British Journal of Radiology 74 (2001),134-141 © 2001 The British Institute of Radiology
Rotational digital subtraction angiography of the renal arteries: technique and evaluation in the study of native and transplant renal arteries
H R Seymour, MRCP, FRCR
1
M B Matson, MRCP, FRCR
1
A-M Belli, FRCR
1
R Morgan, FRCR
1
J Kyriou, BSc, MSc
2 and
U Patel, FRCR
1
1 Department of Radiology
2 The Radiological Protection Centre, St George's Hospital, London, SW17 0QT UK
 |
Abstract
|
|---|
Rotational digital subtraction angiography (RDSA) allows multidirectional angiographic acquisitions with a single injection of contrast medium. The role of RDSA was evaluated in 60 patients referred over a 7-month period for diagnostic renal angiography and 12 patients referred for renal transplant studies. All angiograms were assessed for their diagnostic value, the presence of anomalies and the quantity of contrast medium used. The effective dose for native renal RDSA was determined. 41 (68.3%) native renal RDSA images and 8 (66.7%) transplant renal RDSA images were of diagnostic quality. Multiple renal arteries were identified in 9/41 (22%) native renal RDSA diagnostic images. The mean volume of contrast medium in the RDSA runs was 51.2 ml and 50 ml for native and transplant renal studies, respectively. The mean effective dose for 120° native renal RDSA was 2.36 mSv, equivalent to 1 year's mean background radiation. Those RDSA images that were non-diagnostic allowed accurate prediction of the optimal angle for further static angiographic series, which is of great value in transplant renal vessels.
|
Introduction
|
|---|
Visualization of the entire length of the renal artery is crucial in the assessment and percutaneous therapy of renovascular disease. Atherosclerosis in the native renal arteries affects the proximal third in 87% of cases [1]. Ostial lesions respond poorly to angioplasty. However, the locations of renal artery aortic ostia are variable both in their distribution around the aorta and their level of origin from the aorta [1–3]. Similarly, whilst transplant artery stenoses are usually at or just beyond the anastomosis, the position and orientation of the arterial anastomosis is very variable and the artery may be significantly tortuous [4]. For these reasons, multidirectional angiography is necessary to image adequately native or transplant arteries. Multiple projections and injections increase the radiation dose and the contrast medium load to the patient and to a potentially already compromised kidney. The latter is of particular concern with a failing transplant kidney.
Rotational digital subtraction angiography (RDSA) is a relatively new technique in vascular imaging. It allows multidirectional angiographic acquisition with a single injection of contrast medium, promising savings in time, contrast medium and radiation dose. It has already been evaluated in the cerebral, carotid and coronary arteries [5–9]. The purpose of this study was to evaluate the value of real-time RDSA in the assessment of native and transplant renal arteries.
|
Method
|
|---|
The use of RDSA with iodinated contrast medium, Niopam 300 (Iopamidol, Merck Pharmaceuticals, Middlesex, UK), was prospectively evaluated in the assessment of native and transplant renal arteries. Patients attending for diagnostic angiography over a 7-month period were entered into the study. All patients were studied using a GE Advantx LCA digital system (IGE Medical Systems, Berkshire, UK). All patients received intraarterial 20 mg hyoscine-N-butlybromide (Buscopan, Boehringer Ingelheim Ltd, UK) to reduce bowel peristalsis.
Native renal arteries
A 4 F pigtail catheter was placed in the abdominal aorta, with the pigtail positioned opposite the L1/L2 disc space for assessment of native renal arteries. The rotational field isocentre for native renal angiograms was placed over the midline at the level of L1. The C-arm was rotated through an arc of 180° in the first few patients, but in the remainder this was restricted to an arc of 120°, from 60° left anterior oblique (LAO) to 60° right anterior oblique (RAO) (Figure 1
). Those angiograms that were diagnostic were assessed independently by two readers (MBM and HRS) for the presence of renal artery anomalies; the prevalence of renal artery stenosiswas not evaluated in this study. A third reader (RM) was employed if the two readers differed.
View larger version (69K):
[in this window]
[in a new window]
|
Figure 1. Axial early phase contrast CT through the upper abdomen demonstrating the rotational arc of 120° for native renal artery rotational digital subtraction angiography. RAO, right anterior oblique; LAO, left anterior oblique.
|
|
Transplant renal arteries
For the transplant kidney, a 4 F straight catheter with multiple side holes was positioned just above the anastomosis in the external iliac artery. All transplants had end-to-side anastomosis onto the external iliac artery. The rotational field isocentre for transplant angiograms was placed over the ipsilateral sacroiliac joint on the side containing the transplant kidney, and a wider rotational arc of 150° was used (Figure 2). This arc was chosen after initial pilot studies using arcs of up to 180°. The transplant cases proceeded to renal artery intervention immediately after diagnostic angiography.
