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Biomedical subjects

P J Biggs

Publications and source records attributed to P J Biggs.

At least 19 recordsLinked to original sources
PubMed1992

Potentiation of CB 1954 cytotoxicity by reduced pyridine nucleotides in human tumour cells by stimulation of DT diaphorase activity.

The toxicity of CB 1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide] towards human cells was greatly enhanced by NADH (when foetal calf serum was present in the culture medium) and by nicotinamide riboside (reduced) (NRH), but not by nicotinate riboside (reduced). Co-treatment of human cells with CB 1954 and NADH resulted in the formation of crosslinks in their DNA. The toxicity produced by other DNA crosslinking agents was unaffected by reduced nicotinamide compounds. When caffeine was included in the medium, a reduction in the cytotoxicity of CB 1954 occurred. The toxicity experienced by human cell lines after exposure to CB 1954 and NADH was proportional to their levels of the enzyme DT diaphorase NAD(P)H dehydrogenase (quinone), EC 1.6.99.2. It is concluded that NRH, which we have shown to be a co-factor for rat DT diaphorase (Friedlos et al., Biochem Pharmacol 44: 25-31, 1992), is generated from NADH by enzymes in foetal calf serum, and stimulates the activity of human DT diaphorase towards CB 1954.

Antineoplastic Agents↗
PubMed1991

Remotely controlled positioning lasers.

Positioning lasers used in radiotherapy generally require little adjustment. When required, this is easy to do for sidelights, but can be difficult and time consuming for ceiling mounted lasers. For this purpose, we have modified a commercial positioning laser by incorporating a device for rotating the alignment adjustment screws. This device is driven by a pair of motors remotely controlled through a cable. Two units have been built and installed. In practice, experience with these drive units has shown that it is now easier to adjust the ceiling lasers than the sidelights. Adjustment sensitivity in both units is considerably better than 1 mm, so there is little problem aligning the laser quickly and accurately.

Equipment Design↗
PubMed1991

Analysis of field and custom block sizes used in radiation therapy--implications for multileaf collimator design.

The sizes of radiotherapy treatment fields using customized low melting point alloy blocks have been analyzed for a broad range of treatment fields in a busy radiotherapy department (i.e., 2,000 new cases per year), from small head and neck fields to large mantle fields. The results of this study show that 90% of the blocked fields have an equivalent field size defined by the collimator less than 26 cm and 80%, less than 21 cm. Measurements of the average size of the customized blocks indicate that along one axis 90% have lengths less than 15.5 cm and 80% have lengths less than 13 cm, while for the other axis, 90% have lengths less than 7 cm and 80%, less than 6 cm.

Equipment Design↗
PubMed1991

Calculation of shielding door thicknesses for radiation therapy facilities using the ITS Monte Carlo program.

Shielding calculations for door thicknesses for megavoltage radiotherapy facilities with mazes are generally straightforward. To simplify the calculations, the standard formalism adopts several approximations relating to the average beam path, scattering coefficients, and the mean energy of the spectrum of scattered radiation. To test the accuracy of these calculations, the Monte Carlo program, ITS, was applied to this problem by determining the dose and energy spectrum of the radiation at the door for 4- and 10-MV bremsstrahlung beams incident on a phantom at isocenter. This was performed for mazes, one termed "standard" and the other a shorter maze where the primary beam is incident on the wall adjacent to the door. The peak of the photon-energy spectrum at the door was found to be the same for both types of maze, independent of primary beam energy, and also, in the case of the conventional maze, of the primary beam orientation. The spectrum was harder for the short maze and for 10 MV vs. 4 MV. The thickness of the lead door for a short maze configuration was 1.5 cm for 10 MV and 1.2 cm for 4 MV vs. approximately less than 1 mm for a conventional maze. For the conventional maze, the Monte Carlo calculation predicts the dose at the door to be lower than given by NCRP 49 and NCRP 51 by about a factor of 2 at 4 MV but to be the same at 10 MV. For the short maze, the Monte Carlo predicts the dose to be a factor of 3 lower for 4 MV and about a factor of 1.5 lower for 10 MV. Experimental results support the Monte Carlo findings for the short maze.

Boston↗
PubMed1989

Pituitary adenocarcinoma in an acromegalic patient: response to bromocriptine and pituitary testing: a review of the literature on 36 cases of pituitary carcinoma.

