Tratamiento quirúrgico de la epilepsia asociada a tumores neuroepiteliales de bajo grado / Surgical treatment of low-grade epilepsy-associated neuroepithelial tumors

Resumen Los tumores cerebrales son una causa importante de las epilepsias de difícil manejo, corresponden a un 20-30 % de los casos de cirugía de epilepsia refractaria. En este grupo de pacientes los tumores neuroepiteliales de bajo grado asociados a epilepsia (LEAT) son la principal causa, siendo los más frecuentes los tumores neuroepiteliales disembrioplásticos (DNT) y ganglioglioma (GG). En el presente artículo revisamos los cambios en la definición de epilepsia refractaria, avances en el diagnóstico por imágenes y el diagnóstico histopatológico con los nuevos marcadores moleculares, que han permitido un diagnóstico cada vez más precoz y certero. Se revisa también la cirugía resectiva que permite en estos casos una libertad de crisis cercana un 70-90% de los pacientes. Los mejores resultados en términos de control de crisis, se pueden alcanzar cuando la cirugía es precoz.

Brain tumors are an important cause of epilepsy that is difficult to manage, accounting for 20-30% of cases of refractory epilepsy surgery. In this group of patients, low-grade epilepsy-associated neuroepithelial tumors (LEAT) are the main cause and the most frequent being dysembryoplastic neuroepithelial tumors (DNT) and ganglioglioma (GG). In this article, we review the changes in the definition of refractory epilepsy, advances in diagnostic imaging, and histopathological diagnosis with new molecular markers, which have allowed for an increasingly early and accurate diagnosis. Resective surgery is also reviewed, allowing in these cases a seizure freedom close to 70-90% of patients. The best outcome in terms of seizure control can be achieved when early surgery is performed.

[Central nervous system infections associated with CSF shunt devices in children, at a national reference hospital]. / Infecciones del sistema nervioso central asociadas a dispositivos de derivación de LCR en niños, en un centro neuro-quirúrgico de referencia nacional.

BACKGROUND: Infections associated with CSF shunt devices are a frequent complication in their use. The most common is the presence of gram positive coccaceae, such as coagulase negative Staphylococcus (50% in some series) and Staphylococcus aureus. This complication adds morbidity and mortality to the neurosurgical patient, increasing hospital stay and treatment costs. AIM: To determine the incidence of infections associated with CSF shunt devices in a national referral center. METHODS: Retrospective, descriptive study. Information was collected on pediatric patients between 2018 and 2019. A descriptive and inferential statistical analysis was performed using the statistical language R 3.4.0 and RStudio 1.3.9. The cumulative incidence for each procedure was calculated, evaluating whether there were significant differences between them. This study was approved by the Pediatric Ethics Committee of the SSMO. RESULTS: In the period studied, 175 surgeries were performed. We found 19 cases of ventriculitis associated with ventriculoperitoneal derivative and 7 cases in ventricular-external derivative. The most frequent agents were grampositive coccaceae. It was not possible to identify significant risk factors.

Infecciones del sistema nervioso central asociadas a dispositivos de derivación de LCR en niños, en un centro neuro-quirúrgico de referencia nacional / Central nervous system infections associated with CSF shunt devices in children, at a national reference hospital

INTRODUCCIÓN: Las infecciones asociadas a dispositivos de derivación de LCR son una complicación frecuente en su utilización. Lo más habitual es la presencia de cocáceas grampositivas, como Staphylococcus coagulasa negativa (50% en algunas series) y Staphylococcus aureus. Esta complicación agrega morbimortalidad al paciente neuroquirúrgico, aumentando la estadía hospitalaria y los costos de tratamiento. OBJETIVO: Conocer la incidencia de infecciones asociadas a dispositivos de derivación de LCR en un centro de referencia nacional. METODOLOGÍA: Estudio descriptivo, retrospectivo. Se recolectó la información de los pacientes pediátricos (bajo 18 años) entre 2018 y 2019. Se realizó un análisis estadístico descriptivo e inferencial utilizando el lenguaje estadístico R 3.4.0 y RStudio 1.3.9. Se calculó la incidencia acumulada para cada procedimiento, evaluando si existe diferencias significativas entre ellas. Estudio aprobado por el Comité de Ética Pediátrico del SSMO. RESULTADOS: En el período estudiado se realizaron 175 cirugías. Encontramos 19 casos de ventriculitis asociada a derivativa ventriculo-peritoneal y 7 casos en derivativa ventricular-externa. Los agentes más frecuentes fueron las cocáceas grampositivas. No se logró identificar factores de riesgo significativos.

