Estimation of intra-arterial chemotherapy distribution to the retina in pediatric retinoblastoma patients using quantitative digital subtraction angiography

Interventional neuro-oncology

Interventional neuro-oncology encompasses an array of image-guided therapies-intra-arterial chemotherapy, regional drug delivery, chemoembolization, tumor ablation-along with techniques to improve therapy delivery such as physical or chemical blood-brain barrier disruption and percutaneous catheter placement. Endovascular and percutaneous image-guided approaches to the treatment of the brain, eye, and other head and neck tumors will be discussed.

Angiographic investigation of orbital vascular variations in the rabbit and implications for endovascular intra-arterial chemotherapy models

BACKGROUND

The New Zealand White rabbit (NZWR) is the first small-animal experimental model of intra-arterial chemotherapy (IAC) for retinoblastoma treatment. The NZWR has dual ophthalmic arteries (OA): the external OA (EOA) arises from the external carotid artery and the internal OA (IOA) from the internal carotid artery. We describe the technique that we have refined for OA catheterization in rabbits, and describe the angioanatomical variations in the OA supply to the NZWR eye and implications for IAC delivery, which were identified as part of a larger project exploring IAC effects in a rabbit retinoblastoma model.

METHODS

We developed techniques to perform angiography of the external and internal carotid arteries and superselective angiography of the EOA and IOA in NZWR using transfemoral access and a microwire/microcatheter system. EOA and IOA supply to the eye was determined angiographically and recorded before selective OA catheterization and angiography.

RESULTS

114 rabbits underwent carotid angiographic evaluation and OA catheterization (161 total eyes evaluated, 112 right, 49 left). Most eyes had a single dominant arterial supply; either IOA or EOA. EOA was dominant in 73% (118/161), and IOA was dominant in 17% (27/161). Co-dominant supply was seen in 10% (16/161). Of the rabbits with bilateral OA catheterization, 25/47 (53%) had bilateral dominant EOA.

CONCLUSION

Successful catheterization of the OA in the NZWR can be readily accomplished with nuanced technique. The external OA is the dominant arterial supply in the majority of NZWR eyes. These findings allow for successful reproduction of OA catheterization studies of IAC for retinoblastoma in NZWR.

Severe Periocular Edema after Intraarterial Carboplatin Chemotherapy for Retinoblastoma in a Rabbit (Oryctolagus cuniculus) Model

Endovascular microcatheter-based intraarterial (ophthalmic artery) chemotherapy is becoming widely used for the clinical treatment of intraocular retinoblastoma due to its apparent increased efficacy compared with traditional intravenous chemotherapy; however local ocular complications are not uncommon. Carboplatin is a chemotherapeutic agent used in both intravenous and intraarterial chemotherapy. We used rabbits to assess pharmacokinetics and ocular and systemic toxicity after intraarterial carboplatin infusion. Subsequent to unilateral intraarterial administration of carboplatin, severe unilateral or bilateral periocular edema occurred in 6 adult male New Zealand white rabbits. Time to onset varied from less than 4 h after administration (n = 3, 50 mg) to approximately 24 h afterward (n = 3, 25 mg). After becoming symptomatic, 5 of the 6 animals were promptly euthanized, and the remaining animal (25 mg treatment) was medically managed for 4 d before being euthanized due to intractable edema-related lagophthalmos. Globes and orbits from all 6 euthanized rabbits were harvested en bloc; whole-mount sections were prepared for histologic evaluation, which revealed drug-induced vasogenic edema in confined spaces as the main underlying pathogenesis. Transient and self-limiting periocular edema is a common side effect of intraarterial chemotherapy but is thought to occur predominantly with melphalan monotherapy or combination therapy using melphalan, carboplatin, and topotecan. The severity of this adverse consequence in rabbits was unexpected, and its use in the study was subsequently discontinued. Although the definitive cause for this vasotoxicity and striking clinical presentation is unknown, we suspect species-specific anatomic features and sensitivity might have contributed to amplified complications after intraarterial carboplatin chemotherapy of the eye. Due to the adverse effects of intraarterial carboplatin chemotherapy that we observed in 2 experimental cohorts of rabbits, we recommend caution regarding its use in this species.

