A PROTOCOL BASED CONTROLLER FOR OPTIMIZING COOLING TEMPERATURE OF A MAGNETIC RESONANCE IMAGING SYSTEM
Publication Date: 2016-Jun-08
The IP.com Prior Art Database
A protocol based controller for optimizing cooling temperature according to reliable performance prediction of gradient system components is proposed. Subsequent to determination of scanning parameters, the cooling temperature optimization program can be started in the protocol based controller. The inputs for the program are scan-protocol corner points from host and cooling temperature setting configurations. The program calculates Tj max (maximum value of junction temperature) and del Tj (change range for junction temperature) of power semiconductors and accordingly estimates number of times scan cycle can be repeated. This estimated number is recorded as lifetime. Constant temperature and adjustable temperature is compared to determine an optimized cooling temperature setting protocol, which is communicated to a cooling machine for adjustment in real time while scanning.
The present disclosure relates generally to magnetic resonance imaging (MRI) and more particularly to a protocol based controller for optimizing cooling temperature according to reliable performance prediction of gradient system components.
Generally, a magnetic resonance imaging (MRI) system comprises a power supply for supplying current to a set of magnetic field gradient coils and a chiller for chilling a coolant in a coolant reservoir. The chiller is adapted for providing the coolant at least to the set of magnetic field gradient coils. Both the chiller and the gradient coil power supply use large amounts of electrical power. There are various conventional techniques for efficient consumption of power by the gradient coils and for cooling.
One conventional technique improves cooling efficiency of gradient coils and avoids unnecessary power consumption by utilizing a means to predict temperature and a means to start cooling when the gradient coil reaches a predetermined temperature.
Another conventional technique involves performing peak electrical power consumption by turning off the compressor of the chiller. When detected temperature reaches a certain value, the compressor of chiller system is restarted. Also, the compressor in the chiller can be turned off, when there is a buffer vessel or coolant reservoir present. Assuming a 6 degree minimum and a 15 degree maximum temperature with a buffer vessel of 100 liter (which would be more or less standard), the compressor can be turned off for 2.5 minutes. It is however easy to increase the buffer size. The turn off time increases linearly with the buffer volume. Further, a cryo-compressor can be turned off for several minutes, because a cryostat has a large thermal capacity.
In such conventional techniques, cooling temperature is either not controlled or is controlled as a constant value. Such techniques enable reducing peak power consumption because, for some period the compressor of chiller is not working. However, MRI system's gradient pulsing load feature requires the cooling system to work much harder during and ahead of pulsing period, especially for powering semiconductor, (which typically have different thermal performance as compared to gradient coils) while relaxing during non-pulsing period. Conventional techniques focus on cooling systems for relaxing period and ignore critical periods in which the cooling period is required to work. Ignoring such critical periods presents a risk of reliability, negatively impacting application of the conventional techniques even with pre-cooled down planning.
It would be desirable to have an improved technique for controlling and adjusting cooling temperature according to reliable performance prediction of gradient system components.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 depicts a cooling temperature adjusting program used by the...