Head ultrasound (HUS), also called cranial ultrasound (CUS), is obtained for the diagnosis and follow-up of premature and sick neonates.
Head ultrasound has the advantages of:
mobility, i.e. bedside scanning at the NICU and neonatal ward
requiring no sedation
LI-RADS (Liver Imaging Reporting and Data System) is both a set of standardized terminology and a classification system for imaging findings in liver lesions. The LI-RADS score for a liver lesion is an indication of its relative risk for hepatocellular carcinoma (HCC). The classification system ...
Hickam's dictum is usually stated as "patients can have as many diseases as they damn (or darn) well please". This aphorism has been attributed to John Hickam (1914-1970) an American physician, who was Chair of the Department of Medicine at the University of Indiana 1.
The importance of this d...
Hindfoot equinus describes abnormal plantarflexion (calcaneotibial angle >90°) of the foot that occurs in the hindfoot. It occurs in congenital talipes equinovarus and congenital vertical talus.
High-resolution CT (HRCT) of the chest, also referred to as HRCT chest or HRCT of the lungs, refers to a CT technique in which thin-slice chest images are obtained and post-processed in a high-spatial-frequency reconstruction algorithm. This technique obtains images with exquisite lung detail, w...
Expiratory high-resolution CT (HRCT) imaging corresponds to an additional CT acquisition performed as part of the HRCT chest protocol. It represents a scan performed with the patient on supine and images obtained at the end-expiration.
It is a useful method for detecting small airways obstruct...
A hyperechoic liver lesion on ultrasound can arise from a number of entities, both benign and malignant. A benign hepatic hemangioma is the most common entity encountered, but in patients with atypical findings or risk for malignancy, other entities must be considered.
Hysterosalpingogram (HSG) is a fluoroscopic examination of the uterus and the Fallopian tubes, most commonly used in the investigation of infertility or recurrent spontaneous abortions.
Infertility to assess uterine morphology and tubal patency.
The approach to HRCT chest in patients with suspected idiopathic interstitial pneumonia (IIP) is with the aim to:
make sure an appropriate study requested i.e. HRCT chest with optimal individually adjusted protocol and ensure adequacy of the HRCT chest quality (see imaging protocol below)
Imaging in liver transplantation is aimed to evaluate donor and recipient for successful transplantation and its outcome.
volume of liver
parenchymal disease (diffuse or focal)
Gunshot injuries often require imaging assessment, and this evaluation has both clinical relevance (assessment of organ damage, surgical planning, and prognostication), and often also forensic implications.
Incidence of gunshot injuries to the head is increasing in some countries,...
Incidental lung nodules are encountered commonly in normal clinical practice on CT. The risk of developing cancer in very small nodules (<5 mm) is very low. However, clear-cut recommendations are still not in place with high variation in practice amongst reporting radiologists 1. As a result, it...
Incidental thyroid nodules, sometimes called thyroid incidentalomas, are discrete lesions in the thyroid gland found on cross-sectional imaging performed for indications other than thyroid evaluation. They are common but occasionally represent thyroid cancer 1. This article discusses the epidemi...
Increased retrosternal airspace is an indicator of hyperinflation of the lungs and is usually due to emphysema.
The thickness of the space between the ascending aorta and the posterior margin of the sternum (3 cm inferior to the sternomanubrial joint) and is normally no more than 2.5 cm 1 altho...
It is important to have a systematic way of approaching a case with subfertility in the exam.
Ultrasound is the initial examination of choice. Always say that you would further assess the uterus with 3D ultrasound. You may also say that in my department we would perform a sonohysterogram or HS...
Intercaudate distance to inner table width ratio (CC/IT) is used in assessing patients with neurodegenerative diseases that affect the caudate nuclei. It is best known for assessing individuals with suspected Huntington disease but is in no way specific for the diagnosis, also seen in other less...
The intermetatarsal (IM) angle refers to the angle measured between the 1st and 2nd metatarsal shaft on an axial view of the foot. In normal situations it is considered to be under 9°. The angle can increase with hallux valgus and metatarsus adductus deformities.
An interscalene brachial plexus block is indicated for procedures involving the shoulder and upper arm.
Ultrasound-guided brachial plexus nerve blocks entered the literature in 1989, when Ting et al. detailed their success with axillary nerve blocks in 10 patients 3.
The interseptal distance (ISD) is a measurement used to assess septal area atrophy as a marker for neurodegenerative conditions in patients with memory problems 1.