There are 36 reported cases of metastatic pituitary carcinoma and almost half (44%) of these were associated with syndromes of hormonal hypersecretion. The case of a 56-year-old acromegalic man with cervical lymphatic and spinal metastases from a primary pituitary carcinoma is described. Elevated basal levels of plasma growth hormone (GH) and insulin growth factor-1/Somatomedin C (IGF-1/SmC) were found. GH levels did not increase after TRH or LHRH administration but decreased after L-Dopa and glucose. Immunostaining of the metastatic tumor for GH and electron microscopy findings confirmed the diagnosis of pituitary GH-secreting carcinoma. Striking clinical improvement and a 46% decrease in plasma GH levels were observed with bromocriptine treatment, although IGF-1/SmC levels increased during therapy. The clinical course of most reported cases of pituitary adenocarcinoma has been one of progressive intracranial expansion of a pituitary neoplasm. In only 25% were metastatic lesions discovered antemortem, and disabling symptomatology caused by metastases was rare. Only four previously reported patients of 36 with pituitary carcinoma had acromegaly.

Acromegaly↗
PubMed1988

Effect of a femoral head prosthesis on megavoltage beam radiotherapy.

A few patients undergoing pelvic irradiation present with a prosthetic hip. The presence of this metal object often interferes with the lateral treatment fields if a four-field box irradiation technique is used. Measurements of the effect such a prosthesis may have on the dose delivered to the pelvis for beams of 60Co gamma rays and 10 MV and 25 MV X-rays, as a function of field size and depth have been made. The results show a strong variation in the dose behind the prosthesis depending on the position of the measurement, with little or no increase through the center of the head or ball, but a sharp drop either around its circumference or along the stem of the prosthesis. Measurements made with ionization chambers through the head of the prosthesis indicate an average dose decrease of approximately 2% for 25 MV X rays and average increases of approximately 2% for 10 MV X rays and 5% for 60Co. There is little variation with field size and depth except close to the prosthesis, at 25 MV. Measurements also indicate an increase in dose close to the upstream surface of the prosthesis at all energies, but in the downstream direction, only the data at 25 MV shows an increase.

Hip Prosthesis↗
PubMed1988

Modification to the side rails of a manufacturer's couch.

A new version of a manufacturer's couch no longer has rails that span the length of each side of the couch. Modification of the original couch to include a spinal section and a stretched mylar top have split this rail into three sections. The gaps between these sections have been fitted with interlocking bars that can readily be removed. By this means, the usefulness of the earlier model couch in terms of attaching treatment devices and aids to any part of the side has been restored, while at the same time not interfering with the demands of the new, multipurpose couch.

Beds↗
PubMed1987

Theoretical shape of cavity to locate ovoid sources.

A mathematical technique is described for calculating the shape of a cavity required to position an ovoid source in its appropriate location within an applicator. This locus depends only on the assumption of a fixed angle between the source and wall that the source is touching. This technique has enabled us to avoid the problems of constructing ovoid cavities where the source sticks mid-course or does not seat properly, and has therefore resulted in a considerable saving of machine shop time and hence cost.

Brachytherapy↗
PubMed1987

Malignant rhabdoid tumor of the central nervous system.

Originally described and most frequently reported in association with the kidney, the malignant rhabdoid tumor (MRT) is a highly aggressive neoplasm with distinctive morphologic features. Extrarenal sites reported for this neoplasm include the liver, thymus, and various soft tissue sites. Young infants are affected with rare exceptions. We report the case of a 3-month-old boy who presented with hyperirritability and increasing head size over several weeks. The patient died following a two-week hospital stay marked by development of seizures, paralysis, and apnea. At autopsy, significant findings were limited to the central nervous system. The subarachnoid space contained neoplasm throughout, with multiple areas of parenchymal invasion. A predominating intraparenchymal mass was present in the inferior cerebellum contiguous with the neoplasm in the subarachnoid space and probably represented the site of origin. Microscopically, the neoplasm was composed of a highly cellular monomorphic population of polygonal cells with roughly ovoid vesicular nuclei and conspicuous nucleoli. Variable amounts of cytoplasm were present, and many cells contained a single, well-demarcated eosinophilic hyaline globule adjacent to the nucleus. Ultrastructurally, the cytoplasmic globules were composed of whorled aggregates of intermediate filaments. Immunoperoxidase studies confirmed that the filaments were composed, at least in part, of vimentin. The morphologic and immunohistochemical features are diagnostic of MRT, an entity of unknown histogenesis that has not been reported previously as a primary neoplasm of the CNS.