View larger version (75K):
[in this window]
[in a new window]
|
Figure 2. Axial unenhanced CT through the pelvis demonstrating the rotational arc for transplant renal artery rotational digital subtraction angiography. The rotational field isocentre is placed over the hemipelvis containing the transplant. RPO, right posterior oblique; LAO, left anterior oblique.
|
|
The injection rate of contrast medium and the injection–image delay used for the rotational angiogram were recorded for native kidneys. The volume of contrast medium depended on the time length of the arc and was recorded. However, for transplant artery assessment the rate of injection of contrast medium was 5–6 ml s-1 and was commenced 1 s prior to the start of the rotation and continued to the end of the arc to ensure that opacified arteries were visualized throughout the rotational acquisition.
All angiograms were assessed at the time ofacquisition as to whether they were of diagnostic quality or not. A diagnostic angiogram was defined as requiring no additional static angiographic projections. Angiograms that were non-diagnostic were then examined to evaluate the best static projection required to optimize further imaging of the native renal artery origins or to view the allograft artery anastamosis. The best profile angle for visualization of the native renal artery origin or transplant artery anastomosis was recorded where possible.
Method of dosimetry
Dose–area product (DAP) values are routinely recorded on all patients undergoing renal angiographic studies. The DAP values are recorded pre and post RDSA acquisition, enabling the total acquisition DAP (DAPa) to be calculated for each patient. Effective doses (EDs) were calculated on a frame by frame basis using the PC-based Monte Carlo programme PCXMC [10] for a 120° native renal RDSA acquistion. This requires specification of the following parameters for each frame: X-ray beam dimensions and position co-ordinates at the patient; angle of projection relative to the patient; focus-to-patient distance (FPD); tube potential; total filtration; anode angle; and free-in-air dose (ESDfia) in the centre of the field of view at the patient entrance plane.
The number of frames in each RDSA acquisition sequence and their projection geometry relative to the patient are fixed and known for each arc of rotation, as are FPD, tube potential, total filtration and anode angle. ESDfia (mGy) is assumed to be the same for each frame, given the symmetrical geometry of each rotation, and is given by:
where Cf is the DAP meter calibration factor, A is the X-ray beam area at the patient entrance plane (cm2) and N is the total number of frames in the acquisition, including mask.
|
Results
|
|---|
Native renal arteries
60 patients were studied. 41 (68.3%) native renal artery RDSA images were diagnostic, with good visualization of the renal artery ostia in profile. In the remainder, the RDSA run allowed an accurate prediction of the optimal angle for further angiographic views. Non-diagnostic images were due to a variety of factors including patient habitus, lack of controlled breath-hold and poor opacification. Multiple renal arteries were identified in 9 (22%) diagnostic images, of which 6 (14.6%) were unilateral. The optimal angle for viewing the right renal ostia was 2° RAO (range 43° LAO to 52° RAO) and that of the left renal ostia was 2° LAO (43° LAO to 36° RAO). The angiographic factors recorded, and the volumes and rates of injection of contrast medium are shown in Table 1.
Transplant renal arteries
12 patients with renal transplants were studied, 11 of whom had right-sided transplants. The RDSA study was diagnostic in 8 of the 12 patients (66.7%); the remaining 4 patients required only one further static run for a diagnostic angiogram. The obliquity of the additional static run could be accurately determined from the RDSA image. The profile angle for viewing the anastomosis was unpredictable and highly variable, the range being 105° (Figures 3–6). In all cases the RDSA image alone (n=8) or with a single static run (n=4) was sufficient to confidently proceed to renal artery intervention (angioplasty or stenting). The contrast medium load and the angiographic factors recorded for transplant renal artery RDSA are also given in Table 1
.
