Intravascular brachytherapy: a review of the current vascular biology

Treatment of intracranial aneurysms using the new Surpass Evolve flow diverter: Safety outcomes and six-month imaging follow-up

BACKGROUND AND PURPOSE

Several studies have reported good long-term results in the occlusion of intracranial aneurysms with flow diverter treatment. The aim of this study was to report the safety and six-month follow-up outcomes using the new Surpass Evolve flow diverter in the treatment of intracranial aneurysms.

MATERIALS AND METHODS

Consecutive patients with intracranial aneurysm treated with Surpass Evolve flow diverter in two high-volume neurovascular centers between May 2019 and January 2020 were retrospectively reviewed. Procedure-related complications, aneurysm occlusion (O'Kelly-Marotta grading scale), and clinical outcomes were assessed.

RESULTS

Twenty-nine patients with 30 aneurysms were included in the study. Favorable aneurysm occlusion (O'Kelly Marotta grading scale C-D) at six-month follow-up was achieved in 21/27 (78%) aneurysms. No clinical procedure related thromboembolic complications were encountered. Twenty-three out of 24 patients with unruptured aneurysms treated with Surpass Evolve remained clinically intact at clinical follow-up. There was one fatal hemorrhagic procedure-related complication (3%). In five patients with ruptured aneurysms, no early or late rebleeds occurred from the aneurysms.

CONCLUSIONS

Surpass Evolve FD worked technically well with no intraprocedural thromboembolic complications and occlusion rates comparable to other FDs.

Neurovascular in-stent stenoses: treatment with conventional and drug-eluting balloons

BACKGROUND AND PURPOSE

ISRs remain a major issue in the endovascular management of ICAD, requiring retreatment by reangioplasty. The aim of the present study was to evaluate the technical feasibility, safety, and efficiency of the novel DEBs for neurovascular ISRs.

MATERIALS AND METHODS

Fifty-one patients (median age, 67 years; age range, 34-82 years; male/female ratio, 37:14) underwent 63 balloon dilation procedures for ISRs in intracranial stented arterial segments between November 2007 and August 2010 in a single center. Of the 63 procedures, 20 (32%) were performed by using a conventional balloon and 43 (68%), by using a paclitaxel-eluting balloon (SeQuent Please). Angiographic and clinical follow-up was performed at 6 and 12 weeks, 6 and 12 months, and yearly thereafter. Technical success rate, periprocedural complications, occurrence of recurrent ischemic symptoms, and the development of a recurrent ISR after reangioplasty were analyzed.

RESULTS

Technical success, defined as <50% residual stenosis was achieved in all cases (100%), with failure of the DEB treatment in 6% of the attempts; those lesions were finally successfully treated with a conventional balloon. The combined permanent neurologic morbidity and mortality rate (stroke, ICH, and SAH) at 30 days was 1.6%. Substantial difference was found in the rate of recurrent stenosis when comparing conventional balloons and DEBs, with recurrent stenosis rates of 50% and 9%, respectively.

CONCLUSIONS

The initial results of reangioplasty of intracranial ISRs with DEBs are encouraging; further technical developments are, nevertheless, mandatory.

STEREOTACTIC RADIOSURGERY IMPROVES LOCOMOTOR RECOVERY AFTER SPINAL CORD INJURY IN RATS

OBJECTIVE

Currently, because of the precision of stereotactic radiosurgery, radiation can now be delivered by techniques that shape the radiation beam to the tissue target for a variety of clinical applications. This avoids unnecessary and potentially damaging irradiation of surrounding tissues inherent in conventional irradiation, so that irradiation of the minimum volume of tissue necessary for optimal therapeutic benefit can be achieved. Although conventional x-irradiation has been shown to improve recovery from spinal cord injury in animals, the efficacy of targeted irradiation of the injured spinal cord has not been demonstrated previously. The purpose of these studies was to determine whether stereotactic x-irradiation of the injured spinal cord can enhance locomotor function and spare spinal cord tissue after contusion injury in a standard experimental model of spinal cord injury.

METHODS

Contusion injury was produced in rats at the level of T10 with a weight-drop device, and doses of x-irradiation were delivered 2 hours after injury via a Novalis, 6-MeV linear accelerator shaped beam radiosurgery system (BrainLAB USA, Westchester, IL) in 4 sequential fractions, with beam angles 60 to 70 degrees apart, at a rate of 6.4 Gy/minute. The target volume was a 4 × 15-mm cylinder along the axis of the spinal cord, with the isocenter positioned at the contusion epicenter. Locomotor function was determined for 6 weeks after injury with the 21-point Basso, Beattie, and Bresnahan (BBB) locomotor scale and tissue sparing in histological sections of the spinal cord.

RESULTS

Locomotor function recovered progressively during the 6-week postinjury observation period. BBB scores were significantly greater in the 10-Gy x-irradiated group compared with controls (9.4 versus 7.3; P &lt; 0.05), indicating hind limb weight support or dorsal stepping in contrast to hind limb joint mobility without weight bearing. Doses in the range of 2 to 10 Gy increased BBB scores progressively, whereas greater doses of 15 to 25 Gy were associated with lower BBB scores. The extent of locomotor recovery after treatment with x-irradiation correlated with measurements of spared spinal cord tissue at the contusion epicenter.

