Journal of Neuro-Ophthalmology, March 1982, Volume 2, Issue 1

Intravenous digital subtraction angiography in neuro-ophthalmology.

The development of computer reconstructed images of the extracranial and intracranial vessels after injecting modest doses of intravenous contrast media has significantly altered standard angiography procedures. Intravenous digital subtraction angiography is a reproducible and rapid outpatient procedure that is less expensive and safer than conventional arteriography. The applications and limitations of this new technique to neuro-ophthalmology are discussed.

]. Clin. Neuro-ophth.llmol. 2: 23-31, I Q82. Intravenous Digital Subtraction Angiography in Neuro-ophthalmology ROBERT L. TOMSAK, M.D., Ph.D. MICHAEL T. MODIC M.D. MEREDITH A. WEINSTEIN, M.D. Abstract The development of computer reconstructed images of the extracranial and intracranial vessels after injecting modest doses of intravenous contrast media has significantly altered standard angiography procedures. Intravenous digital subtraction angiography is a reproducible and rapid outpatient procedure that is less expensive and safer than conventional arteriography. The applications and limitations of this new technique to neuro-ophthalmology are discussed. Introduction The evaluation of visual loss, diplopia, visual field defects, proptosis, and other neuro-ophthal­mic problems often requires the use of cerebral angiography. However, conventional cerebral an­giography is potentially hazardous and usually re­quires hospitalization. This communication highlights the neuro-oph­thalmic uses of intravenous digital subtraction an­giography; a new, safer, and less expensive method of studying the extracranial and intracranial cere­bral circulation. Technique Overview Digital radiography represents a new way to record radiographic data. Previously, most radio­graphic data was recorded in an analog mode on either radiographic or cine film. The densities on these films are related to the amount of light or x­rays to which they have been exposed. Once the film is exposed, there can be no further manipu­lation of the image. With digital radiography, the Neuro-ophthalmologist, Department of Ophthalmology (RLn, and Neuroradiologist, Division of Radiology (MTM, MAW), Cleveland Clinic Foundation, Cleveland, Ohio. March 1982 data is stored in a computer and can be postpro­cessed while reviewed on a cathode ray tube. The contrast and density of the image can be changed over a large spectrum. Since the density and con­trast can be modified after the exposure is made, there is no need to repeat exposures because of improper technique. This reduces patient exposure and permits more efficient use of staff and equip­ment. Intravenous digital subtraction angiography is performed by obtaining a radiographic exposure of a portion of the body before and after the intravenous administration of contrast material. The signal produced by a television camera that scans an image intensifier is converted from analog to digital. The image obtained prior to the admin­istration of contrast material (Fig. 1) is electroni­cally subtracted from an image obtained following the administration of contrast material and its ar­rival in the region of interest (Fig. 2). This results in a real-time subtracted image (Fig. 3). With computer reprocessing of images, and di­gitial subtraction of unnecessary background in­formation, an enhanced contrast sensitivity results that allows identification of low concentrations of intravenously injected iodine. The visualization of I-mm objects at 1% contrast is possible. It is pri­marily the subtraction process that allows the vis­ualization of this low concentration of iodine. Elec­tronic digital subtraction is faster, more accurate, and less expensive than conventional film screen subtraction. Equipment ratients were examined on a commercially avail­able production digital subtraction angiography model unit with a 512 X 512 matrix. The produc­tion model used an x-ray tube with a nominal focal spot selection of 0.6/1.2 mm and a heat capacity of 400,000 heat units. A 1,000-MA generator was used. X-rays were detected using a trimodal (9-, 6-, and 4.5-inch) cesium iodide image intensifier tube and a 12:1 grid with 40-line pairs/em. The 23 Digit.11 Sublr.lclion Angiogr,lphy Figure I. left anterior oblique digital radiograph of the ned. before the injection of contrast. ri~ure 2. L,.lIW' ., ... 