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 disk 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 disk disease is a common problem and a source of a great deal of imaging....
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...
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...
Left atrial enlargement 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 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 the ej...
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...
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 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 mea...
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...
The McGregor line is a modification of the Chamberlain line and is used in the evaluation of basilar invagination when the opisthion is not identified on plain radiographs.
It refers to a line connecting posterior edge of the hard palate to the most caudal point of the occipital curve. If the t...
McGrigor-Campbell lines are imaginary lines traced across the face on an occipitomental (Waters) view skull radiograph to assess for fractures:
first line is traced from one zygomaticofrontal suture to another, across the superior edge of the orbits
second line traces the zygomatic arch, cross...
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...
The modified PIOPED criteria for the diagnosis of pulmonary embolus (PE) determine the probability of pulmonary emboli following a VQ scan.
two or more large mismatched segmental defects or equivalent moderate/large defects with a normal x-ray
any perfusion de...
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...
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...
Assessment of nasogastric (NG) tube positioning is a key competency of all doctors as unidentified malpositioning may have dire consequences, including death.
The ideal position should be in the sub-diaphragmatic position in the stomach - identified on a plain chest radiograph as overlying the ...
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 subtle and equivocal. In many instances, by the time imaging findings are clear cut, then the patient...
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:
alert and stable
no focal neurologic deficit
no altered level of co...
Nipple markers can be a useful technique in the evaluation of densities 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 in women, th...
In the pre-multidetector CT era, mesenteric lymph nodes were only really appreciated when enlarged. Following the advent of routine volume acquisition CT (and especially coronal reformats) they are commonly seen in normal individuals, which has raised the obvious question of what counts as mesen...
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
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...
Optic nerve sheath diameter has significance in the assessment of papilloedema 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, whi...
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...
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.
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...
Recognising patterns of sinonasal obstruction is useful to help localise 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 gynaecologic 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...
Penile Doppler in erectile dysfunction or papaverine-induced color duplex Doppler, is a highly accurate means of assessing patients with erectile dysfunction (ED).
Penile erection is a result of a complex interaction between the nervous, arterial, venous and sinusoidal systems. Any d...
Getting a film with perigestational hemorrhage in the exam is one of the many exam set-pieces that can be prepared for.
Transabdominal and transvaginal (TV) pelvic ultrasound shows an anteverted uterus with an intrauterine gestational sac. MSD is 20 mm in TV study with a single, l...
It is important to have a systematic way of approaching a case with per vaginal bleeding in the exam.
intrauterine fetal demise
Physiological pelvic intraperitoneal fluid refers to the presence of a small volume of free fluid in the pelvis, particularly the pouch of Douglas. It occurs in young females of reproductive age and can be a mimic of traumatic free fluid in abdominal trauma.
Unfortunately, pelvic free fluid may...
A systematic approach to the pineal region is crucial as it is at the confluence of many intracranial structures/regions and is the site of origin of a number of unique pathologies as well as playing host to many entities which are more frequently encountered elsewhere. As such an understanding ...
A systematic approach to the pituitary region is crucial as small lesions can have a profound impact on the patient, and can be subtle even on high quality dedicated MRI imaging. Successful assessment of the pituitary region relies not only on a clear understanding of the local anatomy but also ...
Getting a film with placental abruption (premature separation of placenta from uterus) in the exam is one of the many exam set-pieces that can be prepared for.
Transabdominal and transvaginal pelvic ultrasound show a single live fetus with gestational age of 27 weeks. The cervix i...
Measurement of a pleural effusion volume with point-of-care ultrasonography may be a useful tool for intensivists, and is an active area of research in critical care 7.
In controlled settings ultrasound may detect constitutive pleural fluid, can reliably detect effusions >20mL in clinical setti...
Pneumothorax (PTX) (plural: pneumothoraces) refers to the presence of gas (air) in the pleural space. When this collection of gas is constantly enlarging with resulting compression of mediastinal structures, it can be life-threatening and is known as a tension pneumothorax (if no tension is pres...
Getting a film with a pneumothorax in the exam is one of the many exam set-pieces that can be prepared for.
It is unlikely that they will give you a simple pneumothorax - so, it is worth while considering the likely causes and whether it is under tension. Miss it at your peril (both in real l...
The point-of-care ultrasound (PoCUS) curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core applications of ultrasonography in a point-of-care setting.
Point-of-care ultrasound refers to ultrasonography which may be simultaneously performed,...
