Dose measurement in diagnostic radiology.
Explore the source record for details and available documents.
Humans↗
Biomedical subjects
P Cross
Publications and source records attributed to P Cross.
Prognostic significance of lymph node variables in squamous cell carcinoma of the vulva.
BACKGROUND: In patients with squamous cell carcinoma of the vulva, lymph nodal, surgicopathologic variables have been studied rarely, although lymph node status is by far the most important prognostic factor. This study was designed to investigate surgicopathologic variables of lymph node metastases to evaluate their prognostic significance. METHODS: In 75 patients with inguinal and/or pelvic lymph node metastases from squamous cell carcinoma of the vulva, the following parameters were studied: size and location of the tumor, depth of invasion, grade, lymph-vascular space involvement (LVSI), local immune reaction, presence and degree of dystrophic changes in the surrounding skin, FIGO stage, number of positive lymph nodes, greatest dimension of the metastasis within the lymph node, percentage of lymph node replacement, number of lymph nodes with replacement greater than 50%, number of lymph nodes replaced completely by tumor, extracapsular spread, and active immunologic response within the lymph node. RESULTS: Among the variables related to the primary carcinomas, only size of the tumor and LVSI were correlated with survival (P < 0.003 and P < 0.02, respectively). On the contrary, all pathologic variables regarding the lymph nodes significantly influenced survival by univariate analysis. On multivariate analysis, extracapsular spread was the most significant independent prognostic factor (P < 0.0004), followed by FIGO stage (P < 0.03). For patients with only one positive lymph node, the most important prognostic factor was the greatest dimension of the metastasis within the lymph node (P < 0.01). CONCLUSIONS: These data, if confirmed in larger series, can contribute to a more accurate identification of low and high risk patients and, therefore, to a more appropriate employment of adjuvant therapies.
Adult↗
Can children with Gilles de la Tourette syndrome edit their intentions?
In this paper we describe a cognitive mechanism, the Intention Editor, which is triggered whenever there are several intentions competing in parallel with each other. This mechanism is hypothesized to be a subcomponent of a larger mechanism, the Supervisory Attentional System (SAS: Shallice, 1988) which serves inhibition in general. The Intention Editor interrupts one of several simultaneously activated intentions, preventing it from executing its action, utterance, or thought. This mechanism appears to develop during the first five to six years of life. We propose that an impairment in the development of this mechanism may account for the triad of symptoms in children with Gilles de la Tourette Syndrome (GTS): involuntary movements, involuntary utterances, and obsessive thoughts. This mechanism is tested with normal children aged 3-6 years old, and with children with GTS, in two experiments. In Experiment 1, subjects were required to make one hand movement while inhibiting making a (different) hand movement that the other hand was simultaneously making. In Experiment 2, they were asked to say one thing while inhibiting saying something else. On both tasks, normal 6-year-olds were significantly better than normal 4-year-olds, but children with GTS performed worse than normal 6-year-olds, despite having a mean age of 12 years. These results constitute preliminary evidence for the theory that the Intention Editor is dysfunctional in GTS.
Child↗
Malignant pilomatrixoma with bone metastasis.
Explore the source record for details and available documents.
Aged↗
Doses in mammography: from the phantom to the patient.
While the use of a reference phantom is essential for dosimetry in acceptance testing and in regular quality control checks of a mammographic X-ray unit, it is also of importance to be able to estimate the patient dose in each individual investigation. Radiographic and physical data were analysed for a total of 212 women who between them were screened at three locations participating in a breast screening programme. The radiologists made estimates of the individual breast composition (% glandular/adipose ratio) at the film reporting sessions, and then the glandular doses were calculated by the auditor according to the NCRP 85 methodology. Arising from the data analysis of this dosimetry survey, a method is proposed to determine objectively patient breast composition from the photo-timed mAs for a given film optical density setting. This permits the NCRP calculations to be extended from breasts of 'average' (50/50) composition to breasts of individually determined composition. The diversity of the results between the three locations emphasises the need for regular audits of a mammographic X-ray unit's performance by an experienced radiological physicist, at least annually or after any major interventional service on the unit.
