Comparative Study between Centerline and Straight-Line Measurement of the External Carotid Artery Length

Takashi Ohya DDS, PhD, Department of Oral and Maxillofacial Surgery, Yokohama Sakae Kyosai Hospital, Yokohama, Japan
Toshinori Iwai DDS, Department of Oral and Maxillofacial Surgery, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Kenji Mitsudo DDS, PhD, Department of Oral and Maxillofacial Surgery, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Noboru Kanazawa , Department of Precision Engineering, The University of Tokyo Graduate School of Engineering, Tokyo, Japan
Takashi Kato , Department of Precision Engineering, The University of Tokyo Graduate School of Engineering, Tokyo, Japan
Junchen Wang Ph.D., Department of Precision Engineering, The University of Tokyo Graduate School of Engineering, Tokyo, Japan
Etsuko Kobayashi PhD, Department of Precision Engineering, The University of Tokyo Graduate School of Engineering, Tokyo, Japan
Shinsuke Ohta DDS , PhD, Department of Oral and Maxillofacial Surgery, Yokohama Sakae Kyosai Hospital, Yokohama, Japan
Ichiro Sakuma Ph.D., Department of Precision Engineering, The University of Tokyo Graduate School of Engineering, Tokyo, Japan
Iwai Tohnai D.D.S., Ph.D., Department of Oral and Maxillofacial Surgery, Yokohama City University Graduate School of Medicine, Yokohama, Japan
Retrograde superselective intra-arterial chemotherapy is feasible for oral cancer treatment, because the chemotherapy can provide high concentration of anti-cancer drugs into the tumor feeding arteries. However, this method requires surgeon‘s experience and skill for catheterization into the target artery because surgeons rely on only two-dimentional C-arm image intraopelatively. To avoid prolonged operation time,  excessive radiation exposure and contrast medium, we have developed a prototype of electromagnetic maxillofacial catheter navigation system [1]. This system provides surgeons the three-dimensional external carotid artery (ECA) image intraoperatively. However, the difference between three-dimentional ECA measurement (CTA image) and two-dimentional ECA measurement (C-arm image) is not clear. The aim of this study was to clarify the difference between centerline length and straight-line (perpendicular to F-H plane) length of ECA.

A multislice CT scanner (Aquilion 64; Toshiba Medical Systems, Tokyo, Japan) with 0.5-mm × 64-slice collimation was used for scanning CTA image. Twenty patients who were scanned by CTA (pre-treatment for oral cancer) were selected at random and forty arteries were analyzed. The segmentation procedure (binary image processing of CTA images) was carried out using Mimics (Materialize, Leuven, Belgium). CA and maxillofacial surface rendering bone models were reconstructed by the previously reported method [2]. The CA centerlines were extracted automatically by Mimics.

The fiducial bifurcation points were as follows; vA: superior thyroid artery via common carotid artery (CCA), vB: internal carotid artery and ECA via CCA, vC: lingual artery via ECA, vD: facial artery via ECA, vE: occipital artery via ECA, vF: maxillary artery via ECA.    

In addition, F-H plane model (box-shaped surface rendering model) was created and its size was 250 × 250 × 1 mm. Straight-line between F-H plane and CA bifurcation point was measured as follows: First, position coordinates of three points on underside of F-H plane were measured at random. The coefficients a, b, c, d of F-H plane equation (ax+by+cz+d=0) were calculated by these position coordinates. Next, position coordinates A (x1, y1, z1) of bifurcation point were measured using the extracted centerline. Finally, straight-line lengths h (perpendicular to F-H plane) were calculated by equation (h=(ax1+by1+cz1+d)(a2+b2+c2)-1/2  ). Finally, centerlines length of ECA between F-H plane and bifurcation point were compared to straight-lines length. 

The straight-line (a) and centreline (b) lengths from F-H plane to each bifurcation points (vA|vF) were indicated as follows [mean±std. (mm)].vA; (a)81.1±9.8, (b)113.6±11.6, vB; (a)84.1±12.4, (b)117.8±13.3, vC; (a)67.0±7.9, (b)98.1±10.4, vD; (a)59.4±8.6, (b)89.6±12.4, vE; (a)61.3±8.8, (b)91.7±12.3, vF; (a)26.7±3.4, (b)39.3±7.2.

We proved that the centerlines length of ECA were about 34 mm longer than the straight-lines length (perpendicular to F-H plane). This study did not show a strong correlation between centerline and straight-lines length. Therefore, surgeons should measure the three-dimensional ECA length (centerline length) before catheterization.

[1]  Wang, J., Ohya, T., Liao, H., Sakuma, I., Wang, T., Tohnai, I, and Iwai, T (2011) Intravascular catheter navigation using path planning and virtual visual feedback for oral cancer treatment. The International Journal of Medical Robotics and Computer Assisted Surgery 7 (2):214-224.

[2] Ohya, T., Iwai, T., Luan, K., Kato, T., Liao, H., Kobayashi, E., Mitsudo, K., Fuwa,N., Kohno, R., Sakuma, I, and Tohnai, I (2012) Analysis of carotid artery deformation in different head and neck positions for maxillofacial catheter navigation in advanced oral cancer treatment. Biomed Eng Online 11:65.






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