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INTRODUCTION: Transrectal ultrasound-guided (TRUS) prostate biopsy is an established procedure for diagnosis of prostate cancer. Complications after TRUS biopsy are not well reported in Hong Kong. This study evaluated the 5-year incidences of TRUS biopsy complications and potential risk factors for those complications. METHODS: This was a retrospective review of biopsies performed from 2013 to 2017 in two local hospitals, using data retrieved from electronic medical records. The primary outcome was the occurrence of complications requiring either emergency attendances or hospitalisations within 30 days after biopsy. Potential risk factors were examined using multiple logistic regression analysis. RESULTS: In total, 1699 men were included (mean age ± standard deviation: 67 ± 7 years; median prostate-specific antigen level: 7.9 µg/L [interquartile range, 5.5-12.6 µg/L]); 4.3% had pre-biopsy bacteriuria. Overall, 5.7% and 3.8% of post-biopsy complications required emergency attendances and hospitalisations, respectively. Gross haematuria and rectal bleeding requiring emergency attendances developed in 2.1% and 0.4% of men; 0.8% and 0.4% required hospitalisations. Furthermore, 1.5% of men developed acute urinary retention requiring hospitalisations; 1.9% and 1.2% had post-biopsy infections requiring emergency attendances and hospitalisations, respectively, and 0.9% had urosepsis requiring hospitalisations. Prostate volume >48 cc was associated with an increased risk of post-biopsy retention (odds ratio 2.75, 95% confidence interval: 1.23-4.17). CONCLUSIONS: The rate of overall complications after TRUS biopsy was low. The most common complications requiring emergency attendances and hospitalisations were gross haematuria and acute urinary retention, respectively. Prostate volume >48 cc increased the risk of post-biopsy urinary retention.
Assuntos
Aspiração por Agulha Fina Guiada por Ultrassom Endoscópico/efeitos adversos , Hospitalização/estatística & dados numéricos , Neoplasias da Próstata/diagnóstico , Idoso , Serviço Hospitalar de Emergência/estatística & dados numéricos , Hematúria/etiologia , Hematúria/terapia , Hong Kong , Humanos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Tamanho do Órgão , Próstata/patologia , Antígeno Prostático Específico/sangue , Neoplasias da Próstata/sangue , Estudos Retrospectivos , Sepse/etiologia , Sepse/terapia , Retenção Urinária/etiologia , Retenção Urinária/terapia , Infecções Urinárias/etiologia , Infecções Urinárias/terapiaRESUMO
INTRODUCTION: "Ripple Action" and "WE Stand" are projects co-organised by the Hong Kong Women Doctors Association. The two projects organise free cervical screening for low-income women, new immigrants from Mainland China, and ethnic minority women. The objective of this study was to analyse the pattern of cervical smear abnormalities in these marginalised women. METHODS: The study group consisted of 1189 marginalised women who participated in a free cervical screening campaign, including 324 low-income local Chinese, 540 new immigrants from Mainland China, and 325 ethnic minority women. The comparison group consisted of 1141 local Chinese who attended a well women clinic. The prevalence of cervical smear abnormalities was compared using Chi squared test. RESULTS: In the study group, 42.6% of women had never had a cervical smear. Compared with the comparison group, they had a significantly higher prevalence of cervical smear abnormalities (13.7% vs 1.4%; P<0.001), including atypical smear (10.8% vs 0.5%; P<0.001), low-grade lesion (1.8% vs 0.8%; P=0.036), and high-grade lesion (1.1% vs 0.1%; P=0.002). Logistic regression analysis showed that the strongest predictors for abnormal cervical smear were being South Asian (odds ratio=11.859; 95% confidence interval, 4.635-30.341), South-East Asian (6.484; 3.192-13.171), or new immigrant from Mainland China (6.253; 2.463-15.877). CONCLUSIONS: Marginalised women had a significantly higher prevalence of cervical smear abnormality than the general population and almost half had never had a cervical smear before. Outreach strategies are needed to enrol this population into screening programmes.
