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Discuss cardiac sparing for left breast patients with SGRT.
By marko_laaksomaa Finland flag
#692
Hi all

Is there any unit which is acquiring AP+LAT images more than in the first three fractions with AlignRT in DIBH cases? Is anyone updating the surfaces for the AlignRT if the distance between vertebra and sternum has changed in the LAT kV-image, before going to obviously most commonly used tangential imaging protocoll? If there is one, I am interested in to discuss. My e-mail is marko.laaksomaa@pshp.fi

Have a great summer and all the best

Marko
By ellen_herron_bsrtt
#693
We film orthogonal sets on Verification day then weekly during out port films. If the distance has changed between the two then the patient may need to take more or less of a breath. We match spine then compare sternum from port to DRR. The difference in sternum will indicated if they need to take a deeper breath or let air out. (tip-if you have a true beam you can take a MV/KV pair. Start with the MV and you can film ap and lat in one breath) We always recapture a new reference image after films and use that reference until the next set of films.
By marko_laaksomaa Finland flag
#694
Interesting to hear that someone else is also adjusting the breath hold level based on LAT image and vertebra. Can we go to details here or at the e-mail? Based on our experience, for the user, this kind of workflow needs lots of experience and understanding to work in the online match (kV/kV couch shift) situations. This seems to be because the isocenter and the breath hold level are not separated in the system, vertebra match does not always work perfectly if there is a need for the couch shift in the isocenter in addition to BHL. If the "AlignRT isocenter" (the acquisition position in the Offline review) is completely at the sternum match in the first place, then the vertebra match and couch shifts based on that (= BHL- correction) works well, without recapturing the surface after couch shifts. This needs patient guidance, so that the patient understands to inhale more or less to reach the same BH- deltas, because the couch has shifted based on vertebra match. The pre-defined BH- surface that AlignRT has, is in my opinion a great feature, at least for the tangential image accuracy.
By michael_tallhamer_msc_dabr
#695
Marko and Ellen,

I would add (or caution) that vertebra match should be scrutinized as a good indicator for BH as the heart position is a compound motion during the BH. The primary reason for BH is to protect the heart and you have to be careful in making adjustments for BH level based on vertebral match alone. We take kVs on the first day under BH for rough verification of isocenter location and BH level but our final verification is always a tangential port with the heart and heart block relative positions indicating the proper BH and positioning after kV verification.

We find that we rarely have to make any adjustments away from the BH DICOM surface when evaluated against the kVs and/or the MV ports showing the heart and heart block locations.

Best Regards,

Mike
By marko_laaksomaa Finland flag
#696
Hi

We also verify the BH- level with tangential images and check the heart position after three first fraction in n0 DIBH treatments. We have found that tangential image may give false positive signals for BH- correction, because of daily position variation of the heart and poor image quality to check the real position of the heart. Additionally not much corrections can be done based on tangential images. Therefore we check and when needed correct the BH- level based on the information of displacement error between vertebra and sternum (VRT,LNG) at the beginning of the treatment and if systematic errors in the heart position is seen in the tangential images during the treatment. Problematic cases are nowadays rare, but the workflow should be known if the heart is systematically nearer the treatment field in tangential image and BHL is too shallow in LAT image. I think these problematic cases should be taken more into account already at the AlignRT training. If anyone is acquiring AP+LAT images more than once during the treatment in DIBH, I am interested in to compare the  feedback and results with ours. Please e-mail, if you are.

Best regards Marko