Steps to learning Computed Tomography as an Intern Medical Radiographer

I understand that it can be very intimidating to face a CT scanner for the very first time. I was also intimidated…very intimidated. It’s easier if as a student you were introduced to practical CT procedures. But if you were unfortunate to meet a CT scanner for the first time as an intern, it’s pretty tasking to learn it under so much pressure.

I am going to share with us practical steps to learning CT scanning procedures. It could be that simple if you follow it sequentially than trying to learn everything at the same time. Scanning a patient using a computed tomography scanner requires the following

1.       Knowledge of patient surface anatomy. You will need this in patient positioning and centering.

2.       Knowledge of anatomical coordinates. You will be hearing lots of stuffs on axial, sagittal, coronal, cranio-caudal, caudo-cranial, prone, supine etc. It will help you a lot also in patient positioning and the actual scanning.

3.       Theoretical knowledge of the basic concepts of CT scans

4.       And every other relevant knowledge you can get.

CT scan procedures can be divided into these steps:

Step 1:

PATIENT’S PREPARATION: Some patients are given information a day to the scan. You ask the patient questions regarding what they ate and how best they adhered to instructions given earlier (if any). This is the right time to look at the request of the patient *again and review the clinical notes/ history. This is where the patient is given appropriate clothing for the procedure. You also explain the procedure to the patient and take vitals (blood pressure, temperature etc.). There is usually a departmental protocol for patient preparation. Patients requiring oral contrast are given instructions on how to drink it and the duration. For patients requiring IV injections, it’s better to cannulate the patient at before positioning. I have omitted patient registration and documentation pre and post scanning because it is mostly handled by medical records personnel or other designated persons.

What to learn:

·         How the patient request is reviewed; what important information to look at and how that information guides the scanning.

·         How the patient is prepared; what you explain to the patient about the scanning procedures, what the patient should eat and not eat.

·         What patient requires oral contrast and why and how do they take it.

Note: in most departments, it’s the job of the radiologist or medical officer to cannulate the patient and the radiology nurses take vital signs. It’s very important to understand the departmental protocol on patient preparations.  

Step 2:

PATIENT POSITIONING: Bad CT technique starts from bad patient positioning skills.

What to learn:

·         How the patient is supposed to lie; supine/ face up, prone/ face down, lateral/ on the sides, hands by the sides, hands above the head etc?

·         What buttons on the CT gantry moves the table up, down, in and out, angulates the gantry and other motions.

·         Where the centering for each examination is. How to properly use the beam lights/ coordinates in centering the patient. What buttons you need to press to centre a patient and so on.

Step 3

SCANNING: This is where the images are obtained. To do this, you will need to put in patient data, select the appropriate protocol, obtain the scout/topogram images, plan the locations of scan images and the region of interest, confirm and scan and repeat scan (for contrast phase if needed).

What to learn

·         How to put in patient data

·         How to select the appropriate protocol.

·         How the scout image(s) is obtained.

·         How you plan/ plot the locations of scan images and the region of interest

·         How to confirm and scan.

·         How to repeat scan for contrast phase.

NOTE: I have omitted how to adjust protocols and parameters. The simply reason is that the CT scanner has so many settings in it. From exposure factors through slice thickness/ interval, pitch and table increment to dose reconstructions, these figures are standardized for specific protocols. So brain protocol is already set for CT brain scans, Abdomen protocols for CT abdomen and so on. Most protocols also include thin slices/ volume image recons. It is not your business at this stage to worry about adjusting protocols and parameter. You will have enough time to learn that as you progress. However, the supervising radiographer will tell you what is necessary to adjust especially when you need bone windows and for other cases requiring any adjustments.

Step 4

REVIEWING THE IMAGES. This helps you to better appreciate the images and the quality of the work you have done. At this stage of learning, you are to learn how the anatomies as they appear on axial, coronal and sagittal images. You will be guided to know how the normal appears and how the abnormal are different. Text books on sectional anatomy will help you learn faster. But don’t sweat yourself out. You have enough time to learn while you practice.

Step 5

IMAGE REFORMATION: CT images are typically acquired in axial planes. You are going to need to learn how to reformat images into coronal and sagittal planes. These plans are very essential in comprehensive diagnosis by the radiologist. Some machines can produce reformatted plane images automatically. You will learn 3D/ Volume rendering reformations but this is when you have learnt how to scan properly.

1.       Printing and archiving images. This is the final step involving producing the images on film and storing the images in the departments PACS/ Picture Archiving and Communication System.

In summary

·         1. Learn how to prepare the patient

·        2.  Learn how to position the patient

·         3. Learn how to type in patient details

·         4. Learn how to obtain scout/ topogram image(s)

·         5. Learn how to plan/ plot locations for slices

·       6.   Learn how to confirm and scan

·         7. Learn how to repeat scan for contrast administration.

·         8. Learn how to reformat images into coronal and sagittal planes

·         9. Learn how to print and archive images.

 Like I said earlier, learning CT can become very challenging when you have to learn so many things at the same time when in fact CT scan is very easy...at least the basic ones. it is best to develop a timetable to guide you in learning. 1 and 2 can be learnt in a day or 2; 3,4,5, 6 and 7 can be learnt over 2 weeks to 1 month; 8 and 9 can be learnt over 1 week. so in all, within 1-2 months, you are good to go.

It is best to start learning CT scan with CT brain. After that, focus on CT chest and then CT abdomen.  Don't rush to learn CT angiography and the rest. You will end up being confused. Refer to my post on CT Brain: a preview of practice. It will help you.

Good luck