Breast Coverage Research Articles

Comparative study of breast tissue coverage in cone-beam breast CT versus digital mammography

Objective To evaluate the d breast tissue coverage of cone-beam breast computed tomography (CBBCT) compared with conventional digital mammography. Methods CBBCT scans and digital mammography in 96 patients (141 breasts) over the age of 35 were prospectively assessed in the study. CBBCT scans were performed within 1 week after digital mammography. Superior, inferior, medial, lateral, posterior coverage of breast tissue in CBBCT and digital mammography were evaluated, respectively. It wasconsidered as positive if there was a breast coverage. McNemar test was used to assess differences in breast coverage between CBBCT and digital mammography. Results Within all the 141 cases, digital mammography covers the superior aspects in 141 cases (100.0%), inferior aspects in 88 cases (62.4%), medial aspects in 52 cases (36.9%), lateral aspects in 60 cases (42.6%), and posterior aspects in 17 cases (12.0%). CBBCT covers the superior aspects in 136 cases (96.4%), the inferior aspects in 136 cases (96.4%), the medial aspects in 129 cases (91.5%), the lateral aspects in 129 cases (91.5%), and the posterior aspects in 129 cases (91.5%). CBBCT had statistically significant better coverage than digital mammography in the inferior, medial, lateral, and posterior aspects (χ2 values were 42.48, 67.95, 60.05 and 108.08, respectively; all P values<0.01) regions. No statistically significant difference (χ2 value=3.20,P=0.074) was found in the superior aspects. Conclusion CBBCT has better breast tissue coverage than conventional digital mammography, especially in posterior aspects of breast tissues. Key words: Mammography; Cone beam computed tomography

The influence of patient positioning in breast CT on breast tissue coverage and patient comfort

Purpose: The presented study aimed at optimizing a patient table design for breast CT (BCT) systems with respect to breast tissue coverage and patient comfort. Additionally, the benefits and acceptance of an immobilization device for BCT using underpressure were evaluated. Materials and Methods: Three different study parts were carried out. In a positioning study women were investigated on an MRI tabletop with exchangeable inserts (flat and cone-shaped with different opening diameters) to evaluate their influence on breast coverage and patient comfort in various positioning alternatives. Breast length and volume were calculated to compare positioning modalities including various opening diameters and forms. In the second study part, an underpressure system was tested for its functionality and comfort on a stereotactic biopsy table mimicking a future CT scanner table. In the last study part, this system was tested regarding breast tissue coverage. Results: Best results for breast tissue coverage were shown for cone-shaped table inserts with an opening of 180 mm. Flat inserts did not provide complete coverage of breast tissue. The underpressure system showed robust function and tended to pull more breast tissue into the field of view. Patient comfort was rated good for all table inserts, with highest ratings for cone-shaped inserts. Conclusion: Cone-shaped tabletops appeared to be adequate for BCT systems and to allow imaging of almost the complete breast. An underpressure system proved promising for the fixation of the breast during imaging and increased coverage. Patient comfort appears to be adequate. Key points:

SU‐E‐T‐450: How Important Is a Reproducible Breath Hold for DIBH Breast Radiotherapy?

Purpose:Deep inspiration breath hold (DIBH) for left‐sided breast cancer has been shown to reduce heart dose. Surface imaging helps to ensure accurate breast positioning, but does not guarantee a reproducible breath hold (BH) at DIBH treatments. We examine the effects of variable BH positions for DIBH treatments.Methods:Twenty‐Five patients with free breathing (FB) and DIBH scans were reviewed. Four plans were created for each patient: 1) FB, 2) DIBH, 3) FB_DIBH – the DIBH plans were copied to the FB images and recalculated (image registration was based on breast tissue), and 4) P_DIBH – a partial BH with the heart shifted midway between the FB and DIBH positions. The FB_DIBH plans give “worst case” scenarios for surface imaging DIBH, where the breast is aligned by surface imaging but the patient is not holding their breath. Students t‐tests were used to compare dose metrics.Results:The DIBH plans gave lower heart dose and comparable breast coverage versus FB in all cases. The FB_DIBH plans showed no significant difference versus FB plans for breast coverage, mean heart dose, or maximum heart dose (p &gt;= 0.10). The mean heart dose differed between FB_DIBH and FB by &lt; 2 Gy for all cases, the maximum heart dose differed by &lt; 2 Gy for 21 cases. The P_DIBH plans showed significantly lower mean heart dose than FB (p = 0.01). The mean heart doses for the P_DIBH plans were &lt; FB for 22 cases, the maximum dose &lt; FB for 18 cases.Conclusions:A DIBH plan delivered to a FB patient set‐up with surface imaging will yield similar dosimetry to a plan created and delivered FB. A DIBH plan delivered with even a partial BH can give reduced heart dose compared to FB techniques when the breast tissue is well aligned.

