Energy consumption - a comparison

Magnetic Resonance Tomography (MRI), Computer Tomography (CT) and Multidimensional Nonlinear Spectrography (MNLS)

Energy is scarce and we should all reduce our energy consumption as much as possible. From this point of view, it is certainly interesting to see how various medical examination methods deal with energy hunger.

Comparing the energy consumption of different test methods is a difficult matter. You have to be very careful not to compare apples with oranges. Quite apart from the fact that not all methods can achieve the same examination objective, the “ancillary costs” are very different. An MRI spectrometer, for example, consumes huge amounts of energy for cooling and maintaining the superconducting state of the magnet and the standby mode of the measurement electronics, whereas an MNLS system consumes practically no power when idle.

MRI

Magnetic resonance imaging requires a large superconducting magnet to maintain the very strong magnetic field necessary for the examination. Cooling with liquid helium and liquid nitrogen alone typically requires an output of 8 kilowatts [U-Basel]. You also don’t want to switch off the sensitive measuring electronics after every patient examination. In fact, you don’t even want to switch the device off overnight. The reason: it takes a very long time for the electronics to stabilize very precisely. In addition, the system has to be recalibrated every time.

In measurement mode, in addition to the energy consumption, there is the operating power of the measurement electronics and the power of the gradients, which are electromagnets in large superconducting magnets that make imaging diagnostics possible in the first place. A typical load consumption for an MRI device is 30 kW (manufacturer’s specification) [Ham]. This would mean 10 kWh for a scan of the thorax (typical measurement duration 20 min) [med]. Of course, 10 kWh is far too low, this is a typical manufacturer’s specification (we also know this from car manufacturers. They also always understate their fuel consumption). Realistically speaking, the 10 kWh can easily be doubled.

CT

With computer tomography, the actual measurement time is very short (who wants to be bombarded with X-rays for hours on end).

Therefore, most of the energy consumption is generated in stand-by mode [wgkt]. According to [rsna], a typical thorax examination requires 12 kWh of energy.

The energy consumption of the MNLS systems is unbeatably low compared to the other two imaging methods. The METAVITAL HUMAN TS requires a power supply unit with a maximum power consumption of 12 W for the central unit and all connected additional devices and the notebook with a maximum power consumption of 120 watts. If the duration of the examination is assumed to be 20 minutes, as with MRI, then the energy consumption is 0.044 kWh. And that is the absolute maximum imaginable.

Therefore, most of the energy consumption is generated in stand-by mode [wgkt]. According to [rsna], a typical thorax examination requires 12 kWh of energy.

MNLS systems

The energy consumption of the MNLS systems is unbeatably low compared to the other two imaging methods. The METAVITAL HUMAN TS requires a power supply unit with a maximum power consumption of 12 W for the central unit and all connected additional devices and the notebook with a maximum power consumption of 120 watts. If the duration of the examination is assumed to be 20 minutes, as with MRI, then the energy consumption is 0.044 kWh. And that is the absolute maximum imaginable.