The invention provides systems and methods for aligning or guiding instruments during image-guided interventions. A volumetric medical scan (image data) of a patient may first be registered to patient space data regarding the patient obtained using a tracking device. An ultrasound simulator fitted with position indicating elements whose location is tracked by the tracking device is introduced to the surface of the anatomy of the patient and used to determine an imaginary ultrasound scan plane for the ultrasound simulator. This scan plane is used to reformat the image data so that the image data can be displayed to a user in a manner analogous to a handheld ultrasound transducer by re-slicing the image data according to the location and orientation of the ultrasound simulator. The location of an instrument fitted with position indicating elements tracked by the tracking device may be projected onto the re-sliced scan data.