Radiological diagnosis of head injuries with a CT-Scan

Why conduct a head CT? Head CT scans are important for detecting brain diseases and diagnosing tumours. The images can help a doctor prepare for surgery. Usually, a head CT is used to provide an initial diagnosis. Another reason can be a check-up on how well a received treatment is working. Reasons that call for a head CT include: stroke s, head injuries following accidents, skull fracture s, brain tumours, cerebral haemorrhages, cerebral infarcts, vascular malformation s, aneurysms or swelling of the brain.

The course of the examination Prior to the CT, the doctor informs the patient comprehensively about the procedure as well as any possible risks or side effects. Additionally, the physicians make sure that the patient does not have any medical conditions that could interfere with the CT. After this conversation, the patient is required to confirm their consent, and signs it. The radiology technologist communicates with the patient during the scan via a loudspeaker. They say when the examination is starting.

In certain cases, it is necessary for the patient to take a contrast agent (orally or intravenously) to improve the detectability of the vessels and possible tumours or inflammations. Sometimes, due to an allergy or condition (such as thyroid hyper- or hypofunction or renal diseases), the contrast agent cannot be administer ed. The contrast agent is administered by the radiologist after the initial scan. It is best practice to perform a non-contrast CT prior to a contrast- enhance d CT, unless the patient has recently undergone a non-contrast CT, in which case it might not be necessary.

The examination itself is conducted in the X-ray tube (mounted on a gantry) while the patient is lying on their back on the examination table wearing a gown (and without any removable metallic items). The head is fixed to avoid blurred images due to head movements. Using the correct head frame allows for a reduced scan time, thus leading to a lower dose of radiation delivered to the patient. The gantry rotates around the patient’s head taking several thousand sectional images per rotation. A computer transform s these images into a 3D model.

Afterwards, the radiology technologist ensure s the quality and sharpness of the conducted images. Finally, a radiologist will examine the images and report the results to the doctor in charge.

What different head CTs are available? The two most commonly applied methods are a “step-and-shoot” technique and a volumetric acquisition. Step-and-shoot is the older one, and mostly supersede d by the volumetric acquisition due to the modernisation of scanners. Step-and-shoot means the gantry revolves around the stationary patient, then takes one axial image, and then repeats this process. Volumetric acquisition signifies a continuous scanning generating a complete volume of scan data as the gantry is moved. The outcome is a helical scan.

How long does a head CT take? The examination may take up to 30 minutes (mostly 10 to 15 minutes). The X-ray is only actually used for several seconds of this time. The brevity of the examination is the key advantage compared to other methods of examination such as nuclear magnetic resonance imaging (MRI). The duration of the CT, though it is relatively short, might still be too long to endure for children and especially babies. Here, an application of anaesthesia might be necessary.

Which risks and side effects does a head CT harbour ? Due to the X-ray based mode of operation, an increased radiation exposure is associated with a head CT (similar to normal X-ray examinations). This can lead to cell changes and, in the worst case, tumours. During pregnancy, a CT should only be performed in emergencies, as the X-ray radiation can harm the foetus. The technologist can adjust the settings to lower the dose of radiation applied. This is especially relevant for head CTs conduct ed on children since they are more sensitive to radiation. Last but not least, the narrow space and noise of the CT scanner can cause anxiety or claustrophobia. Sometimes, the use of sedatives is the sensible choice. Overall, head CT scans are regarded as being relatively safe and low-risk, which is true for all non-invasive diagnostic procedures.

EXERCISE:

1. Step-and-shoot technique means the gantry revolves around the stationary patient taking one axial image and then repeating this process. A) True B) False

2. Why conduct a head CT? A) brain tumors B) to prepare for surgery C) headache D) cerebral infarct E) aneurysms

3. The outcome of a volumetric acquisition is a helical scan. A) True B) False

You’ll find the answer below.

BIBLIOGRAPHY 1. http://dict.leo.org 2. www.dict.cc 3. www.healthline.com 4. www.radiologyinfo.org 5. www.siemens-healthineers.com 6. www.webster-dictionary.org

CARMEN LOBITZ Carmen Lobitz ist freie Trainerin, Lehrerin und MTA. Sie gründete 1998 in Berlin lobitz seminare, die unter anderem Englischseminare für Health Professionals anbieten.

Kontakt: mail@lobitz-seminare.de www.lobitz-seminare.de

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Lösung für Exercise:

1. A)

2. A), B), D), E)

3. A)

Radiological diagnosis of head injuries with a CT-Scan

Why conduct a head CT?

The course of the examination

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Radiological diagnosis of head injuries with a CT-Scan

Why conduct a head CT?

The course of the examination

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