Clin. Radiol. (1973) 24, 67-71

X E R O R A D I O G R A P H Y - I T S U S E I N P E R I P H E R A L C O N T R A S T M E D I U M A N G I O G R A P H Y

P. JAMES AND H. BADDELEY

From the Department of Radiodiagnosis, University of Liverpool, Liverpool L69 3BX

and J. W. BOAG, H. E. JOHNS* and A. J. STACEY

From the Department of Physics, Institute o.1" Cancer Research, and Royal Marsden Hospital, London, S. W.3

Xeroradiography, tlaat is, the use of photo-conducting selenium plates instead of film as recording medium, allows one to obtain good arteriograms and venograms at considerably lower concentration of contrast medium than is normally used, and thus reduces the pain to the patient. The advantages and limitations of this new technique are described and illustrated.

SINCE the introduction of the use of X-radiation by Roentgen as a means of investigating internal anatomical detail, most records have been made directly onto silver halide emulsion on plates or film. Only recently has it been possible to make permanent records in any other way. The image intensifier with magnetic tape recording and subsequent viewing on a television screen is one way. Xeroradiography is another process which is now becoming important (Schaffert and Oughton, 1948; Dessauer and Clark, 1965; McMaster and Hoyt, 1971; Wolfe, 1972; Boag et al., 1971, 1972).

The Xerox process invented by C. F. Carlson in 1938 is a completely dry photographic process. Developed by the Battelle Memorial Institute in 1947, it was commercialised originally by the Haloid Company. The method depends on the formation of an electrostatic image of the object on a photoconductive surface - usually a thin selenium layer bonded to an aluminium support plate. The surface of the selenium is first covered with a uniform layer of positive charge and then exposed in a cassette holder in the same way as ordinary film. The selenium layer responds to X-rays as it does to visible light, but a thicker layer is required to give adequate sensitivity. These X-ray plates are more sensitive than non-screen film but considerably less sensitive than film used with intensifying screens. X-radiation induces conductivity in the selenium and the amount of charge which leaks through to the aluminium is proportional to the radiation dose received at the point of interest. This leaves a 'charge image' of the object on the surface of the selenium. This

*On leave of absence from the Ontario Cancer Institute, Toronto, Canada.

image is then 'developed' by exposing it to a cloud of finely-divided powder, which adheres to those areas where the electric field normal to the plate is strongest. The resulting powder image can either be photographed or transferred by contact to a plastic coated paper. Xerox images are of low to medium contrast but because of a specific 'edge effect' resolution of fine detail is extremely good.

Mathematical studies of the electric field above the charge image show that the field strength normal to the plate is greatest near any sharp discontinuities in the charge pattern. Thus, any structures which cast a shadow with well-defined edges, such as blood vessels or trabeculae in bone, will be clearly out- lined by deposition of powder along these 'edges', long before much powder is deposited on adjacent uniformly charged areas. This edge contrast is the principal advantage of Xeroradiographic pictures. They show low contrast between large areas coupled with high edge contrast at any discontinuities.

Wolfe (1972) has pioneered the clinical use o f Xeroradiography. He has demonstrated its special advantages in mammography and this application shows great promise. The present communication deals with the use of Xeroradiography to record the presence of contrast medium in arteries and veins.

Angiography has risks associated with the injec- tion of the contrast medium and the puncture of vessels, particularly arteries. This work aims to reduce both areas of risk.

It was hoped that the edge contrast pattern in Xeroradiography would allow blood vessels to be delineated with much reduced concentration of contrast medium. This might bring the procedure below the pain threshold and render a general anaesthetic unnecessary. It could also result in a

67

68 C L I N I C A L RADIOLOGY

FIG. 1

A Xeroradiograph of the hand after the injection of 8 ml of 1 in 10 Urovison (injected concentration 32.5 mgI/ ml). A venous tourniquet was applied above the wrist. Note the excellent definition of the vessels even behind bone despite the low concentration of contrast medium. The vessels disappear as they cross the edge of the bone shadow merely because of powder depletion by this stronger shadow. This artefact is inherent in the edge

contrast pattern.

significant reduction of the amount of contrast medium used. The more remote possibility that arterial outlines might be demonstrated following venous injection seemed worth pursuing, following preliminary tests with a phantom. Reports in Russian publications refer to the use of Xerox recording in angiography, and claim that the standard contrast preparation can be diluted to half normal strength without loss of diagnostic detail (Schneideris et al., 1968).