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Programas de Rastreamento/métodos , Teste de Papanicolaou/estatística & dados numéricos , Neoplasias do Colo do Útero/diagnóstico , Neoplasias do Colo do Útero/epidemiologia , Esfregaço Vaginal/estatística & dados numéricos , Adulto , Idoso , Idoso de 80 Anos ou mais , Emigrantes e Imigrantes/estatística & dados numéricos , Etnicidade/estatística & dados numéricos , Feminino , Hong Kong/epidemiologia , Humanos , Modelos Logísticos , Pessoa de Meia-Idade , Adulto JovemRESUMO
Correct diagnosis must be made before appropriate treatment can be given. The aim of cardiac imaging is to establish cardiac diagnosis as accurate as possible and to avert unnecessary invasive procedures. There are many different modalities of cardiac imaging and each of them has advanced tremendously throughout the past decades. Echocardiography, as the first-line modality in most clinical circumstances, has progressed from two-dimensional, single-planed M-mode in the 1960s to three-dimensional speckle tracking echocardiography nowadays. Cardiac computed tomography angiogram (CCTA) has revolutionised the management of coronary artery disease as it allows clinicians to visualise the coronary arteries without performing an invasive angiogram. Because of the high negative predictive value, CCTA plays an important reassuring role in acute chest pain management. The greatest strength of cardiovascular magnetic resonance (CMR) is that it provides information in tissue characterization. It is the modality of choice in assessing myocardial viability and myocardial infiltration such as haemochromatosis or amyloidosis. Each of these modalities has its own strengths and limitations. In fact, they are complementing each other in different clinical settings. Cardiac imaging will continue to advance and, not long from now, we will not need invasive procedures to make an accurate cardiac diagnosis.
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Cardiomiopatias/diagnóstico , Ecocardiografia , Doenças das Valvas Cardíacas/diagnóstico , Angiografia por Ressonância Magnética , Tomografia Computadorizada por Raios X , Ecocardiografia/instrumentação , Ecocardiografia/métodos , Medicina Baseada em Evidências , Humanos , Angiografia por Ressonância Magnética/instrumentação , Angiografia por Ressonância Magnética/métodos , Guias de Prática Clínica como Assunto , Padrões de Prática Médica , Medição de Risco , Sensibilidade e Especificidade , Tomografia Computadorizada por Raios X/instrumentação , Tomografia Computadorizada por Raios X/métodosRESUMO
INTRODUCTION: The use of motor vehicles is common during pregnancy. Correct seatbelt use during pregnancy has been shown to protect both the pregnant woman and her fetus. This survey aimed to evaluate the practices, beliefs, and knowledge of Hong Kong pregnant women of correct seatbelt use, and identify factors leading to reduced compliance and inadequate knowledge. METHODS: A self-administered survey was completed by postpartum women in the postnatal ward at the United Christian Hospital, Hong Kong, from January to April 2015. Eligible surveys were available from 495 women. The primary outcome was the proportion of pregnant women who maintained or reduced seatbelt use during pregnancy. Secondary outcomes were analysed and included knowledge of correct seatbelt use, as well as contributing factors to non-compliance and inadequate knowledge. RESULTS: There was decreased compliance with seatbelt use during pregnancy and the decrease was in line with increasing gestation. Pregnant women's knowledge about seatbelt use was inadequate and only a minority had received relevant information. Women who held a driving licence and had a higher education level were more likely to wear a seatbelt before and during pregnancy. Women with tertiary education or above knew more about seatbelt use. CONCLUSIONS: Public health education for pregnant women in Hong Kong about road safety is advisable, and targeting the lower-compliant groups may be more effective and successful.
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Educação em Saúde , Conhecimentos, Atitudes e Prática em Saúde , Cintos de Segurança/estatística & dados numéricos , Adulto , Estudos Transversais , Escolaridade , Feminino , Hong Kong , Humanos , Gravidez , Trimestres da Gravidez , Inquéritos e Questionários , Adulto JovemRESUMO
INTRODUCTION: Rainlily, the first one-stop crisis centre in Hong Kong, was set up in 2000 to protect female victims of sexual violence. This study aimed to analyse the characteristics of sexual assault cases and victims who presented to two hospitals in Hong Kong. The data are invaluable for health care professionals and policymakers to improve service provision to these victims. METHODS: This retrospective analysis of hospital records was conducted in two acute hospitals under the Hospital Authority in Hong Kong. Sexual assault victims who attended the two hospitals between May 2010 and April 2013 were included. Characteristics of the cases and the victims, the use of alcohol and drugs, involvement of violence, and the outcome of the victims were studied. RESULTS: During the study period, 154 sexual assault victims attended either one of the two hospitals. Their age ranged from 13 to 64 years. The time from assault to presentation ranged from 1 hour to more than 5 months. Approximately 50% of the assailants were strangers. Approximately 50% of victims presented with symptoms; the most common were pelvic and genitourinary symptoms. Those with symptoms (except pregnancy) presented earlier than those without. The use of alcohol and drugs was involved in 36.4% and 11.7% of cases, respectively. Approximately 10% of the screened victims were positive for Chlamydia trachomatis. There were 11 pregnancies with gestational age ranged from 6 weeks to 5 months at presentation. Less than half of the victims completed follow-up care. CONCLUSIONS: Involvement of alcohol and drugs is not uncommon in sexual assault cases. Efforts should be made to promote public education, enhance coordination between medical and social services, and improve the accessibility and availability of clinical care. Earlier management and better compliance with follow-up can minimise the health consequences and impact on victims.