It is proposed that atrophy of the septal nuclei can commonly be seen in conditions associated with hippocampal atrophy, particular...
Intervertebral disc disease nomenclature has changed over the years, and a familiarity with current definitions is essential if clear communication is to be achieved via radiology reports or referrals, especially as lumbar disc disease is a common problem and a source of a great deal of imaging....
The interzygomatic line is a commonly used reference standard for the evaluation of proptosis due to various etiologies on CT/MRI scans.
A horizontal line should be drawn between the most anterior parts of the zygomatic bones in the axial plane.
The normal distance of the interzygom...
Intracranial nonneoplastic cysts are common findings in magnetic resonance (MR) and computed tomographic (CT) brain scans.
Location-based diagnostic approach
A location-based approach is useful in establishing an appropriate diagnosis; some locations are virtually pathognomonic for certain les...
Intradural spinal mass lesions are relatively uncommon, compared to intracranial or extradural masses, and can be challenging to diagnose. Additionally, the need for a pre-operative/non-operative diagnosis is in many ways greater as biopsy of lesions within the cord has the potential of devastat...
The ventricular system of the brain plays host to a variety of unique tumors, as well as tumors that are more frequently seen elsewhere (e.g. meningiomas). Besides, some intra-axial (parenchymal) masses can be mostly exophytic and thus appear mostly intraventricular. A systematic approach taking...
Iodinated contrast media adverse reactions, popularly but erroneously referred to as contrast allergies (see Terminology below), are an uncommon group of symptoms and signs, with different degrees of severity, that may occur after the administration of these drugs.
Anaphylactic-type reactions ...
The International Ovarian Tumor Analysis (IOTA) group ultrasound rules for ovarian masses are a simple set of ultrasound findings that classify ovarian masses into benign, malignant or inconclusive masses. These rules apply to masses that are not a classical ovarian mass (e.g. corpus luteum, end...
The Isikoff's view is a sonographic view which demonstrates the origins of the right and left renal arteries. It is taken in the longitudinal plane with the patient in the left lateral decubitus position 1.
Isolated free fluid in trauma may or may not represent a significant injury, and this creates a diagnostic dilemma in determining appropriate treatment for these patients.
The presence of isolated free fluid in trauma occurs in 3-5% of blunt trauma patients 1-4.
Isomerism is a term which in general means 'mirror-image'. It is used in the context of heterotaxy and is of two types:
Mirror image of the structures on the left side of the chest along the left-right axis of the body, i.e. patients with isomeri...
A joint effusion is defined as an increased amount of fluid within the synovial compartment of a joint.
There is normally only a small amount of physiological intra-articular fluid. Abnormal fluid accumulation can result from inflammation, infection (i.e. pus) or trauma and may be an exudate, t...
Check for an effusion on the lateral:
peripatellar fat pads should sit next to each other
anterior suprapatellar fat pad
prefemoral fat pad
soft tissue density between them indicates an effusion
if simple effusion (hemarthrosis), think severe ligamentous, menis...
Lanthanum therapy is used to treat hyperphosphatemia in end-stage renal disease 1. It is taken as oral tablets (usually in the chemical form Lanthanum carbonate) which dissociate in the acidic environment of the stomach. The released trivalent Lanthanum cation has a high affinity for dietary pho...
Left atrial enlargement (LAE) may result from many conditions, either congenital or acquired. It has some characteristic findings on a frontal chest radiograph. CT or MRI may also be used for diagnosis.
An enlarged left atrium can have many clinical implications, such as:...
Getting a film with left upper lobe collapse in the exam is one of the many exam set-pieces that can be prepared for.
This frontal chest radiograph shows a hazy (or veil-like*) opacification of the left hemithorax that is associated with superior displacement left hilum and horizon...
Left ventricular ejection fraction (LVEF) is a surrogate for left ventricular global systolic function, defined as the left ventricular stroke volume divided by the end-diastolic volume.
Point-of-care echocardiography protocols typically use a semi-quantitative approach in defining...
Left ventricular outflow tract (LVOT) obstruction describes a state in which the egress of blood from the left ventricle to the systemic circulation is impeded as it traverses the anatomic LVOT to the aortic arch. Echocardiography, particularly with the use of spectral Doppler, may be used to de...
Lines and tubes are important components in chest radiographic evaluation.
Nasogastric (NG) tube
See: nasogastric tube positioning.
