Assessment of an image-guided neurosurgery system using a head phantom.

OBJECTIVE: To acknowledge the challenges and limitations of image-guided neurosurgery systems, we compared the application accuracy of two different image registration methods for one commercial system. (VectorVision, BrainLab, Germany). METHODS: We used an anthropomorphic head phantom for radiosurgery and a custom built add-on to simulate surgical targets inside the brain during an image-guided neurosurgery. We used two image registration methods, fiducial registration using attachable surface markers for computed tomography (CT) and surface registration using infrared laser face scanning. After simulation, we calculated the three-dimensional (3D) distance between the predicted position of a target, and its actual position using a registered pointer and an infrared camera. Deviations were measured for both superficial fiducial markers and internal surgical targets by five different users. RESULTS: Deviations from the location of fiducial markers after each registration method were 2.15 ± 0.93 mm after CT surface marker registration and 1.25 ± 0.64 mm after infrared face scanner registration. The mean target registration errors were 2.95 ± 1.4 mm using fiducial registration and 2.90 ± 1.3 mm using surface registration. The largest deviations (6.2 mm) were found for the targets in the skull base and posterior cranial fossa. Fiducial deviations and target registration errors were statistically uncorrelated. The total application accuracy was 4.87 ± 0.97 mm after CT surface marker registration and 4.14 ± 0.64 mm after infrared face scanner registration. CONCLUSIONS: Despite others have reported differences, we did not find significant variations between both registration methods for the target registration error, although application accuracy was slightly better after surface face registration. Superficial registration errors, but not the target registration error, can be routinely evaluated in the operating room. Since both errors were uncorrelated, surgeons may neglect the achievable accuracy of the procedure. The described method is recommended to assess application accuracy in the operating room.

Effect of correction methods of radiochromic EBT2 films on the accuracy of IMRT QA.

Radiochromic films are dosimeters with more favorable characteristics than other two-dimensional (2D) radiation detectors. Transmission film scanners using a linear charge-coupled device (CCD) array have a drawback of variation in response along the detector array, which may result in a nonuniform transmission of signal over the scanned image. This study uses 2D gamma index analysis to compare two methods for correcting the nonuniform response of EBT2: the first method was based on the new red:blue method proposed by the manufacturer (to compensate for small nonuniformities in the film coating) and the second method, proposed by Menegotti et al. (2008), was based on dose-dependent matrix correction factors. The gamma index analysis shows that both the methods are comparably accurate for all the criteria values used for evaluation (1 mm/1%, 2 mm/2%, 3 mm/3%). Centers around the world use both the methods to correct EBT2 local heterogeneities, but it is important to note that the former method has several advantages such as less time consumption and easy implementation.

Comparative analysis of several detectors for the measurement of radiation transmission and leakage from a multileaf collimator.

The multileaf collimator (MLC) is the standard device used to shape radiation beams for 3-d conformal and intensity-modulated radiation therapy (IMRT). Due to the inherent properties of MLC, there is a small amount of radiation transmitted through the leaves, called radiation transmission (RT). Accurate measurements of this radiation are required to commission and validate IMRT-capable treatment planning systems because this radiation may impact the dosimetry of IMRT-calculated dose distributions. This work compares several detectors in the measurement of RT for a micro-multileaf collimation system. The results show that there are statistically significant differences in the measured RT values between detectors from 3.5 to 12.5% for the same MLC model and less than 0.2% relative to the isocentre dose for an open reference field. However, although small in magnitude, these differences may impact the dosimetry of IMRT treatment planning by up to 1.78 Gy to the healthy tissue surrounding the target for a treatment of 60 Gy in 30 fractions. By the later, these differences must be included as a source of uncertainty in IMRT dose delivery. Also, it must be established which detector offers the most reliable results in the measurement of the RT by using Monte Carlo simulation methods.

Diagnostic approach in suspected recurrent primary brain tumors using (18)FDG-PET/MRI, perfusion MRI, visual and quantitative analysis, and three dimensional stereotactic surface projections. First experience in Mexico.

