Selective angiographic assessment of the erection-related arteries solely guided by conventional DSA can be challenging and time consuming due to underlying variable pelvic artery anatomy (Rogers et al., 2012; Wang et al., 2014). While proximal stenosis of the internal iliac artery or the internal pudendal artery are usually detected by conventional angiography, the absence of proximal stenoses requires superselective assessment of the more peripheral arteries, especially when pre-interventional penile duplex ultrasound indicates arterial insufficiency. Anatomic variation of pelvic arteries is not only an impediment for superselective catheterization but also for identifying erection-related arteries. Accordingly, unintentional non-target vessel stenting has been reported in 17% of patients in the ZEN study (Rogers et al., 2012).
C-arm Cone-Beam computed tomography is integrated in many modern angiographic systems and allows cross-sectional imaging and the possibility to use dedicated planning and navigation software (Floridi et al., 2014). Established clinical applications for CBCT and vessel navigation software are embolization therapies for tumors, arterial bleedings (Grosse et al., 2018; Tacher et al., 2015), and revascularization of pulmonary arteries in patients with chronic thromboembolic pulmonary hypertension (Sugiyama et al., 2014). In our case, we applied current imaging and navigation techniques to evaluate the vascular anatomy and create a 3D roadmap to reduce time to target lesion and to increase interventional safety.
Compared to non-invasive three-dimensional volumetric imaging workup, as CT Angiography (CTA) and MR-Angiography (MRA), CBCT allows of visualizing, planning and treating complex arteriogenic lesions of pelvic arteries in a single session. Compared to CTA, CBCT displays vascular anatomy more accurate and with a higher resolution in smaller and more peripheral arteries due to the direct intra-arterial contrast administration (Tacher et al., 2015). The amount of iodinated contrast medium used in our case was less than 25% of a traditional abdominal CTA in our hospital (CBCT 20 ml Iopamiro® vs. CTA 100 - 120 ml Ultravist 370®, Bayer (Schweiz) AG, ZH, Switzerland). The radiation exposure of a conventional abdominal CTA exceeds an abdominal CBCT by 3–4 times (Tacher et al., 2015). However, as the image section of CBCT usually does not cover the aorta to the root of the penis due to detector size, two selective CBCTs with the diagnostic catheter placed in the internal iliac artery have to be performed, one for each side. This reduces the radiation and contrast saving benefits of CBCT over CTA. Contrariwise, there have been promising developments in MRA, which causes no radiation exposure and does not necessarily require intravenous contrast agent. However, visualization of small, peripheral arteries using MRI techniques is still challenging, especially in tortuous vessels and if motion artifacts come into play, as in the pelvis (Mathew & Kramer, 2018). As conventional MRA using gadolinium based contrast agents still is a frequently used technique, potential systemic effects of gadolinium-based contrast agents also play a relevant role in decision making (Mathur et al., 2020). On top of this, limited availability and high costs are also worthwhile considering. The main disadvantage of on table cone beam CT application compared to CTA or MR-Angiography is that a diagnostic catheter needs to be placed selectively. Nevertheless, appropriate pre-interventional non-invasive diagnostic imaging workup, i.e. duplex ultrasound is required for correct planning of invasive procedures such as CBCT. If duplex ultrasound and the clinical symptoms support arteriogenic pathogenesis of ED, an invasive assessment with the option to treat stenotic lesion in the same session is the recommended diagnostic and therapeutic strategy.