Quantitative color-coded digital subtraction neuroangiography for pediatric arteriovenous shunting lesions

BACKGROUND

Several complex pediatric neurovascular conditions are amenable to endovascular treatment. Given the unique anatomical and physiological challenges in children, there is an ongoing need for tools and techniques that provide accurate information for treatment planning, while minimizing exposure to ionizing radiation and contrast. This is more so for neonates and infants with high-flow arteriovenous (AV) shunts that are challenging to assess using conventional techniques.

OBJECTIVE

In this brief report, we describe, through representative cases, the potential role of quantitative color-coded digital subtraction angiography (qDSA) in neuroendovascular procedures in children with high-flow AV shunting lesions.

METHODS

Images were obtained using an ArtisQ biplane system (Siemens Healthineers, Erlangen, Germany). Post-processing was performed at a dedicated workstation (Syngo, Siemens) using the iFlow module to generate color-coded maps of individual digital subtraction angiography runs.

CONCLUSION

Color-coded qDSA provides real-time quantitative information in high-flow AV shunting neurovascular lesions. This can potentially help direct treatment choices, optimize endovascular treatment protocols, monitor outcomes, and determine treatment end points.

Effectiveness of alternative routes of intra-arterial chemotherapy administration for retinoblastoma: Potential for response and complications

OBJECTIVE

Intra-arterial chemotherapy (IAC) is now the first line treatment for selected patients with retinoblastoma (Rb). Typically, IAC is infused following the selective catheterization of the ophthalmic artery (OA) on the affected side. However, in some patients, the OA alone may not provide vascular supply to the tumor, whereas in other instances the efficacy of IAC could be compromised due to the presence of prominent collateral vessels from the external carotid artery (ECA). We report our experience with catheterizing vessels other than the OA for IAC treatment for Rb.

METHODS

After institutional review board approval, a retrospective analysis was conducted of electronic medical records and imaging of our Rb population.

RESULTS

We identified 13 patients who received IAC for Rb treatment. Of these, five patients required alternative methods of chemotherapy delivery other than through the OA, totaling 17 treatments. Two patients needed balloon-assisted occlusion of the ECA, two patients required selective catheterization of the middle meningeal artery, and one patient had no internal carotid artery supply to the choroidal blush, thus the superficial temporal artery provided access for IAC. Total globe salvage rate was 76% and 80% with the alternative route subset.

CONCLUSIONS

Alternatives to the OA may be necessary to deliver IAC for selected cases of Rb. These routes can be safe and effective. However, thorough understanding of the orbital blood supply is essential. Whether these alternative IAC methods result in similar outcomes to OA infusions has not been established.

Evaluation of skeletal muscle perfusion in canine hind limb ischemia model using color-coded digital subtraction angiography

OBJECTIVE

To evaluate perfusion alterations in skeletal muscle in a canine hind limb ischemia model using color-coded digital subtraction angiography (CC-DSA).

METHODS

Twelve beagles underwent embolization at the branch of their left deep femoral artery. Right hind limbs were used as the control group. Angiography was performed before and immediately after embolization. Upon CC-DSA analysis, time to peak (TTP) was measured before embolization in both sides of the beagles' hind limbs at the middle iliac artery, and the distant, middle and proximal femoral artery. Regions of interest (ROI) peak and ROI peak time were symmetrically computed in proximal and distal thigh muscles before and immediately after embolization. The data were analyzed and compared using the Wilcoxon signed rank test.

RESULTS

Before embolization, ROI peak in the proximal thigh was lower than in the ipsilateral distal thigh, whereas ROI peak time in the proximal thigh was longer than in the distal thigh. In the iliac femoral artery, there was no significant difference in ROI peak, ROI peak time, or TTP between right and left sides. After embolization, ROI peaks in proximal and distal skeletal muscles of the left hind limb were significantly lower than on the contralateral side. ROI peak time was significantly longer in the left proximal and left distal thigh compared to the contralateral side. There were no significant changes in ROI peak or ROI peak time in the right proximal and right distal thigh compared to pre-embolization values. Changes in ROI peak and ROI peak time were larger in the left proximal than in the left distal thigh.

CONCLUSION

CC-DSA provided real-time measurement of changes in vascular hemodynamics and skeletal muscle perfusion without increasing X-ray usage or contrast agent dose.