A medical device comprising: an instrument (710; 720; 820); a shaft (102; 402; 802) including a working channel (230; 330a; 330b; 332a; 430) extending from a proximal end of the shaft (102; 402; 802) to a distal end of the shaft (102; 402; 802), wherein the working channel (230; 330a; 330b; 332a; 430) is configured to receive the instrument (710; 720; 820) and maintain an orientation of the instrument with respect to the shaft; and an ultrasound sensor (150; 350a; 450; 850) disposed radially outward of a distal portion of the working channel (230; 330a; 330b; 332a; 430) such that the ultrasound sensor (150; 350a; 450; 850) at least partially surrounds the working channel (230; 330a; 330b; 332a; 430); the instrument (710; 720; 820) being translatable from the proximal end to the distal end of the shaft (102; 402; 802), wherein a distal end of the instrument has a unique radial location upon exiting the distal end of the shaft (102; 402; 802), wherein the instrument (710; 720; 820) comprises a flexible material and has a preset curved configuration, such that the distal end of the instrument (710; 720; 820) has a substantially straight configuration within the working channel (230; 330a; 330b; 332a; 430) and the curved configuration outside the working channel (230; 330a; 330b; 332a; 430), the shaft (102; 402; 802) including an echogenic area (211; 411; 811), wherein the echogenic area (211; 411; 811) has a fixed position with respect to the working channel (230; 330a; 330b; 332a; 430) and has an echogenic signature that is distinct from a remainder of the shaft (102; 402; 802), and wherein the distal end of the instrument comes within a field of view of the ultrasound sensor when the instrument exits the working channel to adopt the preset curved configuration. an instrument (710; 720; 820); a shaft (102; 402; 802) including a working channel (230; 330a; 330b; 332a; 430) extending from a proximal end of the shaft (102; 402; 802) to a distal end of the shaft (102; 402; 802), wherein the working channel (230; 330a; 330b; 332a; 430) is configured to receive the instrument (710; 720; 820) and maintain an orientation of the instrument with respect to the shaft; and an ultrasound sensor (150; 350a; 450; 850) disposed radially outward of a distal portion of the working channel (230; 330a; 330b; 332a; 430) such that the ultrasound sensor (150; 350a; 450; 850) at least partially surrounds the working channel (230; 330a; 330b; 332a; 430); the instrument (710; 720; 820) being translatable from the proximal end to the distal end of the shaft (102; 402; 802), wherein a distal end of the instrument has a unique radial location upon exiting the distal end of the shaft (102; 402; 802), wherein the instrument (710; 720; 820) comprises a flexible material and has a preset curved configuration, such that the distal end of the instrument (710; 720; 820) has a substantially straight configuration within the working channel (230; 330a; 330b; 332a; 430) and the curved configuration outside the working channel (230; 330a; 330b; 332a; 430), the shaft (102; 402; 802) including an echogenic area (211; 411; 811), wherein the echogenic area (211; 411; 811) has a fixed position with respect to the working channel (230; 330a; 330b; 332a; 430) and has an echogenic signature that is distinct from a remainder of the shaft (102; 402; 802), and wherein the distal end of the instrument comes within a field of view of the ultrasound sensor when the instrument exits the working channel to adopt the preset curved configuration. <EOS>