Optical Surface Monitoring System{Align RT Plus} This is used on Varian's TrueBeam EDGE; Radiology: The AlignRT Plus system is indicated for use to position and monitor patients relative to the prescribed treatment isocentre, and to Withhold the beam automatically during radiation delivery.

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.

There is an anomaly with the Eclipse(TM) Treatment Planning System [TPS] Proton Convolution Superposition [PCS] dose calculation algorithm. The PCS algo- rithm calculates the water equivalent range incorrectly for non-square 3D CT images (either different number of pixels in X and Y, or non-square pixels). Before the dose is calculated, Eclipse resamples the CT images to create a calculation image with a maximum resolution of 256 x 256. The PCS algorithm assumes uniform resolution in X and Y directions, or that X = Y for all images, and erroneously sets the Y = X for dose calcu- lation. For images that are not square, where either X<>Y, or the length of X does not equal the length of Y, the computed water equivalent range R is erroneous compared to the correct range R: 1) X=Y; R =R (R is correct); 2) X<Y: R <R (R is too small) and 3) X>Y R >R (R is too big).

Reports have been received of an anomaly that can result in a treatment without intended gating (respiratory tracking/monitoring). This issue occurs when a patient planned with gating is treated on more than one system.