View larger version (91K):
[in this window]
[in a new window]
|
Figure 3. (a–d) Series of four selected images from left-sided renal transplant rotational digital subtraction angiography. The entire series commences with the first subtraction image acquired at 94° left posterior oblique (compare Figure 2 for rotational arc), with images acquired approximately every 10°. The projections shown are at (a) 75° left anterior oblique (LAO), (b) 31° LAO, (c) 0° and (d) 32° right anterior oblique. (e) Larger view of (a), on which the transplant artery anastomosis is identified best in profile. This is clearly demonstrated on the static angiographic image obtained at 75° LAO.
|
|
View larger version (75K):
[in this window]
[in a new window]
|
Figure 4. (a–f) A selection of six images from right-sided renal transplant rotational digital subtraction angiography, with images from 84° left anterior oblique (LAO) to 34° right anterior oblique. In this example, the transplant can be seen lying in a more horizontal orientation, with the hilum pointing inferiorly. (g) Larger view of (c), in which the transplant artery anastomosis is best seen. The static angiogram performed at 30° LAO clearly shows the end-to-side transplant artery anastomosis in profile.
|
|
View larger version (103K):
[in this window]
[in a new window]
|
Figure 6. (a) Selection of images from right-sided renal rotational digital subtraction angiography (RDSA) showing images acquired from 87° left anterior oblique (LAO) to 10° right anterior oblique. There is an end-to-end anastomosis in this case. The transplant anastomosis is hidden behind the external iliac artery on many of the images, but is best seen at 44° LAO (enlarged in (b)). (b) A small peripheral arteriovenous malformation (arrowhead) noted during the RDSA was thought to be a sequel of post-transplant biopsy. (c) The static image at 44° LAO shows the anastomosis clearly (arrow) but no evidence of stenosis was identified.
|
|
Native renal RDSA dosimetry
45 patients with 120° native renal RDSA were included. A constant tube potential of 80 kV was used for all acquisitions. The anode angle was 14° and the total filtration, including carbon fibre tabletop, was 3.5 mm Al equivalent at 80 kV. The beam dimensions at the patient entrance plane were 20 cmx14 cm and the FPD was constant at 60 cm. The beam dimensions may have differed slightly from patient to patient, but this variation was considered to be negligible compared with the actual dimensions. The DAP meter calibration factor was 1.15 and did not depend on the relative positions of the tube and bed along the arc of acquisition. The 120° renal acquisition series comprised 33x2 images (pre- and post-mask). Table 2 shows the figures for DAPa, ESDfia per frame and total ED. The mean ED for renal RDSA was 2.36 mSv.
View this table:
[in this window]
[in a new window]
|
Table 2. Total acquisition dose–area product (DAPa), free-in-air entrance surface dose (ESDfia) per frame and total effective dose (ED) for 120° native renal rotational digital subtraction angiography acquisition
|
|
|
Discussion
|
|---|
The native arteries of the kidney develop from the arteries of the mesonephros as it ascends from the pelvis. The origins of these arteries are determined by the growth of the suprarenal gland, which displaces some vessels dorsally and some ventrally [1, 2], resulting in a range of origins of the native renal arteries around the aorta [1–3, 11, 12]. Similarly, aortic ectasia with consequent rotation or kinking will alter the distribution of the renal artery ostia.
Many reports have described the anatomy of the native renal vessels from cadaveric studies [1, 3, 12], arterial cast studies [2, 3, 11], angiography [11] and CT [13, 14]. Multiple renal arteries are found in 25–30% [14], with equal frequency bilaterally. All studies confirm the variability of the renal ostia. The majority are located laterally, but in 20% of adults these vessels have an anterior or anterolateral aortic origin [1], often unilateral, and commonly found with a supplementary or accessory vessel [2].
Atherosclerosis of native vessels occurs predominantly at the renal artery origin [1], but true ostial stenoses are resistant to percutaneous transluminal angioplasty and most interventionists now prefer to stent these lesions. Precise demonstration of the renal ostium is therefore helpful in planning treatment for renovascular hypertension.
A discussion of the relative merits of magnetic resonance angiography and CT angiography is beyond the scope of this article, but accurate angiographic imaging can be problematic. Whilst there is some consensus on the optimal angiographic projections to image the renal artery ostia [11, 15, 16], there is a need for multiple angiographic projections where the angiomorphology is complex [17]. A minimum of three runs (anteroposterior (AP), RAO and LAO) is usually required.
RDSA is a means of acquiring multiple projection views during a single breath-hold injection. Digital subtraction images are acquired every 3.5° in a rotational sweep of up to 180°. In fact, the C-arm undergoes two sweeps, the first to acquire mask images and the second to acquire images during the injection of contrast medium. Thus, a 180° arc can take up to 20 s and breath-hold can be difficult. In addition to bowel motion, this is the main limitation to increasing the number of projections, but even with an arc of 120° one can choose from up to 33 different projections of the renal arteries and ostia.
