Sonja Dieterich

University of California, Davis, Davis, California, United States

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Publications (145)315.6 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose This investigation details the time and teamwork required for CT-guided tandem and ring high-dose-rate brachytherapy. Methods and Materials From 2010 to 2012, 217 consecutive implantations were identified on 52 patients. We gathered key workflow times: preoperative, applicator insertion, CT image, treatment planning, treatment, patient recovery, and total time in clinic. Linear fixed-effects models were used, and key workflow times were the outcome variables and factors including age, body mass index, stage, outside referral, number of implant per patient, number of implants per day, and year of implantation were examined as fixed effects. Results Of the 52 patients, 62% of the patients were Fédération Internationale de Gynécologie et d'Obstétrique Stage 2B, 88% were treated with concurrent chemotherapy, and 23% were treated at an outside facility and referred for the procedure. The mean times (minutes) for each step were as follows: preoperative evaluation, 93; insertion, 23; imaging, 45; treatment planning, 137; treatment, removal, and recovery, 115; total clinic time, 401. For the insertion time, the greater implant number per patient was significantly associated with a decreased total insertion time, with and without adjusting for other covariates, p = 0.002 and p = 0.0005, respectively. Treatment planning time was expedited with increasing number of implant per patient and comparing treatment times in 2012 with those in 2010, p = 0.01 and p < 0.0001, respectively. Conclusions Gynecologic brachytherapy requires a skillfully coordinated and efficient team approach. Identifying critical components and the time required for each step in the process is needed to improve the safety and efficiency of brachytherapy. Continuous efforts should be made to enhance the optimal treatment delivery in high-dose-rate gynecologic brachytherapy.
    Brachytherapy 01/2014; · 1.22 Impact Factor
  • Sonja Dieterich, Paul J Keall, Colin G Orton
    Medical Physics 10/2013; 40(10):100601. · 2.91 Impact Factor
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    ABSTRACT: Purpose: To determine how best to time respiratory surrogate-based tumor motion model updates by comparing a novel technique based on external measurements alone to three direct measurement methods.Methods: Concurrently measured tumor and respiratory surrogate positions from 166 treatment fractions for lung or pancreas lesions were analyzed. Partial-least-squares regression models of tumor position from marker motion were created from the first six measurements in each dataset. Successive tumor localizations were obtained at a rate of once per minute on average. Model updates were timed according to four methods: never, respiratory surrogate-based (when metrics based on respiratory surrogate measurements exceeded confidence limits), error-based (when localization error ≥3 mm), and always (approximately once per minute).Results: Radial tumor displacement prediction errors (mean ± standard deviation) for the four schema described above were 2.4 ± 1.2, 1.9 ± 0.9, 1.9 ± 0.8, and 1.7 ± 0.8 mm, respectively. The never-update error was significantly larger than errors of the other methods. Mean update counts over 20 min were 0, 4, 9, and 24, respectively.Conclusions: The same improvement in tumor localization accuracy could be achieved through any of the three update methods, but significantly fewer updates were required when the respiratory surrogate method was utilized. This study establishes the feasibility of timing image acquisitions for updating respiratory surrogate models without direct tumor localization.
    Medical Physics 07/2013; 40(7):071709. · 2.91 Impact Factor
  • Source
    International journal of radiation oncology, biology, physics 05/2013; · 4.59 Impact Factor
  • Tewfik Bichay, Sonja Dieterich, Colin G Orton
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    ABSTRACT: OVERVIEW With most external beam radiotherapy treatments an accuracy of ±3 mm is usually considered desirable and achievable. With stereotactic radiotherapy, however, a somewhat greater accuracy is desired and, with modern techniques, can be achieved, and some claim that even submillimeter accuracy is achievable. This is the topic debated in this month’s Point/Counterpoint.
    Medical Physics 05/2013; 40(5):050601. · 2.91 Impact Factor
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    ABSTRACT: The purpose of this study was to quantify postimplantation migration of percu-taneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migra-tion, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78–2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92–2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52–2.21 mm) and 1.97 mm median FRE (IQR 1.44–4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking.
