Transcript
Dr. Agazaryan: Hi, I'm Nzhde Agazaryan, I'm a professor and chief of clinical physics and dosimetry here at UCLA school of medicine. I've been at UCLA for over 20 years, and today we will be discussing the validation and commissioning process for Brainlab Multiple Brain Mets SRS element. We have done extensive validation and commissioning work with this product for over a year. And we have gone clinical and treated patients with the product.
The purpose of this video is to showcase the validation and commissioning work that we have done, and also make some recommendations as to what other users may decide to do for their commissioning process. For commissioning purposes, we have used Phantoms that hold field, ion chamber, and polymer gels. We have evaluated RTsafe, Quick Phantom, ArcCHECK, and Modus QA. For secondary dose calculations, we have evaluated some Nuclear's PerFRACTION, Eclipse Treatment Planning System, muCheck, and Mobius3D. The most successful results were obtained with RTsafe and Quick Phantom. And in terms of secondary calculations, the most successful results were obtained from PerFRACTION and Eclipse Treatment Planning System.
This is Brainlab's Multiple Brain Mets SRS element, which is a template-based efficient planning system. For commissioning purposes, we have chosen a seven metastases patient. In this specific case, there are multiple target sizes with multiple different prescriptions. We have chosen a template with six couch angles, two of the couch angles however, had two different arc passes, each of the passes covering different subsets of the targets.
We can also review the DVHs of the targets. Since in this planning system, the conformity index is part of the objective function of the optimizer. The heterogeneity is larger than what you would expect with the Multiple isocenter iPlan plans.
Dr. Tenn: My name is Steve Tenn, I'm a medical physicist at UCLA and today we're gonna be discussing some commissioning measurements we've made for the Brainlab Planning System. This is a Phantom from RTsafe. This is a 3D printout of an actual patient that you'll be using for your commissioning measurements. This particular Phantom has a film insert. They also produce a Phantom with ion chamber inserts and a Phantom with gel dosimetry. This particular Phantom we need to fill with water, and so I've already done that. We'll position this exactly as we would for an actual patient. So, we're using the Brainlab head and neck mask system for setup.
So, I'm gonna put, this thermal plastic mask has already been made for this Phantom. When you actually make this mask for your particular Phantom, you'll probably wanna have your therapist involved so that they can see the entire process that they'll be doing for your actual patient. So we're just going to fit this Phantom in this pre-made thermoplastic mask. We'll clip it in place. We'll move it into the bore of this scanner and we'll step out and acquire a CT scan. When you scan your RTsafe Phantom, you're gonna wanna use the same protocols you'll use clinically for your actual patients. Here I'm just gonna select our clinical protocol, first acquire topogram. I''m gonna set my region of interest making sure to cover the entire base plate and the Phantom. I'm gonna load it, position the Phantom and we'll start the scan.
It's important here to use the same protocols you'll be using on your actual patient because you want to validate this along with the entire process. So we have our scan. I'm just gonna scroll through to make sure that we have the entire Phantom anatomy, which we do. It's also important to cover the entire base plate of the Brainlab frame-less system for alignment at the machine with the ExacTrac system.
So, the nice thing about this Phantom is that it reproduces cranial anatomy, and that's important because we're also as part of this commissioning process checking the setup using the ExacTrac system. Typical flat phantom or slab phantom doesn't have the anatomy that will allow you to utilize the ExacTrac system for the alignment process as well. So we're really trying to roll in the entire treatment process with this commissioning.
So we use Phantom that actually mimics patient anatomy. We use the same scan protocols, treatment planning system we're gonna plan to the exact same dose that we would typically use in a patient, and then when we align at the machine with the ExacTrac system, we'll be able to use the full 60-degree to freedom ExacTrac software to do the alignment for confidence in both translational and rotational positioning. With this Phantom, you'll be able to use x-ray correction on the ExacTrac system with the full 60-degree of freedom correction. If you decide to use a Water Phantom that's slab geometry, then be sure to put infrared markers on that so that you can do alignment at the machine for positioning
Dr. Agazaryan: This is RTsafe's ion Chamber Phantom. There are three sites for positioning ion chambers. For the commissioning process, we have placed three targets at the ion chamber positions. Different prescription levels were used for the planning process. The dose levels were measured at the treatment unit and better than 2% accuracy was measured at each of the locations.
Dr. Tenn: At UCLA for commissioning purposes, we took an actual CT scan of a patient treated here and sent that scan to RTsafe. The company then 3D-printed this Phantom and filled it with a dosimeter capable of 3D dosimetric measurement. In order to calibrate the dosimeter, the company also provided us with five vials of the same gel material. These vials we irradiated to known doses and used them to calibrate the actual dosimetric gel. Since then, the company has modified the chemistry of the gel and a new method for cross calibrating the dosimetry. The new method is that the company will provide you with either the same Phantom with ion chambers placed at the known location of the tumors. The ion chambers can be seen here on this particular Phantom, or they can also provide you with a Phantom with a film insert. The film insert can be used with GAFchromic film to get absolute dosimetry that can then be used to crosscalibrate the gel measurement. When setting up your PseudoPatient Gel Phantom from RTsafe for radiation, you wanna treat it just as you would an actual patient.
