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Biomedical subjects

Paul Ryan

Publications and source records attributed to Paul Ryan.

9 recordsLinked to original sources
PubMed2005

Improved targeting device and computer navigation for accurate placement of brachytherapy needles.

Successful treatment of skull base tumors with interstitial brachytherapy requires high targeting accuracy for the brachytherapy needles to avoid harming vital anatomical structures. To enable safe placement of the needles in this area, we developed an image-based planning and navigation system for brachytherapy, which includes a custom-made mechanical positioning arm that allows rough and fine adjustment of the needle position. The fine-adjustment mechanism consists of an XYZ microstage at the base of the arm and a needle holder with two fine-adjustable inclinations. The rotation axes of the inclinations cross at the tip of the needle so that the inclinational adjustments do not interfere with the translational adjustments. A vacuum cushion and a noninvasive fixation frame are used for the head immobilization. To avoid mechanical bending of the needles due to the weight of attached tracking markers, which would be detrimental for targeting accuracy, only a single LED marker on the tail of the needle is used. An experimental phantom-based targeting study with this setup demonstrated that a positioning accuracy of 1.4 mm (rms) can be achieved. The study showed that the proposed setup allows brachytherapy needles to be easily aligned and inserted with high targeting accuracy according to a preliminary plan. The achievable accuracy is higher than if the needles are inserted manually. The proposed system can be linked to a standard afterloader and standard dosimetry planning module. The associated additional effort is reasonable for the clinical practice and therefore the proposed procedure provides a promising tool for the safe treatment of tumors in the skull base area.

Bone Neoplasms↗
PubMed2004

Prevalence of bone marrow micrometastases in esophagogastric cancer patients with and without neoadjuvant chemoradiotherapy.

BACKGROUND: Bone marrow micrometastases are present in a high proportion of patients undergoing curative resection for esophagogastric cancer. The incorporation of preoperative systemic therapies into these patients' treatment is widely practiced. This study investigates the effect of neoadjuvant chemoradiotherapy (CRT) on the incidence of micrometastases and the viability of detected tumor cells. MATERIALS AND METHODS: Rib bone marrow was obtained from patients (n = 106) in three centers, who were selected for potentially curative resection. Patients received neoadjuvant CRT plus surgery (n = 55), or surgery alone (n = 51). To detect micrometastases, mononuclear cells were isolated from fresh marrow and immediately stained immunohistochemically with an anti-cytokeratin-18 antibody using the APAAP technique. Tumor cell viability was assessed by immunohistochemical staining of marrow cell cultures for cytokeratin-positive cells. RESULTS: Micrometastases were detected in fresh marrow in 42% (23/55) of patients who received neoadjuvant CRT plus surgery, and in 67% (34/51) of patients treated with surgery alone. Viable tumor cells were demonstrated in 10 of 18 marrow cultures from CRT plus surgery cases. In this patient subset, combination of results of staining fresh and cultured marrow significantly increased micromet detection to 78%. CONCLUSIONS: A significant proportion of patients with esophagogastric cancer have disseminated viable tumor cells at time of surgery, irrespective of pre-operative treatment. The use of marrow culture in parallel with fresh marrow staining may increase the detection of micrometastases. The persistence of tumor cells resistant to systemic therapy may explain why these regimens fail in a majority of patients.

Adenocarcinoma↗
PubMed2004

Barriers to the effective management of depression in general practice.

OBJECTIVE: The aim of this study was to investigate the effects of prior general practice training in mental health and practice location on general practitioner (GP) attitudes toward depression, self-confidence in assessing and treating depressed patients, identification of doctor, patient and practice barriers to the effective care of depressed patients in general medical practice and GP-reported current clinical practice. METHOD: Fifty-two (out of 123) Divisions of General Practice that responded to an invitation to participate in the study distributed 608 anonymous surveys to a representative sample of GPs; 420 (69%) were returned. The questionnaire focused on current clinical practice, perceived barriers to care of depressed patients and doctors' self-efficacy for assessing and treating depressed patients. It also consisted of two scales, based upon previous research, designed to assess doctors' attitudes towards depression and depressed patients. RESULTS: General practitioners who had undertaken mental health education and training more often used non-pharmacological treatments (p=0.00), as did female GPs (p=0.00). Male GPs (p=0.00) and those in rural settings (p=0.01) more often prescribed medication for depression. Those without mental health training more often identified incomplete knowledge about depression as a barrier to its effective management (p=0.00). Urban-based GPs (p=0.04) and those with prior mental health training (p=0.00) were more confident in the use of non-pharmacological treatments. Female GPs without mental health training were the least confident in the use of these methods (p=0.01). Overall, GPs with mental health training were more positive in their attitudes toward depression and their treatment of these patients (p=0.00). Female GPs appeared more positive in their attitudes toward depression than male GPs (p=0.01), although the results were not entirely consistent. CONCLUSIONS: Participation in mental health training by GPs appears to be related to their attitudes toward depressed patients and to their confidence and abilities to diagnose and manage the common mental disorders effectively.