11\ ri~~ J. bllt "'''-Pil t\\lhl\Vln~ the.' intr~lVetH)lI" 1f111" tl1111 ,II ·10 II III I \Inlr.' .... t 1ll,'II'rl.,1 f':,)te t.unt IIp..lrifit:.llillil ·1 t I·, '1"" "',',1·1-. 1.11 r 11\\", 1 Figure 3. Digital subtracted Image obtamed after the computer subtraction of Figs. I and 2. output phosphor of the image was scanned with a lead oxide video camera tube. The video signal from the camera is logarithmically amplified and digitized for storage in the imager, which has two 512 X 512 X 12 bit memories. A digital POP 11/34 computer is used for image processing. An 8-inch, 1b-gauge angiocatheter is inserted in an arm vein by a nurse in a holding area to expedite the examination. The catheter position is examined fluoroscopically after a small test injection of con­trast media. Forty cc of Renografin-76 is the usual bolus dose with 3 cc/kg, or five injections as the usual limit, depending on the patient's weight, age, and renal function. The injection rate is from 12 to 20 cc/second. A layered 5% Dextrose in water solution acts to flush the contrast material and decrease the time and concentration of contrast material within the vein. T.V. signals are digitized on a variety of formats, including 128 X 128, 256 X 256, and 512 X 512, at rates from 16/second to l/second, depending on the matrix size. Two memory stores allow mask frame storage in one, while the subtracted images are viewed in real time from the second. Interfacing with a computer allows immediate reprocessing of images in various ranges most suitable to image requirements and the observer preference. Hard copies are made on a multiformat camera for rec- Journal of Clinical Neuro-ophthalmology ord keeping. Average doses of radiation per study have been recorded to be 1-5 rads at the skin. Illustrative Cases Case l-Extracranial Carotid Occlusive Disease A 60-year-old man suddenly and painlessly lost vision in the right eye. Examination 3 days later revealed hand movements vision and classic fun­dus findings of embolic retinal artery occlusion (Fig. 4). The remainder of the neuro-ophthalmic examination was normal except for a right carotid bruit. Both the conventional arteriogram (Fig. Sa) and the intravenous digital subtraction angiogram (Fig. 5b) clearly show significant stenosis of the right internal carotid artery just above the bifurcation. Case 2 -lntracavernous Carotid Aneurysm A 61-year-old woman presented with a painless, complete left sixth nerve paresis of 3112 years du­ration. A Tensilon test was negative. Orbital com­puterized tomography and forced ductions failed to document thyroid ophthalmopathy, although she had a past history of hyperthyroidism. How­ever, a slight dilitation of the internal carotid artery posterior to the left anterior clinoid was seen on the CT scan. An intravenous digital subtraction angiogram showed an aneurysm of the juxtasellar portion of the left internal carotid artery (Fig. 6a). An intra­cavernous carotid aneurysm was confirmed by se­lective internal carotid angiography (Fig. 6b). Figure 4. Embolic retinal artery occlusion showing retinal edema and an embolus lodged at an arterial bifurcation. March 1982 Tomsak, Modic, Weinstein (a) Figure Sa. Conventional arteriogram showing significant ste­nosis of right internal carotid artery just above the bifurcation. Case 3 -Carotid Cavernous Sinus Fistula A 77-year-old hypertensive