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1.
Transplant Proc ; 54(6): 1664-1670, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35914967

RESUMEN

Portopulmonary hypertension, a type of pulmonary arterial hypertension in the setting of cirrhotic or noncirrhotic portal hypertension, is associated with elevated morbidity and mortality during and after transplantation. Uncontrolled portopulmonary hypertension may prevent or delay listing for transplant candidates, and the prognosis without treatment and ultimately transplant is extremely poor. We present a 29-year-old White woman, who had a post-liver transplant at infancy due to biliary atresia. Later on, she developed extensive portal vein thrombosis and portopulmonary hypertension and underwent a multivisceral transplant (liver, stomach, pancreaticoduodenal complex, and small and large intestine). Preoperative mean pulmonary artery pressure was <30 mm Hg with a pulmonary vascular resistance of <300 dynes.s/cm5 on oral sildenafil and intravenous epoprostenol. Intraoperatively, management required comprehensive transfusion protocols, a careful balance between correcting blood loss and preventing thrombosis. Intravenous epoprostenol, sildenafil, milrinone, and inhaled nitric oxide were used to reduce elevated mean pulmonary artery pressure and right ventricular strain associated with vascular clamping, reperfusion, and massive fluid shifts. Nitric oxide and epoprostenol use unleashed antiplatelet effects on a patient already susceptible to coagulopathy. A multimodal and multidisciplinary approach continued throughout the surgery and in the postoperative period, which led to a successful outcome.


Asunto(s)
Hipertensión Portal , Hipertensión Pulmonar , Hipertensión Arterial Pulmonar , Adulto , Antihipertensivos/uso terapéutico , Epoprostenol/uso terapéutico , Femenino , Humanos , Hipertensión Portal/complicaciones , Hipertensión Pulmonar/complicaciones , Milrinona , Óxido Nítrico , Citrato de Sildenafil/uso terapéutico
2.
Phys Med ; 77: 64-74, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32791426

RESUMEN

Experimental measurement of Synchrotron Radiotherapy (SyncRT) doses is challenging, especially for Microbeam Radiotherapy (MRT), which is characterised by very high dynamic ranges with spatial resolutions on the micrometer scale. Monte Carlo (MC) simulation is considered a gold standard for accurate dose calculation in radiotherapy, and is therefore routinely relied upon to produce verification data. We present a MC model for Australian Synchrotron's Imaging and Medical Beamline (IMBL), which is capable of generating accurate dosimetry data to inform and/or verify SyncRT experiments. Our MC model showed excellent agreement with dosimetric measurement for Synchrotron Broadbeam Radiotherapy (SBBR). Our MC model is also the first to achieve validation for MRT, using two methods of dosimetry, to within clinical tolerances of 5% for a 20×20 mm2 field size, except for surface measurements at 5 mm depth, which remained to within good agreement of 7.5%. Our experimental methodology has allowed us to control measurement uncertainties for MRT doses to within 5-6%, which has also not been previously achieved, and provides a confidence which until now has been lacking in MRT validation studies. The MC model is suitable for SyncRT dose calculation of clinically relevant field sizes at the IMBL, and can be extended to include medical beamlines at other Synchrotron facilities as well. The presented MC model will be used as a validation tool for treatment planning dose calculation algorithms, and is an important step towards veterinary SyncRT trials at the Australian Synchrotron.


Asunto(s)
Radiometría , Sincrotrones , Australia , Método de Montecarlo , Fantasmas de Imagen , Dosificación Radioterapéutica , Planificación de la Radioterapia Asistida por Computador
3.
Phys Med Biol ; 65(24): 245033, 2020 12 18.
Artículo en Inglés | MEDLINE | ID: mdl-32101808

RESUMEN

In order to fully exploit the ballistic potential of particle therapy, we propose an online range monitoring concept based on time-of-flight (TOF)-resolved prompt gamma (PG) detection in a single proton counting regime. In a proof of principle experiment, different types of monolithic scintillating gamma detectors are read in time coincidence with a diamond-based beam hodoscope, in order to build TOF spectra of PG generated in a target presenting an air cavity of variable thickness. Since the measurement was carried out at low beam currents (< 1 proton/bunch) it was possible to reach excellent coincidence time resolutions, of the order of 100 ps (σ). Our goal is to detect possible deviations of the proton range with respect to treatment planning within a few intense irradiation spots at the beginning of the session and then carry on the treatment at standard beam currents. The measurements were limited to 10 mm proton range shift. A Monte Carlo simulation study reproducing the experiment has shown that a 3 mm shift can be detected at 2σ by a single detector of ∼1.4 × 10-3 absolute detection efficiency within a single irradiation spot (∼108 protons) and an optimised experimental set-up.