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Anticoncepção Pós-Coito/estatística & dados numéricos , Vítimas de Crime/estatística & dados numéricos , Delitos Sexuais/estatística & dados numéricos , Infecções Sexualmente Transmissíveis/epidemiologia , Adolescente , Adulto , Distribuição por Idade , Demografia , Feminino , Hong Kong , Hospitais , Humanos , Pessoa de Meia-Idade , Gravidez , Estudos Retrospectivos , Infecções Sexualmente Transmissíveis/classificação , Adulto JovemRESUMO
PURPOSE: Clinical phenotypes in Immunoglobulin G4-related disease (IgG4-RD) according to the patterns of affecting organs have different risks of malignancies. We attempt to determine the association of malignancies with IgG4-related ophthalmic disease (IgG4-ROD). DESIGN: Retrospective cohort study. METHODS: Review of medical records, orbital images and histopathology reports in a territory-wide cohort of biopsy proven IgG4-ROD patients from 2005-2019. FINDINGS: Among 122 patients who had biopsies taken from adnexal lesions including lacrimal glands (n = 108), orbital mass (n = 30), infiltrated orbital fat (n = 10), conjunctiva (n = 2) or extraocular muscles (n = 3), 13% (16/122) developed malignancies over 73 ± 48months' follow-up. There were 9 cases of ocular adnexal lymphoma (OAL) and 7 extra-orbital malignancies. Compared with the general population, the incidence of OAL was significantly higher (standardized incidence ratios, SIRs = 10.0, 95%CI = 4.5-17.6) while that of extra-orbital malignancies was similar. The SIRs was highest within the first year (SIR = 46.7, 95%CI = 18.5-87.6) when 7 OAL were concomitantly diagnosed. Patients who developed OAL or extra-orbital malignancies were older than other patients at IgG4-ROD diagnosis (64.9 ± 7.1, 68.3 ± 8.5 versus 55.2 ± 15.0 years, P < 0.05). Asymmetric lacrimal gland enlargement (78% versus 13%), lack of frontal (0% versus 12%) or infraorbital nerve enlargement (0% versus 36%) were associated with OAL (all P < 0.05). Pre-treatment serum IgG4 level or extra-orbital IgG4-RD involvement was similar among patients with or without malignancies. CONCLUSION: In this biopsy-proven IgG4-ROD cohort, 7% developed OAL which was 10 times higher than the general population. Patients with asymmetric lacrimal gland enlargement or without trigeminal nerves involvement radiologically were associated with OAL.
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Doença Relacionada a Imunoglobulina G4 , Doenças Orbitárias , Neoplasias Orbitárias , Humanos , Doença Relacionada a Imunoglobulina G4/diagnóstico , Doença Relacionada a Imunoglobulina G4/epidemiologia , Estudos Retrospectivos , Doenças Orbitárias/diagnóstico , Doenças Orbitárias/epidemiologia , Imunoglobulina GRESUMO
Procedural skills training in a developing country is challenging, but can improve the quality of care for patients with an important regional health problem. A structured, brief, teach-the-teacher-based training course supports physicians in developing countries to acquire skills needed to perform a complex procedure independently. A case of a patient diagnosed with esophageal cancer is presented and 10 tips are given for training procedural skills in a developing country.
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Competência Clínica , Médicos , Países em Desenvolvimento , HumanosRESUMO
The purpose of this study is to describe four new delivery schemes for intensity-modulated radiation therapy (IMRT). In the first two schemes the order in which segments are delivered is varied from fraction to fraction. The last two delivery schemes employ fixed order of segments. The obtained results indicate that the suggested approaches can significantly reduce the so-called "overshoot" and "undershoot" phenomena and the associated discrepancies between planned and delivered monitor units.
