Stereotactic radiotherapy (SRT) for patients with intracranial tumours are delivered using a dedicated platform or a conventional linear accelerator with a flattening filter-free beam.

This study compares treatment plans with intracranial tumours. A total of 29 patients were treated on CyberKnife and planned using the Accuray Precision. The same structure sets ws then exported to Varian Eclipse, and plans were made using a 6 MV FFF beam. Both plans were compared for parameters of target coverage, homogeneity index (HI), new conformity index (nCI), gradient index, selectivity index (SI), volumetric and OAR doses.

The treatment plans made for CyberKnife exhibit better results in terms of nCI (1·168 ± 0·08 versus 1·173 ± 0·077), SI (0·885 ± 0·05 versus 0·877 ± 0·05) and GI (3·64 ± 0·5 versus 4·45 ± 1·25), while HI values are better for TrueBeam. For OAR doses, in 65·5% and 72% of treatment plans, brainstem and optic pathways received lower doses on CyberKnife, respectively. In terms of dose spillage, Truebeam plans are better for very low doses (V5%), while for V10%, V20% and V50% CyberKnife plans are better.

CyberKnife is a better modality for the delivery of SRS/SRT to intracranial tumours except for dose homogeneity where TrueBeam offered better results.

The miniaturized conical cones for stereotactic radiosurgery (SRS) make it challenging in measurement of dosimetric data needed for commissioning of treatment planning system. This study aims at validating dosimetric characteristics of conical cone collimator manufactured by Varian using Monte Carlo (MC) simulation technique.

Percentage depth dose (PDD), tissue maximum ratio (TMR), lateral dose profile (LDP) and output factor (OF) were measured for cones with diameters of 5mm, 7·5mm, 10mm, 12·5 mm, 15 mm and 17·5 mm using EDGE detector for 6MV flattening filter-free (FFF) beam from Truebeam linac. Similarly, MC modelling of linac for 6MVFFF beam and simulation of conical cones were performed in PRIMO. Subsequently, measured beam data were validated by comparing them with results obtained from MC simulation.

The measured and MC-simulated PDDs or TMRs showed close agreement within 3% except for cone of 5mm diameter. Deviations between measured and simulated PDDs or TMRs were substantially higher for 5mm cone. The maximum deviations at depth of 10cm, 20cm and at range of 50% dose were found 4·05%, 7·52%, 5·52% for PDD and 4·04%, 7·03%, 5·23% for TMR with 5mm cone, respectively. The measured LDPs acquired for all the cones showed close agreement with MC LDPs except in penumbra region around 80% and 20% dose profile. Measured and MC full-width half maxima of dose profiles agreed with nominal cone size within ± 0·2 mm. Measured and MC OFs showed excellent agreement for cone sizes ≥10 mm. However, deviation consistently increases as the size of the cone gets smaller.

MC model of conical cones for SRS has been presented and validated. Very good agreement was found between experimentally measured and MC-simulated data. The dosimetry dataset obtained in this study validated using MC model may be used to benchmark beam data measured for commissioning of SRS for cone planning.

Medically serious suicide attempts have been recognized as the most important predictor of suicide. The Computerized Suicide Risk Scale based on backpropagation neural networks (CSRS-BP) has been recently found efficient in the detection of records of patients who performed medically serious suicide attempts (MSSA).

To validate the CSRS-BP by: 1) using the CSRS-BP with patients instead of records; 2) comparing the ability of expert psychiatrists to detect MSSA, using the CSRS checklist; and 3) comparing the results of the Risk Estimator for Suicide (RES) and the self-rating Suicide Risk Scale (SRS) with the CSRS-BP.

Two hundred fifty psychiatric inpatients (35 MSSA and 215 non-MSSA) were diagnosed by clinicians using the SCID DSM-IV. Three expert psychiatrists completed the CSRS checklist, and the RES for each patient, and the patients completed the self-report SRS assessment scale. The CSRS-BP was run for each patient. Five other expert psychiatrists assessed the CSRS checklists and estimated the probability of MSSA for each patient. Comparisons of sensitivity and specificity rates between CSRS-BP, assessment scales and experts were done.

Initially, the CSRS-BP, RES, SRS, and experts performed poorly. Although sensitivity and specificity rates significantly improved (two to four times) after the inclusion of information regarding the number of previous suicide attempts in the input data set, results still remained insignificant.

The CSRS-BP, which was very successful in the detection of MSSA patient records, failed to detect MSSA patients in face-to-face interviews. Information regarding previous suicide attempts is an important MSSA predictor, but remains insufficient for the detection of MSSA in individual patients. The detection rate of the SRS and RES scales was also poor and could therefore not identify MSSA patients or be used to validate the CSRS-BP.