UNLABELLED: Thirty patients with primary cerebral tumors WHO III and IV previously treated, undergoing evaluation for tumoral recurrence, they underwent (18)FDG-PET study, MRI and PMRI. PET uptake was determined by visual inspection and was quantified by use of standard uptake values, the ratio of tumor uptake to normal tissue and were z scored using automated voxel-based comparison. PMRI was quantified by use of ratios of cerebral blood volume (rCBV). The accuracies were determined by comparing imaging data with histologic findings and clinical follow up of up to 21 mo. RESULTS: Sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV) and accuracy were 100 %, 82 %, 90 %, 100 % and 93 % respectively for the PET/MRI fusion and 68 %, 82 %, 87 %, 60 % and 73 % respectively for PMRI. There were two false positive cases for PET/MRI fusion that were confirmed by biopsy: chronic inflammation; and foreign body granulomas. The receiver operating characteristic (ROC) curve analysis showed statistically significant difference (p = 0.0225). CONCLUSIONS: (18)FDG SUVs, glucose uptake ratios and 3D stereotactic surface projections in brain tumors were not a reliable measure for evaluating recurrent tumors. PET/MRI fusion was more sensitive and accurate than PMRI for imaging recurrent primary brain tumors. The region of interest can be visually analyzed on the PET/MRI fusion images and described as recurrent tumor when any activity (lower, equal or greater than the contralateral cortex) is presented in the zone of hyperintensity seen on the post-gadolinium T1-weighted MRI.

Diagnostic approach in suspected recurrent primary brain tumors using 18FDG-PET/MRI, perfusion MRI, visual and quantitative analysis, and three dimensional stereotactic surface projections. First experience in Mexico / Enfoque diagnóstico en pacientes con sospecha de tumor cerebral primario recurrente utilizando 18fdg-pet/rm, rm de perfusión, análisis visual y cuantitativo y proyecciones estereotáxicas de superficie tridimensionales. Primera experiencia en México

Thirty patients with primary cerebral tumors WHO III and IV previously treated, undergoing evaluation for tumoral recurrence, they underwent 18FDG-PET study, MRI and PMRI. PET uptake was determined by visual inspection and was quantified by use of standard uptake values, the ratio of tumor uptake to normal tissue and were z scored using automated voxel-based comparison. PMRI was quantified by use of ratios of cerebral blood volume (rCBV). The accuracies were determined by comparing imaging data with histologic findings and clinical follow up of up to 21 mo. Results. Sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV) and accuracy were 100 %, 82 %, 90 %, 100 % and 93 % respectively for the PET/MRI fusion and 68 %, 82 %, 87 %, 60 % and 73 % respectively for PMRI. There were two false positive cases for PET/MRI fusion that were confirmed by biopsy: chronic inflammation; and foreign body granulomas. The receiver operating characteristic (ROC) curve analysis showed statistically significant difference (p = 0.0225). Conclusions. 18FDG SUVs, glucose uptake ratios and 3D stereotactic surface projections in brain tumors were not a reliable measure for evaluating recurrent tumors. PET/MRI fusion was more sensitive and accurate than PMRI for imaging recurrent primary brain tumors. The region of interest can be visually analyzed on the PET/MRI fusion images and described as recurrent tumor when any activity (lower, equal or greater than the contralateral cortex) is presented in the zone of hyperintensity seen on the post-gadolinium T1-weighted MRI

Se ha hecho un estudio con 18FDG-PET, RM y perfusión por resonancia magnética en 30 pacientes con tumores cerebrales primarios grado OMS III y IV, previamente tratados y a los que se les iba a hacer el seguimiento de recurrencia tumoral. La captación de la PET estuvo determinada por la inspección visual y se cuantificó utilizando los valores de captación estándar, la proporción de captación tumoral/tejido normal y la desviación estándar z mediante comparación automatizada con vóxeles. La perfusión por resonancia magnética se cuantificó mediante la utilización de las proporciones del volumen sanguíneo cerebral. La exactitud diagnóstica se determinó comparando los datos de las imágenes con los hallazgos histológicos y el seguimiento clínico durante un período de hasta 21 meses. Resultados. La sensibilidad (Se), la especificidad (Sp), el valor predictivo positivo (VPP), el valor predictivo negativo (VPN) y la exactitud diagnóstica fueron del 100, 82, 90, 100 y 93 %, respectivamente, para la fusión PET/RM; y del 68, 82, 87, 60 y 73%, respectivamente, para la perfusión por resonancia magnética. Hubo dos casos falsos positivos para la fusión PET/RM que se confirmaron mediante biopsia: inflamación crónica y granulomas por cuerpo extraño. El análisis de las curvas características operativas del receptor (ROC) demostró una diferencia estadísticamente significativa (p = 0,0225). Conclusiones. Los valores de captación estandarizados de 18FDG (SUV), las proporciones de captación de glucosa y las proyecciones estereotáxicas de superficie en 3D (3D-SSP) de los tumores cerebrales no demostraron ser mediciones útiles para evaluar tumores recurrentes. La fusión PET/RM resultó ser más sensible y con mayor exactitud diagnóstica que la perfusión por resonancia magnética como diagnóstico de imagen de los tumores cerebrales primarios recurrentes. En las imágenes de fusión PET/RM puede analizarse la región de interés y reportarse como tumor recurrente cuando aparece cualquier actividad (menor, igual o mayor que en la corteza contralateral) en la zona de hiperintensidad observada en la RM con gadolinio y ponderada en T1

Corpus callosotomy using conformal stereotactic radiosurgery.

