Case study with dosimetric analysis: Total Body irradiation to a patient with a left ventricular assist device

Purpose: This case report discusses the safe delivery of total body irradiation (TBI) to a patient with a left ventricular assist device (LVAD).This treatment required radiation-dose determinations and consequential reductions for the heart, LVAD, and an external controller connected to the LVAD.Methods: The patient was treated using a traditional 16MV anterior posterior (AP)/posterior anterior (PA) technique at a source to surface distance (SSD) of 515cm for 400cGy in two fractions.A 3cm thick Cerrobend block was placed on the spoiler to reduce dose to the heart and LVAD to 150cGy.The external controller was placed in a 1cm thick plastic box to reduce neutron dose and positioned as far away as possible, just outside the treatment fields.In vivo measurements were made using optically stimulated luminescence dosimeters (OSLDs) placed inside the box at distances of 2cm, 8.5cm, and 14cm from the field edge, and on the patient along the central axis and centered behind the LVAD block.Further ion chamber measurements were made using a solid water phantom to more accurately estimate the dose delivered to the LVAD.Results: The total estimated dose to the controller ranged from 135.3cGy to 91.5cGy.The LVAD block reduced the surface dose to the patient to 271.6cGy (68.1%).The block transmission factors of the 3cm Cerrobend block measured in the phantom were 45% at 1cm depth and decreased asymptotically to around 30% at 3cm depth.Applying these transmission factors to the in vivo measurements yielded a dose of 120cGy to the implanted device.Conclusion: Physical limitations of the controller made it impossible to completely avoid dose.Shielding is recommended.The block had limited dose reduction to the surface, due to secondary particles, but appropriately reduced the dose at 3cm and beyond.More research on LVADs dose limits is required.