Hello, everyone and welcome to today's Sun Nuclear webinar, part of our Best of QADS series. Today we're joined by Evie Bosette, a certified medical physicist expert in the radiotherapy department of the Radium Network in Antwerp, Belgium, where she has been since 2005. Her work has included a leading range of leading a range of projects, mostly implementing new techniques, improving the quality of patient treatments, including various brachytherapy treatments, VMAT, SVRT and gating techniques. Her current focus lies in the field of transit and vivo dosimetry and its large scale implementation and investigation of possibilities and limitations for reducing errors and deviations. Evie received her Master's in Medical Physics in 2004 at the Catholic University of the Boone, Belgium. Before we get started today, there are just a couple of notes. We want to make everyone aware that all attendees are muted. We do encourage questions and you can enter those at any time in the questions box on the left side of the screen. We will host AQ and A at the conclusion of today's presentation. A recording of today's presentation will be sent out after the broadcast as well to all attendees. So with that, I'd like to go ahead and turn today's presentation over to Evie and let her give her best of Qads presentation. Evie, the floor is yours. Thank you very much for the introduction and also for the chance to give this webinar. Today I'm going to talk about assessing the impact of adaptations to the clinical workflow and identifying head and neck cancer patients needing adaptive radiotherapy using transit invivory. Transit invivial asymmetry, a long title, so let's get into it. I think you all know in Vivot osimetry is recommended in radiotherapy to avoid major treatment errors and to improve accuracy. And the last years more commercial systems have become available and fully automated systems using electronic portal imaging devices make it feasible now to perform transit osimetry on a very large scale. Epitosymmetry based on transmission images can be roughly classified into two types, verification at the epit level using the forward projection models to calculate a predicted image and to compare it with its measured image, and the verification at the patient level using the back projection models to reconstruct or absorb those in the patient. In the Iridium Network Radiotherapy Center in Antwerp, we have 4 sites with 10 machines and more than 6000 patients a year. So efficiency, standardization and automation are key for a good QA program. And that's why we installed Suncheck in 2017 already. This is a fully automated commercially available system offering secondary checks, pretreatment QA and in vivo monitoring. Since 2018. The software is used on all machines, for all patients and for in vivodosimetry. We standardly use the 2D verification at the EPIC level using the forward projection models because it's a fast methods that doesn't require a CBCTI do declare that we are a member of the Sunchek Customer Advisory Board and a reference Center for Sun Nuclear. In 2020, we published the results of our first year of measurements in Fiero, and we saw that our transit in vivotosimetry efficiently revealed a wide variety of deviations using empirically determined parameters for gamma analysis. As described in this publication, these tolerance levels weren't altered since, so we can safely evaluate and compare our results over the years. After the first year, analysis of our results showed the largest number of positioning problems indicated here in red were measured for extremities for boost breast patients and for headache patients. And most failing measurements were due to anatomic changes indicated in blue that were measured for pelvis, rectum, abdomen and esophagus patients. And these were mostly due to weight loss and change in intestinal contents. After that, we introduced several adaptations to the clinical workflow, some of them based on the results of these first measurements. So after the first year, extra imaging was introduced for the boost in breast cancer because we saw a large number of positioning errors for these treatments. Extra education was given to the RTTS on positioning of the shoulders because this turned out to be quite a large cause for failing measurements in head and neck. And we also organized more patient education from dieticians for prostate, rectum, upper abdomen and esophageal patients because of the large number of failing measurements due to bowel filling and weight loss. In the second year, ultra hypo fractionated breast radiotherapy in five fractions with daily online pretreatment imaging was introduced, replacing 15 fraction schemes. This was not really intended to improve results, but was rather a consequence of the COVID epidemic to reduce the treatment time for patients. The introduction of the daily online pretreatment imaging had some interesting consequences though, and I will tell you more about this later. In the third year, we started immobilizing with calculated couch parameters and we introduced a surface IGRT solution. This time, we did aim at reducing the number of field measurements due to positioning issues, especially for extremities. And then we tried to assess the impact of these adaptations by investigating our in vivo osimetry results. In total, more than 100,000 measurements were analyzed of patients treated between September 2018 and August 2023, divided into 5 yearly periods. And we can proudly say that 84% of our patients now complete their treatment without any failing measurement of any kind, compared to 61% in our first year of measurements. The failed measurements were divided perpetology and into four categories of causes of failure, the technical, the planning and positioning problems and anatomic changes. The categories of causes of failure have been assigned using