SU‐E‐T‐451: Hybrid‐VMAT: A Novel Technique Combining VMAT and 3D in Planning Whole Breast Radiotherapy with a Simultaneously‐Integrated Boost (WBRT+SIB)

Purpose:The RTOG 1005 trial offered a hypofractionated arm in delivering WBRT+SIB. Traditionally, treatments were planned at our institution using field‐in‐field (FiF) tangents with a concurrent 3D conformal boost. With the availability of VMAT, it is possible that a hybrid VMAT‐3D planning technique could provide another avenue in treating WBRT+SIB.Methods:A retrospective study of nine patients previously treated using RTOG 1005 guidelines was performed to compare FiF+3D plans with the hybrid technique. A combination of static tangents and partial VMAT arcs were used in base‐dose optimization. The hybrid plans were optimized to deliver 4005cGy to the breast PTVeval and 4800cGy to the lumpectomy PTVeval over 15 fractions. Plans were optimized to meet the planning goals dictated by RTOG 1005.Results:Hybrid plans yielded similar coverage of breast and lumpectomy PTVs (average D95 of 4013cGy compared to 3990cGy for conventional), while reducing the volume of high dose within the breast; the average D30 and D50 for the hybrid technique were 4517cGy and 4288cGy, compared to 4704cGy and 4377cGy for conventional planning. Hybrid plans increased conformity as well, yielding CI95% values of 1.22 and 1.54 for breast and lumpectomy PTVeval volumes; in contrast, conventional plans averaged 1.49 and 2.27, respectively. The nearby organs at risk (OARs) received more low dose with the hybrid plans due to low dose spray from the partial arcs, but all hybrid plans did meet the acceptable constraints, at a minimum, from the protocol. Treatment planning time was also reduced, as plans were inversely optimized (VMAT) rather than forward optimized.Conclusion:Hybrid‐VMAT could be a solution in delivering WB+SIB, as plans yield very conformal treatment plans and maintain clinical standards in OAR sparing. For treating breast cancer patients with a simultaneously‐integrated boost, Hybrid‐VMAT offers superiority in dosimetric conformity and planning time as compared to FIF techniques.

Dosimetric comparison of left-sided whole-breast irradiation with 3DCRT, forward-planned IMRT, inverse-planned IMRT, helical tomotherapy, and volumetric arc therapy

PurposeThis study evaluated the dose distribution and homogeneity of four different types of intensity-modulated radiotherapy (IMRT) in comparison with standard wedged tangential-beam three-dimensional conformal radiotherapy (3DCRT) of the left breast in patients who had undergone lumpectomy. Materials and methodsFive radiotherapy treatment plans, including 3DCRT, forward-planned IMRT (for-IMRT), inverse IMRT (inv-IMRT), helical tomotherapy (HT) and volumetric-modulated arc therapy (VMAT), were created for 15 consecutive patients. ResultsAll modalities presented similar target coverage. Target max doses were reduced with for-IMRT compared to 3DCRT, and these doses were further reduced with inv-IMRT and HT. HT resulted in the lowest max doses delivered to the heart, left anterior descending artery (LAD), and ipsilateral lung, but had higher mean, max, and low doses delivered to contralateral breast. HT resulted in increased low doses to a large volume of healthy tissue. Compared to other techniques, all inverse-planned modalities significantly improved conformity number; however, VMAT had worse homogeneity. The for-IMRT plan significantly lowered monitor unit (MU) compared to the inverse-planned techniques. ConclusionAll modalities evaluated provide adequate coverage of the whole breast. For-IMRT improves target homogeneity compared with 3DCRT, but to a lesser degree than the inverse-planned inv-IMRT and HT. HT decreases the ipsilateral OAR volumes receiving higher and mean doses with an increase in the volumes receiving low doses, which is known to lead to an increased rate of radiation-induced secondary malignancies.

Monitoring ABC-assisted deep inspiration breath hold for left-sided breast radiotherapy with an optical tracking system.

