PubMed Health⌕ Search

Biomedical subjects

A M Morgan

Publications and source records attributed to A M Morgan.

At least 19 recordsLinked to original sources
PubMed2001

Evaluation of in vivo dose measurements for patients undergoing electron boost treatments.

This study evaluated p-type silicon diodes for use in in vivo dosimetry in clinical electron beams. A calibrated p-type silicon diode detector was used to measure the dose received by the patient in the centre of the field. Readings were corrected for energy, temperature and stand-off of the electron applicator from the patient surface. The mean difference between measured and prescribed dose was 1.04% (95% CI 0.72 to 1.36 %).

Breast Neoplasms↗
PubMed2001

The effect of carbon fiber couch inserts on surface dose with beam size variation.

There is little evidence in the literature regarding the effects of a carbon fiber insert on beam parameters with beam size variations. We demonstrated this effect and noted the magnitude of the change of surface dose induced. It was shown that use of the carbon fiber insert panel, despite providing minimal attenuation of the primary radiation, significantly decreased the skin-sparing effect. The magnitude of this decrease was relatively larger for smaller beam sizes. The surface dose was nearly 4 times as large when carbon was added to a 10 x 10-cm beam, and nearly double for a 40 x 40-cm beam.

Carbon↗
PubMed2000

IPEM guidelines on dosimeter systems for use as transfer instruments between the UK primary dosimetry standards laboratory (NPL) and radiotherapy centres.

United Kingdom dosimetry codes of practice have traditionally specified one electrometer for use as a secondary standard, namely the Nuclear Enterprises (NE) 2560 NPL secondary standard therapy level exposure meter. The NE2560 will become obsolete in the foreseeable future. This report provides guidelines to assist physicists following the United Kingdom dosimetry codes of practice in the selection of an electrometer to replace the NE2560 when necessary. Using an internationally accepted standard (BS EN 60731:1997) as a basis, estimated error analyses demonstrate that the uncertainty (one standard deviation) in a charge measurement associated with the NE2560 alone is approximately 0.3% under specified conditions. Following a review of manufacturers' literature, it is considered that modern electrometers should be capable of equalling this performance. Additional constructural and operational requirements not specified in the international standard but considered essential in a modern electrometer to be used as a secondary standard are presented.

Guidelines as Topic↗
PubMed1999

Diagnosis of attention-deficit/hyperactivity disorder in the office.

The evaluation of the child with ADHD can be a complex and time-consuming process. Because there are no specific diagnostic tests, the physician must rely on the old standard of history and observation. An approach to diagnosis has been outlined in this article, which views ADHD as one of many clinical expressions of a more generalized impairment of neurologic processing. This approach suggest that four separate areas should be investigated: family and medical history, behavior, cognition, and coordination, while searching for signs of impairment in each area. This can provide a framework for the private practitioner to effectively and efficiently evaluate a child for ADHD within a busy office practice.

Attention Deficit Disorder with Hyperactivity↗
PubMed1999

Management of stimulant medications in children with attention-deficit/hyperactivity disorder.

In the United States, considerable media attention has been given to the growing number of youth diagnosed with ADHD and treated with psychotropic medications. The efficacy of stimulant medications long has been recognized clinically and is well documented in research. Studies suggest that treatment with stimulant therapy, when properly done, is more effective than psychosocial interventions that did not yield any significant benefits on a range of behavioral, emotional, psychosocial, and academic measures. The purpose of this article is to provide clinicians with everything they need to know but were afraid to ask about stimulant therapy for children and adolescents with ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed1999

Commissioning a p-type silicon diode for use in clinical electron beams.

Commissioning measurements were carried out on a p-type silicon diode detector for use in patient monitoring in high energy electron beams. Characteristics specific to the diode were examined. The variation in diode sensitivity with dose per pulse was found to be less than 1% over a range 0.069-0.237 mGy/pulse. The diode exhibited a sensitivity variation with accumulated dose of 10% per kGy and a sensitivity variation with surface temperature of 0.26%/degree C. The dependence of the diode response on the direction of the incident electron beam was investigated. Results were found to exceed the manufacturer's specifications. Output factors measured with the diode agree to within 1.5% of those measured with an NACP-02 air ionization chamber. The detector showed a variation in response with energy of 0.8% over the energy range 4-15 MeV. Prior to introducing the diode into clinical use, an assessment of beam perturbation directly behind the diode was made. The maximum reduction in local dose directly behind the diode at a depth of 1.0 cm below the surface was approximately 13% at 4 and 15 MeV.

Electrons↗
PubMed1999

Verbal fluency in children: developmental issues and differential validity in distinguishing children with attention-deficit hyperactivity disorder and two subtypes of dyslexia.

