CT-guided multi-catheter insertion technique for partial breast brachytherapy: reliable target coverage and dose homogeneity

US-guided EM tracked system for HDR brachytherapy: A first in-men randomized study for whole prostate treatment

PURPOSE

An electromagnetic tracking device (EMT) has been integrated in an HDR 3D ultrasound guidance system for prostate HDR. The aim of this study was to compare the efficiency of HDR workflows with and without EM tracking.

METHODS AND MATERIALS

A total of 58 patients with a 15 Gy HDR prostate boost were randomized in two arms and two operation room (OR) procedures using: (1) the EMT investigational device, and (2) the Oncentra prostate system (OCP). OR times were compared for both techniques.

RESULTS

The overall procedure median time was about 20% shorter for EMT (63 min) compared to OCP (79 min). The US acquisition and contouring was longer for OCP compared to EMT (23 min vs. 16 min). The catheter reconstruction's median times were 23 min and 13 min for OCP and EMT respectively. For the automatic reconstruction with EMT, 62% of cases required no or few manual corrections. Using the EM technology in an OR environment was challenging. In some cases, interferences or the stiffness of the stylet introduced errors in the reconstruction of catheters. The last step was the dosimetry with median times of 11 min (OCP) and 15.5 min (EMT). Finally, it was observed that there was no learning curve associated with the introduction of this new technology.

CONCLUSIONS

The EMT device offers an efficient solution for automatic catheter reconstruction for HDR prostate while reducing the possibility of mis-reconstructed catheters caused by issues of visualization in the US images. Because of that, the overall OR times was shorter when using the EMT system.

Commissioning of an intra-operative US guided prostate HDR system integrating an EM tracking technology

PURPOSE

Ultrasound-based planning for high-dose-rate prostate brachytherapy is commonly used in the clinic, mainly because it offers fast real-time image-guided capability at a relatively low cost. The main difficulty with US planning is the catheter reconstruction due to artefacts (from multiple catheters) and echogenicity. Electromagnetic tracking (EMT) system offers a fast and accurate solution for automatic reconstruction of catheters using the EMT technology. In this study, the commissioning and performance evaluation of the new real-time prostate high-dose-rate brachytherapy investigational system from Philips Disease Management Solutions integrating EMT was performed before its clinical integration.

METHOD AND MATERIALS

The Philips' clinical investigational system includes a treatment planning software (TPS) that was commissioned based on AAPM TG53 and TG56 recommendations for the use of TPS in brachytherapy. First, the CIRS - model 045A - QA phantom was used to evaluate the ultrasound (US) image quality and 3D image handling. Distances, volumes, and dimensions of the structures inside the phantom were measured and compared to the actual values. The calibration reproducibility and accuracy of the electromagnetic (EM) sensor used to track the US probe (rotation and translation) were performed using a specifically designed QA tool mounted on the probe and immersed in a salted water tank. This was performed for 3 different B&K 8848 US probes to evaluate the sensitivity of EM calibration to the probe geometric properties (manufacturing process). The new TPS performance was compared to that in OncentraBrachy (OcB) V4.5.5 (Elekta) using 30 clinical cases as part of a retrospective study. Following the system commissioning, clinical workflows were explored; tests were performed with the brachytherapy team on phantoms and finally implemented in the clinic.

RESULTS

US image quality evaluation showed a mean difference with actual dimensions (lengths, widths and distances) of 0.4 mm (±0.3 mm) and mean difference in volume sizes of 0.2 cc (±0.2 cc). Then, the calibration of the US-to-EM coordinate system was performed for 3 different probes. For each probe, 3 measurements were acquired for every position of the calibration tool and measurements were repeated 3 times for a total of 27 measurements per probe per plane. The error was slightly higher in transverse mode compared to sagittal mode with mean values of 0.6 ± 0.2 mm and 0.3 ± 0.1 mm respectively. 30 clinical cases were used to compare the new TPS performance to OcB (IPSA). Optimized plans obtained with both systems were all clinically acceptable, but the plans from the Philips system have slightly higher V150% values, V200% values and dose to organs at risk. In the case of organs at risk, plans could have been manually modified to reduce the dose. Philips' system had a larger number of active dwell positions and longer treatment times.

CONCLUSIONS

The first clinical version of Philips' system was proven to be stable, accurate and precise. The fully integrated EM tracking technology opens the way for automated catheter reconstruction and on-the-fly dynamical replanning.