DESCRIPTION OF EQUIPMENT The selenium plates used were 34 cm by 22 cm in

Size. They had been made in the U.S.A. by the Xerox Corporation and were supplied to us by courtesy of Rank Xerox Ltd, The charging unit, developing box, cleaning and relaxing devices were all of the now obsolescent pattern made some 15 years ago and described in detail elsewhere (Boag et al., 1972). These too were placed at our disposal by Messrs. Rank Xerox Ltd, The powder images were photographed onto 2~ inch square film.

RESULTS Preliminary experiments with a phantom consist-

ing of nylon tubes filled with serial dilutions of

FIG. 2--CATHETER AORTOGRAM

Xeroradiograph of knees 10 secs after the injection of 40 cc of Urografin 3 0 ~ (injected concentration 140 mgI/ ml). Catheter tip 2" above aortic bifurcation. Injection time: 10 sees. Factors: 120 kv 20 mAs. Note the block of the left superficial femoral artery. The timing device overlies a collateral vessel. The patient experienced no pain with this injection but had beeu unable to keep still following a conventional high speed injection of 30 cc

Urografin 60 ~ because of pain. i:

:i

contrast medium and immersed in water seemed to indicate that a dilution of 100/1 of the medium :- Urovison would still be visible in 0.5 mm tubes. This proved misleading, however, as the tube wall itself was later found to be casting the main shadow. Similarly filled tubes placed on the back of the hand : 2 also gave too optimistic results. Accordingly the effect was tried of injecting a 1 in 10 dilution of Urovison (injected concentration 32.5 mgI/ml) into veins in the dorsum of the hand of a volunteer subject. The veins were filled with 8 ml of this dilute contrast medium, venous return being restricted by a tourniquet. Figure 1 shows the result. The veins are well outlined even behind bone.

Patients undergoing conventional intravenous pyelography provided a convenient group for our

XERORADIOGRAPHY -- ITS USE IN PERIPHERAL CONTRAST ANGIOGRAPHY 69

Fro. 3

F~6. 3(A)--Conventional brachial arteriogram, 8 cc Urografin 60~ (injected concentration 280 mgI/ml). This examination was excruciatingly painful even with Pethidine premedication. There are widespread irregularities and occlusions of the digital vessels. The patient had severe Raynaud's Disease. A photo-electric timer was used to determine when the bolus arrived at the finger tip, FIG. 3(n)--Brachial Xeroarteriogram at one quarter of the contrast concentration of Fig. 3(A). [8 ce Urografin 15 % (injected concentration 70 mgI/ml]. The patient felt a warm feeling in the hand but stressed that the examination was not painful. This examination is quite as diagnostic as 3(A), for though the overall contrast is less, vessel

edges are well defined.

second experiment. With the patient's consent an exposure was made of the right hand about 20 sec. after the injection of 50 cc of Urografin 60 (282 mgl/ml) into a left arm vein. Although the resulting picture was not diagnostic some arteries were outlined. The dilution between point of injection into a vein and the arteries of the other hand is not easy to assess. The cardiac output in 20 sec would be about 1200 ml, so with 50 ml injected the concentration on the arterial side could not exceed one part in 24. I f mixing with the whole blood volume (6 litres) had been complete the dilution would be 1 in 120. The concentration in the hand must lie between these limits.

The effect of injecting reduced concentrations of contrast medium after arterial puncture was then tried. Using the Seldinger technique, a catheter was inserted via the femoral artery to a point 2 inch above the bifurcation of the aorta. Timing was

obtained at the level of the popliteal artery using the Doppler technique described by James and Gal- loway 097 0. Fig. 2 shows the result of an injection of 40 ml of 3 0 ~ Urografin (140 mgI/ml). The patient felt no pain.