Recent knowledge on the effects of cardiac toxicity warrants greater precision for left-sided breast radiotherapy. Different breath-hold (BH) maneuvers (abdominal vs thoracic breathing) can lead to chest wall positional variations, even though the patient's tidal volume remains consistent. This study aims to investigate the feasibility of using optical tracking for real-time quality control of active breathing coordinator (ABC)-assisted deep inspiration BH (DIBH). An in-house optical tracking system (OTS) was used to monitor ABC-assisted DIBH. The stability and localization accuracy of the OTS were assessed with a ball-bearing phantom. Seven patients with left-sided breast cancer were included. A free-breathing (FB) computed tomography (CT) scan and an ABC-assisted BH CT scan were acquired for each patient. The OTS tracked an infrared (IR) marker affixed over the patient's xiphoid process to measure the positional variation of each individual BH. Using the BH within which the CT scan was performed as the reference, the authors quantified intra- and interfraction BH variations for each patient. To estimate the dosimetric impact of BH variations, the authors studied the positional correlation between the marker and the left breast using the FB CT and BH CT scans. The positional variations of 860 BHs as measured by the OTS were retrospectively incorporated into the original treatment plans to evaluate their dosimetric impact on breast and cardiac organs [heart and left anterior descending (LAD) artery]. The stability and localization accuracy of the OTS was within 0.2 mm along each direction. The mean intrafraction variation among treatment BHs was less than 2.8 mm in all directions. Up to 12.6 mm anteroposterior undershoot, where the patient's chest wall displacement of a BH is less than that of a reference BH, was observed with averages of 4.4, 3.6, and 0.1 mm in the anteroposterior, craniocaudal, and mediolateral directions, respectively. A high positional correlation between the marker and the breast was found in the anteroposterior and craniocaudal directions with respective Pearson correlation values of 0.95 and 0.93, but no mediolateral correlation was found. Dosimetric impact of BH variations on breast coverage was negligible. However, the mean heart dose, mean LAD dose, and max LAD dose were estimated to increase from 1.4/7.4/18.6 Gy (planned) to 2.1/15.7/31.0 Gy (delivered), respectively. In ABC-assisted DIBH, large positional variation can occur in some patients, due to their different BH maneuvers. The authors' study has shown that OTS can be a valuable tool for real-time quality control of ABC-assisted DIBH.

The Influence of Patient Positioning in Breast CT on Breast Tissue Coverage and Patient Comfort.

The presented study aimed at optimizing a patient table design for breast CT (BCT) systems with respect to breast tissue coverage and patient comfort. Additionally, the benefits and acceptance of an immobilization device for BCT using underpressure were evaluated. Three different study parts were carried out. In a positioning study women were investigated on an MRI tabletop with exchangeable inserts (flat and cone-shaped with different opening diameters) to evaluate their influence on breast coverage and patient comfort in various positioning alternatives. Breast length and volume were calculated to compare positioning modalities including various opening diameters and forms. In the second study part, an underpressure system was tested for its functionality and comfort on a stereotactic biopsy table mimicking a future CT scanner table. In the last study part, this system was tested regarding breast tissue coverage. Best results for breast tissue coverage were shown for cone-shaped table inserts with an opening of 180 mm. Flat inserts did not provide complete coverage of breast tissue. The underpressure system showed robust function and tended to pull more breast tissue into the field of view. Patient comfort was rated good for all table inserts, with highest ratings for cone-shaped inserts. Cone-shaped tabletops appeared to be adequate for BCT systems and to allow imaging of almost the complete breast. An underpressure system proved promising for the fixation of the breast during imaging and increased coverage. Patient comfort appears to be adequate. Tissue coverage in breast CT is highly dependent on patient table design. An underpressure fixation system shows potential to increase breast coverage. The proposed breast CT patient table design combines good coverage and patient comfort.

SU‐D‐18A‐06: Variation of Controlled Breath Hold From CT Simulation to Treatment and Its Dosimetric Impact for Left‐Sided Breast Radiotherapy with a Real‐Time Optical Tracking System

Purpose:Different breath‐hold (BH) maneuvers (abdominal breathing vs. chest breathing) during CT simulation and treatment can lead to chest wall positional variation. The purpose of this study is to quantify the variation of active breathing control (ABC)‐assisted BH and estimate its dosimetric impact for left‐sided whole‐breast radiotherapy with a real‐time optical tracking system (OTS).Methods:Seven breast cancer patients were included. An in‐house OTS tracked an infrared (IR) marker affixed over the xiphoid process of the patient at CT simulation and throughout the treatment course to measure BH variations. Correlation between the IR marker and the breast was studied for dosimetric purposes. The positional variations of 860 BHs were retrospectively incorporated into treatment plans to assess their dosimetric impact on breast and cardiac organs (heart and left anterior descending artery [LAD]).Results:The mean intrafraction variations were 2.8 mm, 2.7 mm, and 1.6 mm in the anteroposterior (AP), craniocaudal (CC), and mediolateral (ML) directions, respectively. Mean stability in any direction was within 1.5 mm. A general trend of BH undershoot at treatment relative to CT simulation was observed with an average of 4.4 mm, 3.6 mm, and 0.1 mm in the AP, CC, and ML directions, respectively. Undershoot up to 12.6 mm was observed for individual patients. The difference between the planned and delivered dose to breast targets was negligible. The average planned/delivered mean heart doses, mean LAD doses, and max LAD doses were 1.4/2.1, 7.4/15.7, and 18.6/31.0 Gy, respectively.Conclusion:Systematic undershoot was observed in ABC‐assisted BHs from CT simulation to treatment. Its dosimetric impact on breast coverage was minimized with image guidance, but the benefits of cardiac organ sparing were degraded. A real‐time tracking system can be used in junction with the ABC device to improve BH reproducibility.