American Brachytherapy Society consensus report for accelerated partial breast irradiation using interstitial multicatheter brachytherapy

PURPOSE

To develop a consensus report for the quality practice of accelerated partial breast irradiation (APBI) using interstitial multicatheter brachytherapy (IMB).

METHODS AND MATERIALS

The American Brachytherapy Society Board appointed an expert panel with clinical and research experience with breast brachytherapy to provide guidance for the current practice of IMB. This report is based on a comprehensive literature review with emphasis on randomized data and expertise of the panel.

RESULTS

Randomized trials have demonstrated equivalent efficacy of APBI using IMB compared with whole breast irradiation for select patients with early-stage breast cancer. Several techniques for placement of interstitial catheters are described, and importance of three-dimensional planning with appropriate optimization is reviewed. Optimal target definition is outlined. Commonly used dosing schemas include 50 Gy delivered in pulses of 0.6-0.8 Gy/h using pulsed-dose-rate technique and 34 Gy in 10 fractions, 32 Gy in eight fractions, or 30 Gy in seven fractions using high-dose-rate technique. Potential toxicities and strategies for toxicity avoidance are described in detail. Dosimetric constraints include limiting whole breast volume that receives ≥50% of prescription dose to <60%, skin dose to ≤100% of prescription dose (≤60-70% preferred), chest wall dose to ≤125% of prescription dose, Dose Homogeneity Index to >0.75 (>0.85 preferred), V₁₅₀ < 45 cc, and V₂₀₀ < 14 cc. Using an optimal implant technique coupled with optimal planning and appropriate dose constraints, a low rate of toxicity and a good-to-excellent cosmetic outcome of ≥90% is expected.

CONCLUSIONS

IMB is an effective technique to deliver APBI for appropriately selected women with early-stage breast cancer. This consensus report has been created to assist clinicians in the appropriate practice of APBI using IMB.

Interobserver variations of target volume delineation and its impact on irradiated volume in accelerated partial breast irradiation with intraoperative interstitial breast implant

Purpose

To investigate the interobserver variations in delineation of lumpectomy cavity (LC) and clinical target volume (CTV), and its impact on irradiated volume in accelerated partial breast irradiation using intraoperative multicatheter brachytherapy.

Material and methods

Delineation of LC and CTV was done by five radiation oncologists on planning computed tomography (CT) scans of 20 patients with intraoperative interstitial breast implant. Cavity visualization index (CVI), four-point index ranging from (0 = poor) to (3 = excellent) was created and assigned by observers for each patient. In total, 200 contours for all observers and 100 treatment plans were evaluated. Spatial concordance (conformity index, CI_common, and CI_gen), average shift in the center of mass (COM), and ratio of maximum and minimum volumes (V_max/V_min) of LC and CTV were quantified among all observers and statistically analyzed. Variation in active dwell positions (0.5 cm step) for each catheter, total reference air kerma (TRAK), volume enclosed by prescription isodose (V_100%) among observers and its spatial concordance were analyzed.

Results

The mean ± SD CI_common of LC and CTV was 0.54 ± 0.09, and 0.58 ± 0.08, respectively. Conformity index tends to increase, shift in COM and V_max/V_min decrease significantly (p < 0.05), as CVI increased. Out of total 309 catheters, 29.8% catheters had no change, 29.8% and 17.5% catheters had variations of 1 and 2 dwell positions (0.5 cm and 1 cm), respectively. 9.3% catheters shown variations ≥ 10 dwell positions (5 cm). The mean ± SD CI_common of V_100% was 0.75 ± 0.11. The mean observed V_max/V_min of prescription isodose and TRAK was 1.18 (range, 1.03 to 1.56) and 1.11 (range, 1.03 to 1.35), respectively.

Conclusions

Interobserver variability in delineation of target volume was found to be significantly related to CVI. Smaller variability was observed with excellent visualization of LC. Interobserver variations showed dosimetric impact on irradiation of breast tissue volume with prescription dose.