Asunto(s)
Terapia de Protones/métodos , Rayos gamma , Humanos , Método de Montecarlo , Fantasmas de Imagen
4.
Bone Joint J ; 99-B(2): 283-288, 2017 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-28148674

RESUMEN

AIMS: Computer hexapod assisted orthopaedic surgery (CHAOS), is a method to achieve the intra-operative correction of long bone deformities using a hexapod external fixator before definitive internal fixation with minimally invasive stabilisation techniques. The aims of this study were to determine the reliability of this method in a consecutive case series of patients undergoing femoral deformity correction, with a minimum six-month follow-up, to assess the complications and to define the ideal group of patients for whom this treatment is appropriate. PATIENTS AND METHODS: The medical records and radiographs of all patients who underwent CHAOS for femoral deformity at our institution between 2005 and 2011 were retrospectively reviewed. Records were available for all 55 consecutive procedures undertaken in 49 patients with a mean age of 35.6 years (10.9 to 75.3) at the time of surgery. RESULTS: Patients were assessed at a mean interval of 44 months (6 to 90) following surgery. The indications were broad; the most common were vitamin D resistant rickets (n = 10), growth plate arrest (n = 6) and post-traumatic deformity (n = 20). Multi-planar correction was required in 33 cases. A single level osteotomy was performed in 43 cases. Locking plates were used to stabilise the osteotomy in 33 cases and intramedullary nails in the remainder. Complications included two nonunions, one death, one below-knee deep vein thrombosis, one deep infection and one revision procedure due to initial under-correction. There were no neurovascular injuries or incidence of compartment syndrome. CONCLUSION: This is the largest reported series of femoral deformity corrections using the CHAOS technique. This series demonstrates that precise intra-operative realignment is possible with a hexapod external fixator prior to definitive stabilisation with contemporary internal fixation. This combination allows reproducible correction of complex femoral deformity from a wide variety of diagnoses and age range with a low complication rate. Cite this article: Bone Joint J 2017;99-B:283-8.


Asunto(s)
Fijadores Externos , Fémur/cirugía , Traumatismos de la Pierna/cirugía , Deformidades Congénitas de las Extremidades Inferiores/cirugía , Cirugía Asistida por Computador , Adolescente , Adulto , Anciano , Niño , Femenino , Fémur/anomalías , Fémur/diagnóstico por imagen , Fémur/lesiones , Fijación Interna de Fracturas , Humanos , Traumatismos de la Pierna/diagnóstico , Deformidades Congénitas de las Extremidades Inferiores/diagnóstico por imagen , Masculino , Persona de Mediana Edad , Procedimientos Quirúrgicos Mínimamente Invasivos , Osteotomía , Reproducibilidad de los Resultados , Estudios Retrospectivos , Cirugía Asistida por Computador/instrumentación , Adulto Joven
5.
Australas Phys Eng Sci Med ; 39(4): 943-950, 2016 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-27585452

RESUMEN

Alanine dosimeters from the National Physical Laboratory (NPL) in the UK were irradiated using kilovoltage synchrotron radiation at the imaging and medical beam line (IMBL) at the Australian Synchrotron. A 20 × 20 mm2 area was irradiated by scanning the phantom containing the alanine through the 1 mm × 20 mm beam at a constant velocity. The polychromatic beam had an average energy of 95 keV and nominal absorbed dose to water rate of 250 Gy/s. The absorbed dose to water in the solid water phantom was first determined using a PTW Model 31014 PinPoint ionization chamber traceable to a graphite calorimeter. The alanine was read out at NPL using correction factors determined for 60Co, traceable to NPL standards, and a published energy correction was applied to correct for the effect of the synchrotron beam quality. The ratio of the doses determined by alanine at NPL and those determined at the synchrotron was 0.975 (standard uncertainty 0.042) when alanine energy correction factors published by Waldeland et al. (Waldeland E, Hole E O, Sagstuen E and Malinen E, Med. Phys. 2010, 37, 3569) were used, and 0.996 (standard uncertainty 0.031) when factors by Anton et al. (Anton M, Büermann L., Phys Med Biol. 2015 60 6113-29) were used. The results provide additional verification of the IMBL dosimetry.


Asunto(s)
Absorción de Radiación , Alanina/química , Dosímetros de Radiación , Sincrotrones , Calibración , Diagnóstico por Imagen , Relación Dosis-Respuesta en la Radiación , Polimetil Metacrilato/química , Termodinámica , Incertidumbre , Agua/química , Rayos X
6.
Ann R Coll Surg Engl ; 98(7): 461-7, 2016 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-27388543

