Varian Multileaf Collimator [MLC]; Millenium Multileaf Collimator [52, 80, 120 leaf]; High Definition 120 Multileaf Collimator Model Number(s): product code: H54 and H56; MLC software version 8.5 - Product Usage: is intended to assist the clinician in the delivery of external beam radiation to defined target volumes during radiosurgery and radiotherapy while sparing surrounding normal tissue and critical organs from excess radiation.

Reason: After a recent upgrade to the collimator software version 8.5, the firm became aware that the multi-leaf collimator leaves did not move during an arc treatment. The issue is related to a transient carriage primary- secondary interlock due to carriage fault on the MLC that immediately preceded the initiation of the arc treatment. The issue will occur only with MLC software version 8.5 and only affects conformal arc treatments, including VMAT and RapidArc. There have been no reports of adverse health consequences due to this issue.

Code information: Model Number(s): product code: H54 and H56; MLC software version 8.5. UDIs: HD 120 MLC Head Assembly. UDI: 00899475002318 80 Leaf Assy, MLC Head, UDI: 00899475002325 120 Leaf Assy, MLC Head, UDI: 00899475002332

Distribution pattern: Worldwide distribution - US Nationwide distribution including in the states of TN, FL, IN, PA, NV, WA, DC, CA, AL, IL, MD, VA, TX, MN, AR, GA, OR, MS, MO, NY, SC, DE, AZ, NH, MI, NC, OH, PA and OK. The country of Canada.