Here we're gonna demonstrate how to set your Phantom up in the head and neck mask system from Brainlab. We'll start by placing the backplate of the head holder, followed by placement of the Gel Phantom. Place the top mask on and clip it in place using the same clips as you would for an actual patient. We're now ready to irradiate this Phantom. When utilizing the RTsafe PseudoPatient Gel Phantom, you wanna treat the Phantom exactly as you would your actual patient. In previous video, you saw us do the CT scan and how to set up the patient in the mask system. Next, I'm going to demonstrate how to use the ExacTrac system to align the patient for your radiation.
We'll start out by initial aligning the Phantom with the IRR system. This is the exact same bed that you would use for an actual patient. I'm going to get the patient close, and we'll drive the patient to the correct treatment position using the ExacTrac automatic IRR movements. Once the Phantom is in preposition using the IRR system, we're ready to exit the room and perform x-ray alignment.
Following initial infrared alignment, we're going to proceed to x-ray correction. Back in the console area, we are going to select x-ray correction. We'll acquire our two KV x-rays and click next. The system automatically does 60 alignment of the patient. In this case, you can see that we have a vertical disagreement of about 1.6 millimeters, everything else is under a millimeter, but the system will still correct every single translational and rotational offset before proceeding. I'm gonna click finish. We will make the corrections to the patient. Here we're correcting the rotational misalignments followed by corrections to the translational alignment. Once this is done, we will proceed to x-ray verification. This checks if the patient is actually positioned correctly for treatment.
Once we've completed x-ray correction, we then mode up the patient and proceed to x-ray verification. We require a two-KV x-rays and click next. The system again will do an automatic 60 degrees of freedom registration. In this case, we still have half a millimeter of longitudinal correction to make. And 1.3 degrees of vertical rotation correction to make. We can either ignore these shifts or apply them and move on. Because this is a commissioning measurement, I'm going to choose apply, the shift, we'll make additional correction and we'll repeat this process. We can make these corrections from outside the room, including the couch rotation. Once the shifts have been made, we can again proceed to x-ray verification. Click next, again. In this case, the translation on rotations are all within tolerance. We can proceed to treatment.
Next we are going to proceed with the radiation of the Phantom. I'm going to mode up for first field and prepare it for delivery on the treatment console. Once all the gantry and colometer parameters are correct, we can proceed with treatment. Here we're delivering the first field. As you can see in the small box up here, we can view our MLCs as they move for treatment. For this particular delivery we're treating three targets.
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Dr. Tenn: Once the treatment field is complete, we'll move on to the next treatment field. In this case, we have a 60-degree couch rotation. I'll go in the room, make the couch rotation. We'll come back out and check it with ExacTrac.
We've made our couch rotation in the treatment room. I'm now going to verify that the Phantom is still in position for treatment. I'm going to proceed with x-ray verification again. We require a two-KV x-ray images, proceed to image registration. We can verify the registration visually with a slider between DRR and x-ray. All fields are within tolerance, couch rotation and the translations are all within tolerance as can be seen here. And we can proceed with the next field.
I'll come back over to the console area, mode up the next field. Use the treatment console to align the gantry and colometer rotations. When everything is correct, we can proceed with beam delivery. The same process that I've just shown you, we will repeat for each arc. It's important to do the ExacTrac image guidance check prior to each arc, because as you rotate the couch around, the Phantom can move around a little bit. This will ensure that the Phantom is in the proper location for each gantry angle and each couch angle for treatment delivery. Once the radiation delivery is final, the Phantom is now ready for readout on an MR Scanner. Remember you wanna do this 24 hours after radiation, but not more than five days.
Similar to the RTsafe PseudoPatient Gel Phantom, we can set up the RTsafe PseudoPatient ion chamber Phantom for radiation. The ion chamber Phantom can be manufactured to have the ion chambers placed exactly where the targets will be. In this case, the ion chamber insert is made for a 3D pinpoint chamber. We have three targets in this Phantom and we can irradiate all targets simultaneously and get readings. And this way we can get an absolute dose measurement for the patient, using ion chamber measurement as an absolute dosimeter.
The first thing we'll do is set up the patient with infrared alignment array. We'll do initial positioning of the Phantom using the ExacTrac system. Once the initial positioning has been performed, we can step out of the room and do x-ray correction. Following this precise alignment of the Phantom, we can proceed with the radiation of the ion chambers.
With a PseudoPatient Film Phantom, RTsafe can manufacturer a film slot at a specific location where your target will end up in the patient's Phantom. The film holder has pin fiducial markers which can pierce the film to accurately reposition the film for both CT scanning and treatment delivery. In this case, I'm using EBT-XD Film for the treatment delivery, which is an extended rage high dose film. I simply clamp the film in place, insert the film holder into the Phantom and place the Phantom in the head neck mask system. This is the same method we use for the RTsafe PseudoPatient Gel Phantom, as well as the PseudoPatient ion Chamber Phantom. In fact, they can use the same CT scan for all three Phantoms so that you can have a 3D gel measurement, an ion chamber measurement, and a film measurement of the same plan.
