### Pearson's chi-squared test

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 ...

Article

#### Paired t-test

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...

Article

#### Kappa

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...

Article

#### Confusion matrix

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....

Article

#### Retrospective study

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.

Article

#### Magnetic particle imaging

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...