A device for implanting a plurality of fiducial markers into a tissue, comprising: a needle having a proximal end, a distal end, and a lumen extending therebetween; a stylet having a proximal end and a distal end, wherein the distal end is sized to slide within the lumen of the needle; a multi-stop stylet spacer having a plurality of stopping features (515, 525, 530) configured to engage with the stylet to stop the distal end of the stylet at a plurality of predetermined distances from the distal end of the needle, wherein the multi-stop stylet spacer is adjustable between three positions, wherein: in a first position the proximal end of the stylet engages a first stopping feature to stop the distal end of the stylet in a first location with respect to the distal end of the needle; in a second position the proximal end of the stylet engages a second stopping feature to stop the distal end of the stylet in a second location located distal to the first location; and in a third position the proximal end of the stylet engages a third stopping feature to stop the distal end of the stylet in a third location located distal to the second location; and further comprising a plurality of fiducial markers housed within the lumen of the needle, wherein: in the first position the first stopping feature prevents deployment of any of the plurality of fiducial markers from the distal end of the needle; and in the second position the second stopping feature permits the deployment of a first of the plurality of fiducial markers while preventing the deployment of a second of the plurality of fiducial markers. a needle having a proximal end, a distal end, and a lumen extending therebetween; a stylet having a proximal end and a distal end, wherein the distal end is sized to slide within the lumen of the needle; a multi-stop stylet spacer having a plurality of stopping features (515, 525, 530) configured to engage with the stylet to stop the distal end of the stylet at a plurality of predetermined distances from the distal end of the needle, wherein the multi-stop stylet spacer is adjustable between three positions, wherein: in a first position the proximal end of the stylet engages a first stopping feature to stop the distal end of the stylet in a first location with respect to the distal end of the needle; in a second position the proximal end of the stylet engages a second stopping feature to stop the distal end of the stylet in a second location located distal to the first location; and in a third position the proximal end of the stylet engages a third stopping feature to stop the distal end of the stylet in a third location located distal to the second location; and in a first position the proximal end of the stylet engages a first stopping feature to stop the distal end of the stylet in a first location with respect to the distal end of the needle; in a second position the proximal end of the stylet engages a second stopping feature to stop the distal end of the stylet in a second location located distal to the first location; and in a third position the proximal end of the stylet engages a third stopping feature to stop the distal end of the stylet in a third location located distal to the second location; and further comprising a plurality of fiducial markers housed within the lumen of the needle, wherein: in the first position the first stopping feature prevents deployment of any of the plurality of fiducial markers from the distal end of the needle; and in the second position the second stopping feature permits the deployment of a first of the plurality of fiducial markers while preventing the deployment of a second of the plurality of fiducial markers. in the first position the first stopping feature prevents deployment of any of the plurality of fiducial markers from the distal end of the needle; and in the second position the second stopping feature permits the deployment of a first of the plurality of fiducial markers while preventing the deployment of a second of the plurality of fiducial markers.