RESUMEN

Introduction Oesophagectomy for cancer is a challenging procedure with a five-year overall survival rate of 15-20%. Early enteral nutrition following oesophagectomy is a crucial component of the postoperative recovery and carries a significant impact on the outcome. Different methods of enteral feeding were conducted in our unit. The aim of this study was to examine the efficacy and safety of nasojejunal tube (NJT), jejunostomy tube (JT) and pharyngostomy tube (PT) feeding after oesophagectomy. Methods A retrospective review was carried out of prospectively collected data on patients with oesophageal cancer who underwent an oesophagectomy between 2011 and 2014. The primary outcome was feeding tube related complications such as occlusion, dislocation and leak. The secondary outcomes were length of stay and 30-day morbidity. Results A total of 90 oesophagectomies were included in the study. A NJT was inserted in 41 patients (45.6%), a JT was used in 14 patients (15.5%) and a PT was the route for enteral nutrition in 35 patients (38.9%). In total, five patients (5.5%) developed tube related complications. There were no tube related complications in the NJT group but one JT patient (7.1%) developed tube related cellulitis (p=0.189) and four PT patients (11.4%) developed tube related haemorrhage (p=0.544), tube dislocation (p=0.544) or cellulitis (p=0.189). The median length of stay and 30-day postoperative morbidity were similar between the groups. Conclusions NJT feeding is a less invasive, feasible route for early enteral nutrition following oesophagectomy. A randomised controlled trial is recommended to verify these findings.


Asunto(s)
Nutrición Enteral , Esofagectomía , Adulto , Anciano , Anciano de 80 o más Años , Nutrición Enteral/efectos adversos , Nutrición Enteral/métodos , Nutrición Enteral/estadística & datos numéricos , Neoplasias Esofágicas/cirugía , Femenino , Humanos , Tiempo de Internación/estadística & datos numéricos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Resultado del Tratamiento
7.
Phys Med Biol ; 61(11): 4201-22, 2016 06 07.
Artículo en Inglés | MEDLINE | ID: mdl-27192396

RESUMEN

The absolute dose delivered to a dynamically scanned sample in the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter anticipated to be established as a primary standard for synchrotron dosimetry. The calorimetry was compared to measurements using a free-air chamber (FAC), a PTW 31 014 Pinpoint ionization chamber, and a PTW 34 001 Roos ionization chamber. The IMBL beam height is limited to approximately 2 mm. To produce clinically useful beams of a few centimetres the beam must be scanned in the vertical direction. In practice it is the patient/detector that is scanned and the scanning velocity defines the dose that is delivered. The calorimeter, FAC, and Roos chamber measure the dose area product which is then converted to central axis dose with the scanned beam area derived from Monte Carlo (MC) simulations and film measurements. The Pinpoint chamber measures the central axis dose directly and does not require beam area measurements. The calorimeter and FAC measure dose from first principles. The calorimetry requires conversion of the measured absorbed dose to graphite to absorbed dose to water using MC calculations with the EGSnrc code. Air kerma measurements from the free air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. The two ionization chambers are secondary standards requiring calibration with kilovoltage x-ray tubes. The Roos and Pinpoint chambers were calibrated against the Australian primary standard for air kerma at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Agreement of order 2% or better was obtained between the calorimetry and ionization chambers. The FAC measured a dose 3-5% higher than the calorimetry, within the stated uncertainties.


Asunto(s)
Calorimetría/métodos , Dosis de Radiación , Dosímetros de Radiación/normas , Calibración , Calorimetría/normas , Grafito , Humanos , Radioterapia/instrumentación , Radioterapia/métodos , Estándares de Referencia , Sincrotrones , Rayos X
8.
Phys Med Biol ; 60(22): 8625-41, 2015 Nov 21.
Artículo en Inglés | MEDLINE | ID: mdl-26510214

RESUMEN

Small circular beams of synchrotron radiation (0.1 mm and 0.4 mm in diameter) were used to irradiate ionization chambers of the types commonly used in radiotherapy. By scanning the chamber through the beam and measuring the ionization current, a spatial map of the dosimetric response of the chamber was recorded. The technique is able to distinguish contributions to the large-field ionization current from the chamber walls, central electrode and chamber stem. Scans were recorded for the NE 2571 Farmer chamber, the PTW 30013, IBA FC65-G Farmer-type chambers, the NE 2611A and IBA CC13 thimble chambers, the PTW 31006 and 31014 pinpoint chambers, the PTW Roos and Advanced Markus plane-parallel chambers, and the PTW 23342 thin-window soft x-ray chamber. In all cases, large contributions to the response arise from areas where the incident beam grazes the cavity surfaces. Quantitative as well as qualitative information about the relative chamber response was extracted from the maps, including the relative contribution of the central electrode. Line scans using monochromatic beams show the effect of the photon energy on the chamber response. For Farmer-type chambers, a simple Monte Carlo model was in good agreement with the measured response.