The technique was also used during brachial arteriography by direct puncture, and again the patient felt no pain, only a warm sensation. Figures 3(A) and 3(n) show a comparison of conventional and xero-arteriograms, the latter taken with only one-quarter of t h e concentration of contrast medium used in the former. The exposure was timed photoelectrically.

An ascending venogram was also performed using both Xeroradiography and conventional techniques. Fig. 4(A) shows a conventional venogram using 40 ml of 3 0 ~ Urografin (injected concentration 140 mgI/ml). Fig. 4(B) shows a Xeroradiograph taken with 40 ml of 20 ~ Urografin (90 mgI/ml). The

70 CLINICAL RADIOLOGY

FIG. 4--Ascending Venogram in the same leg.

4(A)--Conventional 3~adiography. 40 ml 30~ Urografin (injected concentration 140 mgI/ml). Injected into a :¢ein on the dorsum of the foot. Ankle tourniquet applied. This examination is not diagnostic. The vessels overlying bone are obscured and those lying superficially are "burned out". 4(B) Xeroradiography. 40 ml 20 ~ Urografin (injected concentration 90 mgl/ml). This examination was conducted in a similar manner though slight rotation occurred between the two pro-

cedures. It demonstrated an occlusion of a deep vein in the calf (arrow). Note the great latitude compared with the conventional radiograph.

X E R O R A D I O G R A P H Y -- ITS USE IN P E R I P H E R A L C O N T R A S T A N G I O G R A P H Y 71

Xerographic method was more diagnostic at a lesser concentration o f contrast medium.

D I S C U S S I O N

These experiments showed that one can reduce the pain of intra-arterial injections o f contrast medium without loss o f diagnostic information. None of the injections in our series were described by patients as painful. This represents in our opinion a worthwhile advance and coupled with the reduction in the use o f general anaesthesia promises safer angiography.

The combinat ion of great latitude and clearly defined edges should make Xeroradiography ideal for stereoscopy of blood vessels. Greatly improved diagnostic information could then be obtained by exposing two plates with appropriate tube shift to fo rm a stereo pair. The brain would reject irrelevant detail f rom planes other than the plane o f interest and this is equivalent to a big improvement in the 'signal-to-noise' ratio (Tuddenham, 1962).

Al though Xerox plates are at present less sensitive than the screen-film combination, thus confining their use to peripheral angiography, work is in progress to improve their sensitivity, Should this effort prove successful the technique would then be app l i cab le to cerebral, thoracic and abdominal angiography.

Aeknowledgements.--We are indebted to Rank Xerox Ltd., for the apparatus used and to the M.R.C. and C.R.C. for financial support.

We should like to thank Dr. G. D. Scarrow, Department of Radiodiagnosis, University of Liverpool, for his help and advice with this project.

REFERENCES BOAG, J. W., STACEY, A. J. & DAVIS, R. (1971), Some

Clinical and Experimental Applications of Xeroradio- graphy. Journal of Photographic Science, 19, 45-48.

BOAG, J. W., STACEY, A. J & DAVIS, R. (1972). Xerographic recording of mammograms. British Journal of Radiology, 45, 633-640.

DESSAUER, J. H. & CLARK, H. E. (1965). Xerography and Related Processes. Focal Press, London and New York.

JAMES, P. & GALLOWAY, R. W. (1971). The Ultrasonic blood velocity detector as an aid to arteriography. British Journal of Radiology, 44, 743-746.

McMAsTER, R. C. & How, H. L. (1971). Xeroradiography in the 70's. Materials Evaluation, 29, 265-274,

SCrtAErZRT, R. M. & OU~HTON, C. D. (1948). Xerography: A New Principle of Photography mad Graphic Repro- duction. Journal of the Optical Society of America, 38, 991-998.

SHNE1DERIS, M., AMBROZAITIS, K., & KAVALYAUSKAS, R. (1968). Medical Xeroradiography. Mintis, Vilna (Lithau- nia).

TODOENHAM, W. J. (1962). Visual Search, Image Organi- zation, and Reader Error in Roentgen Diagnosis. Radio- logy, 78, 694-704.

WOLFE, J. N. (1972). Xeroradiography of the breast. Spring- field, Illinois: Charles C. Thomas.