The overall goal of this technique is to provide an effective and reproducible method for reducing the radiation dose received by the heart during left breast radiotherapy without the need for specialized equipment. The technique uses skin surface pen marks as fiducials to check for breath hold, reproducibility. The first step is to train the patient to hold their breath comfortably and reproducibly for up to 20 seconds.
Breath holding, inflates the lung, thereby pushing the heart down and away from the radiation fields. The second step involves marking and measuring the position of tattoos relative to lasers while the patient is in breath hold before performing a radiotherapy planning CT scan with the patient in breath hole. Using the radiotherapy planning CT scan, a radiotherapy treatment plan is prepared.
Next, the patient is set up on the treatment couch and while the patient is in breath hold the light field borders are marked on the patient's skin with a pen. Finally, radiotherapy is delivered with the patient. In breath hold and breath hold.
Reproducibility is monitored using the pen marks and light fields visible via the treatment room cameras. The main advantage of this technique over existing methods such as those that use spirometry or infrared markers, is that no specialized equipment is required. This may facilitate the implementation of hearts spraying breast radiotherapy.
In centers where resources are limited, the methodology is adaptable for different radiotherapy systems and to different breast radiotherapy techniques, including field and field techniques and nodal radiation. Visual demonstration of this technique is critical as the introduction of breath hold to the radiotherapy. Planning and treatment pathway is a new concept and difficult to visualize since it requires new procedures not used in standard radiotherapy centers.
New to this method should ensure that the treatment room camera resolution and positioning are optimized prior to implementation. Demonstrating the technique will be Karen Carr and Marie Ese, Sally Keber and Gemma Lees radiographers from our center Before beginning the techniques as described in this protocol. First, obtain necessary approval from your institution's research ethics committee or institutional review board.
Begin in the clinic by assessing the patient's suitability for the voluntary breath hold technique. This technique is for patients who have been recommended left breast or chest wall radiotherapy by their radiation oncologist. Also review the patient's performance status and comorbidities, especially lung related comorbidities as these may affect their suitability for the breath hold procedure.
If the subject is suitable, obtain informed consent and ask them to practice holding their breath at home. They should practice while lying down on their back initially holding their breath for five seconds and then building up in five second intervals to a 22nd breath hold at the radiotherapy planning CT session. Begin by positioning the patient on the CT couch in the standard treatment position.
Then define the position of the tattoo markers. Place the CT markers on the patient in free breathing. A midline marker should be placed approximately halfway along the likely field edges.
Also add lateral markers to each side of the patient in free breathing in line with the midline marker. Now ask the patient to practice holding their breath. Instruct them first to breathe in and out twice.
Then take a deep breath in and hold it for five seconds while the patient is holding their breath. Mark the position of the anterior and lateral tattoos relative to the lasers to help establish reproducibility. Repeat this while adding five second intervals of breath Hold and continue until the patient can hold their breath for a total of 20 seconds.
Breathing in and out twice before breath holding relaxes. The patient helps them prepare for the breath hold during the scan and helps breath hold consistency. Record the maximum duration for which the patient can comfortably hold their breath.
Measure the distance moved by the anterior and lateral tattoos away from the lasers. And record this on the CT sheet. Be sure also to record the height of the lateral tattoo above the couch top during the breath hold.
Before proceeding with the CT scan from the CT control room, repeat the standard breath, hold instructions to the patient. Then when satisfied, the patient is in breath hold. Start the CT scan when the scan has completed.
Check and record the height of the lateral tattoos on the CT scan to confirm that a consistent breath hold was performed. However, if the lateral couch height differs by greater than three millimeters from the initial couch height, remeasure the anterior and lateral reference points prior to radiotherapy treatment. Produce a clinical radiotherapy treatment plan for the patient, which fulfills the International Commission on radiation units ICRU criteria.
Then on the day of treatment, first align the patient's tattoos in free breathing. Mark on the patient's skin. The previously obtained posterior and inferior measurements from the left lateral and anterior midline tattoos then instruct the patient to breathe in and out twice before taking a deep breath and holding it.
The reference mark on the patient's skin should rise up to the level of the laser. Ask the patient to repeat the breath hold procedure a couple of times to confirm reproducibility before proceeding with patient setup. Now ask the patient to perform another breath hold and align the midline tattoo to the ISO center position in the superior inferior direction and set the focus to surface distance FSD at the midline.
Then in free breathing, move the bed laterally to the ISO center and measure and mark the medial and lateral field borders in free breathing. Set all other machine parameters such as field size and gantry, collimator, and couch angles for the first anterior oblique beam. Then again, ask the patient to perform a breath hold and check that the medial border aligns with the marks that were just made.
Now mark the field edge as defined by the light field with a pen. This aids visualization of the patient's breath hold. Then repeat these procedures for the posterior oblique beam if the patient's setup is out of tolerance according to local tolerance levels for a standard breast radiotherapy patient, refer to the troubleshooting algorithm seen here.
Assess whether the available camera views are sufficient to monitor the field edge and the position of the gantry relative to the couch from the control room. If not, be sure to assess the can rotation prior to leaving the treatment room in order to avoid collisions. Then in the control room, zoom the treatment room cameras so that the field borders marked on the patient's skin are visible on the surrounding control room.
Monitors once ready to commence treatment, ask the patient to perform a breath hold via the intercom system. Check that the light field aligns satisfactorily with the marked field border and then commence treatment beginning with the posterior oblique beam. Repeat the same procedure for the anterior oblique beam.
Be sure to monitor the patient's breath hold during treatment delivery. The treatment should be interrupted if there is concern that there has been a change in the patient's breath. Hold depth.
Here we can see axial and sagittal CT slices of a patient acquired during free breathing and here we see CT slices of the same patient at the same chest wall level acquired using the voluntary breath hold technique. Note that with this technique, the heart outlined in yellow has been pushed down and away from the radiotherapy fields. Normal tissue doses for the voluntary breath hold technique are seen here.
Median, minimum and maximum NTD mean doses for heart left anterior descending coronary artery ipsilateral and whole lungs are shown as are median minimum and maximum LED max doses osis. In addition, median minimum and maximum cardiac doses for standard free breathing. Left breast radiotherapy at our center are shown for comparison.
And finally here we see planning CT and treatment session times for the voluntary breath hold technique, median minimum, and maximum planning, CT treatment setup. Treatment delivery and total treatment session times are shown in minutes. While attempting this technique, it's important to remember to give the breath holding instructions to the patient in a clear and consistent manner.
Once mastered, this treatment technique can be delivered in under 15 minutes. While the radiotherapy CT planning session should take no longer than 30 minutes, including patient training. Investigators are now exploring integration of this breath hold technique with more complex radiotherapy techniques such as simultaneous integrated boost treatments and arc therapies.
Please remember that the implementation of novel radiotherapy techniques should be coupled with adequate staff training, publication of clear work instructions and auditing of local results.
