PubMed Health⌕ Search

Biomedical subjects

Kenneth B Roberts

Publications and source records attributed to Kenneth B Roberts.

18 recordsLinked to original sources
PubMed2005

PET imaging for suspected residual tumour or thoracic recurrence of non-small cell lung cancer after pneumonectomy.

F-18 fluorodeoxyglucose-positron emission tomography (PET) was investigated in patients with suspected residual disease or intrathoracic recurrence after pneumonectomy. Patients were identified from a prospective database. Impact of PET on staging and patient management was assessed. Clinical outcome was used to assess appropriateness of management. PET was performed in 17 cases, either post-operatively (n = 8), or later for suspected recurrence (n = 9) in patients with good performance status and without extensive disease on conventional imaging. PET changed treatment in 10 cases (59%). In five patients (29%), PET changed treatment intent (curative versus non-curative) from radical radiotherapy (RT) to palliative RT (n = 1), or observation or supportive care (n = 3), or from palliative to radical RT (n = 1). In a further patient with unexplained pain, PET appropriately showed no evidence of disease. In additional five cases (29%), PET influenced choice of RT dose and the use of concurrent chemotherapy (n = 3) or target volume (n = 2). Patients without tumour or with limited disease on PET had favourable outcomes whereas those with extensive disease suffered early tumour progression. PET was discordant with conventional assessment in >50% of cases. PET may be valuable after pneumonectomy if the patient is being considered for adjuvant or salvage radiotherapy although specificity may be reduced due to post-operative inflammatory changes.

Carcinoma, Non-Small-Cell Lung↗
PubMed2004

Relation of clinical success in coronary brachytherapy to dose.

Intravascular brachytherapy is the primary treatment for coronary in-stent restenosis. Variations in dose in the treated artery may represent a potential cause of treatment failure. We compared dose distributions in patients who had developed recurrent restenosis (treatment failure) with those in patients who remained event free at 9 months (treatment success). We followed 140 patients who were receiving brachytherapy for in-stent restenosis with 4 radiation delivery devices to identify treatment failures and successes. Through a nested case-control construct, treatment failures (n = 14) were compared 1:2 with treatment successes (n = 28) matched by radiation delivery system and in-stent restenosis lesion pattern. The dose absorbed by 90% of the artery encompassed by the external elastic membrane (D(90)EEM) was calculated by applying intravascular ultrasound at 2-mm intervals along the treated lesion. Dose calculations were performed using dose kernel integration techniques generated from Monte Carlo simulations. The mean minimum D(90)EEM in treatment failures was 7.46 +/- 1.98 Gy, and that in treatment successes was 8.87 +/- 1.13 Gy (p = 0.007). Using a minimum dose threshold of 8.4 Gy, a minimum D(90)EEM <or=8.4 Gy occurred in 13 patients (93%) whose treatment failed but only in 9 patients (32%) whose treatment was a success (p <or=0.001). No confounding variables were found to be statistically significant between treatment failures and successes. In conclusion, current brachytherapy dose prescriptions allow for inter- and intralesion variations in dose. Arteries that receive <or=8.4 Gy at any point along the external elastic membrane are more likely to result in treatment failures. Dosimetry guided by intravascular ultrasound may be critical to ensure adequate dose delivery and outcomes.

Adult↗
PubMed2004

Optimization of dose distributions for bifurcated coronary vessels treated with catheter-based photon and beta emitters using the simulated annealing algorithm.

The dose distributions in the bifurcated vessels treated with a catheter-based delivery system are complicated by the geometry of bifurcation consisting of a main and a branch vessel at different angles, and it is difficult to generate satisfactory dose distributions. We hypothesize that increasing the number of dwell positions can result in better dose distributions. An optimization method based on the simulated annealing was developed to demonstrate the validity of this idea. In this method, the source in the branch treatment was allowed to take up to five dwell positions. A cost function was constructed to deliver the prescription dose to the planning targets with penalties for both overdosing and underdosing. By using the optimization algorithm, it was found that for 90 degrees to 60 degrees bifurcated vessels an optimized single dwell position treatment scheme can be as effective as the schemes that include up to five dwell positions. As the bifurcation angle becomes smaller than 60 degrees, the dose distributions generated with the single dwell position scheme become less satisfactory than the more complicated treatment schemes with multiple dwell positions. By using a three-dwell-position treatment scheme for the 192Ir source, the overdosing can be kept under 166% even at a bifurcation angle of 20 degrees.