Treatment planning for multicatheter interstitial brachytherapy of breast cancer - from Paris system to anatomy-based inverse planning

In the last decades, treatment planning for multicatheter interstitial breast brachytherapy has evolved considerably from fluoroscopy-based 2D to anatomy-based 3D planning. To plan the right positions of the catheters, ultrasound or computed tomography (CT) imaging can be used, but the treatment plan is always based on postimplant CT images. With CT imaging, the 3D target volume can be defined more precisely and delineation of the organs at risk volumes is also possible. Consequently, parameters calculated from dose-volume histogram can be used for quantitative plan evaluation. The catheter reconstruction is also easier and faster on CT images compared to X-ray films. In high dose rate brachytherapy, using a stepping source, a number of forward dose optimization methods (manual, geometrical, on dose points, graphical) are available to shape the dose distribution to the target volume, and these influence dose homogeneities to different extent. Currently, inverse optimization algorithms offer new possibilities to improve dose distributions further considering the requirements for dose coverage, dose homogeneity, and dose to organs at risk simultaneously and automatically. In this article, the evolvement of treatment planning for interstitial breast implants is reviewed, different forward optimization methods are discussed, and dose-volume parameters used for quantitative plan evaluation are described. Finally, some questions of the inverse optimization method are investigated and initial experiences of the authors are presented.

Lower mean heart dose with deep inspiration breath hold-whole breast irradiation compared with brachytherapy-based accelerated partial breast irradiation for women with left-sided tumors

PURPOSE

For left-sided breast cancer, radiation to the heart is a concern. We present a comparison of mean heart and coronary artery biologically effective dose (BED) between accelerated partial breast irradiation (APBI) and whole breast irradiation with deep inspiration breath-hold technique (DIBH-WBI).

METHODS AND MATERIALS

A total of 100 patients with left-sided, early-stage breast cancer were identified. Fifty underwent single-entry catheter-based APBI and 50 underwent DIBH-WBI. The heart, left anterior descending/interventricular branch, left main, and right coronary artery were delineated. BEDs were calculated from APBI treatment plans (34 Gy in 3.4 Gy twice daily fractions) and for 4 separate plans generated for each DIBH-WBI patient: 50 Gy in 25 fractions (50/25), 50/25 + 10/5 boost, 40/15, and 40/15 + 10/5 boost.

RESULTS

BED to the heart and coronary vessels were statistically significantly higher with APBI than with any of the DIBH-WBI dose/fractionation schedules.

CONCLUSIONS

For women with left-sided early-stage breast cancer, DIBH-WBI resulted in statistically significantly lower mean BED to the heart and coronary vessels compared with APBI. This is likely due to increased physical separation between the heart and tumor bed afforded by the DIBH-WBI technique. Long-term assessment of late effects in these tissues will be required to determine whether these differences are clinically significant.

Multi-catheter interstitial brachytherapy for partial breast irradiation: an audit of implant quality based on dosimetric evaluation comparing intra-operative versus post-operative placement

Purpose

The use of multicatheter interstitial brachytherapy (MIB) for accelerated partial breast irradiation (APBI) in early breast cancer (EBC) patients outside the trial setting has increased. Hence, there is a need to critically evaluate implant quality. Moreover, there is a scarcity of reports using an open cavity technique. We report the dosimetric indices of open and closed cavity MIB techniques.

Material and methods

The dosimetric parameters of 60 EBC patients treated with MIB (open and closed cavity) who underwent three dimensional, computerized tomography (CT) based planning for APBI from November 2011 to July 2015 were evaluated. Coverage Index (CI), Dose Homogeneity Index (DHI), Conformity Index (COIN), Plan Quality Index (PQI), and Dose Non-uniformity Index (DNR) were assessed.

Results

Forty-one patients underwent open cavity and 19 patients underwent closed cavity placement of brachytherapy catheters. The median number of planes was 4 and median number of needles was 20. Median dose was 34 Gy with dose per fraction of 3.4 Gy, given twice a day, 6 hours apart. The D₉₀ of the cavity and clinical target volume (CTV) were 105% and 89%, respectively. The median doses to the surgical clips were greater than 100%. The median CI of the cavity and CTV was 0.96 and 0.82, respectively. The DHI and COIN index of the CTV was 0.73 and 0.67. There were no significant differences in the dosimetric parameters based on whether the technique was done open or closed.

Conclusions

Critical evaluation of the dosimetric parameters of MIB-APBI is important for optimal results. While the open and closed techniques have similar dosimetry, our institutional preference is for an open technique which eases the procedure due to direct visualization of the tumor cavity.

Contemporary Toxicity Profile of Breast Brachytherapy Versus External Beam Radiation After Lumpectomy for Breast Cancer

PURPOSE

We compared toxicities after brachytherapy versus external beam radiation therapy (EBRT) in contemporary breast cancer patients.

