Spatial temperature control with a 27 MHz current source interstitial hyperthermia system.

PURPOSE: This article gives an overview of the properties of a 27 MHz current source interstitial hyperthermia system, affecting temperature uniformity. METHODS AND MATERIALS: Applicators can be inserted in standard flexible afterloading catheters. Maximum temperatures are measured with seven-point constantan-manganin thermocouple probes inside each applicator. Temperature can be controlled automatically using a simple control algorithm. Three-dimensional power absorption and thermal models for inhomogeneous tissues are available to optimize applicator geometry and phase configuration. Properties of the interstitial heating system have been verified both in phantom experiments and in in vivo treatments of rhabdomyosarcomas implanted in the flank of a rat. RESULTS: An experiment with four electrodes in one catheter proves that longitudinal control of the specific absorption rate (SAR) is feasible. Local cooling applied by cold water circulation through a catheter perpendicular to the afterloading catheter could be compensated by independent control of electrode power. Furthermore, comparison of two different phase configurations using four dual electrode applicators shows that the SAR distribution can be manipulated significantly, utilizing the phase of the electrodes. Finally, the temperature can be controlled safely and model calculations are in fair agreement with the measurements. CONCLUSIONS: The features of the 27 MHz current source interstitial hyperthermia system enable spatial temperature control at approximately 1.5 cm.

Clinical thermometry, using the 27 MHz multi-electrode current-source interstitial hyperthermia system in brain tumours.

BACKGROUND AND PURPOSE: In interstitial hyperthermia, temperature measurements are mainly performed inside heating applicators, and therefore, give the maximum temperatures of a rather heterogeneous temperature distribution. The problem of how to estimate lesion temperatures using the multi-electrode current-source interstitial hyperthermia (MECS-IHT) system in the brain was studied. MATERIALS AND METHODS: Temperatures were measured within the electrodes and in an extra catheter at the edge of a 4 x 4 x 4.5 cm(3) glioblastoma multiforme resection cavity. From the temperature decays during a power-off period, information was obtained about local maximum and minimum tissue temperatures. The significance of these data was examined through model calculations. RESULTS: Maximum tissue temperatures could be estimated roughly by switching off all electrodes for about 5 s. Model calculations showed that the minimum tissue temperatures near a certain afterloading catheter correspond well with the temperature of the applicator inside, about 1 min after this applicator was switched off. CONCLUSIONS: Although the electrode temperatures read during heating are not suitable to assess the temperature distribution, it is feasible to heat the brain adequately using the MECS-IHT system with extra sensors outside the electrodes and/or application of decay methods.

Temperature measurement errors with thermocouples inside 27 MHz current source interstitial hyperthermia applicators.

The multielectrode current source (MECS) interstitial hyperthermia (IHT) system uses thermocouple thermometry. To obtain a homogeneous temperature distribution and to limit the number of traumas due to the implanted catheters, most catheters are used for both heating and thermometry. Implications of temperature measurement inside applicators are discussed. In particular, the impact of self-heating of both the applicator and the afterloading catheter were investigated. A one-dimensional cylindrical model was used to compute the difference between the temperature rise inside the applicators (deltaTin) and in the tissue just outside the afterloading catheter (deltaTout) as a function of power absorption in the afterloading catheter, self-heating of the applicator and the effective thermal conductivity of the surrounding tissue. Furthermore, the relative artefact (ERR), i.e. (deltaTin - deltaTout)/deltaTin, was measured in a muscle equivalent agar phantom at different positions in a dual-electrode applicator and for different catheter materials. A method to estimate the tissue temperature by power-off temperature decay measurement inside the applicator was investigated. Using clinical dual-electrode applicators in standard brachytherapy catheters in a muscle-equivalent phantom, deltaTin is typically twice as high as deltaTout. The main reason for this difference is self-heating of the thin feeder wires in the centre of the applicator. The measurement error caused by energy absorption in the afterloading catheter is small, i.e. even for materials with a high dielectric loss factor it is less than 5%. About 5 s after power has been switched off, Tin in the electrodes represents the maximum tissue temperature just before power-off. This delay time (t(delay)) and ERR are independent of Tin. However, they do depend on the thermal properties of the tissue. Therefore, ERR and t(delay) and their stability in perfused tissues have to be investigated to enable a reliable estimation of the tissue temperatures around electrodes in clinical practice.