Algorithms↗
PubMed2003

Dose distributions in bifurcated coronary vessels treated with catheter-based photon and beta emitters in intravascular brachytherapy.

The dose distributions in the bifurcated vessels treated with intravascular brachytherapyline sources are complicated and depend on the bifurcation geometry consisting of a main and a branch vessel at different angles. To investigate the dosimetric effects at the bifurcation, calculations were performed on branching vessels of various bifurcation angles ranging from 20 degrees to 90 degrees. Two catheter based delivery systems were considered in the calculations using a 40 mm long radioactive sources of 192Ir or 90Sr/Y. It was assumed that the bifurcated vessel was treated in twoseparate source insertions, once for the main vessel and later for the branch vessel. Calculations were performed for different values of source gap from 0 to 9 mm, at the junction of main and branch vessels. Our results indicate that main vessel always receives a higher dose (up to 200%) when the branch vessel is also treated. Hot spots at portions of the main vessel near the junction cannot be totally avoided without severely underdosing the branch vessel. For bifurcation angle greater than 45 degrees, a 4 mm source gap can almost ensure that overdosing of the main vessel does not exceed 60% and underdosing of the branch vessel does not exceed 10% for 192Ir. However, for 90Sr/Y, the same is not possible unless the bifurcation angle is larger than 70 degrees. Dose heterogeneity using 90Sr/Y is more sensitive to the value of source gap than 192Ir because 90Sr/Y source provides a sharper dose-fall-off than 192Ir. For both photon and beta emitters, there is no acceptable solution for bifurcation angles less than 30 degrees, where the activity of the line source has a uniform distributions. Appropriate choice of gap at the junction can only help to reduce either overdosing of the main vessel or underdosing of the branch vessel, but not both.

Beta Particles↗
PubMedDate not supplied

Brachytherapy for in-stent restenosis in general interventional practice: a single institution's experience using four radiation devices.

BACKGROUND: The effectiveness of brachytherapy for the treatment of in-stent restenosis (ISR) has been established in a number of large randomized controlled trials. Efficacy of this therapy in general population is less well established. METHODS AND MATERIALS: We report our experience of 207 patients, 236 coronary lesions, treated with brachytherapy between November 2000 and November 2002. All commercially available brachytherapy devices, as well as one investigational device, were utilized. This cohort was followed over 9 months and clinical outcomes were obtained with subsequent analysis of patient and lesion-specific characteristics. RESULTS: Average treatment age was 62.5 years; 73% were male and the most frequent presentation was unstable angina (74%). All patients had successful delivery of radiation, with no in-hospital deaths. Novoste BetaCath device was used for 163 (65%) lesions, Cordis Checkmate for 56 (24%) lesions, Interventional Therapies device in 13 (8%) lesions, and Guidant Galileo in 4 lesions (3%). At a mean follow-up of 9.1 months, 78.7% were free of major adverse cardiac event (MACE). Twenty-one patients required repeat PTCA (10.1%), 19 had CABG (9.2%), 3 had MI (1.4%), and there was 1 death (0.5%). Unadjusted MACE rates for each device were 21% for Novoste, 28% for Checkmate, 8% for Interventional Therapies, and 50% for Galileo. Lesion length, minimal lumen diameter, renal failure, diabetes, and smoking did not predict treatment failure; only age was inversely correlated with MACE (P=.002). CONCLUSION: When applied across a spectrum of patients, lesions, and devices, brachytherapy retains its effectiveness with outcomes similar to those reported in randomized clinical trials.

Adult↗
PubMedDate not supplied

Resident preparedness for practice: a longitudinal cohort study.