METHODS AND MATERIALS

Using MarketScan healthcare claims, we identified 64,112 women treated from 2003 to 2012 with lumpectomy followed by radiation (brachytherapy vs EBRT). Brachytherapy was further classified by multichannel versus single-channel applicator approach. We identified the risks and predictors of 1-year infectious and noninfectious postoperative adverse events using logistic regression and temporal trends using Cochran-Armitage tests. We estimated the 5-year Kaplan-Meier cumulative incidence of radiation-associated adverse events.

RESULTS

A total of 4522 (7.1%) patients received brachytherapy (50.2% multichannel vs 48.7% single-channel applicator). The overall risk of infectious adverse events was higher after brachytherapy than after EBRT (odds ratio [OR] = 1.21; 95% confidence interval [CI] 1.09-1.34, P<.001). However, over time, the frequency of infectious adverse events after brachytherapy decreased, from 17.3% in 2003 to 11.6% in 2012, and was stable after EBRT at 9.7%. Beyond 2007, there were no longer excess infections with brachytherapy (P=.97). The overall risk of noninfectious adverse events was higher after brachytherapy than after EBRT (OR=2.27; 95% CI 2.09-2.47, P<.0001). Over time, the frequency of noninfectious adverse events detected increased: after multichannel brachytherapy, from 9.1% in 2004 to 18.9% in 2012 (Ptrend = .64); single-channel brachytherapy, from 12.8% to 29.8% (Ptrend<.001); and EBRT, from 6.1% to 10.3% (Ptrend<.0001). The risk was significantly higher with single-channel than with multichannel brachytherapy (hazard ratio = 1.32; 95% CI 1.03-1.69, P=.03). Of noninfectious adverse events, 70.9% were seroma. Seroma significantly increased breast pain risk (P<.0001). Patients with underlying diabetes, cardiovascular disease, and treatment with chemotherapy had increased infectious and noninfectious adverse events. The 5-year incidences of fat necrosis, breast pain, and rib fracture were slightly higher after brachytherapy than after EBRT (13.7% vs 8.1%, 19.4% vs 16.0%, and 1.6% vs 1.3%, respectively), but the risks were not significantly different for multichannel versus single-channel applicators.

CONCLUSION

Toxicities after breast brachytherapy were distinct from those after EBRT. Temporal toxicity trends may reflect changing technology and evolving practitioner experience with brachytherapy.

Validation of a novel robot-assisted 3DUS system for real-time planning and guidance of breast interstitial HDR brachytherapy

PURPOSE

In current clinical practice, there is no integrated 3D ultrasound (3DUS) guidance system clinically available for breast brachytherapy. In this study, the authors present a novel robot-assisted 3DUS system for real-time planning and guidance of breast interstitial high dose rate (HDR) brachytherapy treatment.

METHODS

For this work, a new computer controlled robotic 3DUS system was built to perform a hybrid motion scan, which is a combination of a 6 cm linear translation with a 30° rotation at both ends. The new 3DUS scanner was designed to fit on a modified Kuske assembly, keeping the current template grid configuration but modifying the frame to allow the mounting of the 3DUS system at several positions. A finer grid was also tested. A user interface was developed to perform image reconstruction, semiautomatic segmentation of the surgical bed as well as catheter reconstruction and tracking. A 3D string phantom was used to validate the geometric accuracy of the reconstruction. The volumetric accuracy of the system was validated with phantoms using magnetic resonance imaging (MRI) and computed tomography (CT) images. In order to accurately determine whether 3DUS can effectively replace CT for treatment planning, the authors have compared the 3DUS catheter reconstruction to the one obtained from CT images. In addition, in agarose-based phantoms, an end-to-end procedure was performed by executing six independent complete procedures with both 14 and 16 catheters, and for both standard and finer Kuske grids. Finally, in phantoms, five end-to-end procedures were performed with the final CT planning for the validation of 3DUS preplanning.

RESULTS

The 3DUS acquisition time is approximately 10 s. A paired Student t-test showed that there was no statistical significant difference between known and measured values of string separations in each direction. Both MRI and CT volume measurements were not statistically different from 3DUS volume (Student t-test: p > 0.05) and they were significantly correlated to 3DUS measurement (Pearson test: MRI p < 0.05 and CT p < 0.001). The mean angular separation distance between catheter trajectories segmented from 3DUS and CT images was 0.42° ± 0.24°, while the maximum and mean trajectory separations were 0.51 ± 0.19 and 0.37 ± 0.17 mm, respectively. Overall, the new finer grid has performed significantly better in terms of dosimetric indices. The planning target volume dosimetric indices were not found statistically different between 3DUS and CT planning (Student t-test, p > 0.05). Both the skin and the pectoral muscle dosimetric indices were within ABS guidelines.