Implications of using thermocouple thermometry in 27 MHz capacitively coupled interstitial hyperthermia.

The 27 MHz Multi Electrode Current Source (MECS) interstitial hyperthermia system uses segmented electrodes, 10-20 mm long, to steer the 3D power deposition. This power control at a scale of 1-2 cm requires detailed and accurate temperature feedback data. To this end seven-point thermocouples are integrated into the probes. The aim of this work was to evaluate the feasibility and reliability of integrated thermometry in the 27 MHz MECS system, with special attention to the interference between electrode and thermometry and its effect on system performance. We investigated the impact of a seven-sensor thermocouple probe (outer diameter 150 microns) on the apparent impedance and power output of a 20 mm dual electrode (O.D. 1.5 mm) in a polyethylene catheter in a muscle equivalent medium (sigma 1 = 0.6 S m-1). The cross coupling between electrode and thermocouple was found to be small (1-2 pF) and to cause no problems in the dual-electrode mode, and only minimal problems in the single-electrode mode. Power loss into the thermometry system can be prevented using simple filters. The temperature readings are reliable and representative of the actual tissue temperature around the electrode. Self-heating effects, occurring in some catheter materials, are eliminated by sampling the temperature after a short power-off interval. We conclude that integrated thermocouple thermometry is compatible with 27 MHz capacitively coupled interstitial hyperthermia. The performance of the system is not affected and the temperatures measured are a reliable indication of the maximum tissue temperatures.

Design of applicators for a 27 MHz multielectrode current source interstitial hyperthermia system; impedance matching and effective power.

In interstitial heating one of the main requirements for achieving a certain elevated temperature in a tumour is that the effective power per applicator (Peff), i.e. the power which is actually deposited in the tissue, is sufficiently high. In this paper this requirement is discussed for the applicators of the 27 MHz multielectrode current source (MECS) interstitial hyperthermia (IHT) system. To minimize power reflection, the applicator impedance was matched with the generator impedance by adjusting the length of the coaxial cable in between. Transmission line losses, applicator efficiency and subsequently Peff were computed for several applicator types. The actual Peff per electrode was obtained from calorimetric measurements. Experiments with RC loads, which can be seen as perfect applicators, were performed to investigate the effect of mismatching on Peff. Applicator losses were measured for clinically used applicators, both single- and dual-electrode, utilizing saline phantoms. A simple spherical tumour model, using the effective heat conductivity (keff) to account for heat transport, was used to estimate Peff for a given tumour size, implant size and applicator density. Computations of Peff of various MECS-IHT electrodes were in close agreement with the phantom measurements. Most of the initial generator power was absorbed in the transmission line (60-65%). The efficiency of the applicators was about 65%. For both single- and dual-electrode applicators the effective electrode power was found to be about 1 W. Model calculations show that Peff of 1 W is sufficient to reach a minimum tumour temperature of 43 degrees C in well perfused tumours (keff = 3 W m-1 degree C-1), using a typical implant with 2 cm electrodes and 1.5 cm spacing. Mismatching can considerably affect Peff. Both a reduction to almost zero and a two-fold increase are possible. However, because the matching theory is well understood, mismatching is not a serious problem in clinical practice and can even be used to increase Peff if necessary. We conclude that the applicator design and the impedance matching method chosen in the MECS system allow heating to temperatures in the therapeutic range with implants used in clinical practice.

In vitro measurement of kidney size: comparison of ultrasonography and MRI.

In this in vitro study, the accuracy and repeatability of magnetic resonance imaging (MRI) and ultrasound (US) in assessing renal length and volume were determined. US and MR images of 20 cadaver pig kidneys were obtained twice and evaluated by two observers for each modality. The fluid displacement method provided the "gold standard." Renal volumes were calculated from the US and MR images using the ellipsoid formula. Additional volume calculations after segmentation of the kidney on MR images were done using the voxel-count method. Volumes calculated with the ellipsoid formula resulted in an average of 24% underestimation (range 5%-48%) of the renal volume for both US and MRI. With the voxel-count method, no significant deviation from the true renal volume was encountered. Repeatability was also greatest with the voxel-count method. Measuring renal length, repeatability was, again, better with MRI compared to US. For reliable calculation of renal size in vitro, MRI with use of the voxel-count method is preferred.

