STIR Short TI OR tau Inversion Recovery.pptx

MRI basics

1. STIR Short TI OR tau Inversion Recovery

2. STIR IS A T2 weighted images STIR (Short TI Inversion Recovery) or (Short tau inversion recovery ) suppress the signal from fat. FLAIR is a similar technique to suppress water STIR stands for S hort- T I I nversion R ecovery  and is typically used to null the signal from fat.

3. The fat suppression possible by STIR is generally uniform and relatively i ndependent of magnetic field inhomogeneities. http://mriquestions.com/stir.html

4. STIR may be superior to other fat saturation methods (such as spectral "fat-sat") especially near metallic foreign bodies, near tissue interfaces with high susceptibility differences (like the skull base/sinuses), across large body parts (such as the abdomen and pelvis). .  http://mriquestions.com/stir.html

5. It is even possible to perform whole-body STIR imaging as a screening technique for bone metastases . In lower field permanent magnet scanners with relatively poor homogeneity, STIR is one of the only fat suppression methods available.  http://mriquestions.com/stir.html

6. MRI image appearance The easiest way to identify STIR images is to look for fat and fluid filled space in the body (e.g. CSF , synovial fluid in joints, oedema or any other pathological fluid collection in the body ). in a STIR image: Fluids normally appear bright fat appear very dark

7. Tissues and their STIR appearance Muscles : - darker than fat signal White matter - darker than gray Bone marrow: - dark Moving blood- dark Gray matter - gray Fluids – very bright Bone - dark Fat – dark Air - dark

8. Pathological appearance Pathological processes normally increase the water content in tissues. Due to the added water component this results in a signal increase on STIR images . Consequently pathological processes are usually bright on STIR images .

9. Use : Very useful for brachial and lumbar plexus imaging Very useful for any musculoskeletal imaging Very useful for extremity imaging Very useful for spine imaging

10. limitations:  STIR cannot  be used as a fat suppression technique post-gadolinium. STIR does not specifically suppress fat; it only suppresses tissues with T1 values in the range of fat (200-300 ms ). Thus gadolinium-containing tissues with similar relaxation times will also be suppressed . Likewise, suppression proteinaceous materials and other short T1 tissues may occur. Although contrast-to-noise for certain lesions may be improved, overall signal-to-noise may be poor. The multiple 180°-pulses cause deposit extra energy and may result in tissue heating. http://mriquestions.com/stir.html

11. A STIR image, revealing cancer lesions within spinal vertebrae at 1.0 T. http://www.revisemri.com/questions/pulse_sequences/stir

12. STIR coronal sequence used in elbow imaging

13. STIR coronal sequence used in hips imaging

14. STIR coronal sequence used in thigh imaging

15. STIR coronal sequence used in lower legs imaging

16. Short tau inversion recovery (STIR ) also called short T1 inversion recovery is a fat suppression technique with an inversion time TI = T1 ln2 where the signal of fat is zero . This equates to approximately 140 ms at 1.5 T.   To distinguish two tissue components with this technique, the T1 values must be different. FLAIR is a similar technique to suppress water .   Inversion-recovery imaging allows homogeneous and global fat suppression and can be used with low-field-strength magnets. However, this technique is not specific for fat, and the signal intensity of tissue with a long T1 and tissue with a short T1 may be ambiguous. http://radiopaedia.org/articles/short-tau-inversion-recovery

17. http://mriquestions.com/stir.html

18. STIR image with excellent fat suppression, allowing optic neuritis to be well seen. http://mriquestions.com/stir.html

19. STIR (as well as other short and medium-TI sequences) has an additional useful feature —  additive T1+T2 contrast. In routine SE imaging lesions with prolonged T1 and T2 have competitive effects on signal intensity (↑T1 reduces signal while ↑T2 increases signal). In STIR imaging the effects of ↑T1 and ↑T2 are additive. This results from the fact that the longitudinal magnetization of long T1 lesions on STIR remain inverted and produce a high signal as shown below. http://mriquestions.com/stir.html