The objective of this article is to evaluate the dosimetric efficacy of volumetric modulated arc therapy (VMAT) in comparison to dynamic conformal arc therapy (DCAT) and 3D conformal radiotherapy (3DCRT) for very small volume (≤1 cc) and small volume (≤3 cc) tumours for flattened (FF) and unflattened (FFF) 6 MV beams.

A total of 21 patients who were treated with single-fraction stereotactic radiosurgery, using either VMAT, DCAT or 3DCRT, were included in this study. The volume categorisation was seven patients each in <1, 1–2 and 2–3 cc volume. The treatment was planned with 6 MV FF and FFF beams using three different techniques: VMAT/Rapid Arc (RA) (RA_FF and RA_FFF), dynamic conformal arc therapy (DCA_FF and DCA_FFF) and 3DCRT (Static_FF and Static_FFF). Plans were evaluated for target coverage (V100%), conformity index, homogeneity index, dose gradient for 50% dose fall-off, total MU and MU/dose ratio [intensity-modulated radiotherapy (IMRT) factor], normal brain receiving >12 Gy dose, dose to the organ at risk (OAR), beam ON time and dose received by 12 cc of the brain.

The average target coverage for all plans, all tumour volumes (TVs) and delivery techniques is 96·4 ± 4·5 (range 95·7 ± 6·1–97·5 ± 2·9%). The conformity index averaged over all volume ranges <1, 2, 3 cc> varies between 0·55 ± 0·08 and 0·68 ± 0·04 with minimum and maximum being exhibited by DCA_FFF for 1 cc and Static_FFF/RA_FFF for 3 cc tumours, respectively. Mean IMRT factor averaged over all volume ranges for RA_FF, DCA_FF and Static_FF are 3·5 ± 0·8, 2·0 ± 0·2 and 2·0 ± 0·2, respectively; 50% dose fall-off gradient varies in the range of 0·33–0·42, 0·35–0·40 and 0·38–0·45 for 1, 2 and 3 cc tumours, respectively.

This study establishes the equivalence between the FF and FFF beam models and different delivery techniques for stereotactic radiosurgery in small TVs in the range of ≤1 to ≤3 cc. Dose conformity, heterogeneity, dose fall-off characteristics and OAR doses show no or very little variation. FFF could offer only limited time advantage due to excess dose rate over an FF beam.

Los intentos de suicidio médicamente graves se han reconocido como el predictor más importante de suicidio. Recientemente se ha encontrado que la Escala Informatizada de Riesgo de Suicidio basada en redes neurales de retropropagación (CSRS-BP) es eficaz en la detección de historias clínicas de pacientes que realizaron intentos de suicidio médicamente graves (ISMG).

Validar la CSRS-BP: 1) utilizándola con pacientes en lugar de con historias clínicas; 2) comparando la capacidad de psiquiatras expertos para detectar ISMG utilizando la lista de la CSRS, y 3) comparando los resultados del Estimador de Riesgo para el Suicidio (RES) y la Escala de autoevaluación de Riesgo de Suicidio (SRS) con la CSRS-BP.

Profesionales clínicos diagnosticaron a 250 pacientes psiquiátricos hospitalizados (35 con ISMG y 215 sin ISMG) utilizando la SCID del DSM IV. Tres psiquiatras expertos cumplimentaron la lista de la CSRS y el RES para cada paciente, y los pacientes rellenaron la escala de evaluación de autoinforme SRS. La CSRS-BP se pasó en máquina para cada paciente. Otros cinco psiquiatras expertos evaluaron las listas de la CSRS y estimaron la probabilidad de ISMG para cada paciente. Se hicieron comparaciones de las tasas de sensibilidad y especificidad entre la CSRS-BP, las escalas de evaluación y los expertos.

Inicialmente, la CSRS-BP, el RES, la SRS y los expertos obtuvieron malos resultados. Aunque las tasas de sensibilidad y especificidad mejoraron significativamente (de dos a cuatro veces) después de la inclusión de información con respecto al número de intentos previos de suicidio en el conjunto de datos de entrada, los resultados todavía no eran significativos.

La CSRS-BP, que tuvo mucho éxito en la detección de historias clínicas de pacientes con ISMG, no detectó a los pacientes con ISMG en entrevistas cara a cara. La información con respecto a los intentos de suicidio anteriores es un predictor importante de ISMG, pero es insuficiente para su detección en los pacientes individuales. La tasa de detección de la SRS y la escala RES fue también mala y, por tanto, no pudieron identificar a los pacientes con ISMG o utilizarse para validar la CSRS-BP.