Combined Photoacoustic and Acoustic Imaging of Human Breast Specimens in the Mammographic Geometry

A photoacoustic volume imaging (PAVI) system was designed to study breast cancer detection and diagnosis in the mammographic geometry in combination with automated 3-D ultrasound (AUS). The goal of the work described here was to validate the design and evaluate its performance in human breast tissues for non-invasive imaging of deeply positioned structures covering such geometry. The good penetration of near-infrared light and high receiving sensitivity of a broad-bandwidth, 572-element, 2-D polyvinylidene fluoride (PVDF) array at a low center frequency of 1MHz were used with 20 channel simultaneous acquisition. Pseudo-lesions filled with dilute blood were imaged in three human breast specimens at various depths up to 49mm. With near-infrared light illumination and 256-sample averaging, the extrapolated maximum depth in imaging a 2.4-mm blood-rich lesion with a 3-dB contrast-to-noise ratio in a compressed breast was 54mm. Three-dimensional photoacoustic volume image stacks of the breasts were co-registered with 3-D ultrasound image stacks, suggesting for the first time that PAVI, based on the intrinsic tissue contrast, can visualize tissue interfaces other than those with blood, including the inner skin surface and connective tissue sheets. With the designed system, PAVI revealed satisfactory imaging depth and sensitivity for coverage of the entire breast when imaged from both sides in the mammographic geometry with mild compression.

“Field in field” for the treatment of breast cancer with lymph nodes: A comparative study with conventional radiotherapy using wedge filters

Introduction Treatment of breast cancer with lymph nodes (internal mammary and clavicular nodes) is achieved in most of the centers using a conventional radiotherapy based on electron-photon beams with junctions and wedge filters. Wedge filters correct for surface obliquities but do not provide optimal dose homogeneity within the breast volume. This study aims at comparing treatment plans using the ‘‘field in field” technique, equivalent to a ‘‘simplified” intensity modulation with treatment plans using wedge filters. Material and methods This study focused on eight patients (for half of the patients, the internal mammary nodes were included in the breast fields) treated for breast cancer with lymph nodes using wedge filters. For these patients a ‘‘field in field” plan was prepared retrospectively. Patients were positioned supine with ipsilateral arm above the head and head turned to the opposite treatment side. The prescribed dose was 50 Gy to the PTV breast and 46–50 Gy for the lymph nodes. For both technics, after treatment plan optimization, doses delivered to targets, heart and ipsilateral lung are reported. Results For the 8 patients and for the same coverage of breast and lymph nodes PTV, the volume of 105% (52.5 Gy) of the dose remaining in the breast volume was 2.65–24.29 cc (mean 13.9 cc) with the ‘‘field in field” technic and 9.49–231.63 cc (mean 98.5 cc) with wedge filters technic. For ipsilateral lung, the mean dose, V20 and V30 were respectively 15.1–16.6 Gy (average 15.8 Gy), 25.4–27.1 Gy (average 26.1 Gy), and 17.3–19 Gy (mean 17.9 Gy) for both technics. Conclusion For 8 patients, ‘‘field in field” treatment plans showed that remaining volume of 105% of the dose was up to 10 times smaller than using wedge filters treatment plans. This technics allowed reducing significantly overdosage areas and therefore having a better dose homogeneity in the breast.

TH-A-116-10: A Dosimetric Comparison Between Volumetric Modulated Arc and 3D Treatment Plans for Synchronous Bilateral Breast Patients Treated with Simultaneous Integrated Boost

Purpose: To evaluate dosimetric differences between standard tangential and volumetric modulated arc (VMAT) plans for synchronous bilateral breast patients treated with simultaneous integrated boost (SIB). Methods: For 10 bilateral breast patients we created separate left and right tangential plans and a single VMAT plan encompassing both breasts and tumor beds as target volumes. Patients were prescribed to 50 and 60 Gy in 2 and 2.4 Gy daily fractions to breasts and tumor beds respectively. For 3D plans each breast was planned independently. A sum of the independent plans was generated to ensure no dose overlaps, and for comparison with the VMAT plan. VMAT plans were normalized to 95% dose covering 95% breast volume. Optimization objectives for lungs, heart, and spine were based on QUANTEC data. Conformity index (CI) was calculated for all plans. Data were analyzed using the Mann‐Whitney Rank‐Sum test. Results: Tumor bed and breast coverage was similar for 3D and VMAT plans. However, CI for VMAT was significantly better (p<0.001) for both breast and tumor bed. All organ at risk (OAR) metrics (Mean Lung Dose, V20, V5, maximal heart and spine doses) were significantly better (p<0.001) in the 3D plans. Conclusion: Conformity in VMAT plans was superior to 3D plans, indicating that in 3D plans larger volumes of non‐target tissue received high doses. In addition, VMAT treatment setup is much simpler than for 3D plans, where treatment is delivered sequentially to each breast, necessitating separate setups for each side. Thus, VMAT treatment is faster, and much easier for patients. However, 3D plans are overwhelmingly superior to VMAT in terms of doses to OARs. Thus, possibly because the breast is a peripheral organ, it appears to be a unique site, where OARs are better spared by a ‘simple’ tangential plan rather than a more sophisticated VMAT technique.