20. At short to medium TI’s, long T1 substances (such as CSF) are bright on magnitude IR. This is opposite to SE where long T1 values cause reduced signal intensity. http://mriquestions.com/stir.html

21. Additive T1 and T2 effects. MS plaque seen better on STIR image (right) than SE image (left) http://mriquestions.com/stir.html

22. References         Bydder GM, Young IR.  MR imaging: clinical use of the inversion recovery sequence . J Comput Assist Tomogr 1985; 9:659-675.       Krinsky G, Rofsky NM, Weinreb JC.  Nonspecificity of short inversion time inversion recovery (STIR) as a technique of fat suppression: pitfalls in image interpretation . Am J Roentgenol 1996; 166:523-526.      Smith RC, Constable RT, Reinhold C, et al.  Fast spin echo STIR imaging . J Comput Assist Tomogr 1994;18:209–213      Sugimoto H, Sakai O, Shinozaki T et al. Effect of water fraction in selection of optimal TI value for STIR sequences . J Comput Assist Tomogr 1994; 18:119-125. http://mriquestions.com/stir.html

23. MRI image appearance The easiest way to identify STIR images is to look for fat and fluid filled space in the body (e.g. Cerebrospinal fluid in the brain ventricles and spinal canal, free fluid in the abdomen, fluid in the gall bladder and common bile duct, synovial fluid in joints, fluid in the urinary tract and urinary bladder, oedema or any other pathological fluid collection in the body ). Fluids normally appear bright and fat appear very dark in a STIR image. https://mrimaster.com/characterise%20image%20stir.html

24. Tissues and their STIR appearance Muscles: - darker than fat signal White matter - darker than gray Bone marrow: - dark Moving blood- dark Gray matter - gray Fluids – very bright Bone - dark Fat – dark Air - dark https://mrimaster.com/characterise%20image%20stir.html

25. Pathological appearance Pathological processes normally increase the water content in tissues. Due to the added water component this results in a signal increase on STIR images. Consequently pathological processes are usually bright on STIR images. https://mrimaster.com/characterise%20image%20stir.html

26. Use Very useful for brachial and lumbar plexus imaging Very useful for anterior neck orbits and face imaging Very useful for any musculoskeletal imaging Very useful for extremity imaging Very useful for spine imaging Useful for abdominal imaging (respiratory gated STIR) Useful for chest imaging  (respiratory gated STIR) https://mrimaster.com/characterise%20image%20stir.html

27. https://www.startradiology.com/the-basics/mri-technique/ Fat suppression STIR short tau inversion recovery Suppression of fat tissue is one of the many options that can be used in an MRI sequence. In virtually all abdominal MRI examinations, suppressing the fat tissue signal is advisable. The created low signal intensity of fat then contrasts more strongly with the vessels & pathology (high signal intensity!). Also in skeletal imaging, it may be useful to make a sequence with fat suppression. Bone marrow contains fat and may mask bone marrow edema on a T2 weighted image.  There are several technical options to suppress fat tissue.  Frequently used sequences are the STIR (short-tau inversion recovery) and the SPIR (spectral pre-saturation inversion recovery) sequences. Both are T2 weighted images .  You can also recognize fat suppression by the abbreviation FatSat , meaning Fat Saturation (e.g. T2wFatSat ). Tip : you can easily recognize fat suppression by looking at the subcutaneous fat (fig. 19). When it has a low signal, you are looking at a fat suppression sequence. The technique may be used 'as extra’ in T1, T2 and PD weighted images.

28. https://www.startradiology.com/the-basics/mri-technique/ Figure 19. STIR sequence in transversal direction of the upper legs. Note also the good contrast with the vessels (fluid!).

29. https://www.startradiology.com/the-basics/mri-technique/

30. A FLAIR image, revealing periventricular lesions more clearly because the adjacent fluid signal is suppressed. http://www.revisemri.com/questions/pulse_sequences/stir