An apparatus (10, 400, 450, 500, 550, 600) for accessing the lumen of a vessel, the apparatus comprising: a reusable handheld device, wherein the reusable handheld device comprises, an imaging device attachment, wherein the imaging device attachment is adapted to secure an image capturing instrument (175, 420, 470, 520, 570, 620) to the reusable handheld device; an arm (45, 415, 465, 515, 565, 615) coupled to the imaging device attachment, wherein the arm provides a cartridge attachment; and a disposable cartridge (30, 100, 405, 455, 505, 555, 605) attached to the arm of the reusable handheld device, wherein the disposable cartridge comprises: - a slider track having a proximal end and a distal end, and - a needle slider slidably attached to the disposable cartridge (30, 100) to run, by sliding, along the slider track; wherein the disposable cartridge houses a needle (145, 425, 475, 525, 575, 625) coupled to the needle slider that is adapted to advance to an insertion depth to access the lumen of the vessel; characterised in that the arm (45, 415, 465, 515, 565, 615) comprises a slider stop bar coupled to the needle slider, wherein the slider stop bar is adapted to advance with the needle slider; and wherein the reusable handheld device further comprises a slide stop positioned in a sliding direction of the slider stop bar, and the slider stop bar is adapted to impede advancement of the needle (145, 425, 475, 525, 575, 625) when it comes into contact with the slide stop thereby preventing a medical practitioner from over advancing a needle past a target vessel. a reusable handheld device, wherein the reusable handheld device comprises, an imaging device attachment, wherein the imaging device attachment is adapted to secure an image capturing instrument (175, 420, 470, 520, 570, 620) to the reusable handheld device; an arm (45, 415, 465, 515, 565, 615) coupled to the imaging device attachment, wherein the arm provides a cartridge attachment; and a disposable cartridge (30, 100, 405, 455, 505, 555, 605) attached to the arm of the reusable handheld device, wherein the disposable cartridge comprises: - a slider track having a proximal end and a distal end, and - a needle slider slidably attached to the disposable cartridge (30, 100) to run, by sliding, along the slider track; - a slider track having a proximal end and a distal end, and - a needle slider slidably attached to the disposable cartridge (30, 100) to run, by sliding, along the slider track; wherein the disposable cartridge houses a needle (145, 425, 475, 525, 575, 625) coupled to the needle slider that is adapted to advance to an insertion depth to access the lumen of the vessel; characterised in that the arm (45, 415, 465, 515, 565, 615) comprises a slider stop bar coupled to the needle slider, wherein the slider stop bar is adapted to advance with the needle slider; and wherein the reusable handheld device further comprises a slide stop positioned in a sliding direction of the slider stop bar, and the slider stop bar is adapted to impede advancement of the needle (145, 425, 475, 525, 575, 625) when it comes into contact with the slide stop thereby preventing a medical practitioner from over advancing a needle past a target vessel.