Dedicated breast CT: geometric design considerations to maximize posterior breast coverage

An Institutional Review Board-approved protocol was used to quantify breast tissue inclusion in 52 women, under conditions simulating both craniocaudal (CC) and mediolateral oblique (MLO) views in mammography, dedicated breast CT in the upright subject position, and dedicated breast CT in the prone subject position. Using skin as a surrogate for the underlying breast tissue, the posterior aspect of the breast that is aligned with the chest-wall edge of the breast support in a screen-film mammography system was marked with the study participants positioned for CC and MLO views. The union of skin marks with the study participants positioned for CC and MLO views was considered to represent chest-wall tissue available for imaging with mammography and served as the reference standard. For breast CT, a prone stereotactic breast biopsy unit and a custom-fabricated barrier were used to simulate conditions during prone and upright breast CT, respectively. For the same breast marked on the mammography system, skin marks were made along the breast periphery that was just anterior to the apertures of the prone biopsy unit and the upright barrier. The differences in skin marks between subject positioning simulating breast CT (prone, upright) and mammography were quantified at six anatomic locations. For each location, at least one study participant had a skin mark from breast CT (prone, upright) posterior to mammography. However for all study participants, there was at least one anatomic location where the skin mark from mammography was posterior to that from breast CT (prone, upright) positioning. The maximum amount by which the skin mark from mammography was posterior to breast CT (prone and upright) over all six locations was quantified for each study participant and pair-wise comparison did not exhibit statistically significant difference between prone and upright breast CT (paired t- test, p = 0.4). Quantitatively, for 95% of the study participants the skin mark from mammography was posterior to breast CT (prone or upright) by at the most 9 mm over all six locations. Based on the study observations, geometric design considerations targeting chest-wall coverage with breast CT equivalent to mammography, wherein part of the x-ray beam images through the swale during breast CT are provided. Assuming subjects can extend their chest in to a swale, the optimal swale-depth required to achieve equivalent coverage with breast CT images as mammograms for 95% of the subjects varies in the range of ∼30–50 mm for clinical prototypes and was dependent on the system geometry.

Left Breast Cancer Treated in Isocentric Lateral Decubitus (ILD) Position: An Alternative Technique Sparing Organs at Risk (OAR)

Purpose : This study was designed to evaluate the doses delivered to two main organs at risk (OAR): the heart and left lung. Materials and Methods : Field design is as follows: the upper border is situated above the upper limit of the breast; the medial border is in the midline, adapted to the individual patient’s anatomy. The lateral (posterior) border is placed 1-2 cm beyond any palpable breast tissue. The inferior border is 1-2 cm below the inframammary fold. This field design allows the treatment of the whole breast, defined clinically by palpation plus a 1-2 cm margin. The isocenter is placed at mid-thickness of the flattened breast. For the medial field, the gantry is usually inclined up to 10°. A simulator computed tomography (CT) scan (Toshiba LB Aquilion) is used to perform localization films of both fields and several CT slices. The CT images are transferred to the Eclipse three-dimensional (3D) treatment planning system allowing graphic verification of the beam position. Using virtual simulation, two medial and lateral isocentric tangential beams with matching posterior borders are set up. In all patients, the breast volume, heart and lung were delineated and dose-volume histograms (DVH) were evaluated. Day-to-day reproducibility was easily verified by using the distance from the top of the treated breast to the corner of the epoxy disposer. Weekly portal imaging controls of both fields were performed in all patients. Individual dosimetric planning was performed with Eclipse V10 software (Varian) and a photon_AAA_100282 algorithm (calculated grid size: 0.25 cm). Results : From March 2012 to February 2013, fifty consecutive patients with early left breast cancer were studied: 33 received a total dose of 66 Gy dose /33 fractions (50 Gy to the breast and 16 Gy boost to the tumor bed), 17 pts received a dose of 41.6 Gy/13 fractions/ 5 weeks. In the 33 pts who received a total dose of 66 Gy, the heart received a mean dose of 1.71 Gy [1.28;2.69] . In the 17 pts who received a total dose of 41.6 Gy, the heart received a mean dose of 0.77 Gy [0.33;1.60]. In the 33 pts who received a total dose of 66 Gy, the lung received a mean dose of 0.97 Gy [0.57;1.61]. In the 17 pts who received a total dose of 41.6 Gy, the lung received a mean dose of 0.71 Gy [0.23;1.90]. Conclusions : Irradiation of the heart and lungs is extremely low in the lateral position using the 3D isocentric technique, despite the good coverage of the breast. This technique appears to be associated with a limited risk of heart and lung complications.

