Dosimetric feasibility of stereotactic arrhythmia radioablation for ventricular tachycardia in patients with a subcutaneous implantable cardioverter defibrillator

Figures

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  Fig. 1. S-ICDs localized in the left axillary region (sub-serratus, intermuscular, and subcutaneous placement). Exemplary X-rays of S-ICD patients treated in our clinic. Depending on patient anatomy, varying distances between S-ICD and left ventricle occur: A) Normal-weight patient with a small distance between S-ICD and the heart in the left–right direction. B) Patient with a cranially implanted can and a resulting large craniocaudal distance between the S-ICD and the heart. C) Obese patient with a large distance between the S-ICD and the heart in the left–right direction. D) Patient with a caudal can placement and a resulting small craniocaudal distance between the S-ICD and the heart.

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  Fig. 2. Creation of hypothetical targets in three representative heart segments. A) Semi-automated transfer of all 17 segments (American Heart Association) of the left ventricle with CARDIO-RT to the cardiac CT (transversal slice shown, segments in assorted colors; S-ICD left axilla). B) The representative segments 8 (septum, orange), 11 (left lateral, green), and 17 (apical, magenta). C) Transmural expansion to CTVs of the three representative segments. D) Final PTV (CTV + 5 mm). E) Volume rendering of the left ventricle and the semi-automatically transferred 17 segments (CARDIO-RT). Black: aorta. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

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  Fig. 3. Exemplary treatment plans of one case. A-C) Radiotherapy plans (‘spared’) with 25 Gy in one fraction for the PTV of segment 8, 11, and 17 with sparing of the S-ICD from the primary beam (note the arc configuration). A‘-C‘) Radiotherapy plans for the PTV of segment 8, 11, and 17 without sparing of the S-ICD from the primary beam (‘non-spared’). For this patient, sparing of the S-ICD did not result in plan quality compromises in any of the cases.

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  Fig. 4. Exemplary treatment plans with clinically unacceptable spared plan (sparing of the S-ICD). A) Radiotherapy plan with sparing of the S-ICD from the primary beam for the PTV in segment 11 (‘spared’ plan). Note the direct proximity of the S-ICD to lateral parts of the left ventricle. B) Radiotherapy plan for the same patient and segment without sparing of the S-ICD from the primary beam (‘non-spared’). In this case, sparing of the S-ICD resulted in plan compromises with major/unacceptable protocol deviations by means of S-ICD D0.035cm3 over 1 Gy, aorta D0.035cm3 over 20 Gy, spinal canal D0.035cm3/V6Gy over 8 Gy/ > 1 cm3, skin D0.035cm3 over 16 Gy, and esophagus V9Gy over 4 cm3. C) Spared non-coplanar radiotherapy plan. With non-coplanar treatment planning all major protocol deviations could be avoided. Only PTV V25Gy resulted in a minor protocol deviation of 90,1 %. D) Dose/volume histogram of all structures with major protocol deviations in the spared coplanar radiotherapy plan in comparison with the non-spared coplanar and spared non-coplanar radiotherapy plan. Legend: Solid line = spared coplanar radiotherapy plan, dashed line = non-spared coplanar radiotherapy plan, dotted line…