the comments and the notes that were made by the physicists and the physicians for each failing measurement. If a failure was due to more than one reason, the most contributing cost, according to the physicist, was assigned. The technical problems included software bugs, wrong imager position, problems with imager calibration and interrupted beams causing missing those in the image. Planning problems included the errors in contouring of body and immobilization devices, errors in skin flash tool planning and cities with artifacts or wrong wrong Houndsville units used for planning. Positioning problems included amongst others, shoulder and arm positioning, issues related to breath hole technique and errors in positioning of immobilization devices and examples of anatomic changes included weight loss, tumor growth or shrinkage, breast swelling and pneumonia. These are the overall results. The number of failed measurements due to patient related problems gradually decreased from 9 1/2% to 5 1/2 percent over the years. The increase of failed measurements due to the technical problems in the second year was mainly due to a bug in the new version of the individual software, causing a wrongly predicted those for plans with multiple energies. This bug was solved in the third year, so most of the software problems disappeared and then the further reduction of technical problems over the years was mainly due to the gradual replacement of older linear accelerators to new machines. These experience less imager breakdowns and are equipped with a more stable type of imagers. We investigated the improvement of the patient related problems and see if they could be caused by the changes that were made in the clinical workflow. So let's have a look at the results of some specific pathologies, starting with the boost in breast cancer. So we can see that the positioning problems for the boost in breast cancer diminished from 10% in the first year to 5% in the second year. The large number of technical problems in the second year was caused by this software bug I told you about, where the dose prediction of plants with multiple energies was wrongly calculated. This is often used for boost breast plants. It was solved in the third year and the number of positioning problems stayed more or less the same. So I think it's safe to say that the improvement in patient positioning is very likely to be caused by the use of extra imaging. And the further reduction in the 4th and the 5th year could be partly due to the introduction of the immobilization with calculated coach parameters and the surface ITRT solution for head and neck cancer patients. We also saw a large improvement from 9% of positioning problems in the first year to 4% in the second year. And then in the 3rd, 4th and 5th year we see this number gradually getting worse. So we looked into this and we found two possible reasons. A lot of new RTTS started in the last years. So we now decided to organize retraining of the RTTS. And we also found a large deterioration of the headrest. Some of the old headrests changed shape compared to the ones used at simulation and this can also cause a more difficult positioning. So we replaced all the old headrests and we hope these two actions will lead to better results again next year. I would also like to elaborate here a bit more to tell you about a study we completed recently for head and neck cancer patients. We conducted a retrospective study for 182 head and neck cancer patients to investigate the sensitivity of the in feeble system to detect patients that need adaptive radiotherapy and to identify its limitations. The results of the study were published very recently in the Green Journal. We divided the patients into three groups, 22 patients with laryngeal cancer without elective lymph nodes Group A, 39 patients who had post operative radiotherapy Group B and 121 patients who received primary radiotherapy including the elective lymph nodes groups. 45 of these patients received adaptive radiotherapy. 5 patients received ART twice, making a total of 50 ART plants, one in Group A10 in Group B and 39 in Group C Decisions for adaptive radiotherapy were made by the radiation oncologist. This could be based on factors seen on the CBCT like anatomic changes or change in body contour, or based on other factors like weight loss, tumor progression, placement of nasogastric feeding tube, or tracheotomy. Several anatomic and volumetric changes between the plants before and after ART were quantified. The maximum change in body contour. The volume reduction in the PTV and in the parotid glands. The weight loss, the D 98% and the D 2% to the CTV. The mean dose to the parotid glands and the maximum dose to the PTV and to the spinal cord. The patients receiving ART were divided in a group without and with failing. Failing in fever measurements right before ART, indicated here in green and in red. And we noticed that all anatomic changes and almost all volumetric changes were larger for the patients with the failing measurements. So patients with failing measurements experience more severe deviations than ones without. The global gamma passing rates were also significantly improved after ART, with an average of 96% compared to 84% before ART. After that, we correlated the clinical parameters of replanning with the deviations detected by perfection in detail to see if patients that benefit from ART could be identified. In Group A, there was only one ART plan and it was detected by perfection. Laryngeal cancer patients are less exposed to anatomic changes and there was no need for ART in this group except for this one patient. This patient probably swallowed during the simulation and a shift of 1 centimeter was necessary for good tumor matching, but this in turn induced a bad chin and shoulder position having an effect on the dose. In Group B10, ART plans