The next thing we're gonna do is pre-position this Phantom using the IRR array. Once the Phantom has been pre-positioned, we can proceed with x-ray verification. Once we're satisfied with x-ray verification, that the Phantom is exactly where it should be for treatment, we can proceed with the radiation. For this particular example, we're irradiating the film to 20Gy, and we'll read it out tomorrow after the film has had time to develop.
With the RTsafe PseudoPatient Gel Phantom, you want to acquire an MRI scan of the Phantom 24 hours after radiation ideally, but not more than five days. You'll wanna scan the head Phantom with a head coil. The RTsafe company will provide a scan protocol, which is a T2 multi-echo protocol for your scanner.
Dr. Agazaryan: For the commissioning purposes, we irradiated the RTsafe Phantom, and then MRI Scan the Phantom with the 1.5 Tesla MRI scanner. In our example, we also irradiated calibration vials, so our results are in terms of absolute dose values. Once we sent the MRI data to RTsafe, the company provides detailed analysis of the case in a PDF report.
The report that you get from the vendor is pretty comprehensive, and it includes several elements. You can get profiles through each of the targets like shown in this example, when there is pretty good agreement between calculation and measurement. You can also get profiles through multiple targets showing the contribution of the dose distribution from one target to the other. 2D analysis in terms of gamma distributions are also available in the report. Since the complete 3D information is available to the vendor, DVH analyses are included in the PDF report, and here are some examples of those DVH analyses. We obtained clinically acceptable results with the RTsafe Gel Phantom, and it was a very useful tool for our commissioning process. Other users may decide to use this tool for their commissioning purposes. Other Phantoms are available from the vendor as well. There are Phantoms with an ion chamber or film, or ion chamber and film together. These Phantoms can be used for periodic QA tests or patient-specific QAs.
We have also evaluated the use of clear view gel for commissioning purposes. This is from Modus QA, it's a single-time use gel, and it comes in jars shown in these pictures. These jars don't have recognizable features that you can see on KV images. On the left, we show an example of many metastases irradiated in this Phantom. As you can see on those profiles below, the results are pointing towards the right direction. However, there are some misalignment and rotational artifacts that we are further evaluating in clinical practice. Further investigation needs to be done before clinical use of the product.
Dr. Tenn: As part of the commissioning process of Multiple brain Mets SRS Element, we utilized GAFchromic Film. The GAFchromic Film shown here is EBT-XD, that's an extended range EBT Film. This particular film allows us to measure doses up to 40Gy. We've calibrated this particular film to 32Gy for our clinical needs. Shown here is a calibration curve for our EBT-XD Film and you can see the three channels, red, green, and blue calibrated all the way up to 32Gy. When making measurements with this film, you can make a calibration film measurement using a dose near what you were going to deliver for the treatment. For this particular measurement, we made a calibration film at 20Gy, and we also obtained an un-irradiated calibration film. These are scanned along with the actual measurement film and are used to scale the calibration. The system uses the calibration curves obtained for this lot of film along with the calibration films made at the time of irradiation to scale the dosimetric curve. This results in the dose map that you see here. The user can import the treatment planning system dose map for comparison with the film measurement. Shown here is the treatment planning system dose map.
After aligning the dose map from the treatment planning system with the measured dose distribution, user can then compare the two-dose distributions via aligned profile being shown here. FilmQA Pro software can also do a 2D gamma analysis between the treatment planning system dose distribution, and the film measurement. Shown here is a gamma dose distribution compared at 2-millimeters and 2% criteria and a lower dose cutoff of 30% of the maximum dose.
As you can see on this particular example, the gamma pass rate using these criteria is almost 98%. This is excellent agreement for small field dosimetry. Because the FilmQA Pro software was specifically developed for use with the GAFchromic Film from Ashland, we also recommend its use for the commissioning process. We have obtained excellent results clinically using GAFchromic Film for a range of different treatments.
The Multiple Brain Mets SRS Element Software can export planar dose distributions via ASCII format. However, when utilizing the planar dose distributions exported in ASCII format for those comparison in the software, we notice large discrepancies in comparing the two dose distributions. To get around this problem the workflow we utilize in our clinic, is to import the DICOM dose distribution into our Eclipse Treatment Planning System. Within the treatment planning system, we can select the plane that we want to compare against measurement and export the dose distribution from that plane via DICOM. When utilizing a DICOM export and dose distribution, agreement between measurement and calculation is excellent.
During the commissioning process, we have used PerFRACTION software by Sun Nuclear. We have done those calculation comparison between PerFRACTION and Multiple Mets SRS Elements, and we have also dose reconstruction based on DynaLog file, and we have also attempted to recalculate the dose distribution in a patient's CT using EPID-based dosimetry.
