Real-time three-dimensional reconstruction of intravascular ultrasound images of iliac arteries

shunt, proximal left pulmonary artery stenosis and a stenotic ductus arteriosus. Because of the childs small size, implantation of an endovascular stem within the ductus arteriosus wasperformed as palliation with a view toward a future surgical repair. Selective angiography in the ductus arteriosus showed a stenotic segment measuring 2.3 mm at its pulmonary artery insertion (Figure 2A). A 15 mm articulated PalmazSchatz coronary artery stent waspositioned across the length of the ductus and fixed in place with a 4 mm balloon. Repeat angiography demonstrated improved flow through a wider lumen, now measuring 4.0 mm at the narrowest point (Figure 2B). Arterial saturation increased to 84%. The child underwent anticoagulation, and at follow-up 2 months after implantation arterial oxygen saturation measured 85%. During implantation attempts were made to mmimize the degree of protrusion of the sterns into the aorta since the protruding portion of the stent is never covered by endotheliurn, posing the theoretic risk of acting as a nidus for thrombus formation. The experience with renal artery stems, however, suggest that

such protrusions are not associated with increased complications.4 Neither patient experienced any earlyor medium-term complications related to stent implantation. Long-term issues when using endovascular stems in such settings focus upon future requirements of the vessel involved, i.e., the need for further enlargement, ligation or unifocalization. It is possible to redilate such stents with larger balloon sixes if the intraluminal diameter becomes inadequate with time. Likewise, it is possible to cut longitudinally along the length of or ligate the stented vessel, permitting future vessel manipulation.5 Patients with pulmonary atresia and a ventricular septal defect are depcndant on systemic to pulmonary arterial connections to maintain pulmonary blood flow. As the natural history of these vessels is to stenose with time, surgically created system&to-pulmonary arterial shunts are usually required6 In some patients, as illustrated, creation of a surgical shunt may not be possible or dcsirable. A stent prosthesis to maintain patency of a naturally occurring source of pulmonary blood flow may be an attractive management alter-

Real-Time Three-Dimensional Reconstruction of Intravascular images of Iliac Arteries

native. To this end, Coe and Olley5 reported successful stent implantation to maintain ductal patency in an animal model. The experience reported here suggests that such an ap preach is feasible, and warrants further investigation.

1. Palmaz JC, Richter GM, Noeldge G, Schatz RA, Robison PD, Gardiner GA Jr, Becker GJ, McLear GK, Denny DF Jr, Lamer J, Paolini RM, Re.es CR, Alvarado R, Heiss HW, Root HD, Rogers W. Intrahnninal stents in atherosclerotic iliac artery stenosis: Preliminary report of a multicenter study. Radio&y 1988;168:727-731. 2. Schatz RA, Bairn DS, Leon M, Ellis SG, Goldberg S, Hirshfeld JW, Cleman MW, Cabin HS, Walker C, Stagg J, Buchbinder M, T&stein PS, Top01 EJ, Savage M, Perez JA, Curry RC, Whitworth H, Sousa JE, Tio F, Ahnagor Y, Ponder R, Penn IM, Leonard B, Levine SL, Fish RD, Paimu JC. Clinical experience with the Pahnaz-Schatz coronary stent. Initial results of a multicenter study. Cirah?ion 1991;83:148-161. 3. O’Lauehlin MP. Perry SB. Lock JE, Mullins CE. Use of &dovascul& stehts iA congenital heart d& case. Circulation 1991;83:1923-1939. 4. Rces CR, Palmaz JC, Becker GJ, Ehrman KO, Richter GM, Noeldge G, Katzen BT, Dake MD, Schwarten DE. Palmaz stent in atherosclerotic stenoses involving the ostia of the renal arteries: preliinary report of a multicenter study. Radiology 1991; 181-507-514. 5. Cot JY, Olley PM. A novel method to maintain ductus a&x&us aatencv. J Am CoN Cardioll991; 18:837-841. ’ 6. Haworth SG: Collateral acteria in pulmonary atrcsia with ventricular septai defect. A precarious blood supply. Br Heart J 1980;44:5-13.

