Significant reductions in heart and lung doses using deep inspiration breath hold with active breathing control and intensity-modulated radiation therapy for patients treated with locoregional breast irradiation

Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phantom was shifted by ±2,±3, and ±5 mm from the planned position in the anterior/posterior (A/P) direction; these shifts represent setup errors and the uncertainty associated with lung filling during breath‐hold. The two‐dimensional absolute dose distributions measured in the cryogel at the planned position were compared with the distributions at all shifts from this position using gamma analysis (3%/3 mm, 10% threshold). For shifts of ±2,±3, and ±5 mm the passing rates ranged from 94.3% to 95.6%, 74.0% to 78.8%, and 17.5% to 22.5%, respectively. These results are consistent with the same gamma analysis performed on dose planes calculated in the middle of the cryogel and on the phantom surface using our treatment planning system, which ranged from 94.3% to 95.0%, 76.8% to 77.9%, and 23.5% to 24.3%, respectively. The Pinnacle dose planes were then scaled empirically and compared to the cryogel measurements. Using the same gamma metric, the pass rates ranged from 97.0% to 98.4%. The results of this study suggest that cryogels may be used as both a buildup material and to evaluate errors in chest wall treatment positioning during deep‐inspiration breath‐hold delivery. The cryogels are sensitive to A/P chest wall shifts of less than 3 mm, which potentially allows for the detection of clinically relevant errors.PACS number(s): 87.55.km, 87.57.uq

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Translucent poly(vinyl alcohol) cryogel dosimeters for simultaneous dose buildup and monitoring during chest wall radiation therapy

Eyadeh

Weston

Juhász

et al. 2016

“…Motion of the thorax can crucially impact the heart dose in left‐sided breast cancer patients. ( 13 ) Dose homogeneity in the breast has been shown to decrease with organ motion due to respiration. ( 14 , 15 ) In the specific case of breast cancer patients, the external surrogate motion should be directly related to tumor motion; however, this is not necessarily the case for other tumor locations.…”

Section: Introductionmentioning

confidence: 99%

External respiratory motion analysis and statistics for patients and volunteers

Quirk

Becker

Smith

2013

We analyzed a large patient and volunteer study of external respiratory motion in order to develop a population database of respiratory information. We analyzed 120 lung, liver, and abdominal patients and 25 volunteers without lung disease to determine the extent of motion using the Varian Real‐Time Position Management system. The volunteer respiratory motion was measured for both abdominal and thoracic placement of the RPM box. Evaluation of a subset of 55 patients demonstrates inter‐ and intrafraction variation over treatment. We also calculated baseline drift and duty cycle for patients and volunteers. The mean peak‐to‐peak amplitude (SD) for the patients was 1.0 (0.5) cm, and for the volunteers it was abdomen 0.8 (0.3) cm and thoracic 0.2 (0.2) cm. The mean period (SD) was 3.6 (1.0) s, 4.2 (1.1) s, and 4.1 (0.8) s, and the mean end exhale position (SD) was 60% (6), 58% (7), and 56% (7) for patient, volunteer abdomen, and volunteer thoracic, respectively. Baseline drift was greater than 0.5 cm for 40% of patients. We found statistically significant differences between the patient and volunteer groups. Peak‐to‐peak amplitude was significantly larger for patients than the volunteer abdominal measurement and the volunteer abdominal measurement is significantly larger than the volunteer thoracic measurement. The patient group also exhibited significantly larger baseline drift than the volunteer group. We also found that peak‐to‐peak amplitude was the most variable parameter for both intra‐ and interfraction motion. This database compilation can be used as a resource for expected motion when using external surrogates in radiotherapy applications.PACS number: 87.19.Wx, 87.55.Km

“…Although this is a small study, these results suggest that

{BH}_{exp}

is the more appropriate position for BH radiation therapy. Practically, however, there may be significant normal tissue sparing with the

{BH}_{insp}

protocol as is evident during deep‐inspiration breath hold (DIBH) radiation therapy 16 , 19 , 24 …”

Section: Discussionmentioning

confidence: 99%

Comparison of breath‐hold and free‐breathing positions of an external fiducial by analysis of respiratory traces

Hunjan

Starkschall

Rosen

et al. 2008

An internal target volume (ITV) accounting for respiratory‐induced tumor motion is best obtained using 4DCT. However, when 4DCT is not available, inspiratory/expiratory breath‐hold false(BHinsp, BHexpfalse) CT images have been suggested as an alternative. In such cases, an external fiducial on the abdomen can be used as a substitute for tumor motion and CT images are acquired when the marker position matches – as judged by the therapist/physicist ‐ its positions at previously determined free‐breathing (FB) respiratory extrema false(FBinsp, FBexpfalse). In this study we retrospectively determined the accuracy of these matches. Free breathing 4DCT images were acquired, followed by BHinsp and BHexp CT images for 25 patients with non‐small‐cell lung cancer. Respiration was monitored using a commercial external fiducial system, which generates positional information while CT studies are conducted. Software was written for statistically analyzing the displacement of the external fiducial during BHinsp and BHexp CT acquisition and comparing these displacements with corresponding mean FB extrema positions false(FBinsp and FBexp, respectivelyfalse) using a Student's t‐test. In 72% of patients, mean positions at BHinsp differed significantly from mean positions at FBinsp false(normalp<0.05: 0.13–1.40 cmfalse). In 92% of patients, mean positions at BHexp differed significantly from mean positions at FBexp false(normalp<0.05: 0.03–0.70 cmfalse), although this difference was smaller than 0.5 cm in many cases false(median=0.34 cmfalse). Our findings indicate that relying solely on abdominal external markers for accurate BH CT imaging in order to accurately estimate FB extrema positions may be subject to significant error.PACS numbers 87.53.bd, 87.57.C‐, 87.59.Fm, 87.55.Gh