OBJECTIVE: To determine whether the perception of preparedness for practice changes over time. DESIGN: Questionnaire survey of University of Massachusetts residents 5 years after an initial survey. Responses to individual questions in the 2 surveys were compared for each graduate and the Wilcoxon rank sum test applied. A supplementary questionnaire addressed current confidence in areas with relatively low scores in both surveys. RESULTS: All 24 eligible graduates responded. The high rating of overall sense of preparedness was identical in the 2 surveys. Differences were statistically significant in only 3 categories: common illnesses, office gastroenterology, and office gynecology-all from a lower estimate of preparedness initially to a higher estimate in retrospect. Six areas continued to receive relatively low scores: nutrition, patient scheduling, cost-effectiveness, telephone management, office gynecology, and office orthopedics. Respondents feel more confident currently with nutrition, patient scheduling, and telephone management but not with cost-effectiveness, gynecology, or orthopedics. CONCLUSIONS: Residents paired with office-based practitioners for their continuity experience report feeling well prepared for practice both on practice entry and 5 to 9 years later. In the 6 areas of relatively low preparedness, experience improved confidence with nutrition, patient scheduling, and telephone management, but not cost-effectiveness, gynecology, or orthopedics. The hypothesis that clinical areas of relative weakness at the end of residency may remain so years later deserves to be tested.

Clinical Competence↗
PubMedDate not supplied

The APA/HRSA Faculty Development Scholars Program: introduction to the supplement.

BACKGROUND: The purpose of this project was to improve pediatric primary care medical education by providing faculty development for full-time and community-based faculty who teach general pediatrics to medical students and/or residents in ambulatory pediatric community-based settings. Funding for the program came through an interagency agreement with the Health Resources and Services Administration (HRSA) and the Agency for Healthcare Research and Quality (AHRQ). METHODS: A train-the-trainer model was used to train 112 scholars who could teach skills to general pediatric faculty across the nation. The three scholar groups focused on community-based ambulatory teaching; educational scholarship; and executive leadership. RESULTS: Scholars felt well prepared to deliver faculty development programs in their home institutions and regions. They presented 599 workshops to 7989 participants during the course of the contract. More than 50% of scholars assumed positions of leadership, and most reported increased support for medical education in their local and regional environments. CONCLUSIONS: This national pediatric faculty development program pioneered in the development of a new training model and should guide training of new scholars and advanced and continuing training for those who complete a basic program.

Ambulatory Care↗
PubMedDate not supplied

APA/HRSA National Faculty Development Scholars Program: community-based teaching track.

OBJECTIVES: Goals and objectives of the APA/HRSA National Faculty Development Scholars Program are described in a companion article in this supplement. Program objectives of the Community-Based Teaching Track were to 1) identify individuals with faculty development skills to serve as regional leaders, conducting local and regional workshops; 2) create a national network of leaders, thereby promoting sustainability; and 3) increase educational contributions of office-based preceptors. Participant objectives were to 1) meet expectations of the program; 2) possess knowledge, skills, and attitudes needed to recruit and retain community-based preceptors; 3) possess knowledge and skills needed to conduct faculty development workshops for practitioners; and 4) form local and national collegial networks. METHODS: Academicians and practitioners were selected to form 2 cohorts, starting in 1999 (N = 20) and 2000 (N = 22), respectively. Workshops were developed on the basis of projected needs and iterative needs assessments of the participants. Each participant was required to conduct workshops between meetings, first locally and then regionally or nationally. OUTCOMES: Forty-two participants conducted 307 workshops attended by 3815 individuals. Participants reported specific knowledge and skills gained from the program and increases in multiple areas of competence. Networks were formed, leading to collaborative regional and national presentations and formation of an APA Faculty Development Special Interest Group. Participants reported increased recruitment of training sites and preceptors, with enhanced relationships. CONCLUSION: Program and participant objectives of the Community-Based Teaching Track were met, including implementation of multiple new workshops, development of skills, and creation of a support network to enhance the sustainability of that success.

Ambulatory Care↗