CONCLUSIONS

A novel robot-assisted 3DUS system was designed and validated. To their knowledge, this is the first system capable of performing real-time guidance and planning of breast multicatheter HDR brachytherapy treatments. Future investigation will test the feasibility of using the system in the clinic and for permanent breast brachytherapy.

Accelerated partial breast irradiation with brachytherapy: patient selection and technique considerations

Accelerated partial breast irradiation (APBI) through breast brachytherapy is a relatively recent development in breast radiotherapy that has gained international favor because of its reduction in treatment duration and normal tissue irradiation while maintaining favorable cancer-specific and cosmetic outcomes. Despite the fact that several large national trials have not reported final results yet, many providers are currently offering APBI to select patients and APBI is listed as a treatment option for selecting patients in the National Comprehensive Cancer Network guidelines. Multiple consensus guidelines exist in selecting patients for APBI, some with conflicting recommendations. In this review, the existing patient selection guidelines are reported, compared, and critiqued, grouping them in helpful subcategories. Unique patient and technical selection factors for APBI with brachytherapy are explored.

The importance of the implant quality in APBI - Gliwice experience. Dosimetric evaluation

This study includes four years of our clinical trials to improve implant quality in multicatheter accelerated partial breast irradiation (APBI). The progress in dosimetric and volumetric parameters of the treatment plans was evaluated. One hundred and ninety-one women, for whom treatment plans were made based on three dimensional imaging, were selected for the study. To evaluate progress made in our APBI procedure, following parameters and indices were taken into account: percentage of the target volume receiving the reference dose (PTV_ref), minimum dose in the target volume expressed as a percentage of reference dose (PTV_min), dose homogeneity index (DHI), and conformity index (COIN). Additionally, the plan quality index was calculated for every group as the sum of mean values of four evaluated parameters. PTV_ref have increased from the mean value of 83.4% at the beginning to recent 94.8%. The maximum value equals to 95.4%. The same trend can be observed with PTV_min value, which has been improved from 51.7% to 70.1%, maximally. DHI and COIN mean values present similar progress. DHI value increased from 0.53 level to 0.68, and COIN from 0.58 in 2009 to 0.74. Plan quality index has increased from 2.46 in 2009 to 3.06, recently. The implant quality is crucial for the accurate dose distribution. This paper shows the progress that was made in APBI procedure to improve implant quality. Nowadays, our implant technique is based on three-dimensional CT imaging results in acceptable dose distributions.

Review of clinical brachytherapy uncertainties: analysis guidelines of GEC-ESTRO and the AAPM

Background and purpose

A substantial reduction of uncertainties in clinical brachytherapy should result in improved outcome in terms of increased local control and reduced side effects. Types of uncertainties have to be identified, grouped, and quantified.

Methods

A detailed literature review was performed to identify uncertainty components and their relative importance to the combined overall uncertainty.

Results

Very few components (e.g., source strength and afterloader timer) are independent of clinical disease site and location of administered dose. While the influence of medium on dose calculation can be substantial for low energy sources or non-deeply seated implants, the influence of medium is of minor importance for high-energy sources in the pelvic region. The level of uncertainties due to target, organ, applicator, and/or source movement in relation to the geometry assumed for treatment planning is highly dependent on fractionation and the level of image guided adaptive treatment. Most studies to date report the results in a manner that allows no direct reproduction and further comparison with other studies. Often, no distinction is made between variations, uncertainties, and errors or mistakes. The literature review facilitated the drafting of recommendations for uniform uncertainty reporting in clinical BT, which are also provided. The recommended comprehensive uncertainty investigations are key to obtain a general impression of uncertainties, and may help to identify elements of the brachytherapy treatment process that need improvement in terms of diminishing their dosimetric uncertainties. It is recommended to present data on the analyzed parameters (distance shifts, volume changes, source or applicator position, etc.), and also their influence on absorbed dose for clinically-relevant dose parameters (e.g., target parameters such as D₉₀ or OAR doses). Publications on brachytherapy should include a statement of total dose uncertainty for the entire treatment course, taking into account the fractionation schedule and level of image guidance for adaptation.

