A device for ultrasound-based reflection and transmission tomography, comprising: a transducer holder configured to hold a plurality of ultrasonic transducers around an imaging volume to be filled with an ultrasonic coupling medium, the transducer holder having an opening for inserting, into the imaging volume, at least one part of a body to be imaged, wherein the transducer holder is configured to move, during imaging of the at least one part of the body to be imaged, with respect to the body to be imaged; a support member configured to support, during imaging, the body to be imaged, the support member having a support-member-opening allowing access to the transducer holder by the at least one part of the body to be imaged; and an outlet for the ultrasonic coupling medium to flow out of the imaging volume when the at least one part of the body to be imaged is inserted into the imaging volume filled with the ultrasonic coupling medium and/or during imaging; characterized in that the device further comprises: a diaphragm having a diaphragm-opening, the diaphragm being arranged across the support-member-opening such that a center of the diaphragm-opening is placed substantially at a predetermined position, wherein the diaphragm comprises a material that has a higher transmissivity of ultrasound than a material of the support member; and an elastic membrane comprising a fluid-tight material connecting the transducer holder and the outlet in order to guide the ultrasonic coupling medium flowing out of the imaging volume towards the outlet. a transducer holder configured to hold a plurality of ultrasonic transducers around an imaging volume to be filled with an ultrasonic coupling medium, the transducer holder having an opening for inserting, into the imaging volume, at least one part of a body to be imaged, wherein the transducer holder is configured to move, during imaging of the at least one part of the body to be imaged, with respect to the body to be imaged; a support member configured to support, during imaging, the body to be imaged, the support member having a support-member-opening allowing access to the transducer holder by the at least one part of the body to be imaged; and an outlet for the ultrasonic coupling medium to flow out of the imaging volume when the at least one part of the body to be imaged is inserted into the imaging volume filled with the ultrasonic coupling medium and/or during imaging; characterized in that the device further comprises: a diaphragm having a diaphragm-opening, the diaphragm being arranged across the support-member-opening such that a center of the diaphragm-opening is placed substantially at a predetermined position, wherein the diaphragm comprises a material that has a higher transmissivity of ultrasound than a material of the support member; and an elastic membrane comprising a fluid-tight material connecting the transducer holder and the outlet in order to guide the ultrasonic coupling medium flowing out of the imaging volume towards the outlet. a diaphragm having a diaphragm-opening, the diaphragm being arranged across the support-member-opening such that a center of the diaphragm-opening is placed substantially at a predetermined position, wherein the diaphragm comprises a material that has a higher transmissivity of ultrasound than a material of the support member; and an elastic membrane comprising a fluid-tight material connecting the transducer holder and the outlet in order to guide the ultrasonic coupling medium flowing out of the imaging volume towards the outlet.