CONCLUSION

These results suggest a beneficial role for stereotactic radiosurgery in a rat model of acute spinal cord contusion injury and raise hopes for human treatment strategies. Additional animal studies are needed to further define potential benefits.

Edge restenosis: impact of low dose irradiation on cell proliferation and ICAM-1 expression

BACKGROUND

Low dose irradiation (LDI) of uninjured segments is the consequence of the suggestion of many authors to extend the irradiation area in vascular brachytherapy to minimize the edge effect. Atherosclerosis is a general disease and the uninjured segment close to the intervention area is often atherosclerotic as well, consisting of neointimal smooth muscle cells (SMC) and quiescent monocytes (MC). The current study imitates this complex situation in vitro and investigates the effect of LDI on proliferation of SMC and expression of intercellular adhesion molecule-1 (ICAM-1) in MC.

METHODS

Plaque tissue from advanced primary stenosing lesions of human coronary arteries (9 patients, age: 61 +/- 7 years) was extracted by local or extensive thrombendarterectomy. SMC were isolated and identified by positive reaction with smooth muscle alpha-actin. MC were isolated from buffy coat leukocytes using the MACS cell isolation kit. For identification of MC flow-cytometry analysis of FITC-conjugated CD68 and CD14 (FACScan) was applied. SMC and MC were irradiated using megavoltage photon irradiation (CLINAC2300 C/D, VARIAN, USA) of 6 mV at a focus-surface distance of 100 cm and a dose rate of 6 Gy min-1 with single doses of 1 Gy, 4 Gy, and 10 Gy. The effect on proliferation of SMC was analysed at day 10, 15, and 20. Secondly, total RNA of MC was isolated 1 h, 2 h, 3 h, and 4 h after irradiation and 5 microg of RNA was used in standard Northern blot analysis with ICAM-1 cDNA-probes.

RESULTS

Both inhibitory and stimulatory effects were detected after irradiation of SMC with a dose of 1 Gy. At day 10 and 15 a significant antiproliferative effect was found; at day 20 after irradiation cell proliferation was significantly stimulated. Irradiation with 4 Gy and 10 Gy caused dose dependent inhibitory effects at day 10, 15, and 20. Expression of ICAM-1 in human MC was neihter inhibited nor stimulated by LDI.

CONCLUSION

Thus, the stimulatory effect of LDI on SMC proliferation at day 20 days after irradiation may be the in vitro equivalent of a beginning edge effect. Extending the irradiation area in vascular brachytherapy in vivo may therefore merely postpone and not inhibit the edge effect. The data do not indicate that expression of ICAM-1 in quiescent MC is involved in the process.

Intravascular brachytherapy using 90Sr for saphenous vein grafts having diameters ranging from 2.0–5.0 mm

PURPOSE

Symptomatic coronary artery disease is routinely treated with angioplasty and stenting. Unfortunately, treatment failure in the form of in-stent restenosis (ISR) occurs relatively frequently. Intravascular brachytherapy (IVBT) is a safe and effective method proven to markedly reduce the rate of ISR in native coronary arteries. The commercially available devices for IVBT are not FDA-approved for treatment of saphenous vein grafts (SVG). This article presents calculated dosimetry for treatment of a wide range of SVG, in addition to further evaluating the dose homogeneity for native coronary arteries.

METHODS AND MATERIALS

AAPM Task Group 43 and 60 formalisms permitted dose calculations for a wide range of vessel internal diameters (phi) in both native coronary arteries and SVG. Doses were analytically calculated for the Novoste Beta-Cath 5.0 French (F) treatment devices (30, 40, and 60 mm sourcetrains) when employed for the treatment of native vessels with 2.7 <or= phi <or= 4.0 mm and for SVG with 2.0 <or= phi <or= 5.0 mm. This latter range of phi was segmented into 7 bins to facilitate rapid clinical implementation with minimal errors. Calculations of dose and dose rate for the 3.5 F devices were also performed. Dose inhomogeneity in the form of dose maxima and minima were calculated for the 3.5 and 5.0 F catheters, with the 30, 40, and 60 mm sourcetrains, and for 2.0 <or= phi <or= 5.0 mm.

RESULTS

The calculated doses rates for the 30 mm device were in agreement (typically +/- 0.3%) with measured dose rates. Reference dose calculations performed for SVG with 2.0 <or= phi <or= 5.0 mm were in alignment with those used for the more narrow range of native coronary arteries currently approved for IVBT. Errors associated with using a phi binning technique for simplifying clinical implementation did not exceed 15%, and were typically under 9%. The degree of dose inhomogeneity at a depth of 0.5 mm increased as phi increased, catheter size decreased, and sourcetrain length decreased, and was -42% and +101% relative to the prescribed dose for the 40 mm 5.0 F system with phi = 4.0 mm.

CONCLUSIONS

Use of 7 phi bins facilitates rapid clinical implementation of IVBT in the typical cardiac catheterization laboratory. While calculation of reference dose for treatment of large vessels is possible with established formalisms, the degree of dose inhomogeneity in light of current clinical results suggests further research is needed.