Conclusions

This report on brachytherapy clinical uncertainties represents a working project developed by the Brachytherapy Physics Quality Assurances System (BRAPHYQS) subcommittee to the Physics Committee within GEC-ESTRO. Further, this report has been reviewed and approved by the American Association of Physicists in Medicine.

Accelerated partial breast irradiation with low-dose-rate interstitial implant brachytherapy after wide local excision: 12-year outcomes from a prospective trial

PURPOSE

To evaluate the long-term toxicity, cosmesis, and local control of accelerated partial breast irradiation with implant brachytherapy after wide local excision for Stage T1N0 breast cancer (BCa).

MATERIALS AND METHODS

Between 1997 and 2001, 50 patients with Stage T1N0M0 BCa were treated in a Phase I-II protocol using low-dose-rate accelerated partial breast irradiation with implant brachytherapy after wide local excision and lymph node surgery. The total dose was escalated in three groups: 50 Gy (n = 20), 55 Gy (n = 17), and 60 Gy (n = 13). Patient- and physician-assessed breast cosmesis, patient satisfaction, toxicity, mammographic abnormalities, repeat biopsies, and disease status were prospectively evaluated at each visit. Kendall's tau (τ(β)) and logistic regression analyses were used to correlate outcomes with dose, implant volume, patient age, and systemic therapy.

RESULTS

The median follow-up period was 11.2 years (range, 4-14). The patient satisfaction rate was 67%, 67% reported good-excellent cosmesis, and 54% had moderate-severe fibrosis. Higher dose was correlated with worse cosmetic outcome (τ(β) 0.6, p < .0001), lower patient satisfaction (τ(β) 0.5, p < .001), and worse fibrosis (τ(β) 0.4, p = .0024). Of the 50 patients, 35% had fat necrosis and 34% developed telangiectasias ≥1 cm(2). Grade 3-4 late skin and subcutaneous toxicities were seen in 4 patients (9%) and 6 patients (13%), respectively, and both correlated with higher dose (τ(β) 0.3-0.5, p ≤ .01). One patient had Grade 4 skin ulceration and fat necrosis requiring surgery. Mammographic abnormalities were seen in 32% of the patients, and 30% underwent repeat biopsy, of which 73% were benign. Six patients had ipsilateral breast recurrence: five elsewhere in the breast, and one at the implant site. One patient died of metastatic BCa after recurrence. The 12-year actuarial local control, recurrence-free survival, and overall survival rate was 85% (95% confidence interval, 70-97%), 72% (95% confidence interval, 54-86%), and 87% (95% confidence interval, 73-99%), respectively.

CONCLUSION

Low-dose-rate accelerated partial breast irradiation with implant brachytherapy provides acceptable local control in select early-stage BCa patients. However, treatment-related toxicity and cosmetic complications were significant with longer follow-up and at higher doses.

Dose volume uniformity index: a simple tool for treatment plan evaluation in brachytherapy

Purpose

In radiotherapy treatment planning, dose homogeneity inside the target volume plays a significant role in the final treatment outcome. Especially in brachytherapy where there is a steep dose gradient in the dose distribution inside the target volume, comparing the plans based on the dose homogeneity helps in assessing the high dose volume inside the final treatment plan. In brachytherapy, the dose inhomogeneity inside the target volume depends on many factors such as the type of sources, placement of these radioactive sources, distance between the applicators/implant tubes, dwell time of the source, etc. In this study, a simple index, the dose volume uniformity index (DVUI), has been proposed to study the dose homogeneity inside the target volume. This index gives the total dose volume inhomogeneity inside a given prescription isoline.

Material and methods

To demonstrate the proposed DVUI in this study, a single plane implant (breast: 6 catheters), a double plane implant (breast: 9 catheters) and a tongue implant (5 catheters) were selected. The catheters were reconstructed from the CT image datasets in the Plato treatment planning system. The doses for the single, double and tongue implants were prescribed to the reference dose rate as per the Paris technique. DVUI was computed from the cumulative dose volume histogram.

Results

For a volume receiving a uniform dose inside the prescription isoline, the DVUI is 1. Any value of DVUI > 1 shows the presence of a relatively high dose volume inside the prescription isoline. In addition to the concept of DVUI, a simple conformality index, the dose volume conformality index (DVCI), has also been proposed in this study based on the DVUI.

