Biomedical subjects

Susan Billingsley

Publications and source records attributed to Susan Billingsley.

3 recordsLinked to original sources

PubMed2006

Computerized tomographic simulation compared with clinical mark-up in palliative radiotherapy: a prospective study.

PURPOSE: To evaluate the impact of computed tomographic (CT) planning in comparison to clinical mark-up (CM) for palliative radiation of chest wall metastases. METHODS AND MATERIALS: In patients treated with CM for chest wall bone metastases (without conventional simulation/fluoroscopy), two consecutive planning CT scans were acquired with and without an external marker to delineate the CM treatment field. The two sets of scans were fused for evaluation of clinical tumor volume (CTV) coverage by the CM technique. Under-coverage was defined as the proportion of CTV not covered by the CM 80% isodose. RESULTS: Twenty-one treatments (ribs 17, sternum 2, and scapula 2) formed the basis of our study. Due to technical reasons, comparable data between CM and CT plans were available for 19 treatments only. CM resulted in a mean CTV under-coverage of 36%. Eleven sites (58%) had an under-coverage of >20%. Mean volume of normal tissues receiving >/=80% of the dose was 5.4% in CM and 9.3% in CT plans (p = 0.017). Based on dose-volume histogram comparisons, CT planning resulted in a change of treatment technique from direct apposition to a tangential pair in 7 of 19 cases. CONCLUSIONS: CT planning demonstrated a 36% under-coverage of CTV with CM of ribs and chest wall metastases.

Bone Neoplasms↗

PubMed2005

Error in the delivery of radiation therapy: results of a quality assurance review.

PURPOSE: To examine error rates in the delivery of radiation therapy (RT), technical factors associated with RT errors, and the influence of a quality improvement intervention on the RT error rate. METHODS AND MATERIALS: We undertook a review of all RT errors that occurred at the Princess Margaret Hospital (Toronto) from January 1, 1997, to December 31, 2002. Errors were identified according to incident report forms that were completed at the time the error occurred. Error rates were calculated per patient, per treated volume (>/=1 volume per patient), and per fraction delivered. The association between tumor site and error was analyzed. Logistic regression was used to examine the association between technical factors and the risk of error. RESULTS: Over the study interval, there were 555 errors among 28,136 patient treatments delivered (error rate per patient = 1.97%, 95% confidence interval [CI], 1.81-2.14%) and among 43,302 treated volumes (error rate per volume = 1.28%, 95% CI, 1.18-1.39%). The proportion of fractions with errors from July 1, 2000, to December 31, 2002, was 0.29% (95% CI, 0.27-0.32%). Patients with sarcoma or head-and-neck tumors experienced error rates significantly higher than average (5.54% and 4.58%, respectively); however, when the number of treated volumes was taken into account, the head-and-neck error rate was no longer higher than average (1.43%). The use of accessories was associated with an increased risk of error, and internal wedges were more likely to be associated with an error than external wedges (relative risk = 2.04; 95% CI, 1.11-3.77%). Eighty-seven errors (15.6%) were directly attributed to incorrect programming of the "record and verify" system. Changes to planning and treatment processes aimed at reducing errors within the head-and-neck site group produced a substantial reduction in the error rate. CONCLUSIONS: Errors in the delivery of RT are uncommon and usually of little clinical significance. Patient subgroups and technical factors associated with errors can be identified. The introduction of new technology can produce new ways for errors to occur, necessitating ongoing evaluation of RT errors for quality assurance. Modifications to processes of care can produce important reductions in error rates.

Confidence Intervals↗

PubMed2005

Assessing perfusion changes during whole brain irradiation for patients with cerebral metastases.

PURPOSE: To assess perfusion changes within brain and correlate these with clinical symptoms during whole brain radiotherapy (WBRT) for cerebral metastases. MATERIALS AND METHODS: Fourteen patients with cerebral metastases underwent dynamic CT perfusion scans during palliative whole brain irradiation. Perfusion scans were performed on Day 1 prior to initial radiotherapy treatment, then on Day 2, and on Day 5 immediately after completion of radiotherapy. Measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and capillary surface area permeability product (PS) were performed for each perfusion scan, and daily symptom assessment was taken prior to initial perfusion scan and thereafter prior to each daily radiation treatment. RESULTS: Utilizing Day 1 as baseline, a 19% increase (P = 0.033) was noted in PS at Day 2, (median 1.47 ml/100 g/min), which returned to Day 1 range at Day 5 (median 1.31 ml/100 g/min). When symptoms were correlated with perfusion parameters, a statistically significant association between change in MTT with change in headache scores was observed, baseline to Day 2 (P = 0.019), and a trend between change in nausea scores with change in CBV (P = 0.059) as well as change in MTT (P = 0.098), baseline to Day 5. CONCLUSION: This study has demonstrated the feasibility of a non-invasive technique to assess changes occurring within the human brain during a course of radiation treatment. Dynamic perfusion tomography provides insight into the pathophysiological processes taking place and allows correlation with patient symptomatology.

Adult↗