Tracy Ng | European Institute for Jewish Studies in Sweden "PAIDEIA" (original) (raw)
Papers by Tracy Ng
International Journal of Radiation Oncology Biology Physics, 2006
To assess the need for gross tumor volume (GTV) delineation protocols in head-and-neck cancer (HN... more To assess the need for gross tumor volume (GTV) delineation protocols in head-and-neck cancer (HNC) treatment planning by use of positron emission tomography (PET)/computed tomography (CT) fusion imaging. Assessment will consist of interobserver and intermodality variation analysis. Sixteen HNC patients were accrued for the study. Four physicians (2 neuroradiologists and 2 radiation oncologists) contoured GTV on 16 patients. Physicians were asked to contour GTV on the basis of the CT alone, and then on PET/CT fusion. Statistical analysis included analysis of variance for interobserver variability and Student's paired sample t test for intermodality and interdisciplinary variability. A Boolean pairwise analysis was included to measure degree of overlap. Near-significant variation occurred across physicians' CT volumes (p = 0.09) and significant variation occurred across physicians' PET/CT volumes (p = 0.0002). The Boolean comparison correlates with statistical findings. One radiation oncologist's PET/CT fusion volumes were significantly larger than his CT volumes (p < 0.01). Conversely, the other radiation oncologist's CT volumes tended to be larger than his fusion volumes (p = 0.06). No significant interdisciplinary variation was seen. Significant disagreement occurred between radiation oncologists. Significant differences in GTV delineation were found between multiple observers contouring on PET/CT fusion. The need for delineation protocol has been confirmed.
Medical Dosimetry, 2009
The purpose of this study was to assess the efficacy of a gross tumor volume (GTV) contouring pro... more The purpose of this study was to assess the efficacy of a gross tumor volume (GTV) contouring protocol on interobserver variability between 4 physicians in positron emission therapy/computed tomography (PET/CT) treatment planning of head-and-neck cancer. A GTV contouring protocol for PET/CT treatment planning was developed utilizing 4 stages: Preliminary contouring on CT alone, determination of appropriate PET windowing, accurate image registration, and modification of CT contouring with correctly formatted PET/CT display and rules for modality disagreement. Two neuroradiologists and 2 radiation oncologists (designated as A, B, C, and D, respectively) were given a tutorial of PET/CT coregistered imaging individualized to their skill level, which included a step-by-step explanation of the protocol with clinical examples. Opportunities for questions and hands-on practice were given. The physicians were asked to re-contour 16 head-and-neck patients from Part I on PET/CT fusion imaging. Differences in volume magnitude were analyzed for statistical significance by analysis of variance (ANOVA) and paired t-tests (alpha<0.05). Volume overlap was analyzed for statistical significance using Wilcoxon signed-rank tests (alpha<0.05). Volume overlap increased significantly from Part I to Part II (p<0.05). One previously significant difference between physicians disappeared with the protocol in place. The mean fusion volume of Physician C, however, remained significantly larger than that of Physician D (p<0.01). This result is unchanged from Part I. The multidisciplinary contouring protocol significantly improved the coincidence of GTVs contoured by multiple physicians. The magnitudes of the volumes showed marginal improvement in consistency. Developing an institutional contouring protocol for PET/CT treatment planning is highly recommended to reduce interobserver variability.
International Journal of Radiation Oncology Biology Physics, 2005
To determine the feasibility of and patient outcomes using customized high-dose-rate (HDR) brachy... more To determine the feasibility of and patient outcomes using customized high-dose-rate (HDR) brachytherapy to boost the nasopharynx after external beam radiation therapy (EBRT) in patients with carcinoma of the nasopharynx. Patients with nonmetastatic squamous cell carcinoma of the nasopharynx were treated using EBRT followed by a HDR brachytherapy boost delivered via customized catheters in a noninvasive, accurate, and reproducible method under direct fiber-optic visualization. Local control (LC), disease-free survival (DFS), and overall survival (OS) were analyzed. We also measured the change in maximum oral aperture as an indication of temporomandibular joint dysfunction. Between March 1996 and July 2003, we treated 38 patients with this customized brachytherapy method. The procedure was well tolerated without any incidents of soft-tissue or bone necrosis and with minimal decrease of oral aperture. Median follow-up time was 47 months (range, 2-84 months); 35 patients had at least 1 year of follow-up. The 5-year actuarial rate of LC, DFS, and OS were 96.0%, 81.4%, and 92.7%, respectively. The treatment has been well tolerated by all patients. The combination of conformal EBRT with our customized HDR brachytherapy boost has resulted in excellent local control to date, while minimizing temporomandibular joint dysfunction.
International Journal of Radiation Oncology Biology Physics, 2004
Purpose: To investigate the clinical use of a commercially available gating system for minimizing... more Purpose: To investigate the clinical use of a commercially available gating system for minimizing respiratoryinduced anatomic motion over a range of treatment sites. Methods and Materials: The gating system consists of a reflective marker placed on the patient's anterior surface. The motion of the marker is tracked using a camera interfaced to a computer. Gated intervals were defined that limited the motion of the diaphragm to less than 1 cm during free breathing. Patients underwent a computed tomography virtual simulation using a breath-hold technique. At the time of treatment, verification of patient position and gating interval were performed using electronic portal imaging. Results: Between September 2000 and January 2002, 136 patients were simulated with respiratory gating. Of these, 108 patients were treated to 110 sites for a total of 2301 treatment sessions. Ninety-seven percent of patients completed their entire course of therapy with gated treatment delivery. Conclusions: Respiratory gating is a practical and achievable solution for minimizing respiratory-induced target motion during both simulation and treatment. With proper patient selection and training, it can be successfully implemented in a clinical radiation therapy department.