Conclusion

The DVUI and the proposed DVCI in this study provide an easy way of comparing the rival plans in brachytherapy.

Current brachytherapy quality assurance guidance: does it meet the challenges of emerging image-guided technologies?

In the past decade, brachytherapy has shifted from the traditional surgical paradigm to more modern three-dimensional image-based planning and delivery approaches. The role of intraoperative and multimodality image-based planning is growing. Published American Association of Physicists in Medicine, American College of Radiology, European Society for Therapeutic Radiology and Oncology, and International Atomic Energy Agency quality assurance (QA) guidelines largely emphasize the QA of planning and delivery devices rather than processes. These protocols have been designed to verify compliance with major performance specifications and are not risk based. With some exceptions, complete and clinically practical guidance exists for sources, QA instrumentation, non-image-based planning systems, applicators, remote afterloading systems, dosimetry, and calibration. Updated guidance is needed for intraoperative imaging systems and image-based planning systems. For non-image-based brachytherapy, the American Association of Physicists in Medicine Task Group reports 56 and 59 provide reasonable guidance on procedure-specific process flow and QA. However, improved guidance is needed even for established procedures such as ultrasound-guided prostate implants. Adaptive replanning in brachytherapy faces unsolved problems similar to that of image-guided adaptive external beam radiotherapy.

A multidisciplinary approach to the management of breast cancer, part 2: therapeutic considerations

New approaches to breast cancer treatment have enhanced clinical outcomes and patient care. These approaches include advances in breast irradiation and hormonal and systemic adjuvant therapies. In addition to the identification of new drug targets and targeted therapeutics (eg, trastuzumab), there is renewed re-emphasis in the development of biomarkers for the prediction of response to therapy. One example is the pharmacogenetics of tamoxifen metabolism and the individualization of hormonal therapy. The current treatment of breast cancer continues to evolve rapidly, with new scientific and clinical achievements constantly changing the standard of care and leading to substantial reductions in breast cancer mortality. The goal of this article is to provide clinicians who care for women with breast cancer a multidisciplinary, state-of-the art approach to the treatment of these patients.

Evaluation of radiograph-based interstitial implant dosimetry on computed tomography images using dose volume indices for head and neck cancer

Conventional radiograph-based implant dosimetry fails to correlate the spatial dose distribution on patient anatomy with lack in dosimetry quality. Though these limitations are overcome in computed tomography (CT)-based dosimetry, it requires an algorithm which can reconstruct catheters on the multi-planner CT images. In the absence of such algorithm, we proposed a technique in which the implanted geometry and dose distribution generated from orthogonal radiograph were mapped onto the CT data using coordinate transformation method.

Radiograph-based implant dosimetry was generated for five head and neck cancer patients on Plato Sunrise treatment planning system. Dosimetry was geometrically optimized on volume, and dose was prescribed according to the natural prescription dose. The final dose distribution was retrospectively mapped onto the CT data set of the same patients using coordinate transformation method, which was verified in a phantom prior to patient study. Dosimetric outcomes were evaluated qualitatively by visualizing isodose distribution on CT images and quantitatively using the dose volume indices, which includes coverage index (CI), external volume index (EI), relative dose homogeneity index (HI), overdose volume index (OI) and conformal index (COIN).

The accuracy of coordinate transformation was within ±1 mm in phantom and ±2 mm in patients. Qualitative evaluation of dosimetry on the CT images shows reasonably good coverage of target at the expense of excessive normal tissue irradiation. The mean (SD) values of CI, EI and HI were estimated to be 0.81 (0.039), 0.55 (0.174) and 0.65 (0.074) respectively. The maximum OI estimated was 0.06 (mean 0.04, SD = 0.015). Finally, the COIN computed for each patient ranged from 0.4 to 0.61 (mean 0.52, SD = 0.078).

The proposed technique is feasible and accurate to implement even for the most complicated implant geometry. It allows the physicist and physician to evaluate the plan both qualitatively and quantitatively. Dose volume indices derived from CT data set are useful for evaluating the implant and comparing different brachytherapy plans. COIN index is an important tool to assess the target coverage and sparing of normal tissues in brachytherapy.

Dosimetric comparisons between high dose rate interstitial and MammoSite™ balloon brachytherapy for breast cancer

BACKGROUND AND PURPOSE

To make a quantitative dosimetric comparison between treatment plans of multicatheter-based interstitial brachytherapy (IB) and MammoSite brachytherapy (MSB) for breast cancer.

