In-phase and out-of-phase sequences
In-phase (IP) and out-of-phase (OOP) sequences correspond to paired MRI gradient echo (GRE) sequences obtained with the same repetition time (TR) but with two different echo time (TE) values.
Applications
The main application of the IP-OOP sequences is to identify pathological (microscopic) fat content of tissues in the abdomen by showing signal intensities drop on the OOP images compared to the IP images. Examples where IP-OOP sequences are useful include 1,2:
- fatty liver and focal fatty sparing/infiltration
- fat rich adrenal lesions:
- adrenal adenoma (helping differentiate it from carcinomas and metastases)
- adrenal myelolipoma
- lipid-poor angiomyolipoma
- renal cell carcinoma (RCC)
- thymic hyperplasia
- osteoporotic versus neoplastic vertebral wedging: neoplastic lesions display persistence high signals on opposed-phase 3,4
- hemochromatosis of the liver 5
- intrahepatic pneumobilia 5
- metallic objects: by the effect of susceptibility artifact (e.g cholecystectomy clips)
Related Radiopaedia articles
Physics and Imaging Technology: MRI
- MRI (introduction)
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MRI physics
- B0
- chemical shift
- dependence of magnetization (proton density, field strength and temperature)
- echo time
- eddy currents
- electromagnetic induction
- Ernst angle
- flip angle
- Larmor frequency
- magnetic dipole magnetic field gradient
- magnetic susceptibility
- magnetism
- molecular tumbling rate effects on T1 and T2
- net magnetization vector (NMV)
- relaxation
- repetition time
- resonance and radiofrequency (RF)
- units of magnetism
- MRI hardware
- signal processing
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MRI pulse sequences (basics | abbreviations | parameters)
- CSF flow studies
- diffusion weighted sequences (DWI)
- echo-planar pulse sequences
- fat-suppressed imaging sequences
- gradient echo sequences
- inversion recovery sequences
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perfusion-weighted imaging
- techniques
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- saturation recovery sequences
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- spiral pulse sequences
- susceptibility-weighted imaging (SWI)
- T1 rho
- MR angiography (and venography)
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MR spectroscopy (MRS)
- 2-hydroxyglutarate peak: resonates at 2.25 ppm
- alanine peak: resonates at 1.48 ppm
- choline peak: resonates at 3.2 ppm
- citrate peak: resonates at 2.6 ppm
- creatine peak: resonates at 3.0 ppm
- functional MRI (fMRI)
- gamma-aminobutyric acid (GABA) peak: resonates at 2.2-2.4 ppm
- glutamine-glutamate peak: resonates at 2.2-2.4 ppm
- Hunter's angle
- lactate peak: resonates at 1.3 ppm
- lipids peak: resonates at 1.3 ppm
- myoinositol peak: resonates at 3.5 ppm
- MR fingerprinting
- N-acetylaspartate (NAA) peak: resonates at 2.0 ppm
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MRI artifacts
- MRI hardware and room shielding
- MRI software
- patient and physiologic motion
- tissue heterogeneity and foreign bodies
- Fourier transform and Nyquist sampling theorem
- MRI contrast agents
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