This is the user interface of the PerFRACTION software. In this particular example, we are showing you three-target one isocenter Plan. We are using 1-millimeter search radius and PerFRACTION was able to find a perfect match within 1 millimeter for all reference points, shown with 0% difference. On the right side of the user interface, we've shown the results of the gamma analysis. In this example, we have chosen 1 millimeter and 1% dosimetric difference for gamma calculation. And the passing rate with these parameters was almost 99%.
Since this is volumetric secondary calculation, you can also evaluate the plan in terms of DVHs. In this example, we are showing the DVHs of the three targets with the primary and the secondary calculation algorithms. PerFRACTION software allows you to visualize the plant dose distribution. You can also visualize the recalculated distribution, and also look at the gamma analysis of this two distributions. We are able to recommend this software for clinical use for commissioning purposes in all commissioning cases that we have used the software and in all clinical cases that we have used the software, we have been able to achieve clinically acceptable results.
The PerFRACTION software also allows to recalculate the dose distribution based on the DynaLog file. In this example, we are analyzing the results from the DynaLog file using one millimeter search radius, and the software was able to find a perfect match between original calculation and reconstructed dose distribution with the DynaLog file. One millimeter and 1% gamma analysis show almost 99% agreement. Secondary dose calculation based on the DynaLog file can be used for commissioning purposes. It can also be used for periodic QA, and it can also be used for patient-specific QA at some institutions.
Another option that we have looked into is Mobius3D. This is a full three-dimensional calculation. The calculation engine can be adjusted to match your beam parameters. The calculation methods should be compared to avail validated plans. In this example, we'll show you a calculation with seven metastases case. Shown are the DVHs with the primary and secondary calculation. Per target analysis are also made using mean dose and, in this case, 90% coverage of each of the targets and the agreement is less than 5% for all of the targets. The one-dimensional profiles show excellent agreement between the primary and the secondary calculation. In our experience, Mobius3D can be used for commissioning purposes, as well as patient-specific QA. Mobius3D also allows to do 3D dose reconstructions based on DynaLog files.
Dr. Tenn: Part of commissioning in our clinic, we've created a treatment plan on a slab Phantom in the Multiple Brain Mets SRS Element and exported this plan to our treatment planning system, which in our clinic is Eclipse from Varian. And in that treatment planning system, we've recalculated the plan. What is being shown here is the dose distribution from the Brainlab system as compared to the other treatment planning system and the agreement is quite good in all planes. For recalculation in Eclipse, we use the exact same monitor units as come from Brainlab Element software. As you can see in this example that those distributions agree very closely across all planes. Although gamma analysis can't be performed in the Eclipse software, you can compare the two-dose distributions via those profiles.
In this example, we're showing those from the Eclipse planning system, as compared to the Brainlab Elements. As you can see in the peaks, the dose compares very favorably. For commissioning this software at UCLA, we felt it was important to compare the dose distributions coming from the Brainlab software to another independent treatment planning system. Because we have eclipse available to us, we utilize that system with the understanding that small changes may need to be made in the beam model, especially for small field dosimetry. Because Eclipse Treatment Planning System is typically commissioned with beam data extending only down to about a three by three field size, for this particular project we had to extend our field size measurements down to about one by one centimeter for the output factors. In doing this, we've got much better agreement between the Brainlab Planning System and the Eclipse Planning System dosimetrically.
Another consideration when using another treatment planning system for dose verification is a grid size. For this particular calculation, we used a 2-millimeter isotropic grid for the recalculation. The Eclipse Treatment Planning System also allows you to go down to 1-millimeter isotropic grid size. Care must be taken not to use a large grid size when reviewing the calculation.
One additional thing to keep in mind, is when doing the calculation for commissioning measurements in the Brainlab software, you might want to use a 1-millimeter isotropic grid size. The system ships with 2-millimeter isotropic grid size as default. However, for commissioning we recommend this be set to 1 millimeter. The adaptive grid feature in the Brainlab software means that for very small targets, the grid may be even smaller than 1-millimeter isotropic. This should be kept in mind when comparing those distributions coming from the Brainlab software with another vendor's treatment planning system. For small targets, you may have mismatch in dose distribution that are attributable to this effect. In our clinic, we achieve good agreement between the Brainlab system and Eclipse Treatment Planning system. This increased our confidence that the dose distribution being delivered by the Brainlab software is accurate. We can recommend the use of the Eclipse Treatment Planning System with possible minor adjustments to the beam model as an independent verification of the Brainlab system.
Dr. Agazaryan: In collaboration with Brainlab, we have evaluated many methods that can be used for validation and commissioning purposes. Based on our results, we have made a recommendation to go clinical with the product, and we started using it for patient treatments. We have demonstrated many different ways that the product can be commissioned and these methods have resulted to clinically acceptable results and the user should select one or two of them for their commissioning processes. Based on our experience with multiple products, we estimate that the commissioning work after distillation and acceptance of the product should take approximately one month. Before any further inquiries, the user can go to novaliscircle.org where there are many archived webinars, live sessions, or inquiries can be made in live forums.