Brain Neoplasms↗
PubMed1986

Phaeohyphomycosis complicating compound skull fracture.

Intracranial infection is a well-recognized complication of compound skull fractures. In most cases various bacteria are identified as the etiologic agents. Fungal infection complicating open head trauma is unusual. We describe a patient who contracted fatal meningoencephalitis due to Drechslera spicifera, a rarely pathogenic soil saprophyte, after open head trauma.

Adult↗
PubMed1986

An afterloading vaginal applicator.

An afterloading vaginal applicator has been built that incorporates two ovoid sources and two tandem sources arranged in the shape of a T, the tandems forming the upright and the ovoids, orthogonal to the tandems, located at the ends of the crossbar. The body of the applicator was designed and constructed to correspond to the 90 cGy/hr contour for a source loading of 10 mg Ra Eq 137Cs for the ovoids and 15 mg Ra Eq 137Cs for the tandems. TLD measurements made at various points located around the applicator in the AP and lateral planes indicate agreement with the dose calculated by computer to within +/- 1%.

Brachytherapy↗
PubMed1986

Preoperative irradiation, lymphadenectomy, and 125iodine implantation for patients with localized carcinoma of the prostate.

Fifty-four patients with clinically and surgically localized prostatic carcinoma were treated with low-dose preoperative irradiation (1,050 cGy), pelvic lymphadenectomy, and interstitial 125Iodine implantation. The follow-up range is 2 to 9 years with a median follow-up of 5 years. Overall local tumor control is 92%. Actuarial 5-year survival is 86% and the actuarial disease-free survival at 5 years is 73%. Patients with poorly differentiated tumors have a significantly worse actuarial survival (62%) at 5 years than patients with well (95%) or moderately well differentiated tumors (93%), p = 0.04. Disease-free survival at 5 years was influenced by grade: well (100%), moderate (60%), and poor (48%), p = 0.03. Multivariate regression analysis indicates that only the degree of differentiation (p = 0.05) significantly impacts on survival. Both degree of differentiation (p = 0.04) and nodal status (p = 0.03) significantly influence disease-free survival. Potency has been maintained in 71% of patients potent at the time of implantation. Late reactions have been acceptable to date: bladder outlet obstruction (13%), mild proctitis (13%), cystourethritis (6%), incontinence (2%), and prostatic calculi (2%).

Adenocarcinoma↗
PubMed1986

A beam width improving device for a 25 MV X ray beam.

We have made a device that improves the dose distributions of X ray fields from a 25 MV accelerator by increasing the width of the 95% dose relative to the 50%. This device, called a beam width improving device, is a specially designed "compensator," consisting of two lead sheets taped onto a plastic blocking tray and is tailored for each field so that it can accommodate square fields, rectangular fields and fields with corner cuts. Comparison of profiles with and without this compensator indicates an increase in the width of the 95% dose of approximately 8 mm for small fields to approximately 14 mm for large fields.

Humans↗
PubMed1985

A diagnostic X ray field verification device for a 10 MV linear accelerator.

The quality of portal films taken at megavoltage energies is frequently poor, despite the use of various techniques such as lead screens to improve the image. When critical structures, such as the spinal cord, are to be blocked out of the treatment field, it is frequently difficult to determine whether the block is correctly placed. To solve this problem, a diagnostic X ray source has been mounted on the side of a 10 MV linear accelerator to provide accurate verification of patient positioning and location of shielding blocks. The coincidence between the mechanical, 10 MV and diagnostic X ray isocenters is about 1 mm. The system has been designed so that procedures to monitor this coincidence, and adjustment procedures to maintain it, are easily performed.

Humans↗
PubMed1985

Unilateral adrenal hemorrhage: an unusual presentation.

An asymptomatic adrenal mass was discovered in an elderly patient during evaluation of an abnormal urinary sediment. Exploratory laparotomy revealed an adrenal hematoma as the cause of the mass. No clear cause of the adrenal hemorrhage was identified, and postoperatively there was no evidence of adrenal insufficiency. Though rare, signs of adrenal hemorrhage may include an asymptomatic adrenal mass, and should be considered in the differential diagnosis of this problem.

Adrenal Gland Diseases↗