NG tube tip ≥10 cm distal to the gastro-esophageal junction
i.e. below the left hemidiaphragm
insertion into trachea or bronc...
This is a basic article for medical students and other non-radiologists
Lobar collapse is relatively common and occurs following obstruction of a bronchus. Gas is resorbed from the lung parenchyma distal to the obstruction resulting in the collapse of the lung, with volume reduction and negativ...
A lobectomy (plural: lobectomies) is the complete resection of one lobe of the lung and is the commonest lung surgery performed for bronchogenic carcinoma.
A posterolateral thoracotomy is the commonest approach for the resection of lung malignancies. For other surgical approaches for...
The parotid gland consists of a superficial and deep lobe. Determining the location and extent of the lesions affecting the gland is an essential aspect of imaging and vital information which needs to be conveyed to the surgeon.
Method of evaluation
The following lines are proposed for differe...
The lower zone is one of the four chest radiograph zones.
on frontal chest radiographs, extends inferiorly from the inferior aspect of the hilum to the hemidiaphragm
Low grade central osteosarcoma is an uncommon subtype of osteosarcoma accounting less than 1% of all osteosarcomas.
Low grade osteosarcoma affects individuals of higher age group as compare to the other subtypes of osteosarcoma. The usual age of presentation is 19 to 54 years with...
The IASLC (International Association for the Study of Lung Cancer) 8th edition lung cancer staging system was introduced in 2016 and supersedes the IASLC 7th edition.
Standard-of-care lung cancer staging ideally should be performed in a multidisciplinary meeting using the information provided ...
Lymph node imaging is a useful technique, aiding the clinician in determining whether nodes are benign or malignant. Multiple modalities are used for the assessment and characterization of lymph nodes, each with its advantages and drawbacks.
Magnetic resonance neurography (MRN) is a relatively new non-invasive imaging technique for dedicated assessment of peripheral nerves.
It is used to assess peripheral nerve entrapments and impingements as well as localization and grading of nerve injuries and lesions.
Malignant ovarian lesions can have typical sonographic features, and thus ultrasound is the imaging of choice for initial evaluation of suspected ovarian neoplasm.
The features of malignant ovarian neoplasm on ultrasonography include:
mass >10 cm with locula...
Mammography is a dedicated radiographic technique for imaging the breast.
Types of mammography
In general terms, there are two types of mammography: screening and diagnostic.
Mammography differs significantly in many respects from the rest of diagnostic imaging.
The Management of Incidental Adrenal Masses revised in 2017 by the Adrenal Subcommittee of the Incidental Findings Committee of the American College of Radiology is an algorithm for the management of patients who are:
adults (i.e. 18-year-old or over)
asymptomatic for adrenal pathology
The differential diagnosis of a mass in the inguinal region includes:
hydrocele of the canal of Nuck
lymphadenopathy or necrotic lymph node
aneurysm or pseudoaneurysm of the femoral artery
The McGill Thyroid Nodule Score (MTNS) is a scoring system developed to estimate the risk of malignancy of thyroid nodules.1
The MTNS is based on 22 parameters:
eight clinical or laboratory parameters
gender (male): 1 point
age (>45 years old): 1 point
palpable nodule (prese...
McGrigor-Campbell lines are imaginary lines traced across the face on an occipitomental (Waters) view skull radiograph to assess for fractures of the middle third (especially) of the face3:
first line is traced from one zygomaticofrontal suture to another, across the superior edge of the orbits...
The McMurray test is used to assess the presence of meniscal tears within the knee.
Clinical tests used for the detection of meniscal tears provide varying levels of diagnostic parameters including sensitivity and specificity. MRI is considered the most accurate diagnostic tool for ...
The medial temporal lobe atrophy (MTA) score is useful in distinguishing patients with mild cognitive impairment and Alzheimer disease from those without impairment 2 is helpful in the assessment of patients with possible dementia (see neurodegenerative MRI brain - an approach).
Midfoot equinus is an abnormality in foot alignment where there is abnormal plantarflexion of the foot in the midfoot.
Midfoot equinus occurs as a component of congenital talipes equinovarus.
The mid (or middle) zone is one of the four chest radiograph zones.
on frontal chest radiographs, extends between the superior and inferior aspects of the hilum
M-line of Cremin is an imaginary line that can be used to determine the level at which the blind pouch ends in anal atresia, determining whether the anal atresia is a high or a low type.
The line is drawn perpendicular to the long axis of the ischium on the lateral view and passes through the j...
