A medical instrument (200, 400) comprising: - a magnetic resonance imaging system for acquiring magnetic resonance data from a subject within an imaging zone; - a high intensity focused ultrasound system for directing ultrasound along a beam axis for sonicating a target zone, wherein the target zone is within the imaging zone; - a processor for controlling the medical instrument; - a memory for storing machine readable instructions, wherein execution of the instructions causes the processor to: - control the magnetic resonance imaging system to acquire the magnetic resonance data using a pulse sequence, wherein the pulse sequence comprises an acoustic radiation force imaging pulse sequence (500, 600), wherein the acoustic radiation force imaging pulse sequence comprises an excitation pulse, wherein the acoustic radiation force imaging pulse sequence comprises a multi-dimensional gradient pulse applied during the radio frequency excitation pulse for selectively exciting a region of interest, - wherein the region of interest comprises a predetermined volume that encompasses the target zone and at least a portion of the beam axis; and - control the high intensity focused ultrasound system to sonicate the target zone such that the sonication of the target zone occurs during the acoustic radiation force imaging pulse sequence; and - reconstruct a radiation force image using the magnetic resonance data, characterized in that the multi-dimensional gradient pulse is a two-dimensional pencil beam gradient pulse for exciting the region of interest such that the region of interest has a two dimensional cross section, wherein the two-dimensional cross section has rotational symmetry with respect to a region of interest axis, and wherein the region of interest axis and the beam axis are coaxial. - a magnetic resonance imaging system for acquiring magnetic resonance data from a subject within an imaging zone; - a high intensity focused ultrasound system for directing ultrasound along a beam axis for sonicating a target zone, wherein the target zone is within the imaging zone; - a processor for controlling the medical instrument; - a memory for storing machine readable instructions, wherein execution of the instructions causes the processor to: - control the magnetic resonance imaging system to acquire the magnetic resonance data using a pulse sequence, wherein the pulse sequence comprises an acoustic radiation force imaging pulse sequence (500, 600), wherein the acoustic radiation force imaging pulse sequence comprises an excitation pulse, wherein the acoustic radiation force imaging pulse sequence comprises a multi-dimensional gradient pulse applied during the radio frequency excitation pulse for selectively exciting a region of interest, - wherein the region of interest comprises a predetermined volume that encompasses the target zone and at least a portion of the beam axis; and - control the high intensity focused ultrasound system to sonicate the target zone such that the sonication of the target zone occurs during the acoustic radiation force imaging pulse sequence; and - reconstruct a radiation force image using the magnetic resonance data, characterized in that - control the magnetic resonance imaging system to acquire the magnetic resonance data using a pulse sequence, wherein the pulse sequence comprises an acoustic radiation force imaging pulse sequence (500, 600), wherein the acoustic radiation force imaging pulse sequence comprises an excitation pulse, wherein the acoustic radiation force imaging pulse sequence comprises a multi-dimensional gradient pulse applied during the radio frequency excitation pulse for selectively exciting a region of interest, - wherein the region of interest comprises a predetermined volume that encompasses the target zone and at least a portion of the beam axis; and - control the high intensity focused ultrasound system to sonicate the target zone such that the sonication of the target zone occurs during the acoustic radiation force imaging pulse sequence; and - reconstruct a radiation force image using the magnetic resonance data, characterized in that