BACKGROUND: Infections associated with CSF shunt devices are a frequent complication in their use. The most common is the presence of gram positive coccaceae, such as coagulase negative Staphylococcus (50% in some series) and Staphylococcus aureus. This complication adds morbidity and mortality to the neurosurgical patient, increasing hospital stay and treatment costs. AIM: To determine the incidence of infections associated with CSF shunt devices in a national referral center. METHODS: Retrospective, descriptive study. Information was collected on pediatric patients between 2018 and 2019. A descriptive and inferential statistical analysis was performed using the statistical language R 3.4.0 and RStudio 1.3.9. The cumulative incidence for each procedure was calculated, evaluating whether there were significant differences between them. This study was approved by the Pediatric Ethics Committee of the SSMO. RESULTS: In the period studied, 175 surgeries were performed. We found 19 cases of ventriculitis associated with ventriculoperitoneal derivative and 7 cases in ventricular-external derivative. The most frequent agents were grampositive coccaceae. It was not possible to identify significant risk factors.

Statistical controversies in clinical research: publication bias evaluations are not routinely conducted in clinical oncology systematic reviews.

Background: Publication bias is an over-representation of statistically significant results in the published literature and may exaggerate summary effect estimates in oncology systematic reviews. Omitting non-significant results in systematic reviews may therefore affect clinical decision-making. We investigate ways that systematic reviewers attempted to limit publication bias during the search process as well as the statistical methods used to evaluate it. For a subset of reviews not reporting publication bias evaluations, we carried out our own assessments for publication bias to determine its likelihood among these reviews. Design: We examined systematic reviews from the top five highest impact factor oncology journals published between 2007 and 2015. Systematic reviews were screened for eligibility and qualifying reviews (n = 182) were coded for relevant publication bias study characteristics by two authors. A re-analysis of reviews not initially evaluating for publication bias was carried out using Egger's regression, trim-and-fill, and selection models. Results: Of the 182 systematic reviews, roughly half carried out a hand search to locate additional studies. Conference abstracts were the most commonly reported form of gray literature, followed by clinical trials registries. Fifty-one reviews reported publication bias evaluations. The most common method was the funnel plot (80%, 41/51) followed by Egger's regression (59%, 30/51) and Begg's test (43%, 22/51). Our publication bias evaluations on non-reporting reviews suggest that the degree of publication bias depends on the method employed. Conclusion: Our study shows publication bias assessments are not frequently used in oncology systematic reviews. Furthermore, evidence of publication bias was found in a subset of non-reporting reviews. Systematic reviewers in oncology are encouraged to conduct such analyses when appropriate and to employ more robust methods for both mitigating and evaluating publication bias.

Influence of anxiety on temporomandibular disorders--an epidemiological survey with elders and adults in Southern Brazil.

The socio-economic and psychological factors and the use of and need for dental prostheses have been associated with prevalence and severity of temporomandibular disorders (TMD). The aim of this study was to evaluate the association of socio-economic and psychological factors, use of and need for dental prostheses with the prevalence and severity of signs and symptoms of temporomandibular disorders (TMD). A cross-sectional study was conducted in Luzerna/Brazil. All individuals aged 35-44 (adults) and 65-74 (elders) were invited to participate in this study. The measuring instrument included a questionnaire application and the clinical evaluation regarding signs and symptoms of TMD. Descriptive analyses, chi-squared test, unadjusted and adjusted Poisson regression were used for the statistic analysis. The level of statistical significance was given when P ≤ 0·05. In total, 568 individuals (338 adults and 230 elders) were included; among them, 43·5% had absent, 42·6% mild, 11·3% moderate and 2·6% severe TMD. The presence of higher TMD rates was found in females (P = 0·001), and the TMD occurrence increased with anxiety level (P = 0·001). Other socio-economic factors, such as colour (P = 0·115), family structure (P = 0·478), age (P = 0·143), social class (P = 0·935) and education (P = 0·678) showed no influence. In conclusion, the female gender and individuals with higher levels of anxiety had increased prevalence of signs and symptoms of TMD. Additionally, was not founded association between TMD and use of and need for dental prostheses.