Contouring of Breast and Axillary Nodal Volumes per RTOG Guidelines Improves Dose Coverage at a Single Institution

Routine contouring of the RTOG recommended target volumes for breast cancer planning was initiated in our clinic in 2011. The purpose of this study was to assess if the dose to surrounding normal tissues was affected when trying to adequately cover the RTOG recommended target volumes. Ten patients who had undergone treatment planning prior to routine contouring of the RTOG target volumes were identified (Group I). For these patients, standard breast fields were constructed based on marks placed at the time of simulation and modified by the attending physician based on the CT anatomy. The RTOG volumes for the breast/chest wall, supraclavicular nodes (SCV), and axilla were then contoured without knowledge of the dose distributions. Subsequently, dose-volume histograms (DVHs) were constructed for these structures. The DVHs of these 10 patients were compared to the DVHs of 10 patients who were planned with the RTOG target volumes contoured prior to treatment planning (Group II). All patients had Stage IIA-IIIC disease and were treated to the breast/chest wall, axilla, SCV, and internal mammary nodes (IMN) to a median dose of 50.4 Gy. The coverage goals were ≥95% of the prescribed dose to ≥ 95% of the target volume for the breast/chest wall, SCV, and axilla and ≥80% of the prescribed dose to ≥ 95% of IMN. Baseline patient characteristics were compared with a chi-squared test and the difference between coverage goals was compared using a student's t-test. Five patients were treated to the chest wall after lumpectomy in group I vs. 7 patients in group II p = 0.64. Three patients were treated to the right side in each group (2 after mastectomy and 1 after lumpectomy). There was no difference in the maximum separation between the two groups, p = 0.23. The mean dose for the target volumes and normal tissues that were improved with delineation of the target volumes are listed in Table. There was a trend towards improvement in SCV coverage and breast coverage. There was no difference between coverage of the chest wall (p = 0.42), IMN (p = 0.34), axillary level 1 (0.08), axillary level 2 (p = 0.11), axillary level 3 (p = 0.13), ipsilateral lung V20 (p = 0.47), and ipsilateral lung V30 (p = 0.07). Our analysis reveals that contouring the RTOG target volumes prior to treatment planning can help construct plans that will improve coverage to these regions without increasing dose to the surrounding normal tissues.Poster Viewing Abstract 3567; TableMean coverage of target volumes and surrounding organs at riskStructureGroup 1 (mean)Group II (mean)p-valueBreast V9596.9%98.7%0.05SCV74.9%88.5%0.05Heart V2015.5%8%0.03Contralateral breast V54.3%1.5%0.04 Open table in a new tab

Effect of slice thickness on detectability in breast CT using a prewhitened matched filter and simulated mass lesions

Dedicated breast CT (bCT) is an emerging technology with the potential to improve the detection of breast cancer in screening and diagnostic capacities. Typically, the 3D volume reconstructed from the scanner is displayed as sectional images. The purpose of this study was to evaluate the effect of section thickness on the detectability of simulated masses using a prewhitened matched filter (PWMF) as a model observer. A breast CT scanner has been designed and fabricated in the authors' laboratory with more than 200 women imaged in IRB-approved phase I and phase II trials to date. Of these, 151 bilateral data sets were selected on the basis of low artifact content, sufficient breast coverage, and excluding cases with breast implants. BIRADS breast density ratings were available for 144 of these patients. Spherical mass lesions of diameter 1, 2, 3, 5, 11, and 15 mm were mathematically generated and embedded at random locations within the parenchymal region of each bCT volume. Microcalcifications were not simulated in this study. For each viewing plane (sagittal, axial, and coronal) and section thickness (ranging from 0.3 to 44 mm), section images of the breast parenchyma containing the lesion were generated from the reconstructed bCT data sets by averaging voxels over the length of the section. Using signal known exactly (SKE) model observer methodology, receiver operating characteristic (ROC) curve analysis was performed on each generated projected image using a PWMF based model observer. ROC curves were generated for each breast data set, and the area under the ROC curve (AUC) was evaluated as well as the sensitivity at 95% specificity. For all lesion sizes, performance rises modestly to a peak before falling off substantially as section thickness increases over the range of the study. We find that the optimal section thickness tracks the size of the lesion to be detected linearly with a small positive offset and slopes ranging from 0.27 to 0.44. No significant differences were observed between left and right breasts. Performance measures are negatively correlated with measures of breast density, with an average correlation coefficient of -0.48 for the BIRADS breast density score and -0.81 for the proportion of glandular tissue in the breast interior. This study shows quantitatively how PWMF detection performance of a known lesion size is influenced by section thickness in dedicated breast CT. While the optimal section thickness is tuned to the size of the lesion being detected, overall performance is more robust for thin section images compared to thicker images.

