Domain wall propagation and pinning induced by current pulses in cylindrical modulated nanowires.

The future developments in 3D magnetic nanotechnology require the control of domain wall dynamics by means of current pulses. While this has been extensively studied in 2D magnetic strips (planar nanowires), few reports on this exist in cylindrical geometry, where Bloch point domain walls are expected to have intriguing properties. Here, we report an investigation on cylindrical magnetic Ni nanowires with geometrical notches. An experimental work based on synchrotron X-ray magnetic circular dichroism (XMCD) combined with photoemission electron microscopy (PEEM) indicates that large current densities induce domain wall nucleation, while smaller currents move domain walls preferably antiparallel to the current direction. In the region where no pinning centers are present, we found a domain wall velocity of about 1 km s-1. Thermal modelling indicates that large current densities temporarily raise the temperature in the nanowire above the Curie temperature, leading to nucleation of domain walls during the system cooling. Micromagnetic modelling with a spin-torque effect shows that for intermediate current densities, Bloch point domain walls with chirality parallel to the Oersted field propagate antiparallel to the current direction. In other cases, domain walls can be bounced from the notches and/or get pinned outside their positions. We thus found that current is not only responsible for domain wall propagation, but also is a source of pinning due to the Oersted field action.

Tratamiento de lesiones pulmonares mediante radioterapia estereotáxica extracraneal tras colocación guiada por tomografía computarizada de marcador Visicoil (R): experiencia inicial / Treatment of lung lesions by stereotactic body radiation therapy after computed tomography guided placement of a Visicoil ® marker: initial experience

Objetivo. Describir la técnica de radioterapia estereotáxica extracraneal (RTEE) de lesiones pulmonares tras colocar un marcador interno guiada por tomografía computarizada (TC) y valorar los resultados, complicaciones y efectos secundarios de estos procedimientos. Material y método. Analizamos una serie de 39 lesiones en 25 pacientes (8 primarias y 31 metastásicas) tratadas mediante este procedimiento. Se realizó una punción percutánea transtorácica guiada por TC para la colocación de un marcador interno en la lesión o próximo a ella. El procedimiento no requiere sedación. El marcador sirve de guía para el tratamiento de la lesión mediante RTEE con sincronismo respiratorio que permite controlar el movimiento del tumor y disminuir el volumen de irradiación administrando con precisión dosis altas al tumor y mínimas a los tejidos sanos circundantes. Resultados. La única complicación de las punciones transtorácicas fue el neumotórax en 6 pacientes (24%). Fue necesaria la colocación de un drenaje pleural en tres pacientes. Se consiguió el control local en el 96,7% de las lesiones. La irradiación produjo astenia grado 1 en un paciente, neumonitis grado 2 en un paciente y neumonitis grado 1 en el resto. Conclusiones. La colocación guiada por TC de marcadores internos en las lesiones pulmonares es una técnica segura que se puede realizar de forma ambulante. La RTEE con sincronismo respiratorio permite aumentar la dosis al tumor y reducir el volumen de pulmón sano tratado con pocos efectos secundarios (AU)

Objective. To describe the technique of stereotactic body radiation therapy (SBRT) of lung lesions after the computed tomography (CT) guided placement of an internal fiducial marker and to assess the results, complications and secondary effects of these procedures. Material and method. A series of 39 lesions (8 primary and 31 metastases) in 25 patients treated using this procedure were analysed. A CT-guided percutaneous transthoracic puncture was performed for placing the internal marker in the lesion or near to it. The procedure did not require sedation. The marker serves as a guide for the treatment of the lesion using SBRT with respiratory synchronism, which allows the movement of the tumour to be controlled and to decrease the radiation volume, giving high doses withe precision to the tumour, and minimal to the surrounding healthy tissue. Results. The only complication of the percutaneous fiducial placement was a pneumothorax in 6 (24%) patients. A pleural drain had to be placed in 3 patients. Local control was achieved in 96.7% of the lesions. The radiation produced a grade 1 asthenia in 1 patient, a grade 2 pneumonitis in one patient and a grade 1 pneumonitis in the remainder. Conclusions. The CT-guided placement of internal markers in lung lesions is a safe technique that may be performed as ambulatory procedure. SBRT with respiratory synchronism allows the dose to the tumour to be increased, and reduces the volume of healthy lung treated, with few secondary effects (AU)

[Treatment of lung lesions by stereotactic body radiation therapy after computed tomography guided placement of a Visicoil(®) marker: initial experience]. / Tratamiento de lesiones pulmonares mediante radioterapia estereotáxica extracraneal tras colocación guiada por tomografía computarizada de marcador Visicoil(®): experiencia inicial.

OBJECTIVE: To describe the technique of stereotactic body radiation therapy (SBRT) of lung lesions after the computed tomography (CT) guided placement of an internal fiducial marker and to assess the results, complications and secondary effects of these procedures. MATERIAL AND METHOD: A series of 39 lesions (8 primary and 31 metastases) in 25 patients treated using this procedure were analysed. A CT-guided percutaneous transthoracic puncture was performed for placing the internal marker in the lesion or near to it. The procedure did not require sedation. The marker serves as a guide for the treatment of the lesion using SBRT with respiratory synchronism, which allows the movement of the tumour to be controlled and to decrease the radiation volume, giving high doses with precision to the tumour, and minimal to the surrounding healthy tissue. RESULTS: The only complication of the percutaneous fiducial placement was a pneumothorax in 6 (24%) patients. A pleural drain had to be placed in 3 patients. Local control was achieved in 96.7% of the lesions. The radiation produced a grade 1 asthenia in 1 patient, a grade 2 pneumonitis in one patient and a grade 1 pneumonitis in the remainder. CONCLUSIONS: The CT-guided placement of internal markers in lung lesions is a safe technique that may be performed as ambulatory procedure. SBRT with respiratory synchronism allows the dose to the tumour to be increased, and reduces the volume of healthy lung treated, with few secondary effects.

Aplicación clínica de la tomografía por emisión de positrones con fluorocolina en el cáncer de próstata recurrente / Clinical Application of Fluorocholine Positron Emission Tomography in Relapsed Prostate Cancer

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