the device 1 shown in fig1 has a housing 2 , in which a first storage container 3 and a second storage container 4 accommodate a fluid , the storage device 3 is filled with cold water ; it can also be directly connected to a water tap . the storage device 4 is intended for heated fluids ; thus , it has a heating element 5 inside , with which the fluid is heated . moreover , temperature sensors or thermostats that are not shown in fig1 and that are connected with a controller 6 in the housing 2 of the device 1 are arranged in the storage containers 3 , 4 , lines 7 , 8 lead from the storage devices 3 , 4 , respectively , to a valve block 9 , which selectively connects one of the lines 7 , 8 with a supply line 10 . the valve block 9 is actuated by the controller 6 , which connects either the storage container 3 or the storage container 4 with the supply line 10 , so that the fluid is conveyed using a pump 11 arranged within the housing 2 . the supply line 10 at least has a fluid tube , but can be designed as a tube package with additional lines e . g . for transferring sensor signals . the end of the supply line 10 is connected to a compress in the form of a cuff 12 , which goes around the leg of a patient 13 . the cuff 12 in this embodiment is formed of a material compatible with magnetic resonance tomography , such as polytetrafluoroethylene , for example . a detector for temperature is arranged inside the cuff 12 . in the simplest case , this can be an electrical temperature sensor 14 , however , it is also possible to measure the surface temperature in a contact - free manner in order to avoid interfering with the mr sequence . during the examination , the patient 13 lies on a table of the mr tomography device , which is represented schematically in fig1 by the indicated magnets 15 , 16 . this is a conventional magnetic resonance tomography system , also called a magnetic resonance imaging system , and can be used for a wide variety of examinations . an outflow line 17 is attached to the cuff 12 , via which the fluid is fed to a drain , in particular when water is used as the fluid . if an oil or a fluorinated carbon compound is used , however , the fluid is collected for reuse or fed back into the appropriate storage container 3 or 4 , in which it is either reheated or re - cooled as needed . the cuff 12 is designed so that fluid flows through almost the entire interior thereof so that the cuff 12 can be maintained at a constant temperature and this temperature is transferred to the body part of the patient 13 to be examined . the surface temperature of the cuff 12 or the skin of the patient 13 is thereby recorded with the temperature sensor 14 , the measured value of which is transmitted via a line ( not shown in fig1 ) or wirelessly to the controller 6 . during the examination , the current temperature is continuously ascertained via the temperature sensor 14 and saved by the controller 6 . the controller 6 can supply the measured value to an external device via a data line 18 . for example , this can be a pc or the operating unit of an mr device or a similar device . in the depicted embodiment , an mr - inert liquid is used in the examination ; that is , it is non - conducting , non - ferromagnetic , and has no unbalanced protons . a fluorinated carbon is particularly suitable for this purpose . the examination begins with a heating of the leg of the patient 13 to be examined . the fluid in the storage container 4 is brought to the increased temperature by the heating element 5 . the valve block 9 is located in the position indicated in fig1 and the pump 11 pumps the fluid through the supply line 10 to the cuff 12 , which then is heated , which leads to a warming of the leg of the patient 13 . in this state , an image of the body part to be examined and its vessels is generated using magnetic resonance tomography . several images are obtained , which are shifted from image - to - image in the axial direction . the diameter of one or more vessels can be ascertained from this captured image data . with this known diameter , the liquid flow oan be calculated as volume flow according to the hagen - poiseuille equation . in addition to the diameter of the vessels , the pressure difference ap between the two examined sections as well as the distance between the two sections must be known . the liquid flow can be measured with mr without a contrast medium . e . g ., with time - of - flight mr angiography or with phase contrast angiography . as an alternative , the liquid flow can be measured with mr after the administration of a contrast agent . several contrast agent administrations can be made one after the other , if the body part to be examined is in thermal equilibrium . the absolute or relative cross - sectional area or the diameter or radius of one or more blood vessels is calculated from the different flows . the liquid flow is proportional to the fourth power of the diameter or the radius of the vessel . the flow in peripheral vessels is always laminar so that the aforementioned hagen - poiseuille equation may be used . in order to subject the blood vessel to be examined to alternating stress , it is cooled after this first measurement . for this , an appropriate switch signal is given from the controller 6 to the valve block 9 , which then connects the storage container 3 with the cold fluid to the supply line 10 . the cold fluid subsequently is pumped through the line 10 and the cuff 12 so that the body part of the patient 13 to be examined is cooled . once thermal equilibrium is achieved , an mr measurement is then performed . then , a third examination can be performed with yet another changed temperature . it is also possible to set the speed of the reaction of the blood vessel in relation to the temperature in order to obtain information on the condition of the blood vessels . various standard examination programs that run automatically and require no intervention from operating personnel are stored in the controller 6 , but it is also possible to enter examination programs manually . the evaluation of the data can be transferred to a calculating unit of the device 1 . it is also possible to transfer the data via the data line 18 to a pc or to the mr system in order to perform a correlation with the mr data if necessary and to evaluate the examination data . generally , however examination findings can be derived from the obtained mr data alone by comparing at least two measurements with each other at different temperatures . a reproducible and highly accurate analysis of the functional efficiency of blood vessels without contrast media and without administering additional medication is achieved with the inventive device 1 and the inventive procedure . the constriction and dilation of vessels under the effect of temperature can be measured directly by taking the diameter of the vessels from the images . this task is performed manually or automatically via a software program . alternatively or additionally , the diameter and the change in the diameter can be determined from the liquid flow . [ 0047 ] fig2 show examples for measured values of the liquid flow and the vessel diameter depending on the temperature of the respective vessel . the curve progressions are schematic representations and show the corresponding measured values of a healthy and a sick patient . the lower curve shows the vessel diameter of a sick patient , the diameter increases only slightly with an increase in the temperature , which indicates a disease of the vessels . in contrast , in the curve above this one , a greater increase in the vessel diameter is seen between the lower temperature and the increased temperature , which leads us to conclude that the vessels are healthy . both of the upper curves show the liquid flow of a sick and a healthy patient depending on the temperature . it can be seen that the liquid flow of the sick patient lies predominantly below that of a healthy patient . generally , one of the two curves is already sufficient for diagnosis , since the liquid flow and the blood vessel diameter are linked via the hagen - poiseuille equation . although modifications and changes may be suggested by those skilled in the art , it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art ,
in a device and method for examining the function , in particular the responsiveness , of blood vessels in a patient by creating a vascular constriction or dilation , the body part to be examined is heated or cooled in a controlled manner with an arrangement for local heating or cooling , and the blood or body - fluid flow through vessels that are dilated or constricted is measured dependent on the heating or cooling in this part of the body .