International Journal of Radiation Oncology Biology Physics, 2006
To assess the need for gross tumor volume (GTV) delineation protocols in head-and-neck cancer (HN... more To assess the need for gross tumor volume (GTV) delineation protocols in head-and-neck cancer (HNC) treatment planning by use of positron emission tomography (PET)/computed tomography (CT) fusion imaging. Assessment will consist of interobserver and intermodality variation analysis. Sixteen HNC patients were accrued for the study. Four physicians (2 neuroradiologists and 2 radiation oncologists) contoured GTV on 16 patients. Physicians were asked to contour GTV on the basis of the CT alone, and then on PET/CT fusion. Statistical analysis included analysis of variance for interobserver variability and Student's paired sample t test for intermodality and interdisciplinary variability. A Boolean pairwise analysis was included to measure degree of overlap. Near-significant variation occurred across physicians' CT volumes (p = 0.09) and significant variation occurred across physicians' PET/CT volumes (p = 0.0002). The Boolean comparison correlates with statistical findings. One radiation oncologist's PET/CT fusion volumes were significantly larger than his CT volumes (p < 0.01). Conversely, the other radiation oncologist's CT volumes tended to be larger than his fusion volumes (p = 0.06). No significant interdisciplinary variation was seen. Significant disagreement occurred between radiation oncologists. Significant differences in GTV delineation were found between multiple observers contouring on PET/CT fusion. The need for delineation protocol has been confirmed.
Medical Dosimetry, 2009
The purpose of this study was to assess the efficacy of a gross tumor volume (GTV) contouring pro... more The purpose of this study was to assess the efficacy of a gross tumor volume (GTV) contouring protocol on interobserver variability between 4 physicians in positron emission therapy/computed tomography (PET/CT) treatment planning of head-and-neck cancer. A GTV contouring protocol for PET/CT treatment planning was developed utilizing 4 stages: Preliminary contouring on CT alone, determination of appropriate PET windowing, accurate image registration, and modification of CT contouring with correctly formatted PET/CT display and rules for modality disagreement. Two neuroradiologists and 2 radiation oncologists (designated as A, B, C, and D, respectively) were given a tutorial of PET/CT coregistered imaging individualized to their skill level, which included a step-by-step explanation of the protocol with clinical examples. Opportunities for questions and hands-on practice were given. The physicians were asked to re-contour 16 head-and-neck patients from Part I on PET/CT fusion imaging. Differences in volume magnitude were analyzed for statistical significance by analysis of variance (ANOVA) and paired t-tests (alpha<0.05). Volume overlap was analyzed for statistical significance using Wilcoxon signed-rank tests (alpha<0.05). Volume overlap increased significantly from Part I to Part II (p<0.05). One previously significant difference between physicians disappeared with the protocol in place. The mean fusion volume of Physician C, however, remained significantly larger than that of Physician D (p<0.01). This result is unchanged from Part I. The multidisciplinary contouring protocol significantly improved the coincidence of GTVs contoured by multiple physicians. The magnitudes of the volumes showed marginal improvement in consistency. Developing an institutional contouring protocol for PET/CT treatment planning is highly recommended to reduce interobserver variability.
International Journal of Radiation Oncology Biology Physics, 2005
To determine the feasibility of and patient outcomes using customized high-dose-rate (HDR) brachy... more To determine the feasibility of and patient outcomes using customized high-dose-rate (HDR) brachytherapy to boost the nasopharynx after external beam radiation therapy (EBRT) in patients with carcinoma of the nasopharynx. Patients with nonmetastatic squamous cell carcinoma of the nasopharynx were treated using EBRT followed by a HDR brachytherapy boost delivered via customized catheters in a noninvasive, accurate, and reproducible method under direct fiber-optic visualization. Local control (LC), disease-free survival (DFS), and overall survival (OS) were analyzed. We also measured the change in maximum oral aperture as an indication of temporomandibular joint dysfunction. Between March 1996 and July 2003, we treated 38 patients with this customized brachytherapy method. The procedure was well tolerated without any incidents of soft-tissue or bone necrosis and with minimal decrease of oral aperture. Median follow-up time was 47 months (range, 2-84 months); 35 patients had at least 1 year of follow-up. The 5-year actuarial rate of LC, DFS, and OS were 96.0%, 81.4%, and 92.7%, respectively. The treatment has been well tolerated by all patients. The combination of conformal EBRT with our customized HDR brachytherapy boost has resulted in excellent local control to date, while minimizing temporomandibular joint dysfunction.
International Journal of Radiation Oncology Biology Physics, 2004
Purpose: To investigate the clinical use of a commercially available gating system for minimizing... more Purpose: To investigate the clinical use of a commercially available gating system for minimizing respiratoryinduced anatomic motion over a range of treatment sites. Methods and Materials: The gating system consists of a reflective marker placed on the patient's anterior surface. The motion of the marker is tracked using a camera interfaced to a computer. Gated intervals were defined that limited the motion of the diaphragm to less than 1 cm during free breathing. Patients underwent a computed tomography virtual simulation using a breath-hold technique. At the time of treatment, verification of patient position and gating interval were performed using electronic portal imaging. Results: Between September 2000 and January 2002, 136 patients were simulated with respiratory gating. Of these, 108 patients were treated to 110 sites for a total of 2301 treatment sessions. Ninety-seven percent of patients completed their entire course of therapy with gated treatment delivery. Conclusions: Respiratory gating is a practical and achievable solution for minimizing respiratory-induced target motion during both simulation and treatment. With proper patient selection and training, it can be successfully implemented in a clinical radiation therapy department.