[Volume calculations for current intravitreal injections of Lucentis]. / Volumenberechnungen zur aktuellen intravitrealen Injektion von Lucentis.

BACKGROUND: Medications for blocking vascular endothelial growth factor (VEGF) are currently used for therapy of neovascular age-related macular degeneration (AMD). Some users divide the original volume of the medication Lucentis into smaller aliquots to be used for several patients. The aim of this study was to investigate whether the current original aliquot volume of Lucentis can principally be subdivided to be used for treatment two patients each with a 0.05 ml injection volume. MATERIALS AND METHODS: The calculation of the dead space volume of the vessels used for injection was carried out by weighing the empty and full weights using an analytical balance. The sum of all dead space volumes was subtracted from the filling volumes. Additionally, the average extractable volume was determined from 200 original aliquots of Lucentis. RESULTS: Taking all necessary dead space volumes into consideration it was calculated that an extractable volume of at least 0.137 ml is necessary in order to be able to inject the necessary volume of 0.05 ml of the solution containing the active ingredient. The original volume of 0.23 ml contained in an aliquot of Lucentis cannot therefore be divided among two patients. The average extractable volume of 0.16 ml is clearly less than the full volume of 0.23 ml. CONCLUSIONS: The original aliquots of Lucentis contain a full volume of 0.23 ml and are not suitable to be used to treat two patients. The volume can only be divided among several patients if several original aliquots are pooled and refilled. This however, presupposes a renewed filling of aliquots which represents a new potential source of contamination. Also legal aspects and the question of stability of the active ingredient have not been taken into consideration.

Adult acute erythroleukemia: an analysis of 91 patients treated at a single institution.

Acute erythroleukemia (AML-M6) is an uncommon subtype of acute myeloid leukemia (AML); it is considered to have a poor prognosis. From 1 January 1980 to 21 May 2008, 91 patients with newly diagnosed AML-M6 were seen at the University of Texas-M.D. Anderson Cancer Center (UT-MDACC). Forty-five patients (50%) had a history of myelodysplatic syndrome (MDS), compared with 41% in our control group (patients with other AML subtypes) (P=0.08). Poor-risk cytogenetics were more common in patients with AML-M6 (61% versus 38%, P=0.001). Complete remission rates were 62% for patients with AML-M6, comparing with 58% for the control group (P=0.35). Median disease free survival (DFS) for patients with AML-M6 was 32 weeks, versus 49 weeks for the control group (P=0.05). Median overall survival (OS) of patients with AML-M6 was 36 weeks, compared with 43 weeks for the control group (P=0.60). On multivariate analysis for DFS and OS, AML-M6 was not an independent risk factor. AML-M6 is commonly associated with a previous diagnosis of MDS and poor-risk karyotype. The diagnosis of AML-M6 does not impart by itself a worse prognosis, and treatment decisions on this disease should be guided by well known AML prognostic factors.

Phase II study of rabbit anti-thymocyte globulin, cyclosporine and granulocyte colony-stimulating factor in patients with aplastic anemia and myelodysplastic syndrome.

We investigated efficacy and safety of rabbit anti-thymocyte globulin (rATG), cyclosporine and granulocyte colony-stimulating factor (G-CSF) as first-line therapy for patients with aplastic anemia (AA) and low or intermediate-1 or hypoplastic myelodysplastic syndrome (MDS). rATG 3.5 mg/kg (or 2.5 mg/kg per day for patients >or=55 years with MDS) was given for 5 days. Cyclosporine (5 mg/kg) and G-CSF (5 microg/kg) were given daily and continued for up to 6 months or longer. Responses were assessed about 3 and 6 months after therapy. Thirty-six patients have been enrolled on study and 32 patients treated; 25 were evaluable for a response (13 with AA, 12 with MDS); the rest are too early. The median age was 62 years (range, 20-83) for patients with AA and 63 (range, 42-80) for patients with MDS. Of 13 patients, 12 (92%) patients with AA responded (5 complete response (CR), 7 partial response (PR)), whereas of 12 patients, 4 (33%) patients with MDS responded (1 CR, 3 PR). For patients with AA, the median time to response (TTR) was 93 days (range, 79-623), whereas in the MDS group the median TTR was 111 days (range, 77-139). Grade III/IV toxicities were mainly cytopenias and neutropenic fever. Combination of rATG, cyclosporine and G-CSF is safe and effective as first-line treatment of AA and has significant activity in low-risk MDS.