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Algoritmos , Fracionamento da Dose de Radiação , Modelos Biológicos , Radiometria/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Carga Corporal (Radioterapia) , Simulação por Computador , Dosagem Radioterapêutica , Eficiência Biológica RelativaRESUMO
OBJECTIVES: To evaluate the prevalence of affective disorders and identify their associated factors among Chinese mothers of preschool children diagnosed with autism spectrum disorders. METHODS: This cross-sectional study was conducted at the Autism Spectrum Disorders Multidisciplinary Clinic of the United Christian Hospital from August 2012 to June 2013. All mothers of a consecutive series of preschool children diagnosed with autism spectrum disorders at their first visit to the clinic were recruited. Information regarding the child-related, maternal, and environmental factors was collected. Psychiatric diagnoses were made according to the Chinese-Bilingual Structured Clinical Interview for DSM-IV Axis I Disorders. Independent factors associated with maternal affective disorders were determined by univariate and multivariate analyses. RESULTS: Of the 121 subjects, the point prevalence of affective disorders as a group was 29.8%. The point prevalence of major depressive disorders, adjustment disorders, anxiety disorders, and bipolar affective disorders was 14.9%, 10.7%, 3.3% and 0.8%, respectively. A higher level of disruptive and self-absorbed behaviours in the children (as assessed by the Developmental Behaviour Checklist), a higher level of affiliate stigma (as assessed by 22-item Affiliate Stigma Scale), and a history of psychiatric disorders were independently associated with current affective disorders. CONCLUSION: Psychiatric disorders, predominantly affective disorders, are common among Chinese mothers of preschool children with autism spectrum disorders. Identification of independent factors associated with maternal affective disorders can aid in the early detection of cases and planning of early intervention programmes to address both child and maternal psychological needs.
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Transtorno do Espectro Autista/epidemiologia , Transtornos do Humor/epidemiologia , Mães/psicologia , Mães/estatística & dados numéricos , Adulto , Transtorno do Espectro Autista/psicologia , Pré-Escolar , China/epidemiologia , Estudos Transversais , Feminino , Humanos , Masculino , Transtornos do Humor/psicologia , Relações Mãe-Filho , PrevalênciaRESUMO
The photoexcited triplet state of Trp-37 in the C-terminal zinc finger of the HIV-1 p7 nucleocapsid protein was used as a probe of p7 interactions with the heavy atom-derivatized RNA homopolymer, poly-5-mercuriuridylic acid (5-HgU). Binding of p7 to 5-HgU (Hg blocked with 2-mercaptoethanol) produces an external heavy atom effect (HAE) on Trp-37 characterized by fluorescence quenching, reduction of the phosphorescence lifetime by three orders of magnitude, and the appearance of the D+E phosphorescence-detected ODMR signal, absent in unperturbed Trp, but induced by a HAE. The details of the HAE are consistent with out-of-plane van der Waals contact of Hg with the indole chromophore of Trp-37. Steric requirements suggest further that the Trp-RNA contact occurs via an aromatic stacking interaction.
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Proteínas do Capsídeo , Produtos do Gene gag/metabolismo , Poli U/metabolismo , Proteínas Virais , Sequência de Aminoácidos , Produtos do Gene gag/química , HIV-1/metabolismo , Luminescência , Imageamento por Ressonância Magnética , Dados de Sequência Molecular , Poli U/química , RNA Viral/metabolismo , Triptofano/metabolismo , Dedos de Zinco/fisiologia , Produtos do Gene gag do Vírus da Imunodeficiência HumanaRESUMO
New 915 MHz microwave interstitial applicators with improved treatment volume have been developed for clinical hyperthermia. The applicators are made from semi-rigid miniature coaxial cables by removing sections of the outer copper conductor to create multiple nodes while preserving the integrity of the teflon dielectric insulators. The homogeneity of the temperature distribution along the longitudinal axis is optimized by empirically adjusting the spacing of the gaps between sections of the outer conductor along the length of the applicator. In vitro and in vivo testing of the two-node and three-node microwave applicators show that the treatment volume can be improved by 100% over that of a one-node microwave applicator.
