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CT Tube Buying Guide – 4 Metrics to Consider to When Replacing Your CT Tubes

Oct 1, 2020 | Articles, CT

CT scans are a valuable diagnostic tool. They can show a three-dimensional view of the part of the body being examined to help physicians detect conditions that conventional X-rays cannot catch.

With such functionality, CT scanners often come with a high price tag. X-ray tubes are one of the components that drive these high costs. These tubes are an essential part of a CT scanner as they are the ones responsible for producing a more detailed cross-sectional image of a patient’s body.

Considering all of these, it is cost-effective for you to make the most of your x-ray tube before you replace it. However, you must also know when it needs to be changed to continue producing high-quality images.

Different manufacturers have various ways to determine a tube’s life expectancy, which may make things confusing for you. To help you out, here are the four key metrics you must consider when deciding on replacing your CT tubes:

1. Clicks or Counts

Examining the condition of your X-ray tube using clicks or counts lets you know the number of exposures the tube has performed. Furthermore, you can also use this with the gantry rotation speed to calculate the amount of time the tube has been used. However, this won’t tell you how much energy or power was used during these exposures.

Canon Medical (Toshiba) commonly uses this term.

2. Scan Seconds

This metric takes into consideration the duration of the tube exposures. Because of this, scan seconds measurements may give you a more accurate idea of the condition of your X-ray tubes than clicks. The only limitation is that it does not indicate how much effect or heat ran through the tube.

Scan seconds measurement is the most common method used by major manufactures such as Philips, Siemens, GE, and Toshiba.

3. Milliampere Seconds (mAs)

Unlike the first two metrics, mAs provides you with both the duration of the exposures and the amount of power that ran through the X-ray tubes. Because of this, it is the most accurate metric available. Regularly checking it is the most effective way to determine the lifetime of your tubes.

Keep in mind, however, that it can be tricky to predict the lifetime of x-ray tubes. On average, a 7 MHU tube will last more than 150 million mAs, while a 4 HMU tube will hold out for around 70-100 million mAs. With that said, some tubes may last longer than expected despite having high measures.

If you want to further prolong the life of your CT tube and scanner, always warm it up before examination.

4. Total Patient Exams

As its name suggests, this metric indicates the sum of individual cases performed with the X-ray tube. This metric, however, is not commonly used and referred to.

This is because total patient exams can only provide you with a rough estimate of how your tube was used. It cannot give you more specific information such as the length of each exam or how much power was used during those examinations.

Compared to the first three items, total patient exams is the least effective way to determine CT tube usage and life expectancy. However, when no other information is available, this will do.


As a medical facility, you need to make sure that your pieces of equipment are in good working condition. Doing so empowers you to provide smooth and professional services to your patients.

One of the key apparatuses that you must regularly check and maintain is your CT scan and its x-ray tubes. Doing so often comes along with high expenses, so you must make sure that you are getting the most out of the equipment. Use the metrics above to determine the life expectancy of your CT tubes more accurately and have them replaced at the right time.

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