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    ABSTRACT: The purpose of this study was to quantify postimplantation migration of percu-taneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migra-tion, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78–2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92–2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52–2.21 mm) and 1.97 mm median FRE (IQR 1.44–4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking.
    Journal of Applied Clinical Medical Physics 03/2013; 14(2):77. · 0.96 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to quantify postimplantation migration of percu-taneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migra-tion, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78–2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92–2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52–2.21 mm) and 1.97 mm median FRE (IQR 1.44–4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to quantify postimplantation migration of percu-taneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migra-tion, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78–2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92–2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52–2.21 mm) and 1.97 mm median FRE (IQR 1.44–4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to quantify postimplantation migration of percu-taneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migra-tion, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78–2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92–2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52–2.21 mm) and 1.97 mm median FRE (IQR 1.44–4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to quantify postimplantation migration of percu-taneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migra-tion, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78–2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92–2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52–2.21 mm) and 1.97 mm median FRE (IQR 1.44–4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to quantify postimplantation migration of percu-taneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migra-tion, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78–2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92–2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52–2.21 mm) and 1.97 mm median FRE (IQR 1.44–4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking. PACS number: 87.57.N-; 87.57.nm; 87.53.Ly Key words: implanted fiducial marker migration, stereotactic ablative radiotherapy (SABR), stereotactic body radiotherapy (SBRT), endovascular embolization coils, gold seed fiducial markers Conflict of Interest statement: BL and PM have received speaking honoraria from Varian Medical Systems and General Electric Medical Systems, and research fund-ing from Varian Medical Systems to the Department of Radiation Oncology.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to quantify postimplantation migration of percu-taneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migra-tion, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78–2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92–2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52–2.21 mm) and 1.97 mm median FRE (IQR 1.44–4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking.
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    ABSTRACT: To determine the clinical impact of calculated dose differences between effective path length (EPL) and Monte Carlo (MC) algorithms in stereotactic ablative radiation therapy (SABR) of lung tumors. We retrospectively analyzed the treatment plans and clinical outcomes of 77 consecutive patients treated with SABR for 82 lung tumors between 2003 and 2009 at our institution. Sixty treatments were originally planned using EPL, and 22 using MC. All plans were recalculated for the same beam specifications using MC and EPL, respectively. The doses covering 95%, 50%, and 5% (D95, D50, D5, respectively) of the target volumes were compared between EPL and MC (assumed to be the actual delivered dose), both as physical dose and biologically effective dose. Time to local recurrence was correlated with dose by Cox regression analysis. The relationship between tumor control probability (TCP) and biologically effective dose was determined via logistic regression and used to estimate the TCP decrements due to prescribing by EPL calculations. EPL overestimated dose compared with MC in all tumor dose-volume histogram parameters in all plans. The difference was >10% of the MC D95 to the planning target volume and gross tumor volume in 60 of 82 (73%) and 52 of 82 plans (63%), respectively. Local recurrence occurred in 13 of 82 tumors. Controlling for gross tumor volume, higher physical and biologically effective planning target volume D95 correlated significantly with local control (P = .007 and P = .045, respectively). Compared with MC, prescribing based on EPL translated to a median TCP decrement of 4.3% (range, 1.2%-37%) and a >5% decrement in 46% of tumors. Clinical follow-up for local lung tumor control in a sizable cohort of patients treated with SABR demonstrates that EPL overestimates dose by amounts that substantially decrease TCP in a large proportion. EPL algorithms should be avoided for lung tumor SABR.
    Practical radiation oncology. 10/2012; 3(4):294-300.