Intraarticular ganglion between the cruciate ligaments of the knee. A case report.

Intraarticular ganglion cysts arising from the cruciate ligaments are rare. Only 9 cases have been described in the literature. Only in one case was the diagnosis suggested before operation by the appearance on MR imaging. We report a case of a patient presenting with a bone erosion in the proximal tibial epiphysis caused by an intraarticular ganglion cyst arising from the anterior cruciate ligament.

An electric field measurement system, using two-dimensional array of diodes.

In hyperthermia induced by electromagnetic applicators, one way to obtain information about the energy absorption is by measurement of electric field strength (E). This paper describes a system which can measure E-distributions, using a two-dimensional array of diodes. It was designed to be used on patient skin, during hyperthermia treatments of superficial tumours, providing additional data for applicator power control. The first prototype consists of a sheet with Schottky diode sensors with a spacing of 2.5cm, connected to high-resistance leads, printed with carbon ink. The rectified diode voltages are passed through a multiplexer unit to an AD-DA card in a PC. The sensitivity of the sensors is linearly proportional to the electric field and to the length of the extended diode connection pins. Relative E-field distributions obtained with 64 sensors are updated within 1s. Phantom measurements, performed with the sensor matrix under a Lucite Cone Applicator (LCA) and under a 2 x 2 array of Current Sheet Applicators (CSAs) were compared with infrared measurements of the temperature rise after a short power pulse. A fair agreement was found between the square of the diode voltages and the infrared distributions. Movement of a single CSA over the sensor matrix can be visualized clearly by the system. The diode matrix E-field measurement system is sufficiently fast and accurate to give valuable feedback for power steering for an array of LCAs and CSAs. The system has the potential of being a helpful tool in other fields of quality assurance as well.

CT-angiography of abdominal aortic aneurysms after transfemoral endovascular aneurysm management.

OBJECTIVE: To evaluate short-term effect of Transfemoral Endovascular Aneurysm Management (TEAM) on aortic diameters and volumes after aneurysm exclusion, using CT-angiography. DESIGN: Analysis of preoperative, 1 week postoperative and 6 months postoperative CT measurements. SETTING: University Hospital. MATERIALS: Nine patients treated with an endovascular tube prosthesis. CHIEF OUTCOME MEASURES: True cross-sectional diameters of the aorta and the aneurysm, volume of the infrarenal aortic lumen, of the thrombus and of the iliac arteries and length of the aorta and of the endovascular prosthesis. MAIN RESULTS: CT-angiography detected shrinkage of the aneurysm in seven patients. Aneurysm growth was observed in one patient with persistent flow outside the graft and in one patient with fully thrombosed aneurysm sac. In the two patients with increasing thrombus volume, the volume of the aortic lumen decreased. CONCLUSIONS: Although successful aneurysm exclusion can be confirmed by maximum aneurysm diameter measurement, changes in aortic lumen volume and thrombus volume may be more appropriate to discriminate successful from failed exclusion.

Spatial steering with quadruple electrodes in 27 MHz capacitively coupled interstitial hyperthermia.

PURPOSE: The 27 MHz Multi Electrode Current Source (MECS) interstitial hyperthermia system uses probes consisting of multiple independent electrodes, 10-20 mm long, to steer the 3-D power deposition. Seven point thermocouples integrated into the probes provide matching 3-D temperature feedback data. To improve spatial steering the number of independent segments was increased; the feasibility and reliability of four independent electrodes integrated into a single probe were evaluated, with special attention to efficiency and to interference between separate electrodes. METHODS: The contribution of secondary coupling on the apparent electrode impedance and the dependence of cross coupling on the distance between leads, thermocouple and electrodes are computed using simple analytical models. The effect of this secondary coupling was assessed experimentally by comparing power delivery by dual and quadruple electrodes, and by quadruple electrodes in different electrode configurations (segment length 10 or 20 mm) in a nylon catheter in a muscle equivalent medium. RESULTS: Cross coupling with the thermocouple and other electrodes was computed to be of the same magnitude as the primary coupling for a quadruple electrode. Fortunately, this does not affect operation of the electrode, there was no difference in performance between quadruple and dual electrodes, and the output power was effectively independent of the electrode configuration. CONCLUSION: Quadruple MECS electrodes for improved 3-D power control are feasible.

Complications during renal artery stent placement for atherosclerotic ostial stenosis.

