Biomedical subjects

C Beardmore

Publications and source records attributed to C Beardmore.

6 recordsLinked to original sources

PubMed2001

Influence of a vac-fix immobilization device on the accuracy of patient positioning during routine breast radiotherapy.

Continued use of basic planning and treatment techniques, in contrast to the improved methods implemented at many other anatomical sites, has emphasized the need for improved breast dosimetry. Any future technique delivering a superior three-dimensional dose distribution will be of maximum benefit if set-up errors are minimized. To determine the influence of vacuum moulded bag (vac-fix) immobilization on routine breast radiotherapy, 17 patients received half their radiotherapy fractions using our standard breast board technique and half using a vac-fix device positioned on the breast board. Treatment accuracy and reproducibility were assessed for each technique using daily electronic portal imaging and were analysed in terms of random and systematic translational and rotational displacements of treatment fields with respect to corresponding simulation images. In addition, patients completed a short questionnaire aimed at determining which technique they preferred. Results showed that random errors for the two techniques did not differ significantly. Approximately 80% of random translations recorded were less than 3 mm and 80% of random rotations were less than 1.5 degrees. Systematic errors showed some improvement with the vac-fix system. In the anteroposterior direction, approximately 80% of systematic errors were less than 4 mm for both techniques, but in the superoinferior direction the 80% point was reduced from 5.0 mm for the standard set-up to 2.7 mm for treatment in vac-fix. For rotational systematic errors, the corresponding value dropped from 1.8 degrees for the standard set-up to 1.1 degrees in vac-fix. Therefore, for many patients, additional use of a vac-fix device improved the transfer of the planned set-up from simulator to treatment unit. Additionally, answers to the questionnaire indicated that patients generally favoured the vac-fix system over use of the breast board alone. In conclusion, however, introduction of vac-fix immobilization for all patients was not thought justified as the improvements demonstrated are not likely to be clinically significant with the present treatment technique.

Breast Neoplasms↗

PubMed2000

A randomized study of the use of a customized immobilization system in the treatment of prostate cancer with conformal radiotherapy.

PURPOSE: To evaluate the impact of a customized immobilisation system on field placement accuracy, simulation and treatment delivery time, radiographer convenience and patient acceptability. PATIENTS AND METHODS: Thirty men receiving radical radiotherapy for prostate cancer were randomised using a cross over trial design to have radiotherapy planning and treatment given either in a conventional treatment position (CTP) or using an immobilisation system (IMS). The randomisation was to have either the CTP or IMS for the initial 3 weeks of radiotherapy after which patients were replanned and changed to the alternative treatment set-up. Treatment accuracy was measured using an electronic portal imaging device. Radiographers and patients completed weekly questionnaires. RESULTS: Median simulation time was 22.5 min (range 20-30 min) in the CTP and 25 min (range 15-40 min) for the IMS (P < 0.001). Median treatment time was 9 min for CTP (range 8-10 min), and 10 min (range 8.5-13.5 min) for IMS (P < 0.001). Median isocentre displacement for anterior fields was 1.7 mm from the simulated isocentre for the CTP compared to 2.0 mm for IMS (P = 0.07). For left lateral fields values were 1.8 and 1.8 mm (P = 0.98), and for right lateral fields 2.1 and 1.7 mm (P = 0.06), respectively. No clinically significant reduction in either systematic or random field placement errors was demonstrated. Radiographers reported that patients found the IMS more comfortable than CTP (P < 0.001), but when using the IMS, they noticed greater difficulty in patient positioning (P < 0.001), and alignment to skin tattoos (P < 0.001). CONCLUSIONS: Although IMS may have been more comfortable, treatment accuracy was not improved compared to the CTP in our department. In addition, treatment took longer and patient set-up was more difficult.

Aged↗

PubMed1999

Stereotactically guided conformal radiotherapy for meningiomas.