The purpose of this video is to showcase the validation and commissioning work that we have done, and also make some recommendations as to what other users may decide to do for their commissioning process. For commissioning purposes, we have used Phantoms that hold field, ion chamber, and polymer gels. We have evaluated RTsafe, Quick Phantom, ArcCHECK, and Modus QA. For secondary dose calculations, we have evaluated some Nuclear's PerFRACTION, Eclipse Treatment Planning System, muCheck, and Mobius3D. The most successful results were obtained with RTsafe and Quick Phantom. And in terms of secondary calculations, the most successful results were obtained from PerFRACTION and Eclipse Treatment Planning System.
This is Brainlab's Multiple Brain Mets SRS element, which is a template-based efficient planning system. For commissioning purposes, we have chosen a seven metastases patient. In this specific case, there are multiple target sizes with multiple different prescriptions. We have chosen a template with six couch angles, two of the couch angles however, had two different arc passes, each of the passes covering different subsets of the targets.
We can also review the DVHs of the targets. Since in this planning system, the conformity index is part of the objective function of the optimizer. The heterogeneity is larger than what you would expect with the Multiple isocenter iPlan plans.
Dr. Tenn: My name is Steve Tenn, I'm a medical physicist at UCLA and today we're gonna be discussing some commissioning measurements we've made for the Brainlab Planning System. This is a Phantom from RTsafe. This is a 3D printout of an actual patient that you'll be using for your commissioning measurements. This particular Phantom has a film insert. They also produce a Phantom with ion chamber inserts and a Phantom with gel dosimetry. This particular Phantom we need to fill with water, and so I've already done that. We'll position this exactly as we would for an actual patient. So, we're using the Brainlab head and neck mask system for setup.
So, I'm gonna put, this thermal plastic mask has already been made for this Phantom. When you actually make this mask for your particular Phantom, you'll probably wanna have your therapist involved so that they can see the entire process that they'll be doing for your actual patient. So we're just going to fit this Phantom in this pre-made thermoplastic mask. We'll clip it in place. We'll move it into the bore of this scanner and we'll step out and acquire a CT scan. When you scan your RTsafe Phantom, you're gonna wanna use the same protocols you'll use clinically for your actual patients. Here I'm just gonna select our clinical protocol, first acquire topogram. I''m gonna set my region of interest making sure to cover the entire base plate and the Phantom. I'm gonna load it, position the Phantom and we'll start the scan.
It's important here to use the same protocols you'll be using on your actual patient because you want to validate this along with the entire process. So we have our scan. I'm just gonna scroll through to make sure that we have the entire Phantom anatomy, which we do. It's also important to cover the entire base plate of the Brainlab frame-less system for alignment at the machine with the ExacTrac system.
So, the nice thing about this Phantom is that it reproduces cranial anatomy, and that's important because we're also as part of this commissioning process checking the setup using the ExacTrac system. Typical flat phantom or slab phantom doesn't have the anatomy that will allow you to utilize the ExacTrac system for the alignment process as well. So we're really trying to roll in the entire treatment process with this commissioning.
So we use Phantom that actually mimics patient anatomy. We use the same scan protocols, treatment planning system we're gonna plan to the exact same dose that we would typically use in a patient, and then when we align at the machine with the ExacTrac system, we'll be able to use the full 60-degree to freedom ExacTrac software to do the alignment for confidence in both translational and rotational positioning. With this Phantom, you'll be able to use x-ray correction on the ExacTrac system with the full 60-degree of freedom correction. If you decide to use a Water Phantom that's slab geometry, then be sure to put infrared markers on that so that you can do alignment at the machine for positioning
Dr. Agazaryan: This is RTsafe's ion Chamber Phantom. There are three sites for positioning ion chambers. For the commissioning process, we have placed three targets at the ion chamber positions. Different prescription levels were used for the planning process. The dose levels were measured at the treatment unit and better than 2% accuracy was measured at each of the locations.
Dr. Tenn: At UCLA for commissioning purposes, we took an actual CT scan of a patient treated here and sent that scan to RTsafe. The company then 3D-printed this Phantom and filled it with a dosimeter capable of 3D dosimetric measurement. In order to calibrate the dosimeter, the company also provided us with five vials of the same gel material. These vials we irradiated to known doses and used them to calibrate the actual dosimetric gel. Since then, the company has modified the chemistry of the gel and a new method for cross calibrating the dosimetry. The new method is that the company will provide you with either the same Phantom with ion chambers placed at the known location of the tumors. The ion chambers can be seen here on this particular Phantom, or they can also provide you with a Phantom with a film insert. The film insert can be used with GAFchromic film to get absolute dosimetry that can then be used to crosscalibrate the gel measurement. When setting up your PseudoPatient Gel Phantom from RTsafe for radiation, you wanna treat it just as you would an actual patient.