  • G Kalantzis, A Lo, S Dieterich
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    ABSTRACT: Purpose: : Stereotactic radiosurgery (SRS) procedures are known to deliver a very high dose per fraction and thus, the increased risk of secondary types of cancer due to increased peripheral dose could be a limiting factor for the long term survival of the patients. The aim of this study is to evaluate the peripheral dose (PD) received at preselected anatomical sites in an anthropomorphic phantom for treatments of intracranial lesions with the CyberRnife. Methods: Eight patients treated using the CyberRnife were selected for this study. Organs at risk and target were delineated on volumetric CT data and treatment planning (Multiplan v.4.5.0) was optimized accordingly, in order to achieve the required prescribed target dose and critical structures sparing for each patient. The final treatment plan was delivered with a CyberRnife VIS (Accuray, Inc., Sunnyvale, CA) operating with a dose rate of 1000 MU/min at a flattening filter free mode and upgraded shielding. We performed our measurements using a male anthropomorphic RANDO phantom (Alderson Research Laboratories, Inc., Stamford, CT). Groups of three TLD 100 were placed anteriorly inside RANDO at a depth of 5 cm at locations corresponding to the thyroid, breast or lung, uterus and inferior abdomen for each treatment plan. Results: The average percentage dose normalized to the prescribed dose for the thyroid gland was 0.92+0.23 % with a max of 1.95%. The maximum reduction of the PD (expressed as percentage of the prescribed dose) was 80% between the thyroid gland and the lower pelvic area. Similarly the PD normalized to the number of MU showed an average of 0.84×10-3 (cGy/MU), with a max of 0.0025 (cGy/MU) for the thyroid gland region. Conclusions: It is evident that the PD is proportional to the number of MU as well as to the prescribed dose. These correlations can be utilized to estimate the PD during intracranial treatments.
    Medical Physics 06/2012; 39(6):3800-3801. · 2.91 Impact Factor
  • S Dieterich, E Ford, C Halasz
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    ABSTRACT: Purpose: The purpose of this study is to conduct a Failure Modes and Effect Analysis (FMEA) for CyberKnife Stereotactic Radiosurgery to determine the sensitivity of existing QA procedures and determine in which areas new QA procedures needed to be implemented. Methods: Members from each professional team providing service for CyberKnife radiosurgery (Medical Physicists, Nurses, Physicians, Radiation Therapists, and Administrators) were interviewed to gather potential failure modes. A patient flow chart was developed from patient consult to conclusion of last treatment. Failure modes were mapped to nodes in the flow charts to identify potential high-risk areas. A matrix was created to correlate existing QA procedures with failure modes to identify failure modes that were not covered by any QA as well as identify the sensitivity of QA procedures to prevent failures. Results: 180 failure modes were identified. Current AAPM QA recommendations were found to focus preferentially on technical failure modes (15%), while the majority of failure modes found are process failures and human errors (85%). Creating a Venn diagram of CyberKnife and Gamma Knife failure modes revealed a large overlap area. The most effective QA checks are checklists for physics second chart review and pre- treatment time-out checklists. Existing checklists were modified and new checklists added to address high-ranked failure modes. New procedure guidelines, e.g. for contouring workflow and add-on simulations, were developed as QC to address clusters of failure modes. An ARIA-CyberKnife DICOM interface is being implemented to resolve failure modes centering around multiple fraction, multiple plan treatments and total dose tracking. Conclusions: This work is the first FMEA study for the CyberKnife stereotactic radiosurgery. It will facilitate medical physicists using the CyberKnife to deliver SRS/SBRT treatments to transition from experience-based technical QA to a comprehensive new quality paradigm including technical, process, and human safety aspects.