PURPOSE: To describe short-term complications during stent placement for atherosclerotic renal artery ostial stenosis. METHODS: Sixty-one arteries in 50 patients were treated with Palmaz stents. Nineteen patients had a single functioning kidney, 23 had a bilateral stenosis, which was stented bilaterally in 11, and 8 had a unilateral stenosis. The complications were grouped as those related to the catheterization procedure, those related to stent placement, and those possibly related to either category. The complications were divided into those with severe clinical significance (SCS), those with minor clinical significance (MCS), and radiological-technical complications (RTC). The stent placement procedures were ordered chronologically according to examination date and the complications were tabulated per group of 10 patients. RESULTS: Five (10%) SCS, 5 (10%) MCS, and 8 (16%) RTC occurred in 50 patients. The catheterization procedure led to 2 SCS, 3 MCS, and 1 RTC. Stent placement gave rise to 7 RTC. Three SCS and 2 MCS could have been related to either catheterization or stent placement. More SCS occurred in the first group of 10 patients than in the following groups. CONCLUSION: Renal artery stent placement for atherosclerotic ostial stenosis has a considerable complication rate and a learning curve is present. The complications related to the actual stent placement were without clinical consequences.

Computed tomographic angiographic imaging of abdominal aortic aneurysms: implications for transfemoral endovascular aneurysm management.

PURPOSE: To describe anatomic features pertinent to patient selection and graft design for transfemoral endovascular aneurysm management (TEAM) of the infrarenal aorta using computed tomographic (CT) angiography. METHODS: A prospective noncomparative analysis of 102 spiral CT scans of the abdominal aorta of patients with abdominal aortic aneurysms was performed. From the original CT data set, slices were reconstructed perpendicular to the vessel axis (central lumen line) at a 10 mm interval. In these reconstructed slices, diameter measurements were performed. Vessel length was measured along the central lumen line. In each patient possibilities for TEAM were analyzed. RESULTS: Because of technical reasons, 36 scans were excluded from the analysis. Of the remaining 66 patients, 18 could potentially be treated with a bifurcated endovascular device. The infrarenal aortic diameter-to-iliac artery diameter ratio was less than 2 in most patients. The vessel segments judged to be adequate for endovascular graft anchoring had a noncylindrical shape in the majority of cases. CONCLUSION: Only a minority of patients with abdominal aortic aneurysms can at this stage be treated with an endovascular graft. The ideal endovascular graft should be a combination of rigid and flexible components. The proximal and distal attachment systems should have some flexibility with an intrinsic maximum diameter while the midsection of the graft can be relatively rigid.

A 27 MHz current source interstitial hyperthermia system for small animals.

Temperature distribution is an important factor in thermo-radiotherapy and it is greatly dependent on the applied heating technique. Consistency of the heating method is therefore important in translating in vivo experimental data to the clinical situation. To further evaluate the combination of interstitial hyperthermia and interstitial radiotherapy, an experimental interstitial hyperthermia system has been developed for small (500-2000 mm3) tumours growing in the flank of a rat. The system used reproduces the properties of our clinical current source interstitial hyperthermia system. The heating system consists of four applicators, each with independent tuning and power control. The applicators are situated inside plastic afterloading catheters and are capacitively coupled with the surrounding tissue. The tumour is heated through dissipation of a 27 MHz current flowing to an external ground plane. An effective RF-filter allows reliable thermocouple temperature measurements when the power is switched on. The tumour temperature is easily controlled by means of a continuous temperature read-out and a clear temperature display. A minimum temperature up to 46 degrees C can be reached within 4-10 min and maintained (+/-0.5 degrees C) throughout the treatment period. Modelling calculations performed for this heating system indicate that the applicator temperatures should be kept equal in order to minimize the difference between maximum and minimum temperature. Significantly higher applicator currents are needed at larger distances from the ground plane. In addition, the homogeneity of the temperature distribution is improved when either the tumour is isolated or when the environmental temperature is increased. The calculations also show that temperature distribution is strongly dependent on effective heat conductivity. A description of the system and its performance is presented.

Transluminal vascular stent for ostial atherosclerotic renal artery stenosis.

