Anyone having first-hand experience with this image guided RT?
For those not acquainted with it, a brief description:
"MR image guided radiation therapy (IGRT) represents a treatment modality that offers potential solutions to the well-recognized challenges of radiation delivery. Compared with computed tomography (CT)-based strategies, MR imaging (MRI) for treatment guidance offers superior soft tissue definition that is potentially advantageous in numerous disease sites.1 From a patient-safety perspective, daily image guidance with MR also avoids undesirable radiation exposure inherent to the use of CT imaging guidance such as cone beam CT (CBCT). Moreover, cine MRI can be safely employed throughout a patient's entire treatment fraction and course to monitor and manage intrafraction motion. MR-IGRT enables daily imaging of sufficient quality to permit daily plan adjustments in response to interfraction changes in anatomy.2 This approach is valid even in disease sites that are typically poorly visualized with conventional x-ray imaging, such as soft tissues within the abdomen and pelvis.1 This daily plan adjustment, termed online adaptive radiation therapy (ART), has been found in dosimetric studies to potentially improve the therapeutic ratio of radiation therapy (RT) by enhanced sparing of organs-at-risk (OARs) and safe-dose escalation in disease sites where high-dose therapy has been limited.3, 4 Thus, MR-IGRT has the potential to improve the accuracy, precision, and safety of RT delivery."
My RO showed me a comparison of ViewRay with cone beam CT imaging. Viewray was much worse. My RO has a machine but refuses to use it because he believes the image quality is so poor.
This was their original model 5 years ago. After this they have developed a linac version. From the Viewray site:
"How did ViewRay overcome the challenges of incorporating a linac in a compact MRI-guided system like the MRIdian?
ViewRay solved two major long-standing problems to compactly integrate a linac beam with an MRI system: 1) linac radiofrequency interference with the operation of the MRI and 2) MRI magnetic interference with the operation of the linac."
That's a lot better than the Viewray linac - but then the question becomes - is there any advantage over fiducials and cone beam? They both allow sub-mm adjustment. The big advantage of fiducials is that the process of alignment can be automated, not requiring human intervention and mistakes. The RO is not going to come for every treatment to align on soft tissues.
What we need a better solution for is SRT, especially if pelvic LNs are treated simultaneously.
The proponents of this technology claim that the fiducials can (relatively) move during the short/extended course of the RT treatment. On the other hand the state of automated image detection and tracking is such that its a child's play to make the necessary corrections during a single fraction, or at minimum stop the irradiation if the target gets out of predetermined limits. On top of this there is the "cine" mode, at 4 images per second, by which repetitive motion (for example the lungs with breathing) can be detected analyzed and the optimum time for firing the Linac automatically be controlled.
Whether child's play or not, it requires human intervention, which is subject to error and costs a lot of doctor's time. How can a machine judge organs that are in a different place vs the planned image? Have you seen anything about Elekta automating this? Cine is not useful for prostate; respiratory gating is used for lungs on VMAT linacs. Fiducials form a bed of scar tissue that keeps them in place throughout treatment, and have sub-mm accuracy. In this study, they compared using fiducials to using soft tissue landmarks:
The same results are presented for CBCT fiducial markers vs. CBCT soft-tissue. Here, the shift proposed by the kV fiducial marker is considered to be ground truth. This comparison removes possible uncertainties between the two imaging modalities and the temporal uncertainties since the CBCT and EPI's were taken approximately 2 minutes apart. The Pearson's correlations are: R2 = 0.90, 0.55, 0.41 (Fig. 4g-i), while the Bland-Altman analysis reveals that the 95% CI of shift-differences is (−2.15, +1.63), (−4.56, +6.31), (−3.74, +7.30) in LR [left-right], AP{anterior-posterior], SI [superior-inferior] respectively (Fig 5g-i). The percentage of agreement within +/−3mm was 90.8, 63.7, 64.1% for LR, AP and SI. Mean couch shift discrepancies of 0.3mm (SD 1.0), −0.9mm (SD 2.8), and −1.8mm (SD 2.8) in the LR, AP and SI directions (Fig. 8b-d).
As you can see, soft tissue image guidance does fine in the left-right direction, but not in the other two directions. I think Elekta would have to show that their system performs better than CBCT soft tissue imaging.
Probably none of this is critical for conventional external beam prostate therapy, but now that we are undergoing a shift to moderate and extreme hypofractionation treatment, and very tight margins, every beam has to be well placed. They also have to demonstrate how their system can track intra-fractional motion during SBRT.
What you wrote is true for 2D imaging even in the event of rotating the imaging plane so as to get a 3D-ish solid model derived from a limited number of orthogonal body-sections (certainly not a true 3D scanning). Yet, CT and MRI by small step (SI axis) sampling render a more detailed solid model which more accurately controls the aiming and spatial shaping of the beam.
I do not know about any studies, but I know that "War is father of all and king of all".
I also don't know how many of those treated with RT appreciate that klystrons and magnetrons were initially employed in RADAR systems during WW2.
But, I know that Automatic Target Recognition (ATR) stemmed out of the RADAR technology and found its way to smart missiles concurrently with the first Arab -Israeli war (1967).
Currently, the hottest topic in medicine is machine learning, jointly endeavored by the medical and engineering faculties of top universities around the globe.
And kindly be reminded that 2 decades ago there was this debate related to a human-computer chess match: Could the IBM's Deep Blue beat Garry Casparof?
Today, it has given its place to: Can your HOME PC beat the World's Grandmaster?
Speaking of computers, Turing's electro-mechanical machine at Bletchley Park during WW2 and UNIVAC's machine for US Census Bureau come to mind. Census during the ancient times was intended to check on the citizen's arm carrying capability both in numbers and equipment. The rich had to keep a horse for battle and the very rich to sponsor the build of a sea vessel.
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.
Rising PSA after radiation and ADT
PCa Abbreviation List UPDATED 1/26/2023 
Salvage radiation is in my future. What kind / technique is available for Salvage radiation?
Is this an acceptable radiation treatment?
Oligometastatic prostate cancer: Metastases-directed therapy?