Adipose Tissue↗
The inter-rater reliability of the Gudjonsson Suggestibility Scale (form 2).
The Gudjonsson Suggestibility Scale (GSS) is widely used, particularly in the preparation of court reports, to derive information on the memory, suggestibility and confabulation of criminal suspects, victims and witnesses. The inter-rater reliability of all these measures was assessed by three raters, using the data of 101 subjects who were tested on the parallel form of the scale (GSS2). The intra-class correlation coefficients for all the memory and suggestibility measures were both very high (.951-.996) and highly significant (p < .001 for all measures), indicating a high level of inter-rater reliability. In contrast, whilst still highly significant (p < .001), the correlations for confabulation on immediate and delayed recall were much lower (.724 and .803, respectively). Guidelines are provided to refine the scoring of memory and suggestibility and to clarify the definition of confabulation.
Adolescent↗
The variability of language test scores in 3- and 4-year-old children of normal non-verbal intelligence: a brief research report.
Language testing plays an important role in the identification and monitoring of children with communication difficulties. However, the standardisation of many tests in common use remains far from satisfactory, especially at the lower age ranges. Comparisons between age-equivalent scores and chronological age also raise particular problems. The present paper focuses on the disparity between scores on different tests, in spite of the homogeneity of the group of children studied, and stresses the need for caution in the interpretation of test scores.
Child, Preschool↗
Routine linear accelerator calibration measurements and reports logged and generated by the treatment recording and verification computer.
A system is described for recording weekly calibration results for both photon and electron beams for two linear accelerators. The system accommodates all possible combinations of electrometers and ion chambers that can be used in the calibration procedures. The calibration data and dosimetric constants for the instrumentation are password protected with privileged access to make changes only available to the physicist manager of the therapy QA program.
Calibration↗
Lung cancer after radiation therapy for breast cancer.
Explore the source record for details and available documents.
Breast Neoplasms↗
Dosimetric implications of shifts in linear accelerator electron beam energy detected in routine constancy checks: a scanning film densitometry detection method.
The effects of change in electron beam energy are primarily manifest by changes in the range parameters of the depth ionisation/dose curve. Even for a change of up to 10% in the mean energy at the surface, E0, the dose to the depth of maximum on the central axis changes by less than 1%. Using as a limit of acceptability that the change in the therapeutic range (R85) should not be more than +/- 1.5 mm, the precision required by beam energy checking is that a change of 0.4 MeV in E0 should be detectable for all electron beams provided by the accelerator. To satisfy this criterion a routine method is proposed that uses therapy verification film exposed to the electron beam under a perspex wedge. The automatically processed film is then scanned with the densitometer of a beam data acquisition system (BDAS). The optical density versus distance plot is analysed using the BDAS computer that converts it to a quasi-depth dose curve and then calculates E0 and Ep,0 from the range parameters. The results for electron beams from "console" energies of 5 to 14 MeV show that the test criterion is within the capability of the method, and that the method is very practical for routine use in a quality assurance program.
Calibration↗
Tangential breast irradiation: simple improvements.
A series of studies using phantom and in vivo dosimetry measurements with diodes and thermoluminescent dosimetry were undertaken to establish whether simple methods are available to obtain improvements in homogeneity of dose in the treated breast, and reductions of dose to tissues outside it, when using tangential 6MV photon fields. These studies confirmed that the use of an appropriate lung density correction factor in the planning process is likely to cause a reduction in the amount of wedge compensation predicted to be necessary to produce reasonable dose homogeneity in the central axis of the beam. This was shown to be of value in eliminating potential areas of overdosage in the chest wall medial and lateral to the breast mound, and also in reducing unwanted doses to the contralateral breast and lung. Further reductions in dose to contralateral breast were confirmed to occur when the majority, or all, of the wedge compensation predicted necessary is placed on the lateral field and when the lateral tangential field is angled anteriorly in such a way as to align the posterior beam edges. Skin does above, below, and over the breast mound were observed to depend critically upon angle of incidence of the beam, with its consequent effect upon electron build-up, and the position of the breast contour in the beam. Skin doses above and below the breast mound were shown to exceed over the mound itself. This differential effect was observed to increase with increasing wedge compensation. In some situations skin doses below the breast mound nearly reached prescribed dose within the breast. The design and use of simple lead attenuators to reduce these areas of high dosage is discussed.