Previous research studies have shown that in adults, verbal fluency is impaired after lesion to the frontal lobes and left temporal lobe. More recently, there have been a few studies reported which indicated that in children, like adults, left hemisphere and frontal lesions result in pronounced effects on verbal fluency. The present study examined developmental differences in verbal fluency within a sample of 130 normal children, aged 6 to 12 years. Additionally, the same verbal fluency test was administered to two subgroups of children with developmental dyslexia and a group of children with attention-deficit/hyperactivity disorder (ADHD). Analysis of variance (ANOVA) revealed significant between-group differences by age in the normal children. Further, ANOVA demonstrated that the verbal fluency measure was clinically useful in differentiating the Language Disorder/Dysphonetic Dyslexic subgroup from the Visual-Spatial/Dyseidetic Dyslexic subgroup and the ADHD group, with the latter two groups performing within the average range.

Journal Article↗
PubMed1998

Toxicity and dosimetry of fractionated total body irradiation prior to allogeneic bone marrow transplantation using a straightforward radiotherapy technique.

Since 1989, we have used a relatively straightforward technique for giving total body irradiation (TBI), using anterior and posterior parallel opposed fields with the arms and fists acting as compensators. The dosimetry, toxicity and outcome of 48 patients (26 adults, 22 children) treated with TBI using this technique have been audited. A dose of 14.4 Gy in eight fractions over 4 days was prescribed to all patients with an unrelated donor and 12 Gy in six fractions over 3 days to those with a sibling donor. From May 1994, all children received 14.4 Gy because of a recommendation from the United Kingdom Children's Cancer Study Group. The range of lung dosimetry was -6% to +7% when the dose was specified to the lung maximum. The trunk doses were all within +/-10% of the prescribed dose. Doses to other regions of the body were less homogeneous but clinically acceptable in that the minimum doses were never less than -10% of the prescribed dose. Mucositis was the most common side effect; its treatment with opioids was more frequent after 14.4 Gy than after 12 Gy (P=0.0004) and in adults than in children (P=0.01). No cataracts have yet been seen in these patients. The radiation was not found to be a proven cause of clinical pneumonitis, although there was one death due to interstitial pneumonitis, which was likely to have been caused by cytomegalovirus infection in which radiation pneumonitis could not be excluded. There were no other suspected TBI-related deaths. In conclusion, this straightforward technique achieved acceptable dosimetry and was well tolerated.

Abdomen↗
PubMed1996

Persistent cutaneous larva migrans due to Ancylostoma species.

Cutaneous larva migrans is considered to be a self-limited parasitic infection of about 2 to 8 weeks' duration, though it has been reported to persist for as long as 55 weeks. In this case, a healthy 47-year-old white man had multiple serpiginous lesions typical of cutaneous larva migrans for 18 months. A biopsy taken 2 months before presentation showed a parasite consistent with Ancylostoma species deep in a hair follicle. The patient initially responded to topical thiabendazole, but relapse occurred when therapy was discontinued. Oral thiabendazole cured the problem after 22 months of infestation. Cutaneous larva migrans may sometimes be long-standing, here almost 2 years, even in a healthy patient. Organisms may reside deep in the hair follicles. Topical thiabendazole may not penetrate to this depth, necessitating oral thiabendazole therapy.

Administration, Oral↗
PubMed1996

Early identification of cerebral palsy using a profile of abnormal motor patterns.

OBJECTIVE: To determine whether a profile of abnormal motor patterns can identify children with cerebral palsy (CP) in the first year of life. METHODS: The Early Motor Pattern Profile (EMPP) consists of 15 items reflecting variations in muscle tone, reflexes, and movement that have been organized into a standardized format to provide the clinician with an objective picture of neurologic status. A three-point scoring system was applied to each item, delineating a clearly normal response from a clearly abnormal one and placing all partial or inconsistent responses in the middle. Twelve hundred forty-seven high-risk infants who were enrolled in a neonatal intensive care unit follow-up program were examined at 6 and/or 12 months' corrected age using the EMPP. These infants were followed to at least 36 months of age to distinguish those with CP from those with normal motor outcome or minimal impairment (no CP). RESULTS: Predictive validity of the EMPP at the 6- and 12-month examinations was determined using various pass-fail cutoffs. The optimal cutoff score at 6 months was between 9 and 10, at which the positive predictive value was 89.4, sensitivity was 87.1, and specificity was 97.8. The optimal cutoff score at 12 months was between 3 and 4, at which the positive predictive value was 91.0, sensitivity was 91.5, and specificity was 97.9. CONCLUSIONS: The EMPP offers the clinician an effective instrument to identify children in the first year of life who are at greatest risk for the development of CP. The EMPP can be incorporated into a routine health maintenance visit, adding only a few minutes to the process, and has high sensitivity and specificity.

Cerebral Palsy↗
PubMed1993

The incidence of deep venous thrombosis in patients with superficial thrombophlebitis of the lower limbs.