Adult↗
PubMed2004

Bacterial DNA within granulomas of patients with Crohn's disease--detection by laser capture microdissection and PCR.

OBJECTIVES: We previously reported the use of laser capture microdissection (LCM) and PCR to detect the presence of Mycobacterium paratuberculosis DNA in granulomas of patients with Crohn's disease. While this does not imply a cause-effect relationship, it may influence the disease process because bacterial DNA has immunomodulatory effects. The aim of this study was to determine whether DNA from nonmycobacterial commensals, such as Escherichia coli, is also increased in the granulomas of Crohn's disease. METHODS: Archival tissue from 15 surgical cases of Crohn's disease and 10 non-Crohn's granulomatous bowel disease controls were examined. Granulomas were isolated using LCM, and the extracted DNA was examined for presence of E. coli DNA by nested PCR amplification of a 135 base-pair segment of the uidA gene. RESULTS: E. coli DNA was detected in microdissected granulomas in 12/15 Crohn's disease patients and in 1/10 non-Crohn's control granulomas (p < 0.001). Also, E. coli DNA was detected in 8/15 Crohn's full-thickness sections and in 4/10 control full-thickness sections. CONCLUSIONS: E. coli DNA may be detected more frequently in Crohn's granulomas than in other non-Crohn's bowel granulomas. This may indicate a tendency for lumenal bacteria to colonize inflamed tissue, or may be due to increased uptake of bacterial DNA by gut antigen presenting cells. In light of previous detection of M. paratuberculosis DNA in Crohn's granulomas, the nonspecific nature of the type of bacterial DNA present in granulomas is evidence against any one bacterium having a significant causative role in Crohn's disease.

Crohn Disease↗
PubMed2004

Australian GPs' preferences for education about depression and related disorders.

OBJECTIVE: To investigate Australian general practitioners' experiences of accessing education about depression and their preferences for future education on depression and related disorders. METHOD: Six hundred and eight anonymous surveys were distributed to GPs through 52 rural and urban divisions of general practice; 420 were returned. RESULTS: Educational formats involving direct contact with people having mental health expertise were highly valued. Distance education and web based technologies were least used. In the previous year, women and older GPs had spent more time on education about depression. Most intended to undertake more such education in the future and said that education in psychosocial strategies would be very useful. General practitioners' attitudes to further education about depression were influenced by their gender, practice location, and their previous mental health training. DISCUSSION: More face-to-face training may be desirable to take advantage of GPs' willingness to spend more time on education about depression and related disorders.

Adult↗
PubMed2003

Leaf water relations of Eucalyptus cloeziana and Eucalyptus argophloia in response to water deficit.

Leaf water relations responses to limited water supply were determined in 7-month-old plants of a dry inland provenance of Eucalyptus argophloia Blakely and in a humid coastal provenance (Gympie) and a dry inland provenance (Hungry Hills) of Eucalyptus cloeziana F. Muell. Each provenance of E. cloeziana exhibited a lower relative water content at the turgor loss point, a lower apoplastic water content, a smaller ratio of dry mass to turgid mass and a lower bulk modulus of elasticity than the single provenance of E. argophloia. Osmotic potential at full turgor and water potential at the turgor loss point were significantly lower in E. argophloia and the inland provenance of E. cloeziana than in the coastal provenance of E. cloeziana. There was limited osmotic adjustment in response to soil drying in E. cloeziana, but not in E. argophloia. Between-species differences in water relations parameters were larger than those between the E. cloeziana provenances. Both E. cloeziana provenances maintained turgor under moderate water stress through a combination of osmotic and elastic adjustments. Eucalyptus argophloia had more rigid cell walls and reached lower water potentials with less reduction in relative water content than either of the E. cloeziana provenances, thereby enabling it to extract water from dryer soils.

Dehydration↗