Mri contrast

MRI contrast media

1. MRI CONTRAST agenT 1 ASTUTI MISHRA BPKIHS 2012

2. MRI contrast agents  are a group of  contrast media  used to improve the visibility of internal body structures in  magnetic resonance imaging  (MRI). The most commonly used compounds for contrast enhancement are  gadolinium -based. MRI contrast agents alter the  relaxation times  of atoms within body tissues where they are present after oral or  intravenous administration . 2

3. Most clinically used MRI contrast agents work through shortening the  T1 relaxation time  of protons located nearby. T1 shortens with an increase in rate of  stimulated emission  from high energy states (spin anti-aligned with the main field) to low energy states (spin aligned). 3

4. To, enhance the inherent contrast between tissue, Mri contrast must alter rate of relaxation of the proton within tissue. Relaxation must be vary for different tissues in order to produce differential enhancement of signal 4

5. MRI contrast agent must exert a large magnetic field density( a property imparted by their unpaired electron) to interact with the magnetic moment of proton in the tissue and shorten their relaxation time The electron magnetic moment also cause the local change in magnetic field promting more rapid proton dephasing and shortens the relaxation time 5

6. Agents with unpaired electron pair spins used as MRI contrast agent. This may be classified into three group Ferromagnetic Paramagnetic- example gadolinium … have magnetic moment which alinged of magnetic field…as magnetic gradient off alignment is loss. Used as major contrast agent made soluble by chelation …shortens T1 relaxation..bright signal on T1 weighted image i.e Hyperintense Super-magnetic-ferrite.. Used for reduction of T2 relaxation time.. Decreased signal intensity seems black 6

7. Chelates Chelate means “claw” Chelates surround an ion an make a cage around it A chelate of gadolinium occupies all available space around the ion except water molecule Water molecules exchange in and out of that one spot. When in that spot, the spins have an extremely short T1. This accelerates the overall relaxation rate, shortening T1. 7

8. Gd chelate 8

9. MRI contrast agents may be administered by injection into the blood stream or orally, depending on the subject of interest. Oral administration is well suited to  G.I. tract  scans, while intravascular administration proves more useful for most other scans. A variety of agents of both types enhance scans routinely. 9

10. MRI contrast agents can be classified in many ways,  including by their: chemical composition administration route magnetic properties effect on the image presence and nature of metal atoms 10

11. biodistribution and applications: Extracellular fluid agents (also known as intravenous contrast agents) Blood pool agents  (also known as  intravascular contrast agents ) Organ specific agents ( i.e.Gastrointestinal contrast agents and hepatobiliary contrast agents) Active targeting/cell labeling agents (i.e. tumor-specific agents) Responsive (also known as smart or bioactivated ) agents pH-sensitive agents 11

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13. Gadolinium containing MRI contrast agents (often termed simply " gado " or "gad") Used for enhancement of vessels in  MR angiography  or for brain tumor enhancement 13

14. For large vessels such as the  aorta  and its branches, the gadolinium(III) dose can be as low as 0.1  mmol per kg body mass. Higher concentrations are often used for finer vasculature.   Gd (III) chelates do not pass the blood–brain barrier because they are hydrophilic. Thus, these are useful in enhancing lesions and tumors where the Gd (III) leaks out. In the rest of the body, the Gd (III) initially remains in the circulation but then distributes into the interstitial space or is eliminated by the  kidneys . 14

15. Types of gadolinium contrast agents Gadolinium(III) contrast agents can be categorized into: Extracellular fluid agents Ionic (i.e.  Magnevist  and  Dotarem ) Neutral (i.e.  Omniscan ,  Prohance ,  Gadavist ,  OptiMARK ) Blood pool agents Albumin-binding gadolinium complexes (i.e.  Ablavar  and  Gadocoletic acid) Polymeric gadolinium complexes (i.e.  Gadomelitol  and  Gadomer 17) Organ-specific agents (i.e.  Primovist and  Multihance  which are used as hepatobiliary agents) 15

16. Gadolinium-containing contrast agents approved for human use Presently, nine different types of gadolinium-containing contrast agents are available in different territories gadoterate  ( Dotarem ) gadodiamide  ( Omniscan ) gadobenate  ( MultiHance ) gadopentetate  ( Magnevist ,  Magnegita ,  Gado -MRT ratiopharm ) gadoteridol  ( ProHance ) gadoversetamide  ( OptiMARK ) gadoxetate  ( Primovist ) gadobutrol  ( Gadovist ) 16