PURPOSE: The purpose of this study was, first, to determine the incidence of underlying occult deep venous thrombosis (DVT) in patients with superficial thrombophlebitis and, second, to see if any risk factors are helpful in identifying these patients. METHODS: Forty-four consecutive patients with a clinical and duplex ultrasound-confirmed diagnosis of superficial thrombophlebitis were assessed for DVT. All patients had a duplex ultrasound study of the deep venous system. Standard thrombosis risk factors were assessed for each patient. RESULTS: Ten patients (23%) had DVT. All cases were clinically occult. One patient had propagated thrombus in the common femoral vein. Three patients had popliteal vein thrombi. The remaining patients had calf vein thrombus only. Four of these were not in continuity with the superficial thrombus. The site of the superficial thrombophlebitis was not predictive of DVT. None of the known venous thrombotic risk factors were helpful in identifying patients at risk for DVT. CONCLUSION: Noninvasive deep venous studies are recommended in all patients with lower limb superficial thrombophlebitis because of the high incidence of occult DVT. Patients with DVT can then be treated appropriately.

Female↗
PubMed1993

Neuroendocrine (Merkel cell) carcinoma with an intraepidermal component.

We present 11 cases of primary neuroendocrine (Merkel cell) carcinoma of the skin with an intraepidermal component that were identified in a larger review of Merkel cell carcinomas. Among these is a case with a follow-up of over 11 years in which the primary lesion appeared as bowenoid dysplasia, with subsequent recurrences as intraepidermal Merkel cell carcinoma with focal tubular differentiation, and then with dermal invasion and lymph node metastasis. In addition to immunohistochemical markers commonly used in the identification of Merkel cell carcinomas (neuron-specific enolase and cytokeratin), these tumors stained with Ber-EP4, an immunohistochemical marker used to identify carcinomas. We believe that these histopathologic and immunohistochemical features further confirm that Merkel cell carcinomas represent an epithelial tumor with the potential for neuroendocrine and adnexal differentiation.

Aged↗
PubMed1992

Spindle cell neoplasms coexpressing cytokeratin and vimentin (metaplastic squamous cell carcinoma).

Spindle cell squamous carcinoma (SCSC) and atypical fibroxanthoma (AFX) are both spindle cell neoplasms (SCN) that usually arise in areas of solar or ionizing radiation of elderly patients. Both lesions have a similar biologic behavior. In addition, the morphologic and ultrastructural similarities found in AFX and the spindle cell component of SCSC, have led some investigators to conclude that these tumors have a similar cell of origin. We studied 15 SCNs with no evidence of epithelial origin and no morphologic epithelial component, that showed immunohistochemical and ultrastructural evidence that would support metaplastic changes of a squamous cell carcinoma to a neoplasm with mesenchymal characteristics.

Aged↗
PubMed1991

Incidence and neurodevelopmental outcome of periventricular hemorrhage and hydrocephalus in a regional population of very low birth weight infants.

During the years 1984 to 1987, 459 very low birth weight (VLBW) infants were admitted to a state-designated Level III Neonatal Intensive Care Unit. Cerebral sonography performed in a standardized sequence and graded with the Papile scale diagnosed 97 (21.1%) children with periventricular hemorrhage (PVH). The incidence of PVH declined from a peak of 26.6% in 1985 to 16.4% in 1987, associated with an increase in the incidence of inborn admissions (including maternal transport) from 62.0% in 1984 to 80.4% in 1987. During initial hospitalization, the occurrence of both low-grade (Grades I and II) and high-grade PVH was associated with a significantly higher incidence of perinatal risk factors compared with a concurrent population of VLBW infants without PVH. Developmental follow-up was achieved in 93.3% of VLBW infants without PVH and 95.7% of VLBW infants with PVH who survived their initial hospitalization. The incidence of abnormal outcome ranged from 7 of 37 infants with Grade I PVH to 7 of 8 VLBW infants with Grade IV PVH. Only 1 of 16 VLBW infants with high-grade PVH demonstrated normal motor and cognitive development. Active hydrocephalus developed in 12 infants; 11 sustained a high-grade PVH. Appropriate treatment of intracranial hypertension did not modify the neurodevelopmental outcome. In conclusion, this regional population of VLBW infants demonstrated a decline in the incidence of PVH during the years 1984 to 1987 associated with an increase in the incidence of inborn admissions. The risk of abnormal neurodevelopmental outcome was elevated for all grades of PVH. A 12.0% incidence of hydrocephalus was associated with high-grade PVH, and appropriate treatment did not alter the poor prognosis.

Cerebral Hemorrhage↗
PubMed1990

Hydroxypropyl methylcellulose in extracapsular cataract surgery with intraocular lens implantation: intraocular pressure and inflammatory response.

We studied prospectively the effects of 2% hydroxypropylmethylcellulose (HPMC), instilled in to the anterior chamber during extracapsular cataract extraction with posterior chamber intraocular lens implantation in 122 patients. Significant pressure rise was noted at 12 and 24 hours post-operatively when HPMC was not removed at the end of surgery. This was prevented by washing HPMC from the anterior chamber at the end of surgery, or by using either acetazolamide or a combination of oxyphenbutazone and vitamin C without washing HPMC. There was no difference in intraocular inflammation between controls and the HPMC groups. The group receiving combined oxyphenbutazone and vitamin C had the least, the differences between these two groups being sufficient.

Acetazolamide↗