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B Clubb

Publications and source records attributed to B Clubb.

7 recordsLinked to original sources
PubMed1994

Surface doses from combined electron/photon fields in a radiotherapy.

Using mixed modality treatments of photon and electron beams, some skin sparing can be acquired whilst administering a safer dose to crucial structures such as the spine or lung. The combination of 6MV X-rays and 12MeV electron beams in the treatment of breast nodes is a clinical example where such treatments are beneficial. By weighting the photon and electron beams accordingly, the surface dose and dose at depth can be changed whilst not dramatically varying the depth at which the 90% dose level is maintained. In order to accurately predict near surface dose, build up results were obtained using TLD extrapolation, Markus parallel plate and Attix parallel plate ionisation chambers in a solid water phantom. This data was then used to predict surface dose due to different beam weights. Depending on the weightings given to the photon and electron beams, the surface dose and dose at depth varies. For example, when 6MV X-rays and 12MeV electrons are combined the percentage dose at surface and 20cm depth is 46%/23%, 54%/20%, 61%/15% for 60/40, 50/50 and 40/60 X-ray/electron weightings respectively. For these weightings, the depth of the 90% level remained at 30mm. From a clinical point of view this data is important, showing that the 90% level of radiation does not vary in depth significantly provided the ratio of photon/electron weights is kept within a range of 60/40 to 40/60. However by varying the weightings, the ability to control dose to skin in particular to produce the optimum level for both areas whilst still delivering the required tumour dose is obtained.

Electrons↗
PubMed1992

Neutron therapy in Saudi Arabia: an overview and results of dose searching study in head and neck cancer.

The King Faisal Specialist Hospital and Research Centre is the only center in the Middle East that incorporates a neutron therapy facility. The neutron beam is produced by a cyclotron, which produces a beam by either a (d(15)+Be) or (p(26)+Be) reaction. The beam from the proton reaction is selected for therapy because of its superior physical characteristics. These were verified by an intercomparison conducted by the European Organization for Research on Treatment of Cancer (EORTC) Heavy Particle Therapy Group. Full beam data are presented. The first study in the neutron therapy Program is on the treatment of squamous cancers of the head and neck. This consists of two parts. Part I is a dose searching phase and Part II is a comparison of our current photon treatment versus neutrons using the neutron dose selected by Part I of the study. Results of the dose searching phase (Part I) are presented.

Carcinoma, Squamous Cell↗
PubMed1990

Neutron therapy for locally advanced head and neck squamous cell carcinoma: optimum dose search.

28 patients with locally advanced primary squamous cell carcinoma of the head and neck received neutron therapy and were randomized between two dose levels: 145 cGy n gamma x twelve fractions, three fractions per week (total 17.4 Gy n gamma). 155 cGy n gamma x twelve fractions, three fractions per week (total 18.6 Gy n gamma). Acute toxicity for skin, mucous membrane, salivary and subcutaneous tissues was graded using the EORTC/RTOG scoring system. Analysis indicates 17.4 Gy n gamma as "safe". A further twelve patients are to be assigned to the higher dose (18.6 Gy n gamma) before making a final dose selection.

Carcinoma, Squamous Cell↗
PubMed1989

Relative biological effectiveness (RBE) of p(26) + Be neutrons from the King Faisal Specialist Hospital and Research Centre CS-30 cyclotron measured by testis weight loss.

Testis weight loss of C3H and Swiss-Webster (SW) mice was used as endpoint to determine the relative biological effectiveness (RBE) of p(26) + Be fast neutrons with respect to Co-60 gamma irradiation. Percent weight loss versus dose curves showed two components. Comparing first component effects, the RBE was 3.4 (C3H) and 3.7 (SW); when the second component was used, the RBE was 2.6 and 2.7 (C3H), and 3.5 (SW). When percent weight loss was plotted versus log dose, parallel lines were obtained, giving an RBE of 3.9 and 4.1 (C3H), and 4.2 (SW). Results were compared with published values and RBE as a function of fast neutron energy was plotted. A good correlation was found. Discrepancies seem to be mostly due to the use of different baseline radiation. When a constant correction is made, most of the values fit a single line. The possibility of using this approach as a substitute for international comparisons is discussed.

Animals↗
PubMed1988

Nasopharyngeal carcinoma in Saudi Arabia: a retrospective study of 166 cases treated with curative intent.

A retrospective review was performed of the medical records of 166 adult patients with biopsy-proven carcinomas of the nasopharynx treated with curative intent at King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia. All patients were treated between June 1975 and December 1985 using megavoltage therapy equipment. Most patients presented with advanced nodal disease: 23 patients (13.9%) were N0, 16 patients (9.6%) were N1, 29 patients (17.5%) were N2, and 98 patients (59%) were N3. The overwhelming majority of patients had nonkeratinizing lesions (158/166). At the time of analysis, mean follow-up time was 24.2 months (range 2-108). Actuarial curves are presented for local/regional control as a function of T-stage and N-stage and for survival and time to development of distant metastases as a function of N-stage. At 4 years local/regional control was 70% for T1 lesions, 59% for T2 lesions, 30% for T3 lesions, and 35% for T4 lesions. There was little correlation between local/regional control and N-stage being about 50% at 4 years for all nodal subgroups. Only six patients exhibited an isolated first failure in the regional nodes alone, whereas 60 patients failed initially at the primary site (either alone or in conjunction with a simultaneous nodal failure). The development of distant metastases correlated to some extent with nodal disease ranging from 20% at 4 years for T1/T2 N0 patients to 70% for patients who initially presented with N3 disease. Survival data was more difficult to obtain due to cultural biases in a medically unsophisticated patient population. True survival curves are bounded by calculating actuarial curves in two ways: death as the failure endpoint and death plus lost-with-active-disease as failure endpoints. In terms of the latter curves, at 4 years "survival" ranged from 39% for patients with T1/T2 N0 lesions to 23% for patients with N3 lesions.

Adult↗
PubMedDate not supplied

X-ray surface dose measurements using TLD extrapolation.

Surface dose measurements in therapeutic x-ray beams are of importance in determining the dose to the skin of patients undergoing radiotherapy. Measurements were performed in the 6-MV beam of a medical linear accelerator with LiF thermoluminescence dosimeters (TLD) using a solid water phantom. TLD chips (surface area 3.17 x 3.17 cm2) of three different thicknesses (0.230, 0.099, and 0.038 g/cm2) were used to extrapolate dose readings to an infinitesimally thin layer of LiF. This surface dose was measured for field sizes ranging from 1 x 1 cm2 to 40 x 40 cm2. The surface dose relative to maximum dose was found to be 10.0% for a field size of 5 x 5 cm2, 16.3% for 10 x 10 cm2, and 26.9% for 20 x 20 cm2. Using a 6-mm Perspex block tray in the beam increased the surface dose in these fields to 10.7%, 17.7%, and 34.2% respectively. Due to the small size of the TLD chips, TLD extrapolation is applicable also for intracavity and exit dose determinations. The technique used for in vivo dosimetry could provide clinicians information about the build up of dose up to 1-mm depth in addition to an extrapolated surface dose measurement.

Electrons↗