Chemical Shift: The Artifact and Clinical Tool Revisited

Abstract

The chemical shift phenomenon refers to the signal intensity alterations seen in magnetic resonance (MR) imaging that result from the inherent differences in the resonant frequencies of precessing protons. Chemical shift was first recognized as a misregistration artifact of image data. More recently, however, chemical shift has been recognized as a useful diagnostic tool. By exploiting inherent differences in resonant frequencies of lipid and water, fatty elements within tissue can be confirmed with dedicated chemical shift MR pulse sequences. Alternatively, the recognition of chemical shift on images obtained with standard MR pulse sequences may corroborate the diagnosis of lesions with substantial fatty elements. Chemical shift can aid in the diagnosis of lipid-containing lesions of the brain (lipoma, dermoid, and teratoma) or the body (adrenal adenoma, focal fat within the liver, and angiomyolipoma). In addition, chemical shift can be implemented to accentuate visceral margins (e.g., kidney and liver).

Chemical Shift Artifact on Steady-State MRI Sequences for Detection of Vesical Wall Invasion in Placenta Percreta

“…The chemical shift artifact is clinically most often recognized in fluid-filled organs with surrounding fat such as bladder and orbit. The phenomenon is already being utilized in recognizing fat-containing tumors in brain with CSF interface, in detection of adrenal adenomas, renal angiomyolipomas, and to detect lipomatous metaplasia in patients having myocardial infarction [3,4,12,13]. Israel et al studied 23 patients of renal angiomyolipoma and were able to demonstrate india ink artifact within the mass or at its interface with the kidney in all of the patients [5].…”

“…Recently, chemical shift artifact has been evaluated as a diagnostic tool in diagnosis of renal angiomyolipoma, adrenal adenoma, hepatocellular carcinoma with fat degeneration, and to rule out capsular invasion by renal tumors [4,5]. In last several years, there has been increase in interest over use of MRI in characterization of invasive placentae.…”

Intracranial lipomas and epilepsy

“…1). Chemical shift artifact can usually be seen on proton density or T2 weighted images [1] and can help to confirm the diagnosis [13]. Additionally, occasional small hypointense lesions due to calcifications can be found on T2 weighted images [1,21,23].…”

Adrenal MRI: Techniques and clinical applications

“…Adrenal myelolipomas can be managed conservatively unless patients have symptoms from localized mass affect or the uncommon complication of intratumoral hemorrhage (39). While the dual echo gradient echo sequence is ideal for detecting intracellular lipid it can also be used to characterize macroscopic fat by depicting an ''etching'' or ''India-ink'' artifact at an interface between intralesional or perilesional fat and adjacent water containing tissue (40) ( Fig. 3a,b).…”