were made. Six were detected by perfraction and four remains undetected. But when we looked at the dosimetric analysis, it actually showed only minor dosimetric changes of less than two Gray in these plants, suggesting that ART might not have been needed in these cases. In Group C39, ART plants were made, of which 23 were detected and 16 remains undetected. Three of them could not have been detected because ART was done because of the placement of nasogastric feeding tube, tracheotomy, and tumor progression. In 12 cases, the dosimetric analysis showed only minor to moderate dosimetric changes of less than 3 Gray, and only in one case significant dosimetric changes were observed and this was considered a false negative result. The EPITH images are summed over all control points of each arc to give an integrated image, and in this case, positive dose gradients during specific entry angle sectors were compensated with negative dose gradients because of the patient experienced swelling or dispositioning on one side while losing weight on the other. Using the results of the dosometric analysis, a rock curve analysis was carried out to evaluate the performance of perfection. The area under the rocker value was 0.89 for Kleenex and 0.96 for true beams. This can be considered excellent and suggests that perfection has a strong ability to discriminate between the dosometrically acceptable and unacceptable plans. The optimal cutoff value for the gamma passing rate was 95% for Kleenex and 95.2 for the true beams. Using a dose difference of 3% and a distance to agreements of 3mm. The sensitivity for both clinic and true beam was 96%, but the false positive rate for Kleenex was 13% compared to 5% for true beams because the Kleenex experience more calibration and image or position problems and incomplete acquired images. Then let's go back to our adaptations in our clinical workflow. These are the results for the rectum and the prostate patients. We can see the failed measurements because of anatomic changes in blue have dropped from 10% and 7% in the in the first year to 4% and 3% respectively in the second year. So also here we can see an improvement. Notice also the very small number of positioning problems in these patients. This is probably due to the lower sensitivity of the individual dosimetry for this treatment site. Transit oszometry is quite sensitive to a change in patient thickness, but the sensitivity to patient position variations is dependent on the treatment side. In anatomical regions with few density differences like abdominal regions, a shift in the patient's position will have less effect on the transmitted radiation than, for instance, in ANANAC regions. Additionally, a retrospective study was conducted and published in Tips Row to evaluate if additional help with bladder and rectum preparation in prostate cancer patients by home nurses could improve the patient's preparation. But no statistically significant differences could be observed between this test group and the control group receiving the information on bladder and rectum preparation according to the standard protocol. Unfortunately, there was also no improvement for abdominal patients and for the esophageal patients. In the first year, more failed measurements were classified with the cause of positioning problems. But we have seen that these positioning problems are often caused by an anatomic change, so that's probably why the classification changed in the second year. The overall number of failed measurements didn't change much unfortunately in the 2nd and the 3rd year. In the fourth year, we did see a small improvement, which could be caused by the introduction of immobilization with calculated gauge parameters and the surface IGRT solution, but large. Last year, we saw a large increase of the positioning problems and I'll come back to this in a few minutes. As we hoped for after the introduction of C rats in the fourth year, the failed measurements attributed to the patient positioning decreased for more pathologies with most pathologists with the largest effect for the extremities, where this number decreased from 11% in the third year to 4% in the fourth year. But unfortunately, in the fifth year, we saw a very large increase of failed measurements for these patients and we are still not sure if this is something to worry about or if it was just bad luck. You can see also the number of anatomic changes was very high in the 5th year, so of course if extremities experience extreme swelling or shrinking, positioning will get tougher too. The number of measurements for patients with extremities is very low. There are only around 20 patients a year for whom we take around 150 measurements. So if then less than 20 of these measurements failed due to positioning problems, we end up with quite large errors on these numbers with the standard deviations of around 2 to 3%. You can see the difference over the years are actually within each other's error bars of the 95% confidence level. So maybe we did just had bad luck the last year. But anyway, we did not see the large impact we hoped for using C RAT for these patients and we are still searching for a better solution to immobilize and position these patients. I want to come back to the esophagus patients. Now. As you can see, this is a much larger group of more than 70 patients with more than 500 measurements per year, resulting in a much lower standard deviations of around 1/2 to 1%. So I was quite concerned when I saw these numbers and I asked myself what changed in the past year. Something that has changed is that RTTS have been given more responsibility in the past year for the matching. They don't have to call the physician anymore if they are quite happy with online match and for all other pathologies did. This did not lead to any problems or issues. But for the esophagus patients, they had