Here we're gonna demonstrate how to set your Phantom up in the head and neck mask system from Brainlab. We'll start by placing the backplate of the head holder, followed by placement of the Gel Phantom. Place the top mask on and clip it in place using the same clips as you would for an actual patient. We're now ready to irradiate this Phantom. When utilizing the RTsafe PseudoPatient Gel Phantom, you wanna treat the Phantom exactly as you would your actual patient. In previous video, you saw us do the CT scan and how to set up the patient in the mask system. Next, I'm going to demonstrate how to use the ExacTrac system to align the patient for your radiation.
We'll start out by initial aligning the Phantom with the IRR system. This is the exact same bed that you would use for an actual patient. I'm going to get the patient close, and we'll drive the patient to the correct treatment position using the ExacTrac automatic IRR movements. Once the Phantom is in preposition using the IRR system, we're ready to exit the room and perform x-ray alignment.
Following initial infrared alignment, we're going to proceed to x-ray correction. Back in the console area, we are going to select x-ray correction. We'll acquire our two KV x-rays and click next. The system automatically does 60 alignment of the patient. In this case, you can see that we have a vertical disagreement of about 1.6 millimeters, everything else is under a millimeter, but the system will still correct every single translational and rotational offset before proceeding. I'm gonna click finish. We will make the corrections to the patient. Here we're correcting the rotational misalignments followed by corrections to the translational alignment. Once this is done, we will proceed to x-ray verification. This checks if the patient is actually positioned correctly for treatment.
Once we've completed x-ray correction, we then mode up the patient and proceed to x-ray verification. We require a two-KV x-rays and click next. The system again will do an automatic 60 degrees of freedom registration. In this case, we still have half a millimeter of longitudinal correction to make. And 1.3 degrees of vertical rotation correction to make. We can either ignore these shifts or apply them and move on. Because this is a commissioning measurement, I'm going to choose apply, the shift, we'll make additional correction and we'll repeat this process. We can make these corrections from outside the room, including the couch rotation. Once the shifts have been made, we can again proceed to x-ray verification. Click next, again. In this case, the translation on rotations are all within tolerance. We can proceed to treatment.
Next we are going to proceed with the radiation of the Phantom. I'm going to mode up for first field and prepare it for delivery on the treatment console. Once all the gantry and colometer parameters are correct, we can proceed with treatment. Here we're delivering the first field. As you can see in the small box up here, we can view our MLCs as they move for treatment. For this particular delivery we're treating three targets.
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[silence]
[00:14:26]
Dr. Tenn: Once the treatment field is complete, we'll move on to the next treatment field. In this case, we have a 60-degree couch rotation. I'll go in the room, make the couch rotation. We'll come back out and check it with ExacTrac.
We've made our couch rotation in the treatment room. I'm now going to verify that the Phantom is still in position for treatment. I'm going to proceed with x-ray verification again. We require a two-KV x-ray images, proceed to image registration. We can verify the registration visually with a slider between DRR and x-ray. All fields are within tolerance, couch rotation and the translations are all within tolerance as can be seen here. And we can proceed with the next field.
I'll come back over to the console area, mode up the next field. Use the treatment console to align the gantry and colometer rotations. When everything is correct, we can proceed with beam delivery. The same process that I've just shown you, we will repeat for each arc. It's important to do the ExacTrac image guidance check prior to each arc, because as you rotate the couch around, the Phantom can move around a little bit. This will ensure that the Phantom is in the proper location for each gantry angle and each couch angle for treatment delivery. Once the radiation delivery is final, the Phantom is now ready for readout on an MR Scanner. Remember you wanna do this 24 hours after radiation, but not more than five days.
Similar to the RTsafe PseudoPatient Gel Phantom, we can set up the RTsafe PseudoPatient ion chamber Phantom for radiation. The ion chamber Phantom can be manufactured to have the ion chambers placed exactly where the targets will be. In this case, the ion chamber insert is made for a 3D pinpoint chamber. We have three targets in this Phantom and we can irradiate all targets simultaneously and get readings. And this way we can get an absolute dose measurement for the patient, using ion chamber measurement as an absolute dosimeter.
The first thing we'll do is set up the patient with infrared alignment array. We'll do initial positioning of the Phantom using the ExacTrac system. Once the initial positioning has been performed, we can step out of the room and do x-ray correction. Following this precise alignment of the Phantom, we can proceed with the radiation of the ion chambers.
With a PseudoPatient Film Phantom, RTsafe can manufacturer a film slot at a specific location where your target will end up in the patient's Phantom. The film holder has pin fiducial markers which can pierce the film to accurately reposition the film for both CT scanning and treatment delivery. In this case, I'm using EBT-XD Film for the treatment delivery, which is an extended rage high dose film. I simply clamp the film in place, insert the film holder into the Phantom and place the Phantom in the head neck mask system. This is the same method we use for the RTsafe PseudoPatient Gel Phantom, as well as the PseudoPatient ion Chamber Phantom. In fact, they can use the same CT scan for all three Phantoms so that you can have a 3D gel measurement, an ion chamber measurement, and a film measurement of the same plan.