    Medical Physics 06/2012; 39(6):3867. · 2.91 Impact Factor
  • K Yenice, P Petti, S Dieterich, T Solberg
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    ABSTRACT: Since its introduction nearly 60 years ago, stereotactic radiosurgery has become the standard of care for the noninvasive destruction of intracranial tissues or lesions that may be inaccessible or unsuitable for open surgery. Today, modern stereotactic radiosurgery is practiced using advanced image guided treatment planning and specialized delivery systems including micro- MLC equipped linacs, CyberKnife, and Gamma Knife machines. Stereotactic radisourgery delivers a large dose to a precisely defined volume in a short time, and as such requires the utmost attention to precision and quality assurance. Also critical is the meticulous design of treatment processes that eliminate the possibility of potentially disastrous errors. In this presentation we review the fundamental aspects of stereotactic targeting and delivery, the technologies for stereotactic localization and treatment of cranial targets, and the quality assurance aspects associated with establishing and maintaining a clinical radiosurgery program. Examples of radiosurgery cases will be presented from the best practice sites utilizing Gamma Knife, CyberKnife, and linac delivery systems, followed by an expert panel discussion of quality measures for treatment planning and delivery.Learning Objectives:1. Differentiate how radiation is delivered for Gamma Knife, CyberKnife and Linac-based (conventional and robotic) stereotactic radiosurgery.2. Define the treatment planning parameters, imaging requirements and workflow for Gamma Knife, CyberKnife and Linac-based stereotactic radiosurgery.3. Discuss measures for assuring accuracy in stereotactic localization and dose delivery for Gamma Knife, CyberKnife and Linac-based stereotactic radiosurgery.4. Discuss uncertainties and limitations associated with Gamma Knife, CyberKnife and Linac-based stereotactic radiosurgery.
    Medical Physics 06/2012; 39(6):3929. · 2.91 Impact Factor
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    ABSTRACT: OBJECTIVES:: To report outcomes, failure patterns, and toxicity after stereotactic radiosurgery (SRS) for recurrent head and neck cutaneous squamous cell carcinoma with gross perineural invasion (GPNI). METHODS:: Ten patients who received SRS as part of retreatment for recurrent head and neck cutaneous squamous cell carcinoma with GPNI were included. All patients exhibited clinical and radiologic evidence of GPNI before SRS. Previous treatments included surgery alone in 3 patients and surgery with adjuvant external beam radiotherapy (EBRT) in 7 patients. Retreatment included SRS alone in 2 and EBRT boosted with SRS in 8 patients. Magnetic resonance images were obtained every 3 to 6 months after SRS to track failure patterns. RESULTS:: At a median 22-month follow-up, the 2-year progression-free and overall survival rates were 20% and 50%, respectively. Seven patients exhibited local failures, all of which occurred outside both SRS and EBRT fields. Five local failures occurred in previously clinically uninvolved cranial nerves (CNs). CN disease spreads through 3 distinct patterns: among different branches of CN V; between CNs V and VII; and between V1 and CNs III, IV, and/or VI. Five patients experienced side effects potentially attributable to radiation. CONCLUSIONS:: Although there is excellent in-field control with this approach, the rate of out-of-field failures remains unacceptably high. We found that the majority of failures occurred in previously clinically uninvolved CNs often just outside treatment fields. Novel treatment strategies targeting this mode of perineural spread are needed.
    American journal of clinical oncology 04/2012; · 2.21 Impact Factor
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    ABSTRACT: To investigate the effect of tumor site, measurement precision, tumor-surrogate correlation, training data selection, model design, and interpatient and interfraction variations on the accuracy of external marker-based models of tumor position. Cyberknife Synchrony system log files comprising synchronously acquired positions of external markers and the tumor from 167 treatment fractions were analyzed. The accuracy of Synchrony, ordinary-least-squares regression, and partial-least-squares regression models for predicting the tumor position from the external markers was evaluated. The quantity and timing of the data used to build the predictive model were varied. The effects of tumor-surrogate correlation and the precision in both the tumor and the external surrogate position measurements were explored by adding noise to the data. The tumor position prediction errors increased during the duration of a fraction. Increasing the training data quantities did not always lead to more accurate models. Adding uncorrelated noise to the external marker-based inputs degraded the tumor-surrogate correlation models by 16% for partial-least-squares and 57% for ordinary-least-squares. External marker and tumor position measurement errors led to tumor position prediction changes 0.3-3.6 times the magnitude of the measurement errors, varying widely with model algorithm. The tumor position prediction errors were significantly associated with the patient index but not with the fraction index or tumor site. Partial-least-squares was as accurate as Synchrony and more accurate than ordinary-least-squares. The accuracy of surrogate-based inferential models of tumor position was affected by all the investigated factors, except for the tumor site and fraction index.