Asunto(s)
Modelos Teóricos , Fantasmas de Imagen , Radiometría/instrumentación , Radiometría/métodos , Sincrotrones/instrumentación , Electrodos , Humanos , Método de Montecarlo , Fotones , Rayos X
9.
Br J Dermatol ; 172(2): 522-6, 2015 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-25040076

RESUMEN

Pyoderma gangrenosum (PG) is a rare, noninfectious, inflammatory disease characterized by neutrophilic infiltration of the dermis and destruction of tissue. PG is a diagnostic challenge, which can lead to late diagnosis, delayed treatment and detrimental surgical interventions. We describe a presentation not previously reported, affecting deep muscle and tendon leading to tendon rupture. Furthermore, we show the multidisciplinary team approach to management of a patient with PG and the reconstructive surgical element. A 31-year-old woman presented with a rapid onset painful, tender, left calf and ankle, which was associated with a mild flare of ulcerative colitis. Investigations revealed a white cell count of 26 × 10(9) cells L(-1) , a C-reactive protein count of 226 mg L(-1) , no deep vein thrombosis on ultrasound, no bone or joint involvement on X-ray and no organisms on joint aspirate. Debridement was undertaken after the left ankle developed a foul-smelling discharging wound. Repeat debridement led to worsening of the condition (pathergy). Intraoperative tissue cultures and microscopy showed no evidence of fungi, bacteria or mycobacteria. Histology showed granulation, inflammatory infiltrate, abscess formation and focal necrotizing vasculitis. Dermatology opinion confirmed PG. Awareness of the diagnosis of PG, and early involvement of dermatology, in a rapidly progressing wound is essential to avoid delayed treatment and prevent worsening through pathergy.


Asunto(s)
Tendón Calcáneo , Piodermia Gangrenosa/complicaciones , Tendinopatía/etiología , Adulto , Desbridamiento , Femenino , Humanos , Piodermia Gangrenosa/cirugía , Rotura Espontánea/etiología , Rotura Espontánea/cirugía , Tendinopatía/cirugía , Resultado del Tratamiento
10.
Bone Joint J ; 96-B(7): 956-62, 2014 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-24986951

RESUMEN

Unstable bicondylar tibial plateau fractures are rare and there is little guidance in the literature as to the best form of treatment. We examined the short- to medium-term outcome of this injury in a consecutive series of patients presenting to two trauma centres. Between December 2005 and May 2010, a total of 55 fractures in 54 patients were treated by fixation, 34 with peri-articular locking plates and 21 with limited access direct internal fixation in combination with circular external fixation using a Taylor Spatial Frame (TSF). At a minimum of one year post-operatively, patient-reported outcome measures including the WOMAC index and SF-36 scores showed functional deficits, although there was no significant difference between the two forms of treatment. Despite low outcome scores, patients were generally satisfied with the outcome. We achieved good clinical and radiological outcomes, with low rates of complication. In total, only three patients (5%) had collapse of the joint of > 4 mm, and metaphysis to diaphysis angulation of 75º, and five patients (9%) with displacement of > 4 mm. All patients in our study went on to achieve full union. This study highlights the serious nature of this injury and generally poor patient-reported outcome measures following surgery, despite treatment by experienced surgeons using modern surgical techniques. Our findings suggest that treatment of complex bicondylar tibial plateau fractures with either a locking plate or a TSF gives similar clinical and radiological outcomes.


Asunto(s)
Fijación de Fractura/métodos , Fracturas de la Tibia/cirugía , Adolescente , Adulto , Anciano , Placas Óseas , Fijadores Externos , Femenino , Fijación Interna de Fracturas/métodos , Indicadores de Salud , Humanos , Masculino , Persona de Mediana Edad , Radiografía , Estudios Retrospectivos , Fracturas de la Tibia/diagnóstico por imagen , Resultado del Tratamiento , Adulto Joven
11.
Oncogene ; 31(27): 3298-309, 2012 Jul 05.
Artículo en Inglés | MEDLINE | ID: mdl-22020329

RESUMEN

Molecular profiling has allowed a more precise classification of human cancers. With respect to breast cancer, this approach has been used to identify five subtypes; luminal A, luminal B, HER2-enriched, basal-like and claudin-low. In addition, this approach can be used to determine the type of tumor represented by particular cell lines or transgenic animal models. Therefore, this approach was utilized to classify the mammary tumors that develop in MTB-IGFIR transgenic mice. It was determined that the primary mammary tumors, which develop due to elevated expression of the type I insulin-like growth factor receptor (IGF-IR) in mammary epithelial cells, most closely resemble murine tumors with basal-like or mixed gene expression profiles and with human basal-like breast cancers. Downregulation of IGF-IR transgene in MTB-IGFIR tumor-bearing mice leads to the regression of most of the tumors, followed by tumor reappearance in some of the mice. These tumors that reappear following IGF-IR transgene downregulation do not express the IGF-IR transgene and cluster with murine mammary tumors that express a mesenchymal gene expression profile and with human claudin-low breast cancers. Therefore, IGF-IR overexpression in murine mammary epithelial cells induces mammary tumors with primarily basal-like characteristics, whereas tumors that develop following IGF-IR downregulation express a gene signature that most closely resembles human claudin-low breast tumors.