The next thing we're gonna do is pre-position this Phantom using the IRR array. Once the Phantom has been pre-positioned, we can proceed with x-ray verification. Once we're satisfied with x-ray verification, that the Phantom is exactly where it should be for treatment, we can proceed with the radiation. For this particular example, we're irradiating the film to 20Gy, and we'll read it out tomorrow after the film has had time to develop.
With the RTsafe PseudoPatient Gel Phantom, you want to acquire an MRI scan of the Phantom 24 hours after radiation ideally, but not more than five days. You'll wanna scan the head Phantom with a head coil. The RTsafe company will provide a scan protocol, which is a T2 multi-echo protocol for your scanner.
Dr. Agazaryan: For the commissioning purposes, we irradiated the RTsafe Phantom, and then MRI Scan the Phantom with the 1.5 Tesla MRI scanner. In our example, we also irradiated calibration vials, so our results are in terms of absolute dose values. Once we sent the MRI data to RTsafe, the company provides detailed analysis of the case in a PDF report.
The report that you get from the vendor is pretty comprehensive, and it includes several elements. You can get profiles through each of the targets like shown in this example, when there is pretty good agreement between calculation and measurement. You can also get profiles through multiple targets showing the contribution of the dose distribution from one target to the other. 2D analysis in terms of gamma distributions are also available in the report. Since the complete 3D information is available to the vendor, DVH analyses are included in the PDF report, and here are some examples of those DVH analyses. We obtained clinically acceptable results with the RTsafe Gel Phantom, and it was a very useful tool for our commissioning process. Other users may decide to use this tool for their commissioning purposes. Other Phantoms are available from the vendor as well. There are Phantoms with an ion chamber or film, or ion chamber and film together. These Phantoms can be used for periodic QA tests or patient-specific QAs.
We have also evaluated the use of clear view gel for commissioning purposes. This is from Modus QA, it's a single-time use gel, and it comes in jars shown in these pictures. These jars don't have recognizable features that you can see on KV images. On the left, we show an example of many metastases irradiated in this Phantom. As you can see on those profiles below, the results are pointing towards the right direction. However, there are some misalignment and rotational artifacts that we are further evaluating in clinical practice. Further investigation needs to be done before clinical use of the product.
Dr. Tenn: As part of the commissioning process of Multiple brain Mets SRS Element, we utilized GAFchromic Film. The GAFchromic Film shown here is EBT-XD, that's an extended range EBT Film. This particular film allows us to measure doses up to 40Gy. We've calibrated this particular film to 32Gy for our clinical needs. Shown here is a calibration curve for our EBT-XD Film and you can see the three channels, red, green, and blue calibrated all the way up to 32Gy. When making measurements with this film, you can make a calibration film measurement using a dose near what you were going to deliver for the treatment. For this particular measurement, we made a calibration film at 20Gy, and we also obtained an un-irradiated calibration film. These are scanned along with the actual measurement film and are used to scale the calibration. The system uses the calibration curves obtained for this lot of film along with the calibration films made at the time of irradiation to scale the dosimetric curve. This results in the dose map that you see here. The user can import the treatment planning system dose map for comparison with the film measurement. Shown here is the treatment planning system dose map.
After aligning the dose map from the treatment planning system with the measured dose distribution, user can then compare the two-dose distributions via aligned profile being shown here. FilmQA Pro software can also do a 2D gamma analysis between the treatment planning system dose distribution, and the film measurement. Shown here is a gamma dose distribution compared at 2-millimeters and 2% criteria and a lower dose cutoff of 30% of the maximum dose.
As you can see on this particular example, the gamma pass rate using these criteria is almost 98%. This is excellent agreement for small field dosimetry. Because the FilmQA Pro software was specifically developed for use with the GAFchromic Film from Ashland, we also recommend its use for the commissioning process. We have obtained excellent results clinically using GAFchromic Film for a range of different treatments.
The Multiple Brain Mets SRS Element Software can export planar dose distributions via ASCII format. However, when utilizing the planar dose distributions exported in ASCII format for those comparison in the software, we notice large discrepancies in comparing the two dose distributions. To get around this problem the workflow we utilize in our clinic, is to import the DICOM dose distribution into our Eclipse Treatment Planning System. Within the treatment planning system, we can select the plane that we want to compare against measurement and export the dose distribution from that plane via DICOM. When utilizing a DICOM export and dose distribution, agreement between measurement and calculation is excellent.
During the commissioning process, we have used PerFRACTION software by Sun Nuclear. We have done those calculation comparison between PerFRACTION and Multiple Mets SRS Elements, and we have also dose reconstruction based on DynaLog file, and we have also attempted to recalculate the dose distribution in a patient's CT using EPID-based dosimetry.
