Thymic MRI is a targeted mediastinal imaging protocol performed mainly to distinguish surgical from nonsurgical thymic lesions (eg. thymic hyperplasia, thymic cysts, and lymphoma).
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and referrer's preference, institutional protocols, patient factors, and time constraints.
Sequences
A good protocol for this purpose involves at least:
-
T1 in-phase (IP) and out-of-phase (OOP)
plane: axial
sequence: in-phase (IP) and out-of-phase (OOP) T1-weighted fast incoherent gradient-echo imaging
purpose: chemical shift artifact helps differentiate thymic hyperplasia and thymus gland tumors in patients 16 years of age or older
-
T2 weighted
plane: axial and sagittal
sequence: double inversion recovery (IR) T2-weighted imaging, cardiac-gated preferable. A fat-saturated sequence should be considered in at least one plane
purpose: thymic cysts will show marked T2 hyperintensity
-
T1 weighted
plane: axial
sequence: fast spoiled gradient echo (eg. LAVA, VIBE)
purpose: thymic cysts will show marked T2 hyperintensity
If the main purpose of the scan is the differentiation between thymic hyperplasia and malignancy or thymic cyst assessment, the sequences above should be sufficient in most of the cases. Additional sequences may be performed when other conditions are considered, and these may include:
-
diffusion-weighted imaging (DWI)
-
postcontrast sequences (Gd)
plane: axial and coronal (at least two different planes or volumetric 3D)
sequence: post-contrast fast spoiled gradient echo (eg. LAVA, VIBE) - dynamic post-contrast phases usually include acquisitions: immediately after contrast and at 1, 3, and 5 minutes 1
Unable to process the form. Check for errors and try again.