17. Iron oxide: Superparamagnetic Two types of  iron oxide  contrast agents exist:   superparamagnetic  iron oxide (SPIO) and ultra small superparamagnetic iron oxide (USPIO). These contrast agents consist of suspended  colloids  of iron oxide nanoparticles  and when injected during imaging reduce the T 2/ T2 *  signals of absorbing tissues. SPIO and USPIO contrast agents have been used successfully in some instances for liver tumor enhancement . 17

18. Liver Contrast Agents Iron Magnetite, super paramagnetic agent Makes liver black on T2WI, mets show up as bright white. 18

19. Oral administration of contrast agents A wide variety of oral contrast agents can enhance images of the  gastrointestinal  tract. They include gadolinium and manganese chelates , or iron salts for T 1  signal enhancement. SPIO,  barium sulfate , air and clay have been used to lower T 2  signal. Natural products with high manganese concentration such as  blueberry  and  green tea  can also be used for T 1  increasing contrast enhancement. Perflubron , a type of perfluorocarbon , has been used as a gastrointestinal MRI contrast agent for pediatric imaging.  This contrast agent works by reducing the number of hydrogen ions in a body cavity, thus causing it to appear dark in the images. 19

20. Other contrast agents For MR colonography & MRCP Water/saline contrast Negative oral contrast Geritol Blueberry juice, pineapple juice 20

21. Negative contrast agents Used to make stomach contents black in MRCP Geritol , blueberry juice, pineapple juice Iron in Geritol Mn in these juices 21

22. MRCP 22

23. Side effect of MRI contrast The most common, so called normal, side effects of MRI contrast agent are mild and temporary in nature. They include warmth pain or burning at the injection site, low blood pressure, minor skin rash, mild headaches, changes in blood clotting, light headedness and nausea. Typically these side effects do not require any treatments. 23

24. Gadolinium containing contrast agents usually have no effect on blood chemistries and hematologic studies except transient elevation of serum iron and bilirubin levels. These elevations peaked at 4 to 6 hours post injection and returned to baseline values in 24 to 48 hours. The mechanism of these elevations is uncertain but may be related to mild hemolysis . Deoxygenated sickle erythrocytes align perpendicular to a magnetic field in in vitro studies raising the possibility of occlusive complications in patients with sickle cell anemia. No clinical reports of this potential problem have been found  24

25. The most common allergic reaction symptoms to MRI contrast agents include swelling of the face, rashes, itching, sweating, watery or itchy eyes, and shortness of breath. Frequently, the reactions are mild and can be controlled with medication, says Radiology Info. If left untreated, however, allergic reaction can become serious and even life threatening. The patient is advised to contact the doctor as soon as the allergic reactions appear . 25

26. NSF was first described in the medical literature in 2000. The first case of NSF was identified in 1997. The cause of NSF is unknown but it has been reported only in patients who have severe kidney disease.   NSF causes fibrosis of the skin and connective tissues throughout the body. Patients develop skin thickening that may prevent bending and extending joints, resulting in decreased mobility of joints. NSF usually starts in the lower extremities. Fibrosis can also develop in the diaphragm, muscles in the thigh and lower abdomen, and lung vessels. Over time, NSF becomes worse and can cause death. 26

27. NSF Nephrogenic Systemic Fibrosis Most likely caused by free Gd Prevent by screening patients for renal disease Calculate estimated creatinine clearance 27

28. CONTRAINDICATION Patient have history of CKD/renal failure i.e. no normal renal clearance Allergic history pregnancy 28

29. Nephrogenic Systemic Fibrosis The most serious side effect caused by MRI contrasts are attributed to gadolinium. The FDA reports that patients with renal failure and kidney diseases cannot filter the chemical dye quickly enough and it stays in the body. There it causes a serious medical condition called nephrogenic systemic fibrosis, or NSF, according to a study conducted by Dr. Thomas Grobner that was published in "Nephrology Dialysis Transplantation" in January, 2006. NSF symptoms include hardened skin with red patches and are most commonly found in the limbs. Other frequent symptoms include muscle tightening, joint pain, yellow spots on the eyes, and internal organ dysfunction. This rare illness has no cure, but only affects patients with existing kidney problems injected with gadolinium. Patients who received other contrast dyes or those who do not suffer from kidney related problems did not get NSF. Four of the five approved gadolinium contrast agents linked to NSF include Omniscan , Multihance , Magnevist and OptiMARK , says the FDA. 29

30. Pay attention its for you 30