Dosimetric evaluation of breast radiotherapy in a dynamic phantom

This phantom study quantifies changes in delivered dose due to respiratory motion for four breast radiotherapy planning techniques: three intensity-modulated techniques (forward-planned, surface-compensated and hybrid intensity-modulated radiation therapy (IMRT)); using a combination of open fields and inverse planned IMRT) and a 2D conventional technique. The plans were created on CT images of a wax breast phantom with a cork lung insert, and dose distributions were measured using films inserted through slits in the axial and sagittal planes. Films were irradiated according to each plan under a static (modeling breathhold) and three dynamic conditions—isocenter set at mid-respiratory cycle with motion amplitudes of 1 and 2 cm and at end-cycle with 2 cm motion amplitude (modeling end-exhale). Differences between static and moving deliveries were most pronounced for the more complex planning techniques with hot spots of up to 107% appearing in the anterior portion of all three IMRT plans at the largest motion at the end-exhale set-up. The delivered dose to the moving phantom was within 5% of that to the static phantom for all cases, while measurement accuracy was ±3%. The homogeneity index was significantly decreased only for the 2 cm motion end-exhale set-up; however, this same motion increased the equivalent uniform dose because of improved posterior breast coverage. Overall, the study demonstrates that the effect of respiratory motion is negligible for all planning techniques except in occasional instances of large motion.

SU‐E‐T‐822: Dosimetric Comparison of Intensity Modulated Radiotherapy Modes for Breast Cancer after Radical Mastectomy: Forward IMRT vs. IMRT

Purpose: To evaluate the dose distribution of target volume and normal tissues in forward intensity modulated radiotherapy (f‐IMRT) and inverse intensity modulated radiotherapy (IMRT) plans for breast cancer after radical mastectomy. Methods: Ten patients with breast cancer who received radical mastectomy were enrolled in this study. On each patientˈs CT images the supraclavicular, chest wall and internal mammary areas were delineated. F‐IMRT and IMRT plans were performed for each patient. The prescription dose was 50 Gy in 25 fractions. F‐IMRT plans for the supraclavicular and the chest wall area using 6 MV X‐ray irradiation; internal mammary area with 9‐12 MeV electron irradiation, according to the three regions of dose adjust the doses of cold and hot fit. The supraclavicular, chest wall and internal mammary area were considered as a whole target in the IMRT plans, using 6 MV X‐ray. The dose‐volume parameters of target volume and normal tissues, CI and HI of f‐IMRT and IMRT plans were analyzed, using paired t‐test. Results: The target volume coverage of f‐IMRT plans were similar to that of the IMRT plans (93% and 94.5%). The mean CI and mean HI were 0.67±0.02/1.18±0.02 in f‐IMRT and 0.75±0.03/1.14±0.01 in IMRT (P&lt;0.05). The differences of V10, V20, V25, V30 and Dmean of ipsilateral lung were not statistically significant. However, the V15 of ipsilateral lung in IMRT was 4.5% less than that in f‐IMRT, which was statistically significant (P&lt;0.05). There was no significant difference in Dmean and V30 of heart, Dmean of contralateral lung and contralateral breast between two modes. Conclusions: Compared with f‐IMRT, IMRT plans resulted in better conformal dose distribution and homogeneity, with comparable target volume coverage and sparing of lung, heart and contralateral breast.

Dosimetric comparison of left-sided whole breast irradiation with 3DCRT, forward-planned IMRT, inverse-planned IMRT, helical tomotherapy, and topotherapy

Background and purposeTo compare left-sided whole breast conventional and intensity-modulated radiotherapy (IMRT) treatment planning techniques. Materials and methodsTreatment plans were created for 10 consecutive patients. Three-dimensional conformal radiotherapy (3DCRT), forward-planned IMRT (for-IMRT), and inverse-planned IMRT (inv-IMRT) used two tangent beams. For-IMRT utilized up to four segments per beam. For helical tomotherapy (HT) plans, beamlet entrance and/or exit to critical structures was blocked. Topotherapy plans, which used static gantry angles with simultaneous couch translation and inverse-planned intensity modulation, used two tangent beams. Plans were normalized to 50Gy to 95% of the retracted PTV. ResultsTarget max doses were reduced with for-IMRT compared to 3DCRT, which were further reduced with HT, topotherapy, and inv-IMRT. HT resulted in lowest heart and ipsilateral lung max doses, but had higher mean doses. Inv-IMRT and topotherapy reduced ipsilateral lung mean and max doses compared to 3DCRT and for-IMRT. ConclusionsAll modalities evaluated provide adequate coverage of the intact breast. HT, topotherapy, and inv-IMRT can reduce high doses to the target and normal tissues, although HT results in increased low doses to large volume of normal tissue. For-IMRT improves target homogeneity compared with 3DCRT, but to a lesser degree than the inverse-planned modalities.