Asunto(s)
Neoplasias de la Mama/clasificación , Neoplasias de la Mama/genética , Claudinas/metabolismo , Neoplasias Mamarias Experimentales/clasificación , Neoplasias Mamarias Experimentales/genética , Receptor IGF Tipo 1/genética , Transcriptoma , Transgenes/genética , Animales , Neoplasias de la Mama/metabolismo , Femenino , Expresión Génica , Regulación Neoplásica de la Expresión Génica , Humanos , Neoplasias Mamarias Experimentales/patología , Ratones
12.
Radiat Prot Dosimetry ; 150(3): 359-74, 2012 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-22042968

RESUMEN

Low-energy alpha particle and proton heavy charged particle (HCP) relative thermoluminescence (TL) efficiencies are calculated for the major dosimetric glow peak in LiF:Mg,Cu,P (MCP-N) in the framework of track structure theory (TST). The calculations employ previously published TRIPOS-E Monte Carlo track segment values of the radial dose in condensed phase LiF calculated at the Instituto National de Investigaciones Nucleares (Mexico) and experimentally measured normalised (60)Co gamma-induced TL dose-response functions, f(D), carried out at the Institute of Nuclear Physics (Poland). The motivation for the calculations is to test the validity of TST in a TL system in which f(D) is not supralinear (f(D) >1) and is not significantly dependent on photon energy contrary to the behaviour of the dose-response of composite peak 5 in the glow curve of LiF:Mg,Ti (TLD-100). The calculated HCP relative efficiencies in LiF:MCP-N are 23-87% lower than the experimentally measured values, indicating a weakness in the major premise of TST which exclusively relates HCP effects to the radiation action of the secondary electrons liberated by the HCP slowing down. However, an analysis of the uncertainties involved in the TST calculations and experiments (i.e. experimental measurement of f(D) at high levels of dose, sample light self-absorption and accuracy in the estimation of D(r), especially towards the end of the HCP track) indicate that these may be too large to enable a definite conclusion. More accurate estimation of sample light self-absorption, improved measurements of f(D) and full-track Monte Carlo calculations of D(r) incorporating improvements of the low-energy electron transport are indicated in order to reduce uncertainties and enable a final conclusion.


Asunto(s)
Partículas alfa , Cobre/química , Compuestos de Litio/química , Magnesio/química , Protones , Dosimetría Termoluminiscente/métodos , Relación Dosis-Respuesta en la Radiación , Transferencia Lineal de Energía , Matemática , Método de Montecarlo , Fotones , Titanio/química
13.
Int J Surg Case Rep ; 2(7): 185-7, 2011.
Artículo en Inglés | MEDLINE | ID: mdl-22096722

RESUMEN

INTRODUCTION: Pneumatosis intestinalis is a rare condition affecting 0.03% of the population. It has a myriad of aetiological causes and hence presentation can vary immensely. The management of symptomatic pneumatosis intestinalis in an acute and outpatient setting remains a challenge to both physicians and surgeons. CASE PRESENTATION: We present a case of a 79 year old who presented in a gastroenterology outpatients department with a history suggestive of intermittent small bowel obstruction associated with abdominal pain aggravated by eating and posture. He was found to have signs suggestive of Marfan's syndrome. Computed tomography demonstrated extensive pneumatosis intestinalis of the small bowel. Due to deterioration in symptoms, an exploratory laparotomy was performed demonstrating segmental small bowel pneumatosis intestinalis secondary to a hypermobile mesentery. CONCLUSION: This case highlights the importance of both surgical and gastroenterology expertise in successfully managing symptomatic pneumatosis intestinalis.

14.
Radiat Prot Dosimetry ; 145(4): 356-72, 2011 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-21106636

RESUMEN

Three outstanding effects of ionisation density on the thermoluminescence (TL) mechanisms giving rise to the glow peaks of LiF:Mg,Ti (TLD-100) are currently under investigation: (1) the dependence of the heavy charged particle (HCP) relative efficiency with increasing ionisation density and the effectiveness of its modelling by track structure theory (TST), (2) the behaviour of the TL efficiency, f(D), as a function of photon energy and dose. These studies are intended to promote the development of a firm theoretical basis for the evaluation of relative TL efficiencies to assist in their application in mixed radiation fields. And (3) the shape of composite peak 5 in the glow curve for various HCP types and energies and following high-dose electron irradiation, i.e. the ratio of the intensity of peak 5a to peak 5. Peak 5a is a low-temperature satellite of peak 5 arising from electron-hole capture in a spatially correlated trapping centre/luminescent centre (TC/LC) complex that has been suggested to possess a potential as a solid-state nanodosemeter due to the preferential electron/hole population of the TC/LC at high ionisation density. It is concluded that (1) the predictions of TST are very strongly dependent on the choice of photon energy used in the determination of f(D); (2) modified TST employing calculated values of f(D) at 2 keV is in agreement with 5-MeV alpha particle experimental results for composite peak 5 but underestimates the 1.5-MeV proton relative efficiencies. Both the proton and alpha particle relative TL efficiencies of the high-temperature TL (HTTL) peaks 7 and 8 are underestimated by an order of magnitude suggesting that the HTTL efficiencies are affected by other factors in addition to radial electron dose; (3) the dose-response supralinearity of peaks 7 and 8 change rapidly with photon energy: this behaviour is explained in the framework of the unified interaction model as due to a very strong dependence on photon energy of the relative intensity of localised recombination and (4) the increased width and decrease in T(max) of composite peak 5 as a function of ionisation density is due to the greater relative intensity of peak 5a (a low-temperature component of peak 5 arising from two-energy transfer events, which leads to localised recombination).


