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Ask the Expert: Dr. Helene Pavlov, Radiologist-In-Chief Emeritus, Answers Your Questions on Radiology

Ct (computed Tomography) Scanner In Hospital

Q1. When looking to see if someone is a candidate for total knee replacement, what do you look for on the images?

Imaging is used to confirm the specific source and degree of pain or discomfort that a patient is having when a total joint replacement is being considered. The images determine the severity of the wear and tear that can occur in a joint (arthrosis), degree and specific deformity and the pattern of joint space narrowing, cyst formation and size of the cysts, presence or absence of sclerosis and [bone spurs called] osteophytes. Imaging helps to differentiate a degenerative osteoarthritis from an inflammatory arthritis such as Rheumatoid arthritis. Once the patient is recognized as a candidate for a total joint replacement, the images are used as a template for selection of the surgical implant.

Q2. I’m pregnant and know to avoid x-rays until the baby is born. What were to happen if I suffered a sprained or broken ankle while pregnant? Are there certain precautions used for pregnant women or still no x-rays?

There are safe ways to X-ray an ankle and protect the fetus. A lead shield apron is used over the abdomen and the X-ray central beam is focused to the region of interest, in this case your ankle. A dosimeter is provided to monitor fetal exposure. The monitor is worn at waist level underneath the lead apron. The monitor provides a direct exposure level which in this scenario should be nil.

Q3. I have metal plates in my forearm from a prior injury. I’ve heard from people that I won’t be able to have x-rays in the future if I should need them. Do the plates hurt the machine? Does the metal not show up?

There is absolutely no contraindication to having an X-ray following having metal screws, plates or other hardware inserted into the skeleton. Following trauma repair, X-rays are mandatory to evaluate healing and hardware integrity. The metal absolutely shows up on an X-ray. The confusion may be with regard to CT [scan] examination as there can be [a blurred image called] artifact produced by the metal on the CT image which can interfere with the image but is not a contraindication and in most instances, the artifact can be minimized. Metal is a contraindication to having an MR [magnetic resonance] examination, however, only those metals that have magnetic qualities. Most hardware used in orthopedic applications is MR compatible. It is important, however, to disclose information about the hardware prior to an MR examination to determine if the examination can be performed safely.

Q4. Is there a specific risk to children who need imaging in terms of radiation? Are there certain precautions taken?

Yes, less is more. The number of X-ray examinations, the number of images per examination and the area of each exposure should be limited. The child should be given lead shields for those body parts not being examined. The technologist should be questioned if they have adjusted the dose appropriate for the patient’s weight and size. If the child moves during the examination or the image is less than perfect, the radiologist who will be interpreting the examination should review the image to see if a repeat examination is required as the study may be diagnostic [and therefore still useful] even if not meeting the typical quality standards.

Topics: Orthopedics
The information provided in this blog by HSS and our affiliated physicians is for general informational and educational purposes, and should not be considered medical advice for any individual problem you may have. This information is not a substitute for the professional judgment of a qualified health care provider who is familiar with the unique facts about your condition and medical history. You should always consult your health care provider prior to starting any new treatment, or terminating or changing any ongoing treatment. Every post on this blog is the opinion of the author and may not reflect the official position of HSS. Please contact us if we can be helpful in answering any questions or to arrange for a visit or consult.