woman developed the acute, painless onset of vertical diplopia on left gaze a few days after stepping on a garden rake handle that struck her on the forehead. Examina­tion revealed normal vision, pupils, and visual fields. A left hypertropia and left abduction deficit were noted on left lateral gaze consistent with an incomplete left sixth nerve paresis and partial left third nerve paresis. Exophthalmometry disclosed 6 mm of pulsating exophthalmos of the left eye. A thrill could be felt on palpating the left eye, and a bruit was heard on ocular auscultation. The con­junctival vessels of the left eye were moderately arterialized. Ocular tensions were 12 in the right eye and 22 in the left eye. Intravenous digital subtraction angiography (Fig. 7a) showed early opacification of the cavernous sinus with retrograde filling of a dilated left supe­rior ophthalmic vein, confirming the presence of a carotid cavernous sinus fistula. The conventional angiogram is shown for comparison (Fig. 7b). 25 Digital Subtraction Angiography Figure Sb. Digital subtraction angiogram showing same findings as Fig. Sa Figure ob. Intracavemous aneurysm shown by conventional arteriography. (II) Figure oa. Intracavernous aneurysm demonstrated by digital subtraction an~io~raphy. Journal of Clinical Neuro-ophthalmology Tum,.,,,- M"dil, Weinstein (a) Figure 7d. Cuolid cavernous sinus fistula and dilaled superior ophthalmic vein demonstrated by digitial subtraction angiography. Figure 7b, Carotid cavernous sinus fislula and dilated ,uperil1r llphth.llmic vein demonstrated by conventional JrterioKr.,phv. Case 4-Arteriovenous Malformation A 34-year-old white man developed a general­ized seizure. A CT scan demonstrated an enhancing lesion in the atrium of the left ventricle. Past med­ical history was remarkable for cutaneous neuro­fibromatOSiS, but was otherwise negative, Neuro­logic and neuro-ophthalmologic examinations were completely normal. Intravenous digital substraction angiogrdphy demonstrated an arteriovenous malformdtion in March 1982 the region of the posterior thJI.lmus originating from the left posterior cerebr.l1 .1rtery (Fig. 8). The arteriovenous malformJtion was successfully clipped in d two-stage neurosurgical procedure. . Case 5 - Wyburn-Mason Syndrome A 4-year-old white girl WdS eXdmined becduse of an "dbnormal" left eye since birth. Examindtion revealed 20/25 vision in the right eye and 20/400 vision in the left eye. There was 3.5 mm of prop- 27 [)i~it.ll Subtr.Ktion Angiogr.lphy f"gure II. Thal'amlC artenovenous malt'ormatlOn shown by dIgital subtraction angiography. tosis of the left eye and a 3+ Marcus-Gunn pupil noted on the left. Fundus examination was normal on the right, but on the left showed a definite vascular anomaly, which presented mainly as a dilated venous structure arising from the central aspect of the disc and extending inferotemporally (Fig. 9). Computed tomography of the head revealed a soft tissue mass seen in the posterior aspect of the left orbit. A left internal carotid angiogram dem­onstrated a richly vascular plexus in the posterior aspect of the left orbit, and the left suprasellar region supplied primarily by the ophthalmic artery (Fig. lOa). Intravenous digital subtraction angiog­raphy confirmed a vascular mass in the left retro­orbital space (Fig. lab). Case 6 -Hemifacial Spasm Secondary to Dolichoectasia of Basilar Artery A 47-year-old woman was ev,llu.lted for twitch­ing of the right eye and face of 2 ye.lrs duration. No other signs or symptoms were present. Figure 11 shows the intravenous digital subtraction angio­gram that demonstrates dolichoectasiJ of the b,lS­ilar artery with displ.lcement of the vessel into the right cerebellopontine Jngle. Discussion The b.l"ic principles of digit.ll subtr.lCtion .In­. I.'.'