Monoarticular arthropathy can result from a number of causes:
HADD (hydroxyapatite deposition disease)
MR enterography is a non-invasive technique for diagnosis of small bowel disorders.
MR enterography is most commonly used to evaluate patients with Crohn disease where it is used for assessment of the primary disease and any complications. Other indications include celiac disease, ...
MRI of the brachial plexus is used to provide a causal diagnosis for brachial plexopathies. It provides clear structural analysis of the brachial plexus, its intraneural integrity, as well as surrounding structures 1,3.
brachial plexus injuries
grading of brachial plexus inj...
MRI targeted prostate biopsy refers to an imaging targeted technique rather than the traditional systematic approach of a prostate biopsy after respective imaging with multiparametric MRI (mpMRI) of the prostate.
As a consequence of the recent advances of multiparametric MRI (mpMRI) of the pros...
Mulder sign is a clinical test used to examine causes of metatarsalgia associated with Morton neuroma. It has high specificity (100%) but relatively low sensitivity (62%) 2.
With one hand, clasp the metatarsal heads between the thumb and fingers or thenar eminence and fingers. Place ...
Multiphase CT angiography is an evolving imaging technique in acute ischemic stroke. The technique aims to quickly and reliably identify brain which is potentially salvageable with intervention. Brain tissue viability depends on many factors, with this technique assessing collateral leptomeninge...
Myocardial mapping or parametric mapping of the heart is one of various magnetic resonance imaging techniques, which has evolved and been increasingly used in the last decade for non-invasive tissue characterization of the myocardium 1-5. Unlike normal T1-, T2- or T2*- images, parametric mapping...
Occasionally, we will refer to lifeforms in an article or case, and we adhere to standard scientific convention when it comes to naming organisms. as set down by the International Commision on Zoological Nomenclature (ICZN) 1. As per the standard binomial system, the genus and species of the org...
Assessment of nasogastric (NG) tube positioning is a key competency of all doctors as unidentified malpositioning may have dire consequences, including death.
Evaluation of NGT
The ideal position should be in the subdiaphragmatic position in the stomach - identified on a plai...
This is a basic article for medical students and other non-radiologists
Nasogastric (NG) tube position on chest x-ray should be assessed following initial placement and on subsequent radiographs.
This is a summary article; we have a more in-depth reference article NGT.
The neonatal chest radiograph in the exam setting may strike fear into the heart of many radiology registrars, but it need not!
There are only a limited number of diagnoses that will be presented on such films and they are often highlighted by the history.
First of all, have a look ...
Neonatal pneumothorax describes pneumothoraces occurring in neonates. It is a life-threatening condition, associated with high morbidity and mortality. The diagnosis is a challenge especially when the amount of air is small and may accumulate along the anterior or medial pleural space.
Imaging of the brain in patients with suspected neurodegenerative conditions is common and challenging, as in patients with subtle and equivocal signs and symptoms, the imaging findings are also often subtle and equivocal. In many instances, by the time imaging findings are clear cut, then the p...
NEXUS (National Emergency X-Radiography Utilization Study) is a set of validated criteria used to decide which trauma patients do not require cervical spine imaging.
Trauma patients who do not require cervical spine imaging require all of the following:
alert and stable
no focal neurologic de...
Nipple markers can be a useful technique in the evaluation of small radiodensities overlying the expected position of the nipple on a chest radiograph. Not uncommonly a small round opacity projects over the lower thorax on a chest radiograph (see: solitary pulmonary nodule).
Often, especially i...
In the premultidetector CT era, mesenteric lymph nodes (often shortened to mesenteric nodes) were only really appreciated when enlarged. Following the advent of routine volume acquisition CT (and especially coronal reformats) lymph nodes in the mesentery are commonly seen in normal individuals, ...
Normal pulmonary venous blood flow in the pulmonary veins may be investigated during echocardiography with spectral Doppler analysis. Perturbations in the normal pulmonary venous waveform may indicate the presence of diastolic dysfunction and elevated filling pressures in the left atrium and ven...
Normal radiographic measurements of the shoulder are important in evaluation of the osseous relationships in plain film radiography. Normal measurements do not rule out pathology, and must be considered in the context of other findings and the clinical presentation.
AC joint space: 2-4 mm
Occam's razor (also known as lex parsimoniae), an often cited principle of parsimony, economy, or succinctness used in problem-solving. It has also been expressed as the KISS principle or "Keep it simple stupid!".