PURPOSE: Stereotactically guided conformal radiotherapy, (SCRT) is a high precision technique of conformal radiotherapy (RT) which reduces the volume of normal tissue irradiated compared to conventional RT and may lead to a reduction in long-term toxicity We describe the technique and the preliminary results in patients with inoperable, residual or recurrent meningiomas. MATERIAL AND METHODS: From July 1993 to November 1997, 24 patients (median age: 56 years, range: 28-72) with base of skull (n = 21). falx or upper skull (n = 3) meningiomas were treated with SCRT. The technique employed immobilization in a Gill-Thomas-Cosman (GTC) frame and CT localization with a Brown-Roberts-Wells (BRW) fiducial system for stereotactic space definition. The planning target volume (PTV) was defined as gross tumour volume (GTV) and a 0.5-1 cm margin. Treatment was delivered with three (12 patients) or four non-coplanar conformal fixed fields (12 patients) Conformal blocking was achieved either with lead alloy blocks (n = 11) or with a multi-leaf collimator (MLC) (n = 13). Patients were treated on a 6 MV linear accelerator to doses of 50-55 Gy, in 30-33 daily fractions. The treatments were carried out as part of a routine work of a busy radiotherapy department. RESULTS: Median GTV for 24 meningiomas was 21.7 cm3 (range: 4.4-183 cm3). SCRT was well tolerated with minimal toxicity Three months after the end of radiotherapy, seven of 15 patients with neurological deficit had an improvement and eight remained unchanged. Two patients experienced early side effects (one VII nerve palsy, one Addisonian state). At a median follow-up of 13-months (range: 3-43) the 1 year progression free survival and overall survival are 100%. which is within the range expected for conventional fractionated radiotherapy for meningiomas. CONCLUSIONS: SCRT is a feasible technique of high precision conformal RT for patients with meningiomas. Potential advantages in tumour control, survival and toxicity over conventional RT, require evaluation in long-term prospective studies.

Adult↗

PubMed1999

Patient position reproducibility in fractionated stereotactic radiotherapy: an update after changing dental impression material.

The reproducibility of patient positioning within the Gill-Thomas-Cosman relocatable stereotactic frame was re-evaluated following the substitution of a new, softer, dental impression material for the original hard acrylic compound. The average total displacement for a series of 10 patients was 1.1 mm (+/- 0.6 mm). Rotational discrepancies were small. This technique cannot deliver accurate repositioning in the absence of patient co-operation.

Acrylic Resins↗

PubMed1994

Bleeding time at altitude.

Disorders of coagulation during ascent to high altitude in the unacclimatized are well recognized. In order to document the sequence of haematological changes, the bleeding time was estimated weekly in six climbers during a six week climb. The median bleeding time was shown to increase by 50% between the first and fourth week, it then plateaued during continued ascent to 5700 m. During the sixth week the bleeding time rapidly reverted to baseline levels whilst still at altitude. The observations might be explained by the compensatory changes in coagulation factors following the initial prothrombotic phase, compounded by increased capillary fragility. Acclimatization to altitude is accompanied by a series of complex haematological changes. The temporal sequence should be considered when devising a strategy to reduce the risk of thrombosis.

Altitude↗

PubMed1990

Involvement of nucleic acid synthesis in cell killing mechanisms of topoisomerase poisons.

The primary cytotoxic mechanism of camptothecin has been proposed to involve an interaction between the replication machinery and the camptothecin-mediated topoisomerase I-DNA cleavable complex (Y. H. Hsiang, M.G. Lihou, and L.F. Liu, Cancer Res., 49:5077-5082, 1989). In the present study, we show that killing of V79 cells by the topoisomerase II poisons 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) and etoposide may involve ongoing RNA synthesis in addition to ongoing DNA synthesis. V79 cells synchronized by mitotic shake-off were treated with topoisomerase poisons in the presence of inhibitors of nucleic acid synthesis. S-Phase V79 cells were more sensitive to the topoisomerase I poison camptothecin and the topoisomerase II poison m-AMSA than G1-phase cells. The greater sensitivity of S-phase cells to killing by m-AMSA and camptothecin was abolished during cotreatment, but not posttreatment, with aphidicolin, suggesting that ongoing DNA synthesis in involved in cell killing by both topoisomerase I and II poisons. Cotreatment with transcription inhibitors, such as 5,6-dichloro-1-beta-D-ribofuranosyl benzimidazole or cordycepin, partially protected cells from the cytotoxic effects of m-AMSA but had no effect on camptothecin-mediated cytotoxicity. These results suggest that ongoing RNA transcription may be involved in cell killing by topoisomerase II poisons but not topoisomerase I poisons. Cotreatment with camptothecin reduced m-AMSA-mediated cytotoxicity in G1-phase V79 cells, suggesting a possible antagonism between topoisomerase I and II poisons. This antagonistic effect between topoisomerase I and II poisons could be explained by the strong inhibitory effect of camptothecin on RNA transcription.

Amsacrine↗