been given the order to match on Bony anatomy, which they of course follow strictly. Yet for esophagus, this isn't always the best way to go. Let's have a look at an example. You can see here in the top sagittal view with the CT on the left and the CBCT on the right that this patient is perfectly matched on the Bony anatomy of the spine. On the bottom in the frontal view you can see that it is not so perfectly matched on the soft tissues, though for esophagus patients the diaphragm is quite variable, shifting sometimes and the soft tissue around it, including the CTV and the heart, does not always remain in the same position relative to the Bony anatomy. We think that physicians, although they said to be matching on Bony anatomy used to take the soft tissue also into account during the process. So now we discussed this with the physicians, collected some examples and we have given some extra education to the RTTS for matching the esophagus patients. And hopefully next year we will see better results again. And finally, let's have a look at our breast patients. Here we can see there's only a very small difference in patient positioning problems between the first year and the second year. The introduction of the five fraction scheme however has has introduced a drop from 6% to 3% in the third year with a further decrease in the 4th and the 5th year. We have investigated also this group further with a larger retrospective study comparing two groups of 203 patients, one group treated in 2020 with five fractions receiving the daily pre treatment imaging and the other group treated in 2019 with 15 fractions receiving pre treatment imaging on the 1st 3 days of treatment and further weekly. To investigate the influence of the daily imaging, a subgroup was created with only the results of the fraction of the 15 fraction group after the pre treatment imaging. This is the online IGRT 15 fraction group. A manuscript with results of this study has been published recently in Pharaoh also and these are the results. So we can see a large difference in patient positioning problem between the fight five fraction group and the 15 fraction group. But if we compare with the subgroup receiving the online imaging, this difference is almost entirely gone, indicating that the daily online IGRT is the main cause of the difference. You can see even the difference in breast swelling as a cause disappears. This is an indication that using the pretreatment imaging could also bring swollen breasts back within constraints. The only differences that didn't disappear were the technical issues, and these were mainly related to the imager problems in the 15 fraction group and in the five fraction group. This rate was lower because the patients were treated more recently. So the most important conclusions of my talk are that evaluating results of in vivo dosimetry on a regular basis offers important insights in the quality of treatments and can indicate possible items for improvement, leading to a reduction of the number of failed measurements and an improvement of treatment quality. That a broad analysis of in vivo dosimetry results can help to evaluate and assess the impact of adaptations to the clinical workflow and hence be a powerful tool the continuous quality improvement of treatments and that invivodosimetry in combination with CBCT cannot only help to trigger ART but also possibly help to avoid unnecessary replants. And more information about this topic can also be found in this manuscript in Fiero. Are there any questions? Thank you, Evie for the wonderful presentation. We really appreciate you taking the time to go ahead and and reprise your presentation from QEDS which was held in Lisbon, Portugal earlier this year. There are just a couple of questions, but I do encourage folks to go ahead and enter in any additional questions in the bar to the left, lower left hand corner of the screen and we will take those as we have time allowed. So Evie, obviously you talked about a couple of specific cases over the last five years. Any plans to continue this type of work into the future? Yes, we definitely plan to evaluate every year the results and and see what we can get out of it. And for the moment, we will also be analyzing our breast patients again in more detail because we switched to VMAT planning in the race station and we saw some more deviating fractions again. So we will see if our constraints are still valid for the VMAT treatments. We will try to analyze based on the CBCTS what's the clinical impact of everything and we will see if we can again make some conclusions about correlations and and making a raw curve analysis and so on. So that's exciting. Wonderful. Another question just with respects to you notice you noted that the RTTS have been giving some increased responsibility. You know, obviously workflow changes are always something that people take differently in different clinics. And any any insights that you learn there about working with that group and making those changes? I'm sorry, what's the question exactly? Yeah. Were they was, you know, as far as the education and training that you did with the RTTS, was it fairly straightforward and you know was it a quick solution I guess looking at the question here? Yeah, we definitely, we definitely saw the, the improvement as you saw after, after the education of the RTTS. So we definitely think education is, is a very large can be very large help for improving outcomes and well outcomes for improving the, the, the the therapy. And with that, I don't see any additional questions. So I want to thank you again for your time. And in presenting today's presentation, as you did mention, there were a couple of publications you did reference, if anyone wants to take a closer look at those, we do have those as part of the presentation that everyone will be receiving for the recording. And