Articles
Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and continuously improved upon by countless contributing members. Our dedicated editors oversee each edit for accuracy and style. Find out more about articles.
49 results found
Article
Time to peak (TTP)
Time-to-peak (TTP) is the time at which contrast concentration reaches its maximum. For example, for a particular dynamic susceptibility contrast (DSC) imaging acquisition in which images are acquired every 1.5 seconds, possible TTP values could include 20.0 seconds, 21.5 seconds, 23.0 seconds, ...
Article
Laser interstitial thermal therapy
Laser interstitial thermal therapy (LITT) or focal laser ablation is a surgical technique for selective ablation of a lesion or tissue using laser-generated heat. Compared to other minimally invasive techniques such as radiofrequency, microwave, or cryoablation, lasers are able to create a more ...
Article
Creatine peak
Creatine is one of the compounds examined in MR spectroscopy. It resonates at 3.0 ppm chemical shift (with a second usually smaller peak at 3.95 ppm 2).
It is found in metabolically active tissues (brain, muscle, heart), where it is important in the storage and transfer of energy. It tends to b...
Article
Diffusion-weighted imaging in acute ischemic stroke
Diffusion-weighted imaging (DWI) is a commonly performed MRI sequence for the evaluation of acute ischemic stroke and is very sensitive in the detection of small and early infarcts. Conventional MRI sequences (T1WI, T2WI) may not demonstrate an infarct for 6 hours, and small infarcts may be hard...
Article
Mean transit time (MTT)
Mean transit time (MTT) corresponds to the average time, in seconds, that red blood cells spend within a determinate volume of capillary circulation. It is assessed as part of the CT perfusion protocol and MR perfusion.
Mean transit time is calculated by dividing cerebral blood volume (CBV) by ...
Article
T2 shine through
T2 shine-through refers to high signal on DWI images that is not due to restricted diffusion, but rather to high T2 signal which 'shines through' to the DWI image. T2 shine through occurs because of long T2 decay time in some normal tissue.
This is most often seen with subacute infarctions due ...
Article
Thallium-201 scintigraphy
Thallium-201 (Tl-201) is a radiopharmaceutical used for scintigraphy, primarily of the myocardium. The element thallium is treated by the body as an analog of potassium; it is produced in a cyclotron by bombarding thallium-203 with protons.
Characteristics
thallium is a monovalent cation
usua...
Article
Chemical exchange saturation transfer
Chemical exchange saturation transfer (CEST) imaging is a novel molecular MR technique that enables imaging certain compounds at concentrations that are too low to impact the contrast of standard MR imaging and too low to directly be detected in MRS at typical water imaging resolution 1.
Amide ...
Article
Taurine
Taurine is one of the compounds examined in MR spectroscopy. It resonates at 3.4 ppm chemical shift. It is elevated in medulloblastomas.
Article
Nephrogenic systemic fibrosis
Nephrogenic systemic fibrosis (NSF), also known as nephrogenic fibrosing dermopathy, occurs almost exclusively in patients with renal impairment and is associated with the administration of gadolinium-based contrast agents (GBCAs) used in MRI.
The American College of Radiology (ACR) has divide...
Article
Axial plane for imaging of the brain
A consistent axial plane for imaging of the brain needs to be chosen to allow for reproducible image acquisition and comparison. Unlike the sagittal plane, which is intrinsically defined by our inherent left-right plane of symmetry, axial and coronal planes need to be agreed upon and over the ye...
Article
Phase-sensitive inversion recovery
Phase-sensitive inversion recovery (PSIR), also known as phase-corrected inversion recovery (PCIR), refers to an inversion recovery MRI pulse sequence that accounts for the positive and negative polarities and preserves the information of tissue magnetization during the recovery from the initial...
Article
Negative enhancement integral
The negative enhancement integral in MR perfusion is used to calculate the relative cerebral blood volume (rCBV). It represents the area described by the baseline and the signal loss due to passage of contrast bolus in tissue.
Article
Diffusion kurtosis imaging
Diffusion kurtosis imaging (DKI) is an advanced neuroimaging modality which is an extension of diffusion tensor imaging by estimating the kurtosis (skewed distribution) of water diffusion based on a probability distribution function. It provides a high order diffusion of water distribution and a...
Article
Glutamine-Glutamate peak
Glutamate-Glutamine (Glx) peak is one of the regions assessed on MR spectroscopy, and resonates between 2.2 and 2.4 ppm chemical shift. It overlaps with the GABA peak and cannot be routinely separated from each other. The concentration of these two brain metabolites increases in hepatic and hypo...
Article
Cerebral blood flow (CBF)
Cerebral blood flow (CBF) is one of the parameters generated by perfusion techniques (CT perfusion and MR perfusion). CBF is defined as the volume of blood passing through a given amount of brain tissue per unit of time, most commonly milliliters of blood per minute per 100 g of brain tissue 1.
...
Article
Double inversion recovery sequence
Double inversion recovery (DIR) is an inversion recovery MRI pulse sequence that uses two different inversion pulses. The technique can be used to suppress signal from two different tissues or to suppress signal that moved between the two pulses.
In the first instance, used in neuroimaging, two...
Article
FLAIR vascular hyperintensities
FLAIR vascular hyperintensities are hyperintensities encountered on FLAIR sequences within subarachnoid arteries related to impaired vascular hemodynamics 1,2. They are usually seen in the setting of acute ischemic stroke and represent slow retrograde flow through collaterals (and not thrombus) ...
Article
Brain morphometry
Brain morphometry is the act of measuring various dimensions (typically volume) of parts of the brain. Historically, this was only performed post-mortem.
In modern practice, this is performed in vivo using MRI. A volumetric scan of the brain (typically T1 weighted) is obtained and segmented i...
Article
MR vessel wall imaging
MR vessel wall imaging (VW-MRI) refers to MRI techniques used to evaluate for disease within the walls of arteries, beyond the luminal abnormalities depicted on angiographic imaging. This can be used anywhere in the body but is particularly important intracranially in distinguishing between vari...
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