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Braquiterapia/instrumentação , Hipertermia Induzida/instrumentação , Neoplasias/terapia , Animais , Desenho de Equipamento , Humanos , Micro-Ondas/uso terapêutico , CoelhosRESUMO
Total body irradiation is part of the preparatory regimen for allogeneic bone marrow transplantation because of its cytotoxic and immunosuppressive properties. A major toxicity of bone marrow transplantation has been interstitial pneumonitis, which may be, in part, related to the lung irradiation. One hundred and sixty-one consecutive patients receiving allogeneic bone marrow transplantation for leukemia and aplastic anemia at Johns Hopkins Hospital (1968-1979) were retrospectively studied. The present study demonstrated that lung shielding to 600 rad maximum in single dose total body irradiation, fractionation of total body irradiation in comparison to single dose total body irradiation, and absence of graft versus host disease in the leukemia patients, each reduced the risk of interstitial pneumonitis. Total body irradiation significantly reduced the leukemia recurrence rate and/or the failure of remission induction.
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Transplante de Medula Óssea , Fibrose Pulmonar/etiologia , Irradiação Corporal Total/efeitos adversos , Análise de Variância , Bussulfano/efeitos adversos , Reação Enxerto-Hospedeiro , Humanos , Leucemia/radioterapia , RiscoRESUMO
OBJECTIVES: To determine the cellular localization in male and female axillary tissue for apocrine secretion odor-binding proteins 1 (ASOB1) and 2 (ASOB2) and the electrophoretic pattern of female apocrine proteins and to begin characterization of the ASOB1 protein. DESIGN: Immunohistochemical techniques were used with biopsy samples from axillary tissue of male and female subjects. Immunological techniques and microsequencing were used to characterize several of the proteins in male and female apocrine secretions. SETTING: A university medical center. PARTICIPANTS: Healthy male and female volunteers who donated apocrine secretions and/or axillary tissue. RESULTS: Specific immunoreactivity was localized only to the apocrine glands in both sexes. Furthermore, only preabsorption with a mixed apocrine secretion sample eliminated all immunoreactivity. The electrophoretic pattern of proteins in female apocrine secretions is similar to that in male secretions. Western blotting of the separated proteins from female samples using serum samples containing antibodies to ASOB1 and ASOB2 yielded identical results to those found with separated proteins from male samples. Partial sequence data obtained from the N-terminus of ASOB1 suggested that it shares homology with the alpha-chain of apolipoprotein J (Apo J). Apocrine secretion odor-binding protein 1 is not immunologically similar to ApoJ, but 2 other apocrine secretion proteins are. CONCLUSIONS: Male and female subjects appear to have the same glycoprotein carriers for (E)-3-methyl-2-hexenoic acid localized to the apocrine glands. The N-terminal sequence for ASOB1 may be homologous to Apo J, but it is not immunologically similar to it. However, 2 other proteins in the apocrine secretion appear to be the monomer and dimer forms of Apo J.
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Glândulas Apócrinas/metabolismo , Chaperonas Moleculares , Odorantes/análise , Precursores de Proteínas/análise , Receptores Odorantes/análise , Adulto , Sequência de Aminoácidos , Anticorpos/sangue , Glândulas Apócrinas/química , Glândulas Apócrinas/imunologia , Axila , Western Blotting , Clusterina , Feminino , Glicoproteínas/química , Glicoproteínas/imunologia , Humanos , Imuno-Histoquímica , Masculino , Dados de Sequência Molecular , Fragmentos de Peptídeos/química , Precursores de Proteínas/química , Receptores Odorantes/química , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Fatores SexuaisRESUMO
Computer treatment planning systems allow dose computation in planes parallel to the central one (off-axis plans). The beam data may consist of, e.g., percentage depth doses along the central axis plus off-axis ratios (OAR) at several depths. In some systems, the calculation of an off-axis plan is based on the assumption that the OAR can be represented by a separable function: OAR(x,y) = f(x).g(y), where x and y are the symmetry axes perpendicular to the beam axis and the functions f and g are equal for a square open field. The errors of this assumption for a 4-MeV machine were measured for open fields and wedged fields at five different depths. The measured dose was compared with that predicted by the above equation for 50%, 75%, and 88% of the half field width from the beam axis. Maximum deviation of more than 10% was observed with the probable error of the measurement being 1%.
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Neoplasias/radioterapia , Aceleradores de Partículas , Planejamento de Assistência ao Paciente/métodos , Humanos , Dosagem Radioterapêutica , Radioterapia de Alta Energia/instrumentaçãoRESUMO
For the Clinac 4, open field profiles measured in the principal plane have higher intensity "horns" than those in off-axis planes. The maximum deviation occurs at 1-cm depth, where in the worst case of large field sizes and off-axis distances the deviation can be as high as 16% in the region near the horns. A model is proposed to generate open field beam profiles in off-axis planes, based on measured profiles in the transverse principal plane and in the largest field size diagonal plane of the machine. Within the central 90% portion of the field, the maximum deviation of the generated profiles from the measured ones at the same off-axis distance varies from about 3% at 1-cm depth to about 2% at 13-cm depth and then increases to less than 5% at 25-cm depth, even for very large field sizes and off-axis distances. Very little additional computer time and data storage are required for this procedure. Using these profiles, the Milan and Bentley method can be extended to three-dimensional treatment planning with good accuracy.