It states that among competing hypotheses, the one with the fewest assumptions sh...
Esophageal intubation refers to the incorrect placement of an endotracheal tube in the esophagus. Within minutes its consequences can be catastrophic with the seriousness of its outcome depending largely on the timeliness of its diagnosis.
Accidental esophageal intubation can happ...
Bipolar shoulder lesions of anterior glenohumeral dislocations (i.e. combined bony Bankart and Hill-Sachs lesions) put patients at increased risk of Hill-Sachs engagement or recurrent instability. Determining if the Hill-Sachs lesions are on-track or off-track can help guide management, although...
Optic nerve sheath diameter has significance in the assessment of papilledema in cases of elevated intracranial pressure.
The optic nerve sheath demonstrates changes in diameter with CSF pressure changes as there is a layer of subarachnoid space between the nerve and its sheath, whic...
Differential diagnosis of lytic bone lesions with septations and trabeculations include 1:
unicameral bone cyst
aneurysmal bone cyst
giant cell tumor
The Ottawa ankle rules are a clinical decision-making strategy for determining which patients require radiographic imaging for ankle and midfoot injuries. Proper application has high (97.5%) sensitivity and reduces the need for radiographs by ~35% 1,2,4.
There are two components, assessing for...
The Ottawa knee rules are a clinical decision-making strategy for determining which patients require radiographic imaging for knee pain.
A patient with knee pain qualifies for knee radiographs if any of the following apply:
55 years or older
point tenderness at the fibular head
Pediatric elbow radiographs are commonly encountered in the emergency department and, when approached in a systematic fashion, are not as difficult to interpret as most people think!
Check that the ossification centers are present and in the correct position. Th...
The British National Institute for Health and Care Excellence (NICE) published the “Urinary tract infection in under 16s: diagnosis and management” in 2007 as a guideline for pediatric urinary tract infection (UTI) management, including imaging, prophylaxis and follow-up 1.
This article intend...
There are a number of pain rating scales used by clinicians and researchers to gauge the severity of patients' pain. Commonly used methods:
pain numeric rating scale (NRS/NPRS)
visual analog scale (VAS)
verbal rating scale (VRS)
faces pain scale-revised (FPS-R)
Pain numeric rating scale
Pancreatic ultrasound can be used to assess for pancreatic malignancy, pancreatitis and its complications, as well as for other pancreatic pathology.
Fast the patient to reduce interference from overlying bowel gas, which may otherwise make visualization difficult.
Paragonimiasis is a disease caused by several species of the trematode genus Paragonimus.
More than 50 different species of Paragonimus have been described in Asia, Africa, and the Americas and of those nine species infecting humans. The most important species is Paragonimus Westermani, which ...
The term pathognomonic in radiology, as well as clinical medicine in general, refers to a finding or a sign that is only found in a single specific condition or specific group of conditions, i.e. the finding has 100% specificity. Thus by implication, a pathognomonic finding cannot and does not h...
Pathology checklists are really helpful when reporting a radiograph, ultrasound or cross-sectional examination. It is a key way to ensure that you fully review a film and don't fall foul of satisfaction of search.
Plain film radiographs
skull radiograph checklist
facial bones ra...
Recognizing patterns of sinonasal obstruction is useful to help localize the area of pathology and narrow the differential diagnosis.
Babbel et al described five pattern of sinonasal obstruction 1, which are readily apparent on CT:
The PECARN (Pediatric Emergency Care Applied Research Network) traumatic brain injury algorithm is a clinical decision rule that aims to identify children at very low risk of clinically important traumatic brain injury (ci-TBI) 1. This validated pediatric algorithm predicts likelihood of the abo...
It is important to have a systematic way of approaching a case with pelvic pain in the exam.
Most examinations are performed using ultrasound. Always say that you would further assess the uterus with 3D ultrasound. You may also say that in my department we would perform a sonohysterogram. Only...
trace the main pelvic ring and two obturator foramina
if a ring is disrupted, think fracture... then look for a second one
the sacroiliac joints should be symmetrical, joint space range 2-4 mm
the symphysis pubis joint space should be ≤5 mm
Pelvic ultrasound is usually the initial modality for imaging gynecologic pathology, including acute pelvic pain and chronic pelvic pain. The exam normally involves two components: a transabdominal (TA) evaluation and a transvaginal (TV) / endovaginal (EV) evaluation.
Normal ultrasound anatomy