Asunto(s)
Fluoruros/química , Compuestos de Litio/química , Magnesio/química , Método de Montecarlo , Nanotecnología/instrumentación , Dosis de Radiación , Dosimetría Termoluminiscente/métodos , Titanio/química , Relación Dosis-Respuesta en la Radiación , Electrones , Diseño de Equipo , Calor , Iones , Fotones , Pesos y Medidas
15.
Radiat Prot Dosimetry ; 138(4): 320-33, 2010 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-19934115

RESUMEN

The dose response of LiF:Mg,Ti (TLD-100) chips was measured from 1 to 50,000 Gy using 100 keV X rays at the European Synchroton Radiation Facility. Glow curves were deconvoluted into component glow peaks using a computerised glow curve deconvolution (CGCD) code based on first-order kinetics. The normalised dose response, f(D), of glow peaks 4 and 5 and 5b (the major components of composite peak 5), as well as peaks 7 and 8 (two of the major components of the high-temperature thermoluminescence (HTTL) at high levels of dose) was separately determined and theoretically interpreted using the unified interaction model (UNIM). The UNIM is a nine-parameter model encompassing both the irradiation/absorption stage and the thermally induced relaxation/recombination stage with an admixture of both localised and delocalised recombination mechanisms. The effects of radiation damage are included in the present modelling via the exponential removal of luminescent centres (LCs) at high dose levels. The main features of the experimentally measured dose response are: (i) increase in f(D)(max) with glow peak temperature, (ii) increase in D(max) (the dose level at which f(D)(max) occurs) with increasing glow peak temperature, and (iii) decreased effects of radiation damage with increasing glow peak temperature. The UNIM interpretation of this behaviour requires both strongly decreasing values of ks (the relative contribution of localised recombination) as a function of glow peak temperature and, as well, significantly different values of the dose-filling constants of the trapping centre (TC) and LC for peaks 7 and 8 than those used for peaks 4 and 5. This suggests that different TC/LC configurations are responsible for HTTL. The relative intensity of peak 5a (a low-temperature satellite of peak 5 arising from localised recombination) was found to significantly increase at higher dose levels due to preferential electron and hole population of the trapping/recombination complex giving rise to composite glow peak 5. It is also demonstrated that possible changes in the trapping cross section of the LC and the competitive centres due to increasing sample/glow peak temperature do not significantly influence these observations/conclusions.


Asunto(s)
Fluoruros/efectos de la radiación , Compuestos de Litio/efectos de la radiación , Compuestos de Magnesio/efectos de la radiación , Modelos Teóricos , Dosimetría Termoluminiscente , Titanio/efectos de la radiación , Calor , Dosis de Radiación , Rayos X
16.
Arch Dis Child ; 94(12): 938-43, 2009 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19689968

RESUMEN

UNLABELLED: OBJECTIVES, SETTING AND PATIENTS: With complete case referral for prolonged parenteral nutrition (PN) beyond term equivalent, serving a stable population of 1.25 million people, we describe the long-term outcome and survival of patients referred to an intestinal failure (IF) nutrition support team over the first 8 years of existence at a regional paediatric centre, and extrapolate to potential numbers of national home parenteral nutrition (HPN) cases and intestinal transplantation data. DESIGN AND OUTCOME MEASURES: Retrospective analysis detailing patient demographics, interventions, use of HPN, occurrence of intestinal failure-associated liver disease (IFALD), and outcomes of enteral adaptation, survival, and referral for and receipt of organ transplantation. RESULTS: 23 patients were referred over 8 years, 20 being PN dependent within the neonatal period. Diagnoses included short bowel syndrome (SBS) (18), neuromuscular abnormalities (4) and congenital enterocyte disorder (1). 12 696 days of PN were delivered with 314 confirmed episodes of sepsis at a median of 12 episodes per patient. 144 central venous catheters (CVCs) were required at a median of four per patient. IFALD occurred in 17 (73%) patients, with 10 (44%) referred for transplant assessment. Thirteen (56%) children received HPN. Overall mortality was 44%. A significant predictor for survival in the SBS group was residual bowel >40 cm (82% vs 28%, p = 0.049). CONCLUSIONS: Survival for IF at 56% was lower than reported from non-UK supra-regional centres, and nationally collected data, possibly reflecting pre-selected referral populations. Data from regional centres with complete ascertainment may be important both when counselling parents and when planning regional and national HPN and IF specialist services.