Arsenic and heavy metal accumulation by Pteris vittata L. and P. umbrosa R. Br.

This study compared the accumulation of arsenic, copper and chromium by Pteris vittata and Pteris umbrosa grown in a glasshouse in soil from a timber treatment facility. Soil was collected from three locations. Accumulation (as percentage removed) varied between these soils but was not related to soil concentration. P. vittata was more efficient than P. umbrosa, both in accumulating As and metals in the below-ground plant parts and in translocating As to the fronds. Under the experimental conditions, only P. vittata could be effectively used in soil from one location for phytoremediation purposes.

Practical assessment of the display performance of radiology workstations.

The performance of 14 primary clinical display monitor workstations in use in the Radiology Department of a large acute NHS Trust was assessed using the methods and guidelines described by the American Association of Physicists in Medicine Task Group 18. Tests undertaken included the measurement of ambient light, display uniformity, luminance ratio, luminance response, maximum luminance and spatial resolution. Four display monitors failed to meet at least one of the test's guideline tolerances. In addition a number of display monitors were found to be operating at settings that might reduce their useful life span. These devices were either replaced or recalibrated by the installers, or were subject to local adjustment to ensure applicable standards were met. Consequently the study suggests that quality assurance testing of display monitors used for image reporting is necessary and valuable to ensure that images are viewed at an appropriate standard.

Malformación arteriovenosa de la vena de Galeno: reporte de un caso / Vein of galen arteriovenous malformation: a case report

Las malformaciones arteriovenosas de la vena de Galeno comprenden un raro grupo de anomalías congénitas que pueden causar una morbimortalidad importante, especialmente en neonatos, pero también en lactantes y niños mayores. Presentamos un caso de detección prenatal de aneurisma de la vena de Galeno a las 35 + 5 semanas de gestación en el Centro de Referencia Perinatal Oriente. Al examen ultrasonográfico se evidenció una imagen quística supratentorial de 47 por 16 mm, en la línea media del cerebro, asociado a polihidroamnios. El examen con Doppler color demostró el origen vascular de la lesión, con flujo turbulento venoso y arteria. Se realiza resonancia magnética (RM) cerebral fetal que confirma diagnóstico. A las 37 + 2 semanas de gestación se interrumpe el embarazo vía cesárea por inicio de trabajo de parto con monitorización electrónica fetal sospechosa de hipoxia. Evaluado con RM cerebral y angiorresonancia posnatal, en el Instituto de Neurocirugía se declara fuera del alcance terapéutico debido al gran compromiso encefálico. El recién nacido fallece a los siete días de vida. En la presente publicación se realiza una revisión de la literatura referente al tema, destacando la importancia de la consejería prenatal y el manejo multidisciplinario de esta compleja patología.

A survey of MRI quality assurance programmes.

There are currently no national guidelines on appropriate quality assurance (QA) test frequencies for MRI equipment in clinical use. From a random selection of 45 hospitals in England, who were contacted by phone, 35 hospitals agreed to participate in a survey of MRI QA and were sent a questionnaire requesting information on the range and frequency of QA tests, as well as the staff groups who conduct these tests. Twenty-four completed replies were received, representing a 68% response rate from the distributed questionnaires. Of these, 79% undertook some form of QA, typically conducted by the radiographic staff. Tests were most often undertaken on the head coil, but there was a considerable variation in the frequency and range of tests undertaken at different hospitals. For example, exactly half of the respondents conducted signal to noise ratio (SNR) tests on both head and body coils, but only 13% of centres extended this test to other coils. Results from this survey should inform radiology departments regarding practice at other hospitals and should assist in formulating the frequency and scope of appropriate MRI QA programmes.