<ll',r,lrhv h,lV(' been reported. ' · 11I The major ad- Figure 9. Vascubr malformation of left optic nerve head in Wyburn-Mason syndrome. vantages of digital subtraction angiography over conventional angiography include enhanced con­trast sensitivity, computer subtraction, and intra­venous injection, which eliminates the risk of dis­lodging emboli and causing vasospasm. Digital subtraction angiography is an outpatient procedure Journal of Clinical Neuro-ophthalmology TOn1sak, Modic, Weinstein (a) Figure lOa. Left internal carotid angiogram showing nchly vascular plexus in left orbit and suprasellar region in Wyburn-Mason syndrome. Figure lob. Vascular mass in left orbit demonstrated by digital subtraction angiography in Wyburn-Mason syndrome (ar­rows), that takes from 20 to 30 minutes to perform. We have not had a major complication in over 3,000 cases. Patient motion remains the major problem. In­travenous injections of currently available contrast March 1982 material induce a swallowing reflex in many pa­tients and a sensation of heat, which is uncomfort­able and often produces patient motion, Swallow­ing moves the hyoid bone and larynx in the area of the carotid bifurcation, and creates motion arti­facts because of misregistration between the mask and contrast frames, Remasking can offset the effect of motion, but often changes are present between all frames of the study, Currently, soft­ware programs are being evaluated that will aid in the reregistration and remasking process, Another limitation of digital subtraction angiog­raphy is that spatial resolution is inferior to con­ventional angiography. Furthermore, because of the venous route of injection, contrast concentra­tion in the region of interest is comparatively di­minished, Overlap of contrast-opacified structures and a limited field of view due to the image inten­sifier field size are two other relative disadvant.lges, Examination of the Extracranial Carotid System When carotid bifurcations .He well visualized with digital subtraction .lngiography, the .lCcuracv of detecting stenosis of internal .lnd exten1.l1 ca­rotid arteries, when compared with conventional angiography, is Q7%, II At this time, good to excel­lent studies of both bifurcations .He obtained 85% of the time, I~ In addition to atherosclerotic disease, digitial subtraction angiography is accurate and useful in postoperative evaluations of carotid end­arterectomy as well as in detecting carotid artery abnormalities following trauma. Furthermore, fi­bromuscular dysplasia, chemodectomas, and arte- 29 Digit,ll Subtr,Ktion Angiogr,lphy Figure 11. Digital subtracbon angiography of doiJchoectatic basilar artery causing hemifaCial spasm riovenous malformations of the extracranial carotid system have been detected. Intracranial Studies with Digital Subtraction Angiography In a comparative study of 55 patients with intra­cranial lesions studied with both conventional se­lective catheterization and intravenous digital sub­traction angiography, the digital subtraction an­giography examination was completely diagnostic in 65% of the cases studied. l : l In an additional 23% of studies, digital subtraction angiography pro­vided useful but incomplete diagnostic informa­tion. As illustrated by our cases, intravenous digital subtraction angiography can detect aneurysms, ar­teriovenous malformations, and carotidcavernous sinus fistulas. Digital subtraction angiography can replace conventional cerebral angiography for the preoperative evaluation of the juxtasellar carotid arteries prior to transsphenoidal surgery. Further­more, the major dural sinuses are better visualized than with conventional angiography. The tech­nique is also useful for determining patency of extracranial-intracranial bypasses, the status of vascular lesions following embolization or surgery, and in assessing the degree of vascularity of intra­cranial tumors. Other applications of intravenous digit.ll subtr.lction .lngiography include study of the ,lfll'ric<; of the thor.lX, .lbdomen, .lnd