1. Implantable sensor for intraoperative and postoperative monitoring of blood flow: A preliminary report 
Raphael S. Rabinovitz, PhD, Craig J. Hartley, PhD, Lloyd H. Michael, PhD, Mark L. Entman, MD, Hal K. Hawkins, PhD, MD, Michael E. Sekela, MD, George P. Noon, MD 
Journal of Vascular Surgery 
Volume 12, Issue 2, Pages (August 1990)
DOI: / (90)90103-H
Copyright © 1990 Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter Terms and Conditions

2. Fig. 1
A perspective view of the WRAP sensor when it is wrapped around a blood vessel. See text for explanation.
Journal of Vascular Surgery  , DOI: ( / (90)90103-H)
Copyright © 1990 Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter Terms and Conditions

3. Fig. 2
The nonsurgical extraction procedure of the WRAF sensor. The external sutures holding the flexible tubing to the skin have already been removed. In a the external end of the sensor is shown before the extraction process. The end of the release cable is covered by a cap to assure that the release mechanism is not accidentally actuated. When sensor extraction is desired, the cap is removed as shown in b. A portion of the release cable extends outside. In c the end of the release cable is grasped and pulled back which releases the suture at the other end of the cable. Consequently, the sensor unwinds from around the vessel. Further traction on the flexible tubing will pull the sensor out of the patient.
Journal of Vascular Surgery  , DOI: ( / (90)90103-H)
Copyright © 1990 Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter Terms and Conditions

4. Fig. 3
Duration of sensor application in dogs. Bar height indicates the total number of vessels implanted with the sensor for specified duration (in days). As an example, one carotid artery, 1 LCX artery and 2 LAD arteries (a total of four arteries) were implanted for 3 days. LCX, Left circumflex coronary artery; LAD, left anterior descending coronary artery.
Journal of Vascular Surgery  , DOI: ( / (90)90103-H)
Copyright © 1990 Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter Terms and Conditions

5. Fig. 4
Histologic cross sections of canine epicardial left anterior descending coronary arteries 7 days after operation. In Fig. 4, a, the artery was subjected to blunt dissection as if for placement of a WRAF sensor, but with no sensor placement. There is granulation tissue and focal fat necrosis near the vessel (arrow), and a mild chronic inflammatory infiltrate best seen at a branch point (asterisk). (Hematoxylin-eosin stain; original magnification × 85.) In Fig. 5, b, the vessel was encircled with a WRAF sensor for 7 days. There is a mild inflammatory reaction with a few foreign body giant cells immediately adjacent to the sinus tract where the sensor resided (arrow). A box indicates the segment of the arterial wall that is enlarged in Fig. 4, c. (Hematoxylin-eosin stain; original magnification × 85.) As shown in Fig. 4, c, the arterial wall is essentially unaltered by the presence of the sensor, except for a mild endothelial reaction (asterisk). (Hematoxylin-eosin stain; original magnification × 425.)
Journal of Vascular Surgery  , DOI: ( / (90)90103-H)
Copyright © 1990 Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter Terms and Conditions

6. Fig. 5
In vitro a and in vivo b relationship between volume flow measured by timing the collection of fluid in a graduated cylinder and the WRAF sensor output. The pulsed Doppler sample volume was located at a site where the velocity signal had a maximum value. WRAF sensor volume flow was estimated by calculating the spatially averaged blood velocity (which was assumed to be half the maximum spatial velocity) from the Doppler equation (equation 1 in the Appendix), and multiplying by the cross-sectional area.
Journal of Vascular Surgery  , DOI: ( / (90)90103-H)
Copyright © 1990 Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter Terms and Conditions

7. Fig. 6
In vitro relationship between the outputs of electromagnetic flow (EMF) sensor and WRAF sensor (the velocity signal is scaled in KHz of Doppler shift). The pulsed Doppler sample volume was located at a site where the velocity signal had a maximum value.
Journal of Vascular Surgery  , DOI: ( / (90)90103-H)
Copyright © 1990 Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter Terms and Conditions

8. Fig. 7
Intraoperative comparison of canine a and human b blood flow measurements by EMF sensor and WRAF sensor (the velocity signal is scaled in KHz of Doppler shift). The pulsed Doppler sample volume was located at a site where the velocity signal had a maximum value. In the dog a, both sensors were attached to the left anterior descending coronary artery (LAD), which was about 2.5 mm in diameter. The EMF sensor was removed before the chest was closed, and the WRAF sensor was left in place and extracted from the conscious animal 7 days after operation with no adverse effects. In the patient b, both sensors were attached to the right coronary saphenous vein bypass graft, which was approximately 3.5 mm in diameter. The sensors were removed before the chest was closed.
Journal of Vascular Surgery  , DOI: ( / (90)90103-H)
Copyright © 1990 Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter Terms and Conditions