it does look Nick, now there are a couple of questions piling in here. So if you've got just another minute or two Evie, we can go ahead and and answer those 111 question is how does in vivo dosimetry impact efficiency of the physics staff and bringing higher quality treatments, You know, so I think looking at a physicist role within vivodosymmetry, any comments on that? Well, I think I have. Well, there are a lot of examples where we can see that in vivodosymmetry impacts the quality of the treatments. So we can also in the publications there are a lot of examples about how we can detect possible issues in planning or with individual patients. But I'm not really sure how the the efficiency of the physics staff. It's, it's like two different questions, no? It. Does take some time, of course to invest by the physics group, but also by by the. I think it's definitely also necessary to involve the the doctors into this. So it's not only the physics staff that has to put some effort and time into it, but also also the doctors. Wonderful. There's another question about the accuracy of the dose reconstruction used aside of AR adaptive radiotherapy is needed in a head and neck treatment plan. Can you speak to the accuracy that that you were using with respects to the reconstruction of the dose for the head and neck in particular? Accuracy of the dose reconstruction. Used to decide. It's, it's, but it's just based on a new, a new city. So that's the, the accuracy of the of the those reconstruction is, is the same in the original city and in the evaluation city. So it's not that we have have made plans on on the CBCT with with the lower or lower accuracy or something. So I don't really under. I don't know if this answers the question. Yeah. I think your publications obviously have some parameters that you've used with respects to gamma analysis and those sorts of things that that someone can refer to. But as far as the the presentation today, I think that answers that. Uh huh. Yeah, you can. Also you can always have a look at at indeed that at the publication. And if there are any questions about that, I'm happy to be contacted through mail or to answer any questions about it. Wonderful. It looks like there there's a question. You know, you can't thinking about the future work of this, this future studies, you know, tying these results and, and these changes that you've made both to workflow and, and parameters and anything that you're doing to correlate that to clinical outcomes at this point. For the patients, well, that's that's a difficult question. Of course, clinical outcomes, it's always how, how does we definitely see differences in in, in dose, but it's sometimes difficult to say if this also has impact on the clinical outcome. Of course that's always the case and that's more a question for the physicians. I think how, how, how can possible differences in those affect clinical outcomes. But I do think that in certain cases I can, I can give some examples for instance, for esophageal patients where where we had a very large dose on the heart suddenly because of the some, some, yeah, some changes, some anatomic changes and also some clearing of lung fluids. And I do think that these differences were so large that they could have had clinical outcome if they weren't addressed. So yeah, I think possibly and also we can we, we have detected some, some, some errors in like for instance using the wrong city for for planning with, with house filled units. Yeah, that's has that had a few percentages of difference. So I don't know if this would have this would not have an A direct clinical outcome change, I think, but it does impact how accurate your your planning is. So it's, it's more that's not individual case, but you can also detect and something that is well for for has an impact on on all patients. Wonderful. Thank you. I think in one of your summary slides you mentioned replants and replanting are. Are there times that in vivo has shown that a patient doesn't need replanting? Maybe in the past you would have made efforts to do a replan or perhaps investigate further had you not had this technology. Yeah, we have had some cases in which the the physician did look at the at the results of perfection and and said, well, we, we would have we we don't need to replan this patient and we don't need to take an evaluation city because we see that, that, that it's still, it's still fine with with perfection. Wonderful. And it looks like the the physics question that we we had earlier, there was a restating of it by by the the person who asked is in vivo DOS symmetry the most efficient approach to ensuring quality in in your opinion, this may be another way to state that question. Well, the most efficient approach? Maybe not, but it can definitely help in improving quality. And I think in vivo the symmetry can definitely not be the only thing for ensuring quality. You still need other checks. And in vivo the symmetry cannot solve everything, but it's something that definitely adds in ensuring your quality. And it's a quite. I do think it's quite efficient to to detect a large a large gamma of of errors. Wonderful. But not everything. Sure. Certainly. Thank you, Evie. With that, we have reached the end of the questions that came in. Thank you everyone for your questions and asking those today. And again, Evie, thank you for the wonderful presentation. We encourage everyone to join us for our next of the QADS series later on this summer. Thank you so much. _1732170250085

In-vivo dosimetry is a key tool used in Radiation Therapy clinics to avoid major errors and improve the accuracy of treatments. This webinar will provide insight into the metrics used to identify head and neck patients who might need adaptive radiotherapy, while discussing changes to the clinical workflow to drive improved treatment quality._1732170250768