    International journal of radiation oncology, biology, physics 04/2012; 82(5):e709-16. · 4.59 Impact Factor
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    ABSTRACT: To evaluate Hotelling's T(2) statistic and the input variable squared prediction error (Q((X))) for detecting large respiratory surrogate-based tumor displacement prediction errors without directly measuring the tumor's position. Tumor and external marker positions from a database of 188 Cyberknife Synchrony™ lung, liver, and pancreas treatment fractions were analyzed. The first ten measurements of tumor position in each fraction were used to create fraction-specific models of tumor displacement using external surrogates as input; the models were used to predict tumor position from subsequent external marker measurements. A partial least squares (PLS) model with four scores was developed for each fraction to determine T(2) and Q((X)) confidence limits based on the first ten measurements in a fraction. The T(2) and Q((X)) statistics were then calculated for every set of external marker measurements. Correlations between model error and both T(2) and Q((X)) were determined. Receiver operating characteristic analysis was applied to evaluate sensitivities and specificities of T(2), Q((X)), and T(2)∪Q((X)) for predicting real-time tumor localization errors >3 mm over a range of T(2) and Q((X)) confidence limits. Sensitivity and specificity of detecting errors >3 mm varied with confidence limit selection. At 95% sensitivity, T(2)∪Q((X)) specificity was 15%, 2% higher than either T(2) or Q((X)) alone. The mean time to alarm for T(2)∪Q((X)) at 95% sensitivity was 5.3 min but varied with a standard deviation of 8.2 min. Results did not differ significantly by tumor site. The results of this study establish the feasibility of respiratory surrogate-based online monitoring of real-time respiration-induced tumor motion model accuracy for lung, liver, and pancreas tumors. The T(2) and Q((X)) statistics were able to indicate whether inferential model errors exceeded 3 mm with high sensitivity. Modest improvements in specificity were achieved by combining T(2) and Q((X)) results.
    Medical Physics 04/2012; 39(4):2042-8. · 2.91 Impact Factor

Publication Stats

754 Citations
315.60 Total Impact Points

Institutions

  • 2013–2014
    • University of California, Davis
      • Department of Radiation Oncology
      Davis, California, United States
    • Loyola University Maryland
      Baltimore, Maryland, United States
  • 2011–2013
    • Trinity Health
      Livonia, Michigan, United States
    • Universität zu Lübeck
      • Institut für Robotik und Kognitive Systeme
      Lübeck, Schleswig-Holstein, Germany
  • 2007–2013
    • Stanford University
      • Department of Radiation Oncology
      Palo Alto, CA, United States
  • 2012
    • University of Maryland, Baltimore
      • Department of Radiation Oncology
      Baltimore, MD, United States
  • 2011–2012
    • Stanford Medicine
      • Department of Radiation Oncology
      Stanford, California, United States
  • 2005–2012
    • University of Maryland, College Park
      • Department of Physics
      Maryland, United States
  • 2001–2011
    • Rutgers, The State University of New Jersey
      New Brunswick, New Jersey, United States
  • 2009
    • University of Miami Miller School of Medicine
      • Department of Radiation Oncology
      Miami, FL, United States
  • 2003–2008
    • Georgetown University
      • • Department of Radiation Medicine
      • • Department of Radiology
      Washington, D. C., DC, United States
  • 2006–2007
    • Virginia Commonwealth University
      • Department of Radiation Oncology
      Richmond, VA, United States
  • 2003–2005
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States
  • 2002
    • University of Illinois, Urbana-Champaign
      • Department of Physics
      Urbana, Illinois, United States
    • College of William and Mary
      • Department of Physics
      Williamsburg, Virginia, United States