extremi- I't>t, At this time, the cost for the system is about $260,000. At our institution, the cost of a single digital subtraction angiography examination is about $200 as compared to about $800 for conven­tional cerebral angiography. In summary, the development of computer re­constructed images of various parts of the cranio­vascular system following modest doses of intra­venous contrast media has extended a significant portion of angiography to an outpatient status. In comparison studies with conventional arteriog­raphy of the extracranial carotid and intracranial vasculature, it has been shown to be safe accurate, and reproducible. Digital subtraction angiography has wide application to the neurosciences and a special place in neuro-ophthalmology. References 1. Buonocore, L Meaney, T.F., Borkowski, G.P., Pav­licek, W.A.. and Gallagher, J.: Digital subtraction angiography of the abdominal aorta and renal arter­ies. Radiology 139: 281-28b. 1981. 2. Buonocore, E., Borkowski, G.P., Meaney, T.F., Tar­azi, R.C., Shirev, E.K., and Fuod, F.M.: Computer­ized angiography of the human heart. Presented at the Fifty-third Scientific Session of the American Heart Association, Miami, Florida, Nov. 17-20,1980. 3. Christensen, P.c., Ovitt, T.W., Fisher, HD., Frost, M.M., Nudelman, S., Roehrig, H., and Seeley, G.: Intravenous angiography using a digital video sub­traction: Intravenous cervicocerebrovascular angiog­raphy. Am. /. Neuro-radio/. 1: 379-387, 1981. Jo~rnal of Clinical Neuro-ophthalmology 4. Ergun, D.L., Mistretta, CA., Kruger, R.A., Riederer, S.}., Shaw, CG., ,md Carbone, D.P.: A hybrid com­puterized fluoroscopy technique for noninv.lsive cardiov,lscular im,lging. R.Jdiology 132: 739 -742, 1979. 5. Kruger, R.A., Mistrett,l, C.A., Hou", T.L., Riederer, S.}., Sh,lw, CG., Goodsitt, M.M., Crummy, A.B., SwiebeL W., Lanc,lster, '.c., Rowe, e.G., .md Flem­ming, D.: Computerized fluoroscopy in 1'1'.11 time for noninv.1sive visualization llf the c.udiov.lscul.u sys-tem. R.Jdiology 130: 49-57, 1979. . 0. Meaney, T.F., Weinstein, M.A., Buononlre, L, P.IV­lice I... W., Bor"llws"i. G.P., G.111.1gher, I.H., Suf".I, B., and M,Klntyre. W.E.: Digit.11 suhtr.Ktion .mgiog­r. 1phy of the hum.m c.udiov.1scul.u system. Soc. Photll-l1ptic.JI Instrument. Engin. 233: 272-278, 1980. 7. Meanev. T.F., Weinstein, M.A., Buonocore, E., Pav­lice", W.. Bor"ows"i, G.P., G.lllagher, I.H., Suf".J, B.. and M.Klntvre, W.l.: Digit.ll suhtr.lction angiog­raphy of the human cardiov.lscul.u system. Am. /. Radiol. 139: 1153-1100, 1980. 8. Mistretta, CA.: Digital videoangiography. Diagn. Imago 14-25.1981. 9. Ovitt. T.W.. Christensen, P.C, Fisher, H.o., Frost, M.M.. Nudelman,S., Roehrig, H., and Seeley, G.: March 1982 Tomsak, Modic, Weinstein Intravenous .mgiography using a digital video sub­traction x-ray imaging system. Am. ]. Neuro-radiol. I: 387-390, 1980. 10. Strother, C.M., S,ICkett, I.R., Crummy, A.B., Lilleas, F.G., Swiebel, W.J,. Turnipseed, W.o., lavid, M., Mistrett.l, C.A., Kruger, R.A., Ergun, DL, and Shaw, C.B.: Clinical applications of computerized fluoros­copy. [~.ldiology 136: 781-783,1980. II. Chilcote, W.A., Modic, MT., Pavlicek, W.A., Little, '.R., Furlan, A.j., Duchesneau, P.M., and Weinstein, M.A.: Digitial subtraction angiography of the carotid .uteries: A comp.Hative study in 100 patients. Ra­diology 139: 287-295, 1981 12. Modic. M.T., Weinstein, M.A., Buonocore, E.. Pav­licek, W.A., and Meaney, T.F.: Intravenous digital angiography of the head and neck: A clinical update. Soc. Photo-optical Instrument. Engin. (in press.) 13. Modic, M.T., Weinstein, M.A., Chilcote, W.A., Pav­licek, W.A., Duchesneau, P.M., Furlan, A.l., and Little, l.R.: Digital subtraction angiography of the intracranial vascular system-A comparative study in 55 patients. Am. ]. Neuro-radiol. (in press.) Write for reprints to: Robert L. Tomsak, MD., 9500 Euclid Avenue, Cleveland, Ohio 44106. 31