Getting a film with polycystic ovarian syndrome in a subfertile patient is one of the many exam set-pieces that can be prepared for.
Transabdominal and transvaginal pelvic ultrasound show an anteverted uterus with a normal size. There is diffuse thickening of the endometrium to 17...
Polydactyly (less commonly called hyperdactyly) refers to the situation where there are more than the usual number of digits (five) in a hand or foot. It can be broadly classified as:
pre-axial polydactyly: extra digit(s) towards the thumb/hallux (radially)
post-axial polydactyly: extra digit(...
Prosthetic cardiac valves are a routine finding on chest X-ray. The frequency and degree of exposure is greatest in larger hospitals with cardiothoracic centers, however, prosthetic valves are commonplace universally.
Recognition of which valve has been replaced, any other related cardiothoraci...
Pulmonary nodules are small, rounded opacities within the pulmonary interstitium. Pulmonary nodules are common and, as the spatial resolution of CT scanners has increased, detection of smaller and smaller nodules has occurred, which are more often an incidental finding.
Five lines have been described and used by most of the radiologists to evaluate basilar invagination on frontal and lateral skull plain radiographs as well as coronal and midsaggital reconstructed CT images.
This is based on the relative projection of odontoid process to these lines, which is a...
Radiographic evaluation of anterior cruciate ligament (ACL) reconstruction involves:
a line is drawn along the posterior cortex of the femur
a second line is drawn along the roof of the intercondylar notch of the femur (Blumensaat line)
the point of intersection of these tw...
Radiographic positioning terminology is used routinely to describe the position of the patient for taking various radiographs. Standard nomenclature is employed with respect to the anatomic position.
Basic terms of relations
anterior is towards the front of the body (Latin: before...
Response assessment in neuro-oncology criteria (RANO), published in 2010 1, are used to assess response to first-line treatment of glioblastoma (as well as lower grade astrocytoma 3) and have largely superseded the older Macdonald criteria (which only dealt with glioblastoma multiforme) 2.
The rapid ultrasound in shock (RUSH) protocol is a structured point-of-care ultrasound (POCUS) examination performed at the time of presentation of a shocked patient. It is a more detailed and longer exam than the FAST scan, with the aim to differentiate between hypovolemic, cardiogenic, obstruc...
Lower back pain is very common and often referred for imaging, with the vast majority of cases due to benign self-limiting causes which don't require imaging and resolve with conservative measures. Numerous authors have described various methods for supporting appropriate imaging for the investi...
Renal artery stenosis (RAS) refers to a narrowing of a renal artery. When the process occurs slowly, it leads to secondary hypertension. Acute renal artery stenosis does not lead to hypersecretion of renin.
When the stenosis occurs slowly, collateral vessels form and supply the kidne...
The central approach of renal transplant ultrasound is to evaluate for possibly treatable surgical or medical complications arising in the transplanted kidney.
Institutions vary in the exact schedule of renal transplant ultrasound assessment, but it is common to obtain an initial ultrasound 24-...
When issuing an MRI or CT report on a patient with an aortic aneurysm, whether it be thoracic or abdominal, a number of features should be mentioned to aid the referring clinician in managing the patient. Reporting tips for aortic aneurysms include 1-2:
size and shape
sac dimensions (outer sur...
Retained barium in appendix refers to the presence of barium in appendix beyond 72 hours from the start of procedure.
Previously used as a sign of appendicitis.
Retained barium outlining the appendiceal lumen allows evaluation of its width and contou...
In chest radiology, reticular and linear opacification refers to a broad subgroup of pulmonary opacification caused by a decrease in the gas to soft tissue ratio due to a pathological process centred in or around the pulmonary interstitium. This includes thickening of any of the interstitial com...
The retrosternal airspace is seen as a normal lucency between the posterior aspect of the sternum and anterior aspect of the ascending aorta on lateral chest radiographs. This space normally measures less than 2.5 cm in width. Increased retrosternal airspace is a sign of pulmonary emphysema, whi...
The retrotracheal space (or Raider triangle) is a radiolucent mediastinal space best seen on lateral chest x-rays. It is normally triangular in shape but can vary greatly in size and shape depending on the patient's body habitus and lung volume 1.
anterior: posterior tracheal stripe...
Reversal of umbilical artery end-diastolic flow (REDF) or velocity is often an ominous finding if detected after 16 weeks. It is classified as Class III in severity in abnormal umbilical arterial Dopplers 6.
The estimated incidence is at ~0.5% of all pregnancies with a much higher...