The following is excerpted from a report received from the
Georgia Department of Natural Resources:
On August 8th, a patient was undergoing a gynecological treatment using a ring applicator with the microSelectron HDR utilizing Oncentra Brachy Software version 4.5.2. On the 2nd of a 4 fraction treatment of ring and tandem, a mistreatment occurred due to inconsistent step size when treating the ring source path. A source step size of 2.5 mm was planned. What was reported in the case explorer was a 5 mm step size. This plan was sent to the TCS [Treatment Control System] and delivered at a 5 mm steps size.
It was intended to treat specific areas, but the delivered areas were 2.5 mm - 60 mm different than intended.
This was confirmed using gafchromic film on a QA plan after treatment was completed.
This event was reported by the State of Mississippi - see related EN 52914.
Elekta identified that this issue occurs when using Applicator Models with a measured source path in combination with a specific afterloader configuration, as follows:
Oncentra Brachy - Version 4.5, 4.5.1, 4.5.2, Applicator Modeling with a measured source path, RDStore default step size 5.0 mm, 10.0 mm
Afterloader - microSelectron HDR/PDR V2, V3/Digital
Applicators - Ring Applicator Sets, Ring CT/MR Applicator sets, Interstitial CT/MR Rings, Vienna CT/MR Rings, Advanced Gynecological Applicator - Venezia with Lunar-shaped ovoids
In Elekta bulletin [IFSN 806-01-BTP-001] the Ring applicator will be used to represent all applicable applicators. Where ring is mentioned also lunar-shaped ovoids apply (Advanced Gynecological Applicator). Where 5.0 mm is used as a default step size this could also be 10.0 mm.
Oncentra Brachy incorrectly handles the placement of the ring applicator models with the measured source path in combination with the microSelectron treatment unit, for which the default step size differs from 2.5 mm.
Three other facilities previously reported this issue and the manufacturer had started working on a bug fix and field notification. All other cases found the issue during QA, so no patients were involved. Veenendaal has put a stop to the delivery of the Applicator Modeling until the Oncentra Brachy v 4.5.3 is released.
An Important Field Safety Notification was sent to all customers concerning the use of ring source paths with applicator modeling on 8/11/17 (IFSN 806-01-BTP-001 attached).
An Oncentra Brachy patch is in process to fix this safety issue.