PATIENTS AND METHODS

Seventeen patients treated with IB and twenty-four with MSB were selected for the study. The irradiations for IB patients were planned using conventional two-film reconstruction technique. Following the implantation each patient was CT scanned, then the planning target volume (PTV) was retrospectively defined on the CT data set, and the original plan was reconstructed (CONV plans). Furthermore, conformal plans were also created by dose optimization on target (CONF plans). The planning for MammoSite applicator was based on CT imaging. The dose distributions were evaluated with dose-volume histograms. The following parameters were calculated and compared: volume of the PTV and its percentage receiving 90, 100, 150 and 200% of the prescribed dose (V90, V100, V150 and V200, respectively), percentage dose covering 90% of the PTV (D90), minimum dose in the PTV (D(min)), maximum dose in the PTV (D(max)) for MSB only, dose homogeneity index (DHI), and conformal index (COIN). To assess the dose to organs at risk maximum point dose to skin, lung and heart was used.

RESULTS

The median number of implanted catheters for IB was 11 (range: 6-13), the average balloon volume for MSB was 59.1cm(3) (range: 43.4-75.3 cm(3)). The average volume of PTV was 63.4 and 109.6 cm(3) for IB and MSB patients, respectively. The average V90, V100, V150, V200 were 76, 70, 26 and 9% for IB(CONV); 92, 87, 55 and 32% for IB(CONF) and 96, 88, 27 and 3% for MSB, respectively. The average D90 was 72, 94 and 99%, the D(min) was 47, 58 and 67%, respectively. The mean D(max) was 258% for MSB. The average DHI was 0.63, 0.37 and 0.70 for IB(CONV), IB(CONF) and MSB, respectively. D(max) to skin, lung and heart were 45, 54 and 31% for IB(CONV), 50, 55 and 29% for IB(CONF,) 97, 66 and 27% for MSB, respectively.

CONCLUSIONS

Target volume coverage was better for MSB than conventional IB, and it was comparable to conformal IB. The suboptimal coverage for IB patients is due to radiography based planning, which is unable to provide 3D information of the target. Dose homogeneity was somewhat better for MSB than IB(CONV), but the dose to skin and lung was higher for MSB. The MSB provides dosimetrically acceptable dose plans. The quality of interstitial implants can be improved with image-guided catheter insertions regarding both homogeneity and conformality.

Image-guided breast brachytherapy: an alternative to whole-breast radiotherapy

Lumpectomy and whole-breast radiotherapy (ie, breast-conservation treatment) are accepted as viable alternatives to mastectomy in locoregional management of breast cancer. These techniques are used to keep morbidity to a minimum, optimise cosmesis, and maintain treatment outcomes. Pathological and clinical data suggest that most recurrences of cancer in the ipsilateral breast are in the vicinity of the index lesion, and that remote recurrences are uncommon, whether or not whole-breast radiotherapy is delivered. These data lend support to the idea of partial-breast radiotherapy. Such a restricted treatment volume allows safe delivery of an accelerated hypofractionated regimen over a shortened course of 1 week. This technique differs from that of standard whole-breast tangential external-beam radiotherapy and necessitates investigation of accelerated partial-breast irradiation (APBI). Several techniques of APBI are being investigated; however, most experience, and the most favourable early outcomes, has been obtained with image-guided breast brachytherapy. This review highlights the rationale and outcomes of brachytherapy techniques.

Update on accelerated partial-breast irradiation

Progress in radiotherapy technology, particularly the advent of CT-guided simulation and three-dimensional conformal planning, has given the radiation oncologist the ability to precisely treat part of the breast, instead of the whole breast, using either brachytherapy or external-beam techniques. Treating such a limited area may allow the course of treatment for patients with early-stage breast cancer to be drastically shortened and could reduce toxicity to other organs. This article summarizes the rationale for accelerated partial-breast irradiation (APBI), techniques for performing it, and outcome to date of studies of APBI.

Accelerated partial breast irradiation: the case for current use

The treatment of early stage breast cancer is evolving from traditional breast conservation techniques, employing conventionally fractionated whole breast irradiation, to techniques in which partial breast irradiation is used in an accelerated fractionation scheme. A growing body of evidence exists, including favorable findings. Additional studies are under way that may ultimately prove equivalence. The logic behind this approach is reviewed, and the currently available data are presented to support the current use of carefully applied partial breast irradiation techniques in appropriately selected and informed patients.