Clinical and patient background
1. When planning a CT scan, the Scout (a 2D X-ray of the patient) is used to plan where to perform the scan. In some cases it is easy to distinguish the different anatomic points on the Scout, but in many cases it is quite difficult. There can be many reasons for that: air or gas in the colon, and obese patients can, amongst others things, make it more difficult to see where the liver ends and to spot the placement of the kidneys. This makes the planning of different scans difficult. Furthermore, the fact that the shape and size of the different organs vary a lot from person to person, makes it difficult for the radiographer to estimate the optimal placement of the scan. When doing a contrast CT, it is very important to get it right the first time since it is not always possible to redo the scans if all of the relevant anatomy is not covered in the initial scan. In many cases it is not possible to give the patient an extra dose of contrast the same day, because of the strain on the kidneys. This would mean that the patient would have to come back another day for a new scan. In addition to the extra and unnecessary patient dose, this would be futile for the patient. This is why many radiographers tend to plan the scan in a way where they ensure that an extra couple of inches will be scanned, in order to make sure that the entire anatomy is being scanned. However, every inch of the patient that is scanned without good reason means a lot of unnecessary radiation is applied to sensitive tissue. Even when taking precautions, you may sometimes end up missing a part of the liver due to a wrong estimation of the livers size.
2. A CT Urography is a common type of scan that is quite often performed on young patients. To visualize the urethra, the protocol has a delayed phase - this delay is 6-10 minutes p.i. At this time the contrast has left the kidney and is in the ureter. However, in some cases the contrast isn't in the ureter after the 10 minutes delay.
Dose management methods and techniques that were used
A “Tracker” is a one slice low dose scan, which is used to place the ROI when doing a scan that requires bolus tracking. It provides the radiographer with clear information of the anatomy in one slice. The aim of this study is to show that a tracker can be used in many other cases beyond just in planning of the ROI. If the radiographer finds it difficult to estimate whether or not the interior liver is covered in the area, a tracker can be used. A tracker can be placed over the location in the patient where the radiographer thinks the liver ends, to make sure that he or she is not scanning a part of the patient that is too small or too large. If the radiographer wants to make sure that there is contrast in the ureter, a tracker can be used. If a tracker is used when doing a CT urography to detect if there is a contrast in the ureter or not, it can avert an unnecessary scan for the patient. The radiographer would in this case ask the patient to cough a couple of times and then wait a few minutes before doing another tracker. Furthermore the tracker can be used when the radiographer is planning the urography to detect the kidneys, which are impossible to see on a scout.
Conclusions and results
Every inch of a patient that is scanned needlessly causes a great deal of unnecessary radiation to the patient. Every time a scan has to be redone it causes a great deal of unnecessary radiation. Therefore the use of additional/extra trackers is a good technique to conduct scans that are more precise and can possibly lower radiation dose for the patient.
Discussion of case outcome(s) and future implications
Using additional trackers might seem an obvious and easy way to manage patient dose. However in the way most protocols are set up today, it is quite time consuming to do this. If it is possible to make the additional trackers an integrated part of the most common protocol, it may save some time. It could be very beneficial to make it an option in the “user interface”.