Asunto(s)
Síndromes de Malabsorción/epidemiología , Peso al Nacer , Cateterismo Venoso Central/estadística & datos numéricos , Colestasis Intrahepática/epidemiología , Colestasis Intrahepática/etiología , Edad Gestacional , Humanos , Lactante , Recién Nacido , Intestino Delgado/trasplante , Síndromes de Malabsorción/complicaciones , Síndromes de Malabsorción/terapia , Evaluación de Necesidades , Nutrición Parenteral en el Domicilio/estadística & datos numéricos , Pronóstico , Derivación y Consulta/estadística & datos numéricos , Programas Médicos Regionales , Estudios Retrospectivos , Síndrome del Intestino Corto/complicaciones , Síndrome del Intestino Corto/epidemiología , Síndrome del Intestino Corto/terapia , Análisis de Supervivencia , Resultado del Tratamiento , Reino Unido/epidemiología
17.
J Vasc Access ; 9(4): 231-5, 2008.
Artículo en Inglés | MEDLINE | ID: mdl-19085891

RESUMEN

OBJECTIVE: Vascular access (VA) procedures are rapidly becoming the most prevalent surgery in the United States. It is estimated that there will be over 500,000 VA procedures done this year. Previously, surgeons in the US were attempting many more non-autogenous grafts than autogenous fistulae. In recent years, there has been a great push called 'Fistula First' to promote arteriovenous fistulae (AVF) as the first line of treatment vs. nonautogenous grafts. The goal of this investigation is to determine if too many fistulae are now being performed without attention to specific patient profiles. METHODS: A retrospective review of 1700 consecutive cases was performed by one surgeon at one institution between 1997 and 2005. Patients were categorized by demographics, co-morbidities, previous access procedures, access location, and type of graft. Patency was calculated. Kaplan-Meier, Cox regression and the Log Rank Test were used to analyze data. Access endpoints and complications were also documented. RESULTS: The study reviewed 1700 procedures. The median age was 52 (60.2% male) with 58.7% fistulae and 41.3% grafts. Median patency time was 10 months, with no statistically significant difference between access types. There was no significant difference in length of patency when comparing upper arm (70.1%), lower arm (24.5%) and thigh (5.4%). Graft infection rate was 9.5% and fistula infection rate was 0.9% (p<0.001). The overall infection rate was 4.5%, and decreased patency significantly (4 vs. 11 months). Thrombosis occurred in 24.7% of grafts and 9.0% of fistulae. Thrombosed grafts had better salvage rates (8 vs. 4 months, p<0.001). The data showed diabetes, HTN and HIV have no overall impact on patency. CONCLUSIONS: AVF and grafts are both useful in providing VA for patients requiring hemodialysis. Our data shows that grafts are equivalent in long-term patency. Therefore, it is apparent in those patients who are not candidates for an AV fistula; an AV graft for VA should be placed.


Asunto(s)
Derivación Arteriovenosa Quirúrgica , Implantación de Prótesis Vascular/instrumentación , Prótesis Vascular , Diálisis Renal , Grado de Desobstrucción Vascular , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Derivación Arteriovenosa Quirúrgica/efectos adversos , Prótesis Vascular/efectos adversos , Implantación de Prótesis Vascular/efectos adversos , Femenino , Oclusión de Injerto Vascular/etiología , Humanos , Estimación de Kaplan-Meier , Masculino , Persona de Mediana Edad , Selección de Paciente , Guías de Práctica Clínica como Asunto , Modelos de Riesgos Proporcionales , Infecciones Relacionadas con Prótesis/etiología , Reoperación , Estudios Retrospectivos , Medición de Riesgo , Infección de la Herida Quirúrgica/etiología , Trombosis/etiología , Factores de Tiempo , Resultado del Tratamiento , Adulto Joven
18.
Dis Colon Rectum ; 51(1): 10-9; discussion 19-20, 2008 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-18043968

RESUMEN

PURPOSE: A proportion of patients, who receive preoperative chemoradiation for locally advanced (T3, T4, NX) rectal cancer achieve a complete clinical response and a pathologic complete response in the region of 15 to 30 percent. Support is growing in the United Kingdom for the concept of "waiting to see" and not proceeding to radical surgery when a complete clinical response is observed. The purpose of this review was to use a literature search to assess how often complete clinical response is achieved after neoadjuvant chemoradiation, the concordance of this finding with pathologic complete response, and to determine whether it is feasible to observe patients who achieve complete clinical response rather than proceed to surgery. RESULTS: In total, 218 Phase I/II or retrospective studies and 28 Phase III trials of preoperative radiotherapy or chemoradiation were identified: 96 percent of trials documented the pathologic complete response, but only 38 trials presented data on the achievement of a complete clinical response/partial clinical response. Only five studies were found in which patients with clinically staged T2/T3 tumors were treated with radiotherapy/chemoradiation and did not routinely proceed to surgery and also reported on the long-term outcome of a "wait and see" policy. DISCUSSION: It remains uncertain whether the degree of response to chemoradiation in terms of complete clinical response or pathologic complete response is a useful clinical end point. Studies that include T3 rectal cancer are associated with high local recurrence rates after nonsurgical treatment. Few studies report long-term outcome after achievement of a complete clinical response. CONCLUSIONS: The end point of complete clinical response is inconsistently defined and seems insufficiently robust with only partial concordance with pathologic complete response. The rationale of a "wait and see" policy when complete clinical response status is achieved relies on retrospective observations, which are currently insufficient to support this policy except in patients who are recognized to be unfit for or refuse radical surgery.