A wider rotational arc (180°) was initially used but this was restricted when it became apparent that the extremes of the arc did not contribute to the diagnostic power and that movement artefact was degrading images. With 120°, 67% of RDSA images of native renal vessels were of diagnostic quality and no further static angiographic views were required. This facility reduced both the injected volume of contrast medium and the overall time taken for the procedure. In the remaining patients, the optimal angiographic projection could be accurately determined for further imaging. Limitations also arose when patients were of large body habitus or when contrast opacification was poor.
The native right and left renal artery origins were best profiled at mean angles of 2° RAO and 2° LAO, respectively. However, the range of angles over which the ostia were profiled was large (95° and 79° for right and left, respectively). Many of the vessels studied would therefore not have been imaged accurately without the RDSA facility. This is in close agreement with previous workers who analysed the renal artery origins in the transverse plane [11] and the best angiographic views to use to adequately view the renal ostia [13]. They found that, overall, the AP projection viewed in profile 47% of left renal artery origins but only 16% of right arteries, concluding that additional angiographic views, principally the 20° LAO and 40° LAO, were required to visualize 92% of renal artery ostia [11]. It is possible that 120° is still too liberal a choice of arc, and could usefully be narrowed further, perhaps to 100°, further maximizing the cost and radiation efficiency of RDSA.
The mean ED calculated for the 120° native renal RDSA was 2.36 mSv, equivalent to about three conventional plain abdominal radiographs (UK mean 0.7 mSv [18]) or approximately one year's mean UK background radiation (UK mean 2.5 mSv). For low linear energy transfer radiation at low dose rates, the lifetime risk of fatal cancer for the whole population from exposure to ionizing radiation is 5x10-2 per Sv [19]. The mean risk, therefore, of fatal cancer from native renal 120° RDSA is 11.8 per 100 000, which is small compared with the overall lifetime risk of cancer [20].
Renal allograft vascular complications arise in 3–15% of patients owing to atherosclerosis, preservation injury, mechanical kinking and rejection, and may be focal or diffuse, and over short or long segments. These complications include renal artery stenosis, occlusion or thrombosis, pseudoaneurysm and arteriovenous fistulae post biopsy. Stenosis is the most common and may occur at any time in the post-transplant period, but especially immediately post transplant, and tends to occur near the anastomosis. Unexplained allograft dysfunction or hypertension should prompt renovascular assessment. In most institutions, post-operative assessment is with Doppler ultrasound supported by renal scintigraphy, but angiography is confirmatory and therapeutic when percutaneous techniques such as percutaneous transluminal angioplasty are performed [21, 22]. It is therefore essential to accurately diagnose potentially correctable lesions to prevent significant morbidity.
Previous literature emphasizes the need for several views to assess the transplant artery [4, 17, 23]. However, there is no consensus on the optimal angle for angiographic imaging of the anastomosis. This is not surprising, as the very nature of renal transplant surgery results in wide variability of the orientation of this region. We have found a wide range (105°) for the optimal projection. Because of this variability, prior to RDSA at our institution, most patients previously required multiple angiographic projections, four or five attempts being common, and often 100 ml, sometimes 100–150 ml, of contrast medium was required for accurate angiographic diagnosis. This subsequently limited the use of contrast medium during any required intervention. In comparison, with RDSA the dose of contrast medium is reduced, as in two-thirds of patients only a single injection and RDSA run is necessary.
A further advantage is the wider choice of projections to plan arterial intervention, a 150° arc typically encompassing up to 41 projections. The optimal projection can be readily chosen. Any renal artery intervention is carried out confidently, rather than struggling with poor visualization from projections that are limited in number because of concerns about volume of contrast medium and radiation dose. Because of these advantages, RDSA is now an indispensable part of renal transplant angiography and intervention at our institution. The advantages and disadvantages of RDSA are listed in Table 3.
Received for publication January 17, 2000.
Revision received August 1, 2000.
