To Use Contrast, Or Not Use Contrast: That Is The Question

A doc­tor may order a con­trast dye to be used dur­ing some MRI exams in order for the radi­ol­o­gist to bet­ter view inter­nal tis­sues and blood ves­sels on the com­plet­ed images. Con­trast mate­ri­als are not dyes that per­ma­nent­ly dis­col­or inter­nal organs. They are sub­stances that tem­porar­i­ly change the way MRIs, X‑rays or oth­er imag­ing tools inter­act with the body. Often, con­trast mate­ri­als allow the radi­ol­o­gist to dis­tin­guish nor­mal from abnor­mal conditions.

When intro­duced into the body pri­or to an imag­ing exam, con­trast mate­ri­als make cer­tain struc­tures or tis­sues in the body appear dif­fer­ent on the images than they would if no con­trast mate­r­i­al had been admin­is­tered. Con­trast mate­ri­als help dis­tin­guish or con­trast” select­ed areas of the body from sur­round­ing tis­sue. By improv­ing the vis­i­bil­i­ty of spe­cif­ic organs, blood ves­sels or tis­sues, con­trast mate­ri­als help physi­cians diag­nose med­ical con­di­tions. In some cas­es, an injec­tion of a spe­cial con­trast dye is giv­en into the blood­stream via a vein on the arm. This helps to give more infor­ma­tion about the cer­tain tis­sues or organs being examined.

Usu­al­ly, you will be advised before you have the MRI scan that part­way through the scan, a con­trast medi­um will be inject­ed. Some­times, based on the notes pro­vid­ed by your doc­tor on your refer­ral, it will not indi­cate that you require a con­trast injec­tion, but after some of the scan­ning is done, the radi­ol­o­gist may decide that gadolin­i­um would help to make the imag­ing diag­no­sis clear­er. If you are told that con­trast will be need­ed, you should not wor­ry that this is an indi­ca­tion that some­thing is seri­ous­ly wrong. Most often this is just being done to give more infor­ma­tion for inter­pre­ta­tion so that the diag­no­sis is more definitive.

If a gadolin­i­um injec­tion is giv­en, some pre­lim­i­nary scans are required imme­di­ate­ly pri­or to the gadolin­i­um injec­tion and it is impor­tant to lie still between these scans and the gadolin­i­um injec­tion. A gadolin­i­um con­trast medi­um is giv­en by intra­venous injec­tion, that is, through a small nee­dle into a vein in your arm. You will either be brought out­side the machine while on the scan table so the con­trast can be hand-inject­ed by the tech­nol­o­gist who per­forms the MRI scan, or while you remain in the scan­ner by a mechan­i­cal injec­tor by an auto­mat­ed injec­tor through an IV placed in your arm pri­or to the begin­ning of the exam. More scans will then be tak­en to com­plete the exam.

Gadolin­i­um con­trast medi­um is gen­er­al­ly very safe. Most patients will not notice any sen­sa­tions, although a small num­ber will report a cold feel­ing in the arm dur­ing the injec­tion. The most com­mon side effects of a brief headache, nau­sea and dizzi­ness only occur in a small num­ber of patients for a brief time fol­low­ing the injec­tion. Reac­tions such as hives tend to occur with­in sev­er­al min­utes of the injec­tion, when a patient is most like­ly in the scan­ner or still in the radi­ol­o­gy depart­ment. Aller­gic (ana­phy­lac­tic) reac­tions to gadolin­i­um con­trast medi­um have occurred but are extreme­ly rare. Severe reac­tions, which may involve dif­fi­cul­ty breath­ing and swelling of the lips and mouth, occur in about 1 in every 10,000 peo­ple who have gadolin­i­um. These severe reac­tions gen­er­al­ly respond very well to emer­gency drug treatment.

Gadolin­i­um con­trast medi­um is used in up to 30% of MRI scans to improve the diag­nos­tic accu­ra­cy of the MRI scan or images of your body’s inter­nal struc­tures. For exam­ple, it increas­es the vis­i­bil­i­ty of inflam­ma­tion, a tumor or growth, blood ves­sels, car­diac (heart) mus­cle scar­ring and assess­es the blood flow to organs such as the brain, abdomen and heart. If you have any con­cerns about the use of gadolin­i­um, please dis­cuss these with your refer­ring doc­tor and the staff where you are hav­ing your procedure. 

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