Asunto(s)
Neoplasias del Recto/patología , Quimioterapia Adyuvante , Terapia Combinada , Determinación de Punto Final , Histocitoquímica , Humanos , Neoplasia Residual/patología , Cuidados Preoperatorios , Radioterapia Adyuvante , Ensayos Clínicos Controlados Aleatorios como Asunto , Neoplasias del Recto/tratamiento farmacológico , Neoplasias del Recto/radioterapia , Neoplasias del Recto/cirugía
19.
Int J Surg ; 5(6): 399-403, 2007 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-17631431

RESUMEN

BACKGROUND: The pre-operative staging in oesophageal cancer is often challenging and underestimation of the extent of the disease may lead to unnecessary surgery. AIM: To audit the use and assess the value of fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F FDG-PET) as a staging tool for thoracic oesophageal and gastro-oesophageal junction (GOJ) cancers in our oncological surgical practice. PATIENTS AND METHODS: Over a 3 year period, between 2002 and 2004, 134 patients with thoracic oesophageal or GOJ cancer were referred to our unit for treatment. The standard preoperative staging investigation in all cases was CT (thorax, abdomen and pelvis). A preoperative FDG-PET scan was further requested in 22 patients. The case notes of all the patients that underwent a FDG-PET scan were reviewed and compared with the preoperative imaging, the operative findings and the histopathology of the resected tumours. RESULTS: Eighteen men and 4 women with a median age of 65 (range 43-79) years were studied. After FDG-PET, 13 out of 22 patients (59%) were deemed suitable for tumour resection. Twelve of the 13 patients were fit to undergo surgery. At laparotomy, 2 of those (17%) were found inoperable due to widespread disease. The sensitivity of CT versus FDG-PET to detect infiltrated lymph nodes was 29% (95% CI: 3-70) versus 71% (95% CI: 29-96) (P=0.0412), whereas both tests had 67% specificity (95% CI: 9-99) in detecting lymph nodes. The sensitivity and the specificity of CT versus FDG-PET to detect distant organ metastases (M1b) were 33% (95% CI: 4-77) and 88% (95% CI: 47-99) versus 50% (95% CI: 6-93) and 100% (95% CI: 69-100), respectively (P>0.05). The FDG-PET regarding the N and M status differed from the CT in 11 patients and led to modification of the planned management in 5 of them. CONCLUSIONS: FDG-PET is more accurate than CT in defining N and M status. It can result in a reduction of unnecessary surgery in a significant number of patients. The combined PET-CT scan as a single imaging modality is expected to further improve diagnostic accuracy of FDG-PET.


Asunto(s)
Adenocarcinoma/diagnóstico por imagen , Carcinoma de Células Escamosas/diagnóstico por imagen , Neoplasias Esofágicas/diagnóstico por imagen , Unión Esofagogástrica , Tomografía de Emisión de Positrones , Adenocarcinoma/patología , Adenocarcinoma/cirugía , Adulto , Anciano , Carcinoma de Células Escamosas/patología , Carcinoma de Células Escamosas/cirugía , Neoplasias Esofágicas/patología , Neoplasias Esofágicas/cirugía , Esofagectomía , Femenino , Fluorodesoxiglucosa F18 , Humanos , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Cuidados Preoperatorios , Estudios Prospectivos , Radiofármacos , Cavidad Torácica
20.
J Orthop Surg (Hong Kong) ; 15(1): 12-4, 2007 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-17429110

RESUMEN

PURPOSE: To evaluate the intra- and inter-observer reproducibility of the Gartland radiographic classification for supracondylar humeral fractures in children. METHODS: Anteroposterior and lateral radiographs of 50 supracondylar humeral fractures in children were graded on 2 separate occasions by 4 orthopaedic surgeons according to the Wilkins modification of the Gartland classification. Data were analysed by calculating the Kappa values for intra- and inter-observer agreement to indicate the reproducibility of the classification. RESULTS: There was moderate inter-observer agreement, except for poor agreement over type I fractures. Type II fractures only showed fair to moderate agreement. Type III fractures and the flexion group showed good to very good agreement. Intra-observer agreement was good to very good. CONCLUSION: Surgeons should treat paediatric supracondylar humeral fractures based on an assessment of the degree of displacement rather than by employing the Gartland classification.


Asunto(s)
Fracturas del Húmero/diagnóstico por imagen , Fracturas del Húmero/cirugía , Humanos , Fracturas del Húmero/clasificación , Variaciones Dependientes del Observador , Radiografía , Reproducibilidad de los Resultados
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