Tumor cerebral fetal / Fetal brain tumors

Los tumores cerebrales en el período perinatal son una patología de excepcional ocurrencia. Se describe el caso clínico de un tumor cerebral fetal con diagnóstico prenatal a las 30 semanas de gestación en el Hospital Santiago Oriente Dr. Luis Tisné Brousse; al examen ultrasonográfico se evidenció un tumor sólido supratentorial derecho de 51 por 40 mm asociado a macrocefalia, hidrocefalia y polihidramnios. Se realiza resonancia magnética fetal que confirma diagnóstico. A las 32 semanas de gestación se interrumpe el embarazo por rotura de membranas; se realiza biopsia al tumor que informa teratoide rabdoide atípico. Debido al tamaño tumoral y gran compromiso encefálico se declara fuera de alcance terapéutico; el lactante fallece a los 43 días de vida. En la presente publicación se realiza una revisión de la literatura referente al tema, destacándose aspectos relevantes en relación al diagnóstico, tipos histológicos, estudio fetal, manejo y pronóstico. Cabe destacar la importancia de la consejería prenatal y el manejo multidisciplinario de esta compleja patología, que en términos generales tiene un pronóstico ominoso.

Complejo de Dandy Walker, experiencia en el Centro de Referencia Perinatal Oriente / Dandy-Walker complex: the experience of Centro de Referencia Perinatal Oriente

La malformación de Dandy Walker es una anomalía congénita caracterizada por un ensanchamiento quístico del cuarto ventrículo e hipoplasia o agenesia del vermis cerebeloso, que secundariamente produce hidrocefalia congénita e hipertensión intracraneal. La tríada característica para establecer el diagnóstico consiste en hidrocefalia, ausencia de vermis cerebeloso y quiste de la fosa posterior con comunicación con el cuarto ventrículo. Actualmente se han descrito tres variantes de esta malformación: Malformación Clásica de Dandy Walker (SDW), Hipoplasia vermis cerebeloso, y dilatación de cisterna magna (CMD). Se revisaron todos los casos de malformación de Dandy Walker controlados en Centro de Referencia Perinatal Oriente (CERPO) entre abril 2003 y septiembre 2006. Se controlaron once casos durante este período, diez de ellos con diagnóstico prenatal de alguna de las variantes de Dandy Walker (ocho casos de CMD y dos casos de SDW) y un caso con diagnóstico prenatal de agenesia del cuerpo calloso, diagnosticándose postnatalmente síndrome de Dandy Walker. A estas pacientes se les manejó en CERPO mediante seguimiento ultrasonográfico, cordocentesis para estudio de cariograma fetal, ecocardiografía, resonancia magnética fetal, consejería y apoyo psicológico. No se encontró asociación con los factores de riesgo descritos en la bibliografía. Sólo existe en un caso el antecedente de consanguinidad paterna y otro caso con antecedente de prima en primer grado materna con síndrome de Down. Destaca la alta asociación con aneuploidías (siete de los once casos, 64 por ciento): cinco casos de trisomías 18 (71 por ciento), una trisomía 21 y una translocación 6-13. Hay una alta tasa de mortalidad tanto pre como postnatal (46 por ciento), falleciendo cinco de los once casos durante la gestación o el primer año de vida. Ninguno de los casos ha requerido de manejo quirúrgico postnatal. Sólo tres casos (24 por ciento) no presentaron otra malformación asociada, todos con diagnóstico...

Patient dose optimization in plain radiography based on standard exposure factors.

A computational technique for assessing patient dose in plain radiography is described allowing a large number of examinations to be assessed and enabling dose optimization to be promoted. Entrance surface dose (ESD) was calculated for more than 1500 standard exposure settings in an initial dose assessment. Validation of the technique showed good agreement with thermoluminescent dosimetry and showed broad agreement between the standard exposures and the exposure settings used in practice. The dose assessment was repeated 18 months later using the same techniques for almost 2000 standard exposure settings. In both cases, calculated doses showed good compliance with national diagnostic reference levels where available. Suggested investigation levels were established and set at twice the mean dose for each of 47 examinations. Radiology departments were encouraged to review and optimize doses exceeding these levels. The computed mean ESD in the review study was less than the corresponding value in the initial study in 37 of the 47 examinations. The dose reduction was attributable partly to equipment replacement, but primarily to optimization of exposure settings. The technique employed here provides a valid and cost effective method of complying with statutory requirements for the assessment of representative patient dose and is useful in assisting the ongoing process of dose optimization.