detailed IU data, facilitating comparison of selected cross-sectional Ultrasound images with those that are proximal and distal. Previous studies from our laboratory have outlined the conKenneth Rosenfield, MD, Jenifer Kaufman, BS, Ann Pieczek, RN, cepts, technique and instrumentation R. Eugene Langevin, Jr., MD, Syed Razvi, MD, and Jeffrey M. Isner, MD used for 3-DR, and demonstrated the feasibility and potential use of 3ntravascular ultrasound (IU) im- segment in a composite format; de- DR.4-6 Whereas off-line analysis of aging provides detailed tomotailed cross-sectional images are thus such 3-DRs has provided insight into mechanisms of recanalization, to be graphic images of the vascular wall provided at the expense of a longituand lumen.1-3 One liability of this dinal perspective. The circumferenclinically useful during interventionnovel imaging modality, however, is tial nature of a postangioplasty dis- al procedures, 3-D image generation the inability to view a given vascular section may be well demonstrated by must be rapid, if not instantaneous. We report here the use of real-time 3IU, for example, but the fidl longituFrom tbe Departments of Medicine (CardiolDR from IU images recorded during dinal extent may not be readily ap ogy), Radiology, Surgery (Vascular), and Biomedical Research, St. Elizabeth’s Hospital, parent, even after repeated review of percutaneous iliac artery revascular736 Cambridge Street, Tufts University the videotaped images recorded over ization in 2 patients. School of Medicine, Boston, Massachusetts. CASE I. A 59-year-old woman the length of the involved segment. This study was supported in part by grant HL Computer-based 3dimensional (3- presented with IO-yard claudication 405 18 from the National Institutes of Health, D) reconstruction (R) from serially due to a critical 90% luminal diameBetheada, Maryland, and grants from the John and Cora Davis Foundation, Washingrecorded IU images offers a potential ter narrowing of the left common iliton, D.C., and the Women’s Aid for Heart solution to this problem. By creating ac artery. After baseline IU and Research, Boston, Massachusetts. Manuscript a longitudinal display of the entire measurement of a 40 mm Hgpresreceived February 12, 1992. Revised maxmvascular segment, 3-DR offers a sure gradient across the narrowing, script received March 30, 1992, and accepted April 4. composite format for presentation of percutaneous transluminal coronary

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angioplasty (PTA) was performed. Post-PTA, repeat angiography, IU, and gradient measurement (15 mm Hg) indicated a residual stenosis. An endovascular stent (Johnson and Johnson Interventional Systems, Warren, New Jersey) was therefore

FIGURE ~voyny6

delivered to the PTA site with subsequent elimination of the pressure gradient and stenosis. The IUcatheter (Boston Scientijc, Watertown, Massachusetts) and imaging console (Diasonics, Milpitas, California) have been described previous-

IY.‘-,~For each of the nine 3-DR.7 obtained in this case, a systematic, timed pullback of the IU catheter was performed through the diseased iliac artery at 2 mm/s. As the catheter was withdrawn, live IU images were acquired directly into a 3-D

1. Real-time

3dmen~hd b (3-DR) behe and after percutaneous trand~minal angiophty (PTA) and in cemmon iE”. artery of patient 1. Panel A, frames 1 to 6, reprerrentative *hages from expanding 3-DR ~concurentvnthpre-pTApulbadcOti~~~ulbawund(IU)~.Aortaisat topofLnagcs ade~~Piac-abottonr.IU~~~irsrmwilhinvesrelknnn.Atkvclot~*indiukdin~a~6,plrque dlUtSIU compromising vasadar hewn. Pam/ 6, frames 1 to 6, expanding 3-DR sagRtal image dwing post-,==-a PTACdh@kfpdMCk dememtratesehance6hmliil(#Pame S), but extensive plaque fracture encroaching upon lumen. Pane/ C, Irames 2 to 6, real-time 3-DR post&d deployment. Expanding sagittal image depicts effacement ofpbclwfractweinareaofstentdeploymentwithinproximal cemmen ‘WC artery (hame S), producing enlarged lumen. CASE REPORTS

413

processing station (Stat VIEW”, ImageComm Systems, Sunnyvale, Caltfornia) and added to an enlarging 3-D data map. Fresh data points were immediately displayed on the expanding reconstructed sagittal image. Generation of the 3-D image is thus accomplished in real time, with no perceptable delay between display of the tomographic IUimage and incorporation of that 2-dimensional image into the expanding 3DR. Representative images from 3 real-time 3-DRs, obtained before

and after PTA, and poststent deployment are shown in Figure I. In panel A, frames 1 to 6 illustrate development of the reconstructed sag ittal image in real time during the IU pullback performed before PTA. The fully reconstructed image Cframe 6) is seen concurrent with completion of the catheter pullback. Although only I sagittal plane is shown for a given pullback, the image can be subsequently rotated about the long axis of the IU catheter to display 360” of orthogonal views of this segment. The 3-DR im-