We implanted transluminal stents in 24 hypertensive patients with a critical atherosclerotic ostial renal artery stenosis (28 arteries). Immediate revascularisation was successful in all. Follow-up angiography at 6 months, available in 18 patients, revealed restenosis twice. In another patient restenosis was suspected and confirmed by angiography at 2 months. Hence, the total restenosis rate was 3 of 19 patients (16%) and 3 of 23 arteries (13%). Two patients developed renal insufficiency due to cholesterol embolism. In the remaining 22 patients renal function improved (n = 8) or stabilised (n = 14). Although all had to resume antihypertensive treatment, blood pressure normalised in 15 patients, improved in one, remained unchanged in five and worsened in one.

Renal volume measurements: accuracy and repeatability of US compared with that of MR imaging.

PURPOSE: To determine the accuracy and repeatability of ultrasonography (US) with the ellipsoid formula in calculating the renal volume. MATERIALS AND METHODS: The renal volumes in 20 volunteers aged 19-51 years were determined by using US with the ellipsoid formula and magnetic resonance (MR) imaging with the voxel-count method by two independent observers for each modality. The observers performed all measurements twice, with an interval between the first and second examinations. The voxel-count method was the reference standard. Repeatability was evaluated by calculating the SD of the difference (method of Bland and Altman). RESULTS: Renal volume was underestimated with US by 45 mL (25%) on average. A comparable underestimation was found when the ellipsoid formula was applied to MR images. This indicates that the inaccuracy of US renal volume measurements (a) occurred because the kidney does not resemble an ellipsoid and (b) was not primarily related to the imaging modality. Intra- and interobserver variations in US volume measurements were poor; the SD of the difference was 21-32 mL. For comparison, the SD of the difference in reference-standard measurements was 5-10 mL. CONCLUSION: Use of US with the ellipsoid formula is not appropriate for accurate and reproducible calculation of renal volume.

Arterial stenting and balloon angioplasty in ostial atherosclerotic renovascular disease: a randomised trial.

BACKGROUND: Percutaneous transluminal angioplasty (PTA) for ostial atherosclerotic renal-artery stenosis has poor results. Angioplasty with stent placement (PTAS) may be more effective. We undertook a randomised prospective study to compare PTA with PTAS in patients with ostial atherosclerotic renal-artery stenosis. METHODS: Patients with ostial atherosclerotic renal-artery stenosis were assigned to receive PTA or PTAS. Secondary PTAS was allowed if PTA failed immediately or during 6 months' follow-up. Analysis was by intention to treat. FINDINGS: 42 patients were assigned PTA and 43 were assigned PTAS, but one patient in the PTAS group was excluded from the study. Primary success rate (<50% residual stenosis) of PTA was 57% (24 patients) compared with 88% (37 patients) for PTAS (difference between groups 31% [95% CI 12-50]). Complications were similar. At 6 months, the primary patency rate was 29% (12 patients) for PTA, and 75% (30 patients) for PTAS (46% [24-68]). Restenosis after a successful primary procedure occurred in 48% of patients for PTA and 14% for PTAS (34% [11-58]). 12 patients underwent secondary stenting for primary or late failure of PTA within the follow-up period: success was similar to that of primary PTAS. Evaluation based on intention to treat showed no difference in clinical results at six months for PTA or PTAS. INTERPRETATION: PTAS is a better technique than PTA to achieve vessel patency in ostial atherosclerotic renal-artery stenosis. Primary PTAS and primary PTA plus PTAS as rescue therapy have similar outcomes. However, the burden of reintervention after PTA outweighs the potential saving in stents, so primary PTAS is a better approach to use.

Spiral CT angiography of the renal arteries: should a scan delay based on a test bolus injection or a fixed scan delay be used to obtain maximum enhancement of the vessels?