Esquizencefalia: diagnóstico prenatal por medio de ultrasonografía y resonancia magnética / Schizencephaly: prenatal diagnosis by means of ultrasonography and magnetic resonance image

La esquizencefalia es una malformación cerebral congénita, de baja incidencia, que se caracteriza por hendiduras en la corteza cerebral comunicando el espacio subaracnoídeo con el sistema ventricular. Se manifiesta en la infancia con alteraciones motoras y convulsiones y en este período se realiza la mayoría de los diagnósticos. Los reportes de diagnóstico en la vida fetal son escasos, pero han aumentado desde el advenimiento de la ultrasonografía de alta resolución (US), la tomografía computada (TC) y la resonancia magnética (RM). Presentamos dos casos en los que se realizó diagnóstico prenatal; a las 28 y 35 semanas de gestación. El diagnóstico se realizó mediante US y RM fetal, en mujeres embarazadas sanas referidas al CERPO por malformación cerebral en US de rutina. Se muestran imágenes de US y RM de ambos fetos y de uno de los recién nacidos. Destacamos la utilidad de la TC o RM para efectuar el diagnóstico de certeza cuando se ha sospechado esta malformación a la US asimismo para efectuar el diagnóstico diferencial con otras entidades como la holoprosencefalia, hidrocefalia y porencefalia, poniendo énfasis en la RM por su mejor resolución y su despligue multiplanar de la anatomía fetal.

Defectos del tubo neural: diagnóstico prenatal y seguimiento / Neural tube defects: prenatal diagnosis and surveillance

Entre las malformaciones congénitas, los defectos del tubo neural (DTN) tienen una alta incidencia situándose en segundo lugar luego de las cardiopatías congénitas. La fortificación con ácido fólico en harina de panificación en Chile ha logrado una reducción de la incidencia de un 42 por ciento. Estos niños presentan una alta letalidad perinatal. Se analizan 12 casos de DTN, controlados en Centros de Referencia Perinatal Oriente, entre abril 2003 y julio 2004, factores de riesgo asociados, evolución prenatal y seguimiento postnatal. Resultados: Ninguna paciente tenía antecedentes de hijos previos afectados. El consumo de ácido fólico medicamentoso fue tardío en todas las pacientes y el consumo de pan en este grupo fue bajo (135 g = 228 g ácido fólico). Siete de doce pacientes fallecieron en los primeros días de vida o nacieron muertos. Se detectó dilatación ventricular progresiva en todas las pacientes con espina bífida y todas requirieron instalación de válvula derivativa durante el primer mes de vida. Todas las pacientes desarrollaron paraparesia fláccida en diferentes grados, dos desarrollaron vejiga neurogénica y dos presentaron alteraciones ortópedicas de las extremidades. Conclusión: Este grupo de pacientes tenía como factor de riesgo un bajo consumo de pan y el aporte tardío de ácido fólico. La evolución de los recién nacidos corresponde a la reportada con la cirugía postnatal del mielomeningocele.

Centro de Referencia Perinatal Oriente (CERPO): evaluacion de la experiencia del primer a¤o

Chile ha logrado una reducción importante en los índices de salud perinatal, con un aumento de la importancia relativa de las malformaciones congénitas en la mortalidad perinatal e infantil. Para mantener esa tendencia es necesario desarrollar estrategias para reducir la mortalidad asociada a malformaciones congénitas. En respuesta a esta nueva situación, se creó el Centro de Referencia Perinatal Oriente (CERPO), constituido por un equipo multidisciplinario de profesionales. El objetivo principal es el trabajo coordinado para mejorar la calidad de atención y los resultados perinatales dependientes de malformaciones congénitas del área oriente y regiones. Para lograr esos objetivos se establece un modelo de atención integral, multidisciplinario, orientado a satisfacer sus necesidades. Se describe en detalle el modelo de atención CERPO y las actividades realizadas en el primer a¤o.

Variations in radiation dose between the same model of multislice CT scanner at different hospitals.

The variation in exposure factors and patient dose, between seven centres using identical multislice CT scanners, was investigated for six standard examinations. Dose values were compared with each other and the relevant diagnostic reference level (DRL) for each examination. The range in weighted CT dose index (CTDI(w)) values between the seven centres was small for abdominal scans and head scans. For other scans however, such as functional endoscopic sinonasal surgery (FESS) the variations in CTDI(w) were as high as a factor of seven between the lowest and the highest values. At one centre a program of dose optimization had been undertaken and this centre had CTDI(w) values ranging from 3% to 64% lower than the average value for the seven centres. This demonstrates that significant dose reduction can be achieved through close collaboration between medical physicists, radiologists and radiographers.