OBJECTS: To show the clinical results of a corpus callosotomy (CC) treatment using conformal stereotactic radiosurgery (SRS) on a patient with medically intractable multifocal epilepsy. MATERIALS AND METHODS: A 17-year-old male patient underwent corpus callosotomy conformal SRS using a dedicated linear accelerator (linac) with dynamic arcs technique. The prescribed dose was 36.0 Gy at the periphery of the rostrum, genu, and a half of the body of the corpus callosum (CCA). At 8 months after conformal SRS, the patient developed a significant brain edema and moderate transitory motor deficit, which were controlled with steroids. After 32 months follow-up, there is an improvement of 84% on drop attacks and generalized tonic-clonic seizures. CONCLUSIONS: Conformal SRS for corpus callosotomy with a single isocenter reproduce the results reported on literature using Gamma Knife-based SRS. The results show that this technique is safe and demonstrate its efficacy to control seizures.

[Intracranial arteriovenous malformations and radiosurgery with LINAC: review article]. / Malformaciones arteriovenosas intracraneales y radiocirugía con LINAC: artículo de revisión.

Among all vascular malformations, the intracranial arteriovenous malformations (AVM's) have the most powerful impact from the clinical point of view. The manifestations include hemorrhage, seizures, headacheh, but sometimes they are incidentally found during the diagnostic approach of patients with head trauma or chronic headache. There are three different types of treatments: microsurgery, endovascular treatment and radiosurgery. The actual role of the endovascular treatment is as an adjuvant therapy before microsurgery or radiosurgery just to diminish the nidus size. The goal of all treatments is complete nidus obliteration without causing a new neurological deficit. The overall obliteration index with LINAC based radiosurgery is about 80% and the result is dose, volume and time dependent. The mean dose reported in the literature fluctuates between 15 and 25 Gy, and the isodose coverage curve for the AVM with LINAC is generally the one of the 80%. There can be a treatment failure defined as the necessity to retreat the patient after three years from the first radiosurgical treatment in about 26% of the patients. There is a lack of evidence, principally from randomized trials, to point out the role of each of the modalities in the treatment of the AVM.

Malformaciones arteriovenosas intracraneales y radiocirugía con LINAC: artículo de revisión / Intracranial arteriovenous malformations and radiosurgery with LINAC: review article

De las malformaciones vasculares, las malformaciones arteriovenosas (MAV) intracraneales son las que tienen una mayor repercusión desde el punto de vista clínico. Se pueden manifestar con hemorragia, epilepsia, cefalea, o pueden aparecer en forma incidental durante el abordaje diagnóstico de pacientes con traumatismos o cefalea crónica. Existen tres tipos de tratamientos disponibles: microcirugía, embolización y radiocirugía. El papel actual de la terapia endovasculares como adyuvante como tratamiento previo a microcirugía o a radiocirugía para disminuir el tamaño del nido. La meta final de cualquier tratamiento es la obliteración completa del nido sin causar un nuevo déficit neurológico. El índice general de obliteración por radiocirugía con LINAC es alrededor de 80% yes dependiente de la dosis, del volumen y del tiempo de seguimiento. La dosis promedio publicada en la literatura va de 15 a 25 Gy y la curva de isodosis para conformar la MAV con LINAC es por lo general la del 80%. Puede haber fallo en el tratamiento definido como la necesidad de volver a tratar al paciente después de n tres años de seguimiento por falta de obliteración en alrededor del 26% de los pacientes. Faltan pruebas principalmente a partir de ensayos clínicos, para seguir definiendo el papel de cada una delas modalidades en el tratamiento integral de las MAV

Among all vascular malformations, the intracranial arterio venous malformations (AVM's) have the most powerful impact from the clinical point of view. The manifestations include hemorrhage, seizures, headache, but sometimes they are incidentally found during the diagnostic approach of patients with head trauma or chronic headache. There are three different types of treatments: microsurgery, endovascular treatment and radiosurgery. The actual role of the endovascular treatment is as an adjuvant therapy before microsurgery or radiosurgery just to diminish the nidus size. The goal of all treatments is complete nidus obliteration without causing a new neurological deficit. The overall obliteration index with LINAC based radiosurgery is about 80% and the result is dose, volume and time dependent. The mean dose reported in the literature fluctuates between15 and 25 Gy, and the is dose coverage curve for the AVM with LINAC is generally the one of the 80%.There can be a treatment failure defined as the necessity to retreat the patient after three years from the first radio surgical treatment in about 26% of the patients. There is a lack of evidence, principally from randomized trials, to point out the role of each of the modalities in the treatment of the AVM