This is the user interface of the PerFRACTION software. In this particular example, we are showing you three-target one isocenter Plan. We are using 1-millimeter search radius and PerFRACTION was able to find a perfect match within 1 millimeter for all reference points, shown with 0% difference. On the right side of the user interface, we've shown the results of the gamma analysis. In this example, we have chosen 1 millimeter and 1% dosimetric difference for gamma calculation. And the passing rate with these parameters was almost 99%.
Since this is volumetric secondary calculation, you can also evaluate the plan in terms of DVHs. In this example, we are showing the DVHs of the three targets with the primary and the secondary calculation algorithms. PerFRACTION software allows you to visualize the plant dose distribution. You can also visualize the recalculated distribution, and also look at the gamma analysis of this two distributions. We are able to recommend this software for clinical use for commissioning purposes in all commissioning cases that we have used the software and in all clinical cases that we have used the software, we have been able to achieve clinically acceptable results.
The PerFRACTION software also allows to recalculate the dose distribution based on the DynaLog file. In this example, we are analyzing the results from the DynaLog file using one millimeter search radius, and the software was able to find a perfect match between original calculation and reconstructed dose distribution with the DynaLog file. One millimeter and 1% gamma analysis show almost 99% agreement. Secondary dose calculation based on the DynaLog file can be used for commissioning purposes. It can also be used for periodic QA, and it can also be used for patient-specific QA at some institutions.
Another option that we have looked into is Mobius3D. This is a full three-dimensional calculation. The calculation engine can be adjusted to match your beam parameters. The calculation methods should be compared to avail validated plans. In this example, we'll show you a calculation with seven metastases case. Shown are the DVHs with the primary and secondary calculation. Per target analysis are also made using mean dose and, in this case, 90% coverage of each of the targets and the agreement is less than 5% for all of the targets. The one-dimensional profiles show excellent agreement between the primary and the secondary calculation. In our experience, Mobius3D can be used for commissioning purposes, as well as patient-specific QA. Mobius3D also allows to do 3D dose reconstructions based on DynaLog files.
Dr. Tenn: Part of commissioning in our clinic, we've created a treatment plan on a slab Phantom in the Multiple Brain Mets SRS Element and exported this plan to our treatment planning system, which in our clinic is Eclipse from Varian. And in that treatment planning system, we've recalculated the plan. What is being shown here is the dose distribution from the Brainlab system as compared to the other treatment planning system and the agreement is quite good in all planes. For recalculation in Eclipse, we use the exact same monitor units as come from Brainlab Element software. As you can see in this example that those distributions agree very closely across all planes. Although gamma analysis can't be performed in the Eclipse software, you can compare the two-dose distributions via those profiles.
In this example, we're showing those from the Eclipse planning system, as compared to the Brainlab Elements. As you can see in the peaks, the dose compares very favorably. For commissioning this software at UCLA, we felt it was important to compare the dose distributions coming from the Brainlab software to another independent treatment planning system. Because we have eclipse available to us, we utilize that system with the understanding that small changes may need to be made in the beam model, especially for small field dosimetry. Because Eclipse Treatment Planning System is typically commissioned with beam data extending only down to about a three by three field size, for this particular project we had to extend our field size measurements down to about one by one centimeter for the output factors. In doing this, we've got much better agreement between the Brainlab Planning System and the Eclipse Planning System dosimetrically.
Another consideration when using another treatment planning system for dose verification is a grid size. For this particular calculation, we used a 2-millimeter isotropic grid for the recalculation. The Eclipse Treatment Planning System also allows you to go down to 1-millimeter isotropic grid size. Care must be taken not to use a large grid size when reviewing the calculation.
One additional thing to keep in mind, is when doing the calculation for commissioning measurements in the Brainlab software, you might want to use a 1-millimeter isotropic grid size. The system ships with 2-millimeter isotropic grid size as default. However, for commissioning we recommend this be set to 1 millimeter. The adaptive grid feature in the Brainlab software means that for very small targets, the grid may be even smaller than 1-millimeter isotropic. This should be kept in mind when comparing those distributions coming from the Brainlab software with another vendor's treatment planning system. For small targets, you may have mismatch in dose distribution that are attributable to this effect. In our clinic, we achieve good agreement between the Brainlab system and Eclipse Treatment Planning system. This increased our confidence that the dose distribution being delivered by the Brainlab software is accurate. We can recommend the use of the Eclipse Treatment Planning System with possible minor adjustments to the beam model as an independent verification of the Brainlab system.
Dr. Agazaryan: In collaboration with Brainlab, we have evaluated many methods that can be used for validation and commissioning purposes. Based on our results, we have made a recommendation to go clinical with the product, and we started using it for patient treatments. We have demonstrated many different ways that the product can be commissioned and these methods have resulted to clinically acceptable results and the user should select one or two of them for their commissioning processes. Based on our experience with multiple products, we estimate that the commissioning work after distillation and acceptance of the product should take approximately one month. Before any further inquiries, the user can go to novaliscircle.org where there are many archived webinars, live sessions, or inquiries can be made in live forums.