Breast Neoplasms↗
Post-operative necrotizing granulomas of the thyroid.
Explore the source record for details and available documents.
Female↗
Skin adnexal tumours.
Explore the source record for details and available documents.
Carcinoma, Merkel Cell↗
The use of parallel plate ion chambers to determine surface dose of a 6 MV photon beam.
The shape of the measured photon build-up curve and the surface dose are strongly dependent on the chamber geometry and side wall density. This study examines the response at the phantom surface to a 6 MV beam for the NACP and MARKUS chambers and also for the recently available commercialized ATTIX chamber; and checks the consistency of a published correction term applied to these chambers by comparison of the corrected data sets. The MARKUS and ATTIX chamber results of surface dose versus field size agree to within less than 0.5% over the field size range, whereas the NACP results show an average discrepancy of 22.1% (absolute percentage points), although the slope of the dose versus field size plot is very similar for all three chambers. It is confirmed then that the NACP electron chamber is not optimal for photon dosimetry at an air-tissue interface, and that the chamber of choice from fabrication material and geometrical considerations is the ATTIX solid water chamber.
Models, Structural↗
Breast conservation, the problem of treating the excision site effectively: physical criteria for the choice of technique used.
This paper examines how physical factors such as the depth of the excision cavity below the skin surface and its distance from the underlying lung may impact upon the choice between the use of an electron field (from a Varian Clinac 1800) or an implant (using a double plane of iridium-192 wires). Data have been derived from a phantom dosimetry experiment simulating different permutations of breast size and depth of excision cavity. An anthropomorphic female phantom with two different-sized wax breast phantoms has been used to simulate the clinical circumstances envisaged and isodose distributions have been estimated from an array of TLD readings. The biological significance of doses measured in skin and lung have been examined using the linear-quadratic (LQ) model. Both on physical and biological grounds, the results favour the implant under the experimental conditions adopted. The use of the electron beam to definitively treat the excision cavity (omitting breast tangents) to 60 Gy would result in unacceptable late effects in the skin and an observable incidence of pneumonitis if the excision cavity were near the chest wall. Small carcinogenic risks, particularly to the lung, are apparent with each modality, but may be moderated for the iridium-192 implant by a reduced carcinogenic potential associated with low-dose rate radiation. The use of the newer radionuclides iodine-125 and samarium-145, with less penetrating gamma ray emissions, might be preferred to iridium-192 from the point of view of bronchial carcinogenesis if definitive treatment of the excision cavity became widespread practice.
Brachytherapy↗
Faecal indicator bacteria on the hands and the effectiveness of hand-washing in Zimbabwe.
Two aspects of hand-washing were explored in this study. Mothers and children from 80 families in Zimbabwe were asked to wash their hands in the traditional manner in sterile water. Mothers were asked to answere a socio-economic questionnaire. By using the questionnaire and observations in conjunction with the microbiological data from hand-washing, factors were identified which contributed to high counts on the hands. These were: high relative humidity, living on a commercial farm, and having an infant in the family. Mothers and children 1-5 years of age had higher counts than children of 6-12 years. People recently involved in outdoor physical activities such as farming had higher counts than those involved in other activities. The traditional hand-washing method was also compared with two other hand-washing methods: hand-washing using soap and hand-washing using a container known as the mukombe. Hand-washing with soap was the most effective method closely followed by hand-washing using the mukombe. The least effective method was traditional hand-washing.
Adult↗
On a learning curve.
Explore the source record for details and available documents.
Computer User Training↗