PURPOSE: The purpose of this work was to assess the optimal scan delay for spiral CT angiography (SCTA) of the renal arteries in achieving optimal vascular contrast enhancement and to compare the utility of a delay based on these bolus injection versus that of a fixed scan delay. METHOD: Seventy patients underwent renal artery SCTA with a 140 ml bolus of contrast agent injected a 3 ml/s. In 35 patients (Group A), a fixed scan delay of 27 s was used; in the other 35 (Group B), the scan delay was based on the transit time (TTest) of a test bolus injection. The scan delays in this group were set at TTest + 5 s (n = 5), TTest + 10 s (n = 8), TTest + 15 s (n = 4), or TTest + 20 s (n = 18). For all 70 patients, the time intervals between TRA (time to scanning the renal arteries) and TMax (time to maximum aortic enhancement after 140 ml bolus injection) were calculated, after which it was determined in which group of patients TRA occurred closest to TMax. Linear regression and mean squared error (MSE) were used for statistical analysis. RESULTS: For Group A, mean TRA and TMax were 38 and 50 s, respectively. Mean (TRA - TMax) was -12 s with MSE of 185.76. For Group B, mean TRA and Tmax were 45 and 52 s. Mean (TRA - TMax) values were -15, -12, -11, and -1 s for scan delays of TTEST + 5 s, TTEST + 10 s, TTest + 15 s, and TTEST + 20 s, respectively, with MSEs of 253.80, 158.00, 137.50, and 30.00. CONCLUSION: SCTA of the renal arteries was best performed with a scan delay of TTEST + 20 s. However, analysis of our data showed that similar results could be expected with a delay of 44 s.

Angiotensin converting enzyme inhibitor-induced renal dysfunction in atherosclerotic renovascular disease.

Ischemic nephropathy due to bilateral renovascular disease (RVD) is increasingly recognized as cause of end-stage renal failure in the elderly, but a reliable non-invasive method of detection is nor available. Angiotensin converting enzyme inhibition (ACEi) may impair renal function in such patients, but a prospective study of its diagnostic validity has not been undertaken. We studied the effects of controlled exposure to ACEi on plasma creatinine in 108 patients at risk for severe bilateral atherosclerotic RVD, and compared the findings with subsequent angiography. ACEi was given for two weeks, or, to avoid acute renal failure, for four days if plasma creatinine had increased by 20% or more. If after two weeks of ACEi plasma creatinine had not increased by > or = 20%, while blood pressure was still elevated, plasma creatinine was remeasured after blood pressure control by addition of diuretics. The severity of RVD was scored by the stenosis grade of the best perfused kidney. Fifty-two patients had severe bilateral RVD, defined as > or = 50% stenosis to both kidneys (N = 23) or a solitary functioning kidney (N = 29). Of the others, 21 had less severe bilateral RVD, 20 unilateral RVD, and 15 no apparent RVD. Basal plasma creatinine was higher in severe bilateral RVD (median 170 mumol/liter, range 85 to 654 mumol/liter) than in the others (122 mumol/liter, 62 to 675 mumol/liter; P < 0.01), but not discriminative due to a large variability. The increase during ACEi was correlated with the degree of RVD (r = 0.53, P < 0.001). In 69 patients ACEi caused at least a 20% increase in plasma creatinine, in 26 cases by four days, in 31 after two weeks, and in 12 only after blood pressure control by diuretics. Among these were all 52 patients with severe bilateral RVD, 15 of the 41 patients with lesser forms of RVD, and two with normal renal arteries. Thus, in this selected population the criterion of > or = 20% rise in plasma creatinine upon ACEi was 100% sensitive to detect severe bilateral RVD, while its specificity was 70%. No case of acute renal failure was encountered, and plasma creatinine always recovered after stopping ACEi. In conclusion, controlled exposure to ACEi in these patients is safe, and ACEi-induced increase in plasma creatinine is a very sensitive detector of severe bilateral RVD in a high risk population.

Atherosclerotic renal artery stenosis: ostial or truncal?

PURPOSE: To evaluate a discrepancy between the location of renal artery stenoses on intraarterial digital subtraction angiographic (DSA) images and that on spiral computed tomographic (CT) angiograms. MATERIALS AND METHODS: The spiral CT angiograms and intraarterial DSA images of 40 consecutive patients with atherosclerotic renal artery stenoses were examined retrospectively. Stenoses were classified as truncal or ostial. The atherosclerotic changes in the abdominal aorta were graded. RESULTS: Fifty-eight stenoses were demonstrated. In 48 ostial stenoses, there was no discrepancy in the location of the stenoses on spiral CT angiograms and DSA images. In 10 patients, spiral CT angiography showed an ostial lesion, whereas DSA demonstrated an apparent truncal lesion. Most of these stenoses ("pseudotruncal" ostial stenoses) were in patients with severe aortic atherosclerotic disease. CONCLUSION: A renal artery stenosis at or within 10 mm of an atherosclerotic aorta at DSA may be diagnosed as an ostial stenosis.