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Doses de Radiação , Tomografia Computadorizada por Raios X , Modelos Teóricos , Tecnologia RadiológicaRESUMO
AIM: To assess the ocular effect of interferon alfa 2b prescribed with ribavirin in patients undergoing therapy for chronic hepatitis C. METHODS: 19 patients with chronic hepatitis C who satisfied the follow up criteria were assessed for ocular complications using slit lamp biomicroscopy and indirect ophthalmoscopy before, during, and after the treatment at regular intervals. RESULTS: 8/19 patients, while on treatment, developed an asymptomatic retinopathy. Among these 3/8 were relapsers and 5/9 were non-responders to interferon monotherapy. All retinal changes faded, often while the patients continued the therapy. There was no significant association in occurrence of retinopathy with haematological and/or biochemical changes. CONCLUSION: Retinopathy was more common in interferon monotherapy non-responders than relapsers when treated with interferon alfa 2b with the addition of ribavirin. The changes were transient, disappearing while the patients were still being treated.
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Antivirais/uso terapêutico , Hepatite C Crônica/tratamento farmacológico , Interferon-alfa/uso terapêutico , Doenças Retinianas/induzido quimicamente , Ribavirina/uso terapêutico , Adulto , Quimioterapia Combinada , Feminino , Humanos , Interferon alfa-2 , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Proteínas Recombinantes , Remissão Espontânea , Hemorragia Retiniana/induzido quimicamente , Resultado do TratamentoRESUMO
To calculate dose distributions in off-axis planes for wedged fields, some commercial radiotherapy treatment planning systems use the Milan and Bentley method and simply modify the transverse principal-plane profile in the wedge direction with the value of its orthogonal open-field profile at the off-axis distance. For the Clinac 4 this simple modification may introduce serious distortions in off-axis dose distributions. The error can be considerably reduced if the basic beam data are supplemented with longitudinal principal-plane profiles and depth doses measured for the largest wedged field (14 X 32 cm2). These added data enable the determination of position-dependent effective attenuation coefficients of the wedges and hence, with the model proposed here, the calculation of transverse off-axis and longitudinal profiles as required. Even for very large field sizes and off-axis distances, the maximum deviation of generated profiles from measured ones varies from about 1% to the worst case of slightly above 4%. This procedure requires little extra computer time and data storage. The computed profiles are of sufficient accuracy for 3-dimensional treatment planning.
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Modelos Teóricos , Dosagem Radioterapêutica , Radioterapia de Alta Energia/métodos , Filtração , HumanosRESUMO
A digital imaging system has been constructed to obtain the treatment portal image of a patient during external beam radiotherapy. A DEC LSI-11/23 microcomputer controls a stepper motor, which moves a linear array of 256 silicon diodes to scan the radiation transmitted through the patient. The computer also processes the collected data to generate an image for displaying on a video monitor. The quality of the digital image is comparable to that of the conventional verification radiographs. Major advantages of the system include the speed and simplicity in data storage and retrieval and in its capability of direct comparison with simulation radiographs.
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Sistemas On-Line , Radioterapia Assistida por Computador , Humanos , Métodos , Modelos Estruturais , Sistemas On-Line/instrumentação , Software , Gravação em VídeoRESUMO
An on-line electronic portal imaging system was used in a quantitative measurement of field placement errors in external beam radiotherapy. Data from 30 patients, giving a total of 150 portals with 66% in the thoracic region and 34% in the abdominal region, were analysed. Displacements from the prescription delineated by physicians were measured. The displacements included errors to block malposition, field malposition, field malrotation and patient malposition, and these were classified in two categories of displacements, those associated with the portal boundary and those with anatomic structures. Except for one rotational error, only translational errors were found. Displacements greater than 1 cm amounted to 17% with respect to the portal boundary and between 10% and 46% with respect to anatomic landmarks within the portal. From the results of the study, a margin of 1 cm around the tumour is barely sufficient if a 5% accuracy in dose delivery is desired.