FlDURE 2. Real-time 3dmsdmd remhudh lng intravasadar dtrasemd (IVUS) dheter tramhminai mgiopb@

plbadc (PTA),

(3-DR) of sagiRal images duin patisni 2. Upper pmeh repremhlive 2dmemiem

of 220 in&l&al images inaperated inta sagittal3-DR image, shswn expanding in hwnes 2 b 3. IVUS cahter, bcated withb~ vasadar hnsn, is abutted by alh~pb
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age depicts luminal encroachment by plaque which is not readily appreciated on the 2-dimensional IU images. Panel B shows real-time 3-DR in the sagittal mode during IUpullback after PTA. Frame 6 demonstrates increased luminal patency and a plaque crack, seen here in longitudinal relief: Real-time 3-DR in panel C shows further improvement in luminal patency and effacement of the plaque fracture consequent to stent deployment. CASE 2. A 68-year-old woman presented with bilateral claudication due to severe iliac stenoses. After baseline IU, PTA was performed on both iliac arteries. IU examination, angiography and hemodynamic assessment performed after PTA indicated a satisfactory result on the left side, but a residual stenosis due to a spiral dissection on the right. This was treated successfully by directional atherectomy. Figure 2 demonstrates real-time 3-DR performed during PTA of the right external iliac artery. Two-dimensional lU images are shown on the left. Before PTA, the sagittal 3-DR image recorded during pullback (upper panel) demonstrates the longitudinal extent of the luminal narrowing and atherosclerotic plaque. After PTA (lower panel), the developing 3-DR shows an improvement in luminal diameter but persistent encroachment due to a PTA-induced plaque fracture immediately distal to the internal iliac artery. After atherectomy, this plaque fracture was no longer seen.

Initial 3-DRs performed in our laboratory, using nonautomated software, required 60 minutes or more to generate a single image.4 While useful for post-hoc (off-line) analyses, the time required for 3-DR by such techniques precluded its use during diagnostic or therapeutic procedures. Subsequent software and hardware modifications, including upgrading from an 80386 to an 80486 processor and incorporation of a RISC co-processor (Intel i860, ImageComm Systems), greatly reduced the labor involved and time required for 3-D processing and image generation5 although 3-DR was still limited to a postprccedural process. More recently, however, “on-line” 3-DR6 was achieved during interventional pro-

cedures, where images were generated within 30 to 60 seconds of catheter pullback in 42 patients. For those patients, IU images were acquired during pullback by the 80486 processor, written to hard disc, then loaded into the RISC coprocessor memory for 3D processing and image rendering. The newest software configuration, used for the 2 patients in the present report, eliminates the 30-second delay necessitated by the storage of acquired IU frames into the 80486 hard disc. Instead, images are acquired directly into RISC co-processor memory (bypassing the 80486), at rates up to 30 frames per second for immediate processing. The IU data are entered into an expanding 3-

D map during the actual pullback, enabling concurrent (real-time) display of a sag&al 3-DR image as the catheter is pulled back. Display of alternative 3-D formats is then rapidly accomplished by way of mouse manipulation. The expedited, real-time rendering of 3-DR described in this report thus makes 3-DR a practical tool for guiding interventional procedures. 1. Tohis JM, Mallery JA, C&.se.rt J, Griffith JM. Mahon D, Bessen M, Moriuchi M, McLeay L, h&Rae. M, Hem-y WL. Intravasctdar ultrasound cross+ectional arterial imaging hefore and after balloon angioplasty in vilro. Circularion 1989;BO: 873-882. 2. Yock PG, Fitzgerald PJ, Lmdcr DT. Angelsen BAJ, Tech DR. Intravascular ultrasound guidance

for catheter-based coronary interventions. J Am Chll Chrdiol 1991;17:39B-458. 3. hkin BN, Bartorelfi AL, Gessert JM, Nevil e RF, Almagor Y, Roberts WC, Leon MB. Coronary artery imaging with intravascular high-frequency ultrasuund. Circularion 1990;81:157S1585. 4. Dekus ST, Rosenfield K, Loscrdo DW, Kelly S, Pakfski P, Lang&n RE Jr, Razvi S, fsner JM. Three-Dimensional rwonstruction of vascular lumen from images recorded during percutaneous 2D intravascular ultrasound (abstr). Clin Res 1989;373838A. 5. Rosenfield K. Lmordo DW, Ramaswamy K, Pastore JO, Langevin RE Jr, Razvi S, Kasowsky BK, her JM. Three-dimensional reconstruction of human coronary and peripheral arteries from images recorded during two-dimensional intravascular ultrasound examination. Circulation 1991;884: 1938-1956. 6. Rcsenfield K, Kaufman J, Pieczek A, Langevin RI% Palefski P. Razvi S. lsner JM. On-Iii (live) three-dimensional reconstruction from twudimensional intravascular uhrasound imags recorded during percutaneous revascularization of human corenary and peripheral arteries: work in progress. Rediolqy; in press.

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