A simple technique for an accurate shielding of the lungs during total body irradiation

Abstract

During total body irradiation (TBI), customized shielding blocks are positioned in front of the lungs to reduce radiation dose. The difficulty is to accurately position the blocks to cover the entire lungs. A new technique based on Computed Tomography (CT) simulation was developed to determine the exact position of lung blocks prior to treatment in order to decrease overall treatment time and reduce patient discomfort. Material/Methods: Patients were CT simulated and lungs were contoured using a treatment planning system. Anteroposterior/posteroanterior (AP/PA) fields were designed with MLC aperture conforming to lung contours. The fields were used to represent the extent of the lungs, which was subsequently marked on the patient's skin. The lung blocks were positioned with their shadow matching the lungs' marks. Their position was radiographically verified prior to the delivery of each beam. To evaluate the efficiency of this technique, the treatment session time and the number of repeated attempts to correctly position the shielding blocks was recorded for each beam. Exact treatment times for patients treated with the old technique were not available and were hence approximated based on previous experience. Results: We succeeded in positioning the shielding blocks from the first attempt in 10/12 beams. The position of the shielding blocks was adjusted only one time prior to treatment in 2/12 beams. These results are compared to an average of 3 attempts per beam for each patient using the conventional technique of trial and error. The average time of a treatment session was 29 min with a maximum of 41 min versus approximately 60 min in past treatments and a maximum of 120 min. Conclusion: This new technique succeeded in reducing the length of the overall treatment session of the conventional TBI procedure and hence reduced patient discomfort while ensuring accurate shielding of the lungs.

New strategy of a lung compensating technique with STR for total body irradiation

“…reported a simple technique using a field designed with a multi‐leaf collimator aperture conforming to lung contours using computed tomography (CT) simulations and a treatment planning system (TPS) to represent the lung that was subsequently marked on the patient's skin before TBI therapy. 24 Although Mekdash et al. marked directly on the patient's skin, the shape of STR can easily be made in real time by projecting the irradiation field of the lung made using a CT simulator.…”

“…Mekdash et al. reported a simple technique using a field designed with a multi‐leaf collimator aperture conforming to lung contours using computed tomography (CT) simulations and a treatment planning system (TPS) to represent the lung that was subsequently marked on the patient's skin before TBI therapy 24 . Although Mekdash et al.…”

“…Mekdash et al reported a simple technique using a field designed with a multileaf collimator aperture conforming to lung contours using computed tomography (CT) simulations and a treatment planning system (TPS) to represent the lung that was subsequently marked on the patient's skin before TBI therapy. 24 Although Mekdash et al marked directly on the patient's skin, the shape of STR can easily be made in real time by projecting the irradiation field of the lung made using a CT simulator. In addition, the size and shape of the compensating materials can be estimated and easily used by contouring compensating materials in a required area in a TPS and creating the digitally reconstructed radiograph, as indicated in Figure 5.…”

A Review of Image-Based Simulation Applications in High-Value Manufacturing

“…CBCT was used to segment the hepatic arterial tree to predict microsphere transport using multiscale CFD modelling and Monte Carlo simulation. Bespoke manufacturing is also used within personalised radiotherapy treatment, mainly shielding blocks to protect regions of the body not intended to receive a dose [ 283 ]; and boluses to alter dosing received from the beam [ 284 ]. There are examples where the performance of custom boluses have been modelled with IBSim [ 285 ] (Fig.…”

Evaluation of the surface dose for total body irradiation (TBI) technique with parallel-opposed anterior posterior geometry

“…In TBI, a surface dose (normally 1 mm deep or greater) of at least 90% of prescribed dose is required to ensure that sufficient dose is received by skin, superficial lymphatics, rib bone marrow, skull, and sternum. 13 The purpose of this study was to evaluate the superficial dose in TBI technique. First, the TBI technique was implemented on human-like phantom, in parallel-opposed (POP) anterior/posterior (AP/PA) geometry with 18-MV photon beam.…”