Accepted for publication August 11, 2000.
|
References
|
|---|
-
Bauer FW, Robbins SL. A postmortem study comparing renal angiograms and renal artery casts in 58 patients. Arch Path 1967;83:307–14.[Medline]
-
Bauer FW. The aortic origin of renal arteries in man and other mammals. Arch Path 1968;86:230–4.[Medline]
-
Odman P, Ranniger K. The location of the renal arteries: an angiographic and post-mortem study. AJR 1968;104:283–8.[Abstract/Free Full Text]
-
Gedroyc WMW, Reidy JF, Saxton HM. Arteriography of renal transplantation. Clin Radiol 1987;38:239–43.[Medline]
-
Bosanac Z, Miller RJ, Jain M. Rotational digital subtraction carotid angiography: technique and comparison with static digital subtraction angiography. Clin Radiol 1998;53:682–7.[Medline]
-
Hoff DJ, Wallace C, terBrugge KG, Gentili F. Rotational angiography assessment of cerebral aneurysms. Am J Neuroradiol 1994;15:1945–8.[Abstract]
-
Tu RK, Cohen WA, Maravilla KR, Bush WH, Patel NH, Eskridge J, et al. Digital subtraction rotational angiography for aneurysms of the intracranial anterior circulation: injection method and optimization. Am J Neuroradiol 1996;17:1127–36.[Abstract]
-
Fahrig R, Fox AJ, Lownie S, Holdsworth DW. Use of a c-arm system to generate true three-dimensional computed rotational angiograms: preliminary in vitro and in vivo results. Am J Neuroradiol 1997;18:1507–14.[Abstract]
-
Thron A, Voight K. Rotational cerebral angiography: procedure and value. Am J Neuroradiol 1983;4:289–91.[Abstract]
-
Tapiovaara M, Lakkisto M, Servomaa A. A PC-based Monte Carlo program for calculating patient doses in medical x-ray examinations, STUK-A139. 1997.
-
Verschuyl E, Kaatee R, Beek FJA, Patel NH, Fontaine AB, Daly CP, et al. Renal artery origins: best angiographic projection angles. Radiology 1997;205:115–20.[Abstract/Free Full Text]
-
Wijesinghe LD, Scott DJA, Kessel D. Analysis of renal artery geometry may assist in the design of new stents for endovascular aortic aneurysm repair. Br J Surg 1997;84:797–9.[Medline]
-
Verschuyl E, Kaatee R, Beek FJA, Pasterkamp G, Bush WH, Beutler JJ, et al. Renal artery origins: location and distribution in the transverse plane at CT. Radiology 1997;203:71–5.[Abstract/Free Full Text]
-
Platt JF, Ellis JH, Korobkin M, Reige K. Helical CT evaluation of potential kidney donors: findings in 154 subjects. AJR 1999;169:1325–30.[Abstract/Free Full Text]
-
Gerlock AJ, Goncharenko V, Sloan OM. Right posterior oblique: the projection of choice in aortography of hypertensive patients. Radiology 1999;127:45–8.[Abstract]
-
Harrington DP, Levin DC, Garnic JD, Davidoff A, Bettman MA, Kuribayashi S, et al. Compound angulation for the angiographic evaluation of renal artery stenosis. Radiology 1983;146:829–31.[Abstract/Free Full Text]
-
Rankin SC, Saunders AJS, Cook GJR, Scoble JE. Renovascular disease. Clin Radiol 2000;55:1–12.[Medline]
-
Hart D, Hillier MC, Wall BF, Shrimpton PC, Bungay D. Doses to patients from medical x-ray examinations in the UK—1995 review, NRPB-R289. Oxford, UK: NRPB, 1996.
-
1990 Recommendation of the International Commission on Radiological Protection, ICRP 60. Oxford, UK: Pergamon Press, 1990:22.
-
Broad statement on diagnostic medical exposures during pregnancy and estimates of late radiation risk to the UK population. In: Documents of the National Radiological Protection Board. Oxford. NRPB, 1993:11.
-
Orons PD, Zajko AB. Angiography and interventional aspects of renal transplantation. Radiol Clin N Am 1995;33:461–71.[Medline]
-
Curry NS, Cochran S, Barbaric ZL, Schabel SI, Pagani JJ, Kangarloo H, et al. Interventional radiologic procedures in the renal transplant. Radiology 1984;152:647–53.[Abstract/Free Full Text]
-
Picus D, Neeley JP, McClennan BL, Weyman PJ, Heiken JP. Intraarterial digital subtraction angiography of renal transplants. AJR 1985;145:93–6.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
J. W. Olin, J. A. Kaufman, D. A. Bluemke, R. O. Bonow, M. D. Gerhard, M. R. Jaff, G. D. Rubin, and W. Hall
Atherosclerotic Vascular Disease Conference: Writing Group IV: Imaging
Circulation,
June 1, 2004;
109(21):
2626 - 2633.
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