Cone-Beam CT for Breast Imaging: Radiation Dose, Breast Coverage, and Image Quality

The primary objectives of this pilot study were to evaluate the radiation dose, breast coverage, and image quality of cone-beam breast CT compared with a conventional mammographic examination. Image quality analysis was focused on the concordance of cone-beam breast CT with conventional mammography in terms of mammographic findings. This prospective study was performed from July 2006 through August 2008. Twenty-three women were enrolled who met the inclusion criteria, which were age 40 years or older with final BI-RADS assessment category 1 or 2 lesions on conventional mammograms within the previous 6 months. The breasts were imaged with a flat-panel detector-based cone-beam CT system, and the images were reviewed with a 3D visualization system. Cone-beam breast CT image data sets and the corresponding mammograms were reviewed by three qualified mammographers. The parameters assessed and compared in this pilot study were radiation dose, breast tissue coverage, and image quality, including detectability of masses and calcifications. The mammograms and cone-beam breast CT images were independently reviewed side by side, and the reviewers were not blinded to the other technique. The observed agreement and Cohen's kappa were used to evaluate agreement between the mammographic and cone-beam breast CT findings and interobserver agreement. Each subject responded to a questionnaire on multiple parameters, including comfort of the cone-beam breast CT examination compared with mammography. For a conventional mammographic examination, the average glandular radiation dose ranged from 2.2 to 15 mGy (mean, 6.5 [SD, 2.9] mGy). For cone-beam breast CT, the average glandular dose ranged from 4 to 12.8 mGy (mean, 8.2 [SD, 1.4] mGy). The average glandular dose from cone-beam breast CT was generally within the range of that from conventional mammography. For heterogeneously dense and extremely dense breasts, the difference between the mean dose of conventional mammography and that of cone-beam breast CT was not statistically significant (7.0 vs 8.1 mGy, p = 0.06). Breast tissue coverage was statistically significantly better with cone-beam breast CT than with mammography in the lateral (p < 0.0001), medial (p < 0.0001), and posterior (p = 0.0002) aspects. Mammography had statistically significantly better coverage than cone-beam breast CT in the axilla and axillary tail (p < 0.0001). Overall, most calcifications and all masses detected with mammography were also detected with cone-beam breast CT. The interobserver agreement on cone-beam breast CT was 83.7% in the detectability of imaging findings. The overall interobserver agreement on type of findings, size of findings (<1, 1-4.99, and > or = 5 mm), and location of findings was 77.2%, 84.8%, and 78.3%, respectively. The results of this study show that cone-beam breast CT can be used to image the entire breast from chest wall to nipple with sufficient spatial and contrast resolution for detection of masses and calcifications at a radiation dose within the range of that of conventional mammography.

Pharmacokinetic mapping for lesion classification in dynamic breast MRI

To prospectively investigate whether a rapid dynamic MRI protocol, in conjunction with pharmacokinetic modeling, could provide diagnostically useful information for discriminating biopsy-proven benign lesions from malignancies. Patients referred to breast biopsy based on suspicious screening findings were eligible. After anatomic imaging, patients were scanned using a dynamic protocol with complete bilateral breast coverage. Maps of pharmacokinetic parameters representing transfer constant (K(trans)), efflux rate constant (k(ep)), blood plasma volume fraction (v(p)), and extracellular extravascular volume fraction (v(e)) were averaged over lesions and used, with biopsy results, to generate receiver operating characteristic curves for linear classifiers using one, two, or three parameters. Biopsy and imaging results were obtained from 93 lesions in 74 of 78 study patients. Classification based on K(trans) and k(ep) gave the greatest accuracy, with an area under the receiver operating characteristic curve of 0.915, sensitivity of 91%, and specificity of 85%, compared with values of 88% and 68%, respectively, obtained in a recent study of clinical breast MRI in a similar patient population. Pharmacokinetic classification of breast lesions is practical on modern MRI hardware and provides significant accuracy for identification of malignancies. Sensitivity of a two-parameter linear classifier is comparable to that reported in a recent multicenter study of clinical breast MRI, while specificity is significantly higher.