4 Measures of CT Tube Life Expectancy

This article has been updated 02-04-2024

The CT tube is one of the most important parts of a CT scanner as it creates the X-rays and is expensive to replace.

CT tubes are defined by the amount of heat they can endure, measured in MHU (Mega Heat Unit).

The bigger the number of MHU, the more heat the tube can take.
And hence, perform more examinations.

The usage of the tube is defined by:

  • Effect x time = tube usage

Essentially, you are counting the CT tube life expectancy.

Since a new tube is relatively expensive, with prices from 50.000 to 150.000 Euro, there is great interest in predicting the CT tube life expectancy.

And despite the importance of CT tube count when purchasing used CT scanners, we have experienced some confusion regarding the types of CT tube life expectancy count measures.

Especially because different manufacturers have different ways of measuring it.

Therefore, we are providing a simple explanation for each of the following tube measures:

  • Total patient exams
  • Clicks/counts
  • Scan seconds
  • mAs (milliampere seconds)

You can read more about each of the tube count methods below.

Total Patient Exams

Total Patient Exams is simply the sum of individual cases performed with the CT X-ray tube.

It does not include info on the length of the exams or how much energy they required.

Hence, it is the most uncertain way to determine the tube use and CT tube life expectancy.

Therefore, it is rarely used, and is mostly given when no other info is available.


This method of measuring CT tube life expectancy tells you how many exposures the tube has performed.

However, it does not include how much energy has been used during these exposures.

From clicks, you can calculate the amount of time the tube has been used, based on gantry rotation speed.

This term is most commonly used by Toshiba, now Canon Medical.

Scan Seconds

This is a measure of the duration of the tube exposures, so how much time has the tube been used for. Hereby, it is a more accurate measure than the ones described above.

However, this does not indicate how much effect/heat ran through the tube either.

This is the measure of X-ray tube counts that we see most often and it is popular among most manufacturers, like Philips, GE, Siemens, and Toshiba.


Milliampere Seconds (mAs) provides you with information on both, the duration of the exposures and on how much power has run through the tube.

Hereby, it is the most accurate measure of CT tube life expectancy and is mainly used by GE on their CT scanner tubes.

Predicting the life expectancy of CT tubes is very difficult. But on average a 7 MHU tube will last more than 150 million mAs, and a 4 MHU tube will last approximately 70-100 million mAs.

All in all, the best way to determine the CT tube life span is to have the mAs because this is the most precise measure of the CT tube life expectancy.

But the CT tube life expectancy is unpredictable and we have seen tubes with high measures last a long time as well.

For example, Philips MRC tubes are very long lasting, and therefore, you cannot apply the estimate above.

In the below video, we share with you what you should consider when looking to buy a used Canon Medical​ CT tube.

We talk about the two main aspects that determine what type of CT tube to buy. We also give exact examples of the type of CXB tube that goes with your CT scanner.

4 Measures of CT Tube Life Expectancy
Tips and tricks to prolong your CT tube life expectancy

Maintenance is important for tube life and plays a huge role in prolonging the CT tube life. Therefore, we want to share with you a few ways in which you can help extend the life of your CT tube.

A few tips are to:

  • Warm up your CT scanner before every examination. This is because warming up the system will help prevent heat shocks as the machine produces a high level of heat during usage.
  • Remember to only perform the suggested amount of examinations. In this way, you will protect the X-ray tube from any potential melting.
  • Only operate within the recommended level of mA, exposure time, and voltage needed for the specific examination of your patients.
  • Make sure that the temperature in the room is right for your system – not too hot and not too humid. This will prevent the tube from being worn down.
  • Ensure that the machine has a stable power supply at all times. This ensures that there are no spikes or dips in the power that could potentially harm the machine.

All machines come with a planning guide in which you can find information about what environmental requirements your machine has.

Do check this, to ensure you give your system the best care and that you get the highest X-ray tube efficiency.

Even when you are cautious when it comes to system care, sometimes one can accidently overlook signs that the CT tube might fail.

Some of the signs are:

  • If the machine starts making loud noises. This can mean that the bearing inside the tube housing is becoming worn down.
  • If error messages occur. Especially, if these messages are related to arcing and if the messages either interrupt the scanning, or if they are followed by a system shut-down.
  • If the systems start to take longer breaks between scans. This means that the system is reaching its limit for operating temperature. CTs take breaks between scans to give the tube a break. But, if the breaks become unusually long this may indicate an issue.

Therefore, to ensure high X-ray tube efficiency, it is very important to pay extra attention to your system so you can notice the signs before anything inconvenient happens. 

Now that we have gone through some general information about CT tube measures and how to extend your CT tube life, you are prepared to take great care of your CT tube.

4 Measures of CT Tube Life Expectancy

If you’re looking for a CT X-ray tube, reach out to us at sales@lbnmedical.com – you can also check out our parts inventory yourself.

We hope that after reading this blog post, you have a better understanding of the different methods.

If you are seeking more information about used CT scanners, sign up for our new mail course and receive an e-book: How to pick a CT scanner. It only costs your e-mail.

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