Characterization of the radiation field surrounding the Leksell Gamma Knife® and shielding applications.

The aim of this study is to improve the characterization and modeling of the radiation field surrounding the Leksell Gamma Knife®-Perfexion. The improved characterization of the radiation field enables more accurate shielding calculations to be performed for the areas adjacent to the treatment room. With the aid of a high-purity germanium detector and a satellite dose rate meter, γ-ray spectra and ambient dose equivalent H*(10) data were acquired at various locations in the field of a Leksell Gamma Knife unit in a treatment room at Karolinska University Hospital, Sweden.

On the stability of Leksell Vantage stereotactic head frame fixation in Gamma Knife radiosurgery: a study based on cone-beam computed tomography imaging and the High Definition Motion Management system.

Objective: The authors' objective was to investigate the stability of the newly introduced Vantage stereotactic frame fixation in single-fraction Gamma Knife radiosurgery.

Methods: A total of 255 patients were included in this work and treated with the Vantage frame and Leksell Gamma Knife (LGK) Icon equipped with cone-beam computed tomography (CBCT) imaging. After the frame was mounted on the patient's head, a CT scan was acquired.

Experimental investigation of TRS-483 reference dosimetry correction factors for Leksell Gamma Knife® Icon™ beams.

Purpose: Radiosurgery using the Leksell Gamma Knife® (LGK) Icon™ is an established technique used for treating intracranial lesions. The largest beam field size the LGK Icon can produce is a 16 mm diameter sphere. Despite this, reference dosimetry on the LGK Icon is typically performed using ionization chambers calibrated in 10 × 10 cm fields.

Integrating navigated transcranial magnetic stimulation motor mapping in hypofractionated and single-dose gamma knife radiosurgery: A two-patient case series and a review of literature.

Background: The aim of the study was to demonstrate the feasibility of integrating navigated transcranial magnetic stimulation (nTMS) in preoperative gamma knife radiosurgery (GKRS) planning of motor eloquent brain tumors.

Case Description: The first case was a 53-year-old female patient with metastatic breast cancer who developed focal epileptic seizures and weakness of the left hand. The magnetic resonance imaging (MRI) scan demonstrated a 30 mm metastasis neighboring the right precentral gyrus and central sulcus.

Investigation of a synthetic diamond detector response in kilovoltage photon beams.

Purpose: An important characteristic of radiation dosimetry detectors is their energy response which consists of absorbed-dose and intrinsic energy responses. The former can be characterized using Monte Carlo (MC) simulations, whereas the latter (i.e.

6-MV small field output factors: intra-/intermachine comparison and implementation of TRS-483 using various detectors and several linear accelerators.

Purpose: To investigate the applicability of output correction factors reported in TRS-483 on 6-MV small-field detector-reading ratios using four solid-state detectors. Also, to investigate variations in 6-MV small-field output factors (OF) among nominally matched linear accelerators (linacs).

Methods: The TRS-483 Code of Practice (CoP) introduced and provided output correction factors to be applied to measured detector-reading ratios to obtain OFs for several small-field detectors.

Pituitary carcinomas: Rare and challenging.

Background: Pituitary carcinomas (PCs) are defined as adenohypophyseal tumors with metastatic activity within and outside the boundaries of the central nervous system (CNS). The condition is rare and therefore seldom reported; most lesions are hormone producing and have a tendency for complex evolution. As such, the management of PCs remains difficult.

Adaptive hybrid surgery analysis (AHSA) for adjuvant gamma knife radiosurgery treatment of vestibular schwannoma residuals.

Objectives: Adaptive Hybrid Surgery Analysis (AHSA, Brainlab, Munich, Germany) is a software application generating in real-time conceptual dose plans for tumor residuals but has so far not been assessed for usability in a Gamma Knife (Elekta, Stockholm, Sweden) radiosurgery practice. We aimed to compare AHSA stereotactic radiosurgery dose plans with Leksell Gamma Plan (LGP, Elekta, Stockholm, Sweden) plans for adjuvant radiosurgical treatment of Vestibular Schwannoma (VS) residuals.

Patients And Methods: In this retrospective comparative study, we compared the automatically calculated AHSA dose plans with clinical LGP treatment plans in 13 patients radiosurgically treated for VS residuals.

Adaptive hypofractionated gamma knife radiosurgery in the acute management of brainstem metastases.

Background: Intrinsic brainstem metastases are life-threatening neoplasms requiring rapid, effective intervention. Microsurgery is considered not feasible in most cases and systemic treatment seldom provides a successful outcome. In this context, radiation therapy remains the best option but adverse radiation effects (ARE) remain a major concern.

The concept of rapid rescue radiosurgery in the acute management of critically located brain metastases: A retrospective short-term outcome analysis.

Background: Adaptive hypofractionated gamma knife radiosurgery has been used to treat brain metastases in the eloquent regions while limiting the risk of adverse radiation effect (ARE). Ablative responses might be achieved within days to weeks with the goal to preserve the neurological function. The application of this treatment modality in selected acute/subacute settings has been termed Rapid Rescue Radiosurgery (RRR) in our department.

Development of a PMMA phantom as a practical alternative for quality control of gamma knife® dosimetry.

Background: To measure the absorbed dose rate to water and penumbra of a Gamma Knife® (GK) using a polymethyl metacrylate (PMMA) phantom.

Methods: A multi-purpose PMMA phantom was developed to measure the absorbed dose rate to water and the dose distribution of a GK. The phantom consists of a hemispherical outer phantom, one exchangeable cylindrical chamber-hosting inner phantom, and two film-hosting inner phantoms.

Comment on 'Origins of the changing detector response in small megavoltage photon radiation fields'.

A clarification is made with regard to the erroneous statement that assigns an incorrect conclusion to a paper by Andreo and Benmakhlouf (2017 Phys. Med. Biol.

Beneficial and harmful effects of cyclodextrin-vitamin E complex on cryopreserved ram sperm.

Vitamin E is a potent molecule, especially when loaded in cyclodextrin, in modulating oxidative stress during the freeze-thawing process. The present study aimed to investigate the effect of different concentrations of cyclodextrin-vitamin E complex (CD-Vit E) on cryopreserved ram sperm. Ejaculates collected from five adult rams were pooled and divided into four aliquots.

Gamma knife radiosurgery in the management of endolymphatic sac tumors.

Background: Although widely regarded as rare epithelial tumors with a low grade of malignancy, endolymphatic sac tumors (ELST) often lead to disabling petrous bone destruction and significantly impairing symptoms at the time of primary diagnosis and/or recurrence. ELST is not uncommon in von Hippel Lindau (VHL) patients. Although open surgery is regarded as the best treatment option, recurrence remains a challenge, particularly when gross tumor resection (GTR) is deemed unachievable due to topographic conditions.

Determination of kQmsr,Q0fmsr,fref factors for ion chambers used in the calibration of Leksell Gamma Knife Perfexion model using EGSnrc and PENELOPE Monte Carlo codes.

Purpose: To calculate the kQmsr,Q0fmsr,fref factors for nine common ionization chamber types following the small fields dosimetry formalism for the calibration of the Leksell Gamma Knife (LGK) Perfexion using Monte Carlo simulation. This study also provides the first independent comparison of EGSnrc and PENELOPE for the calculation of kQmsr,Q0fmsr,fref correction factors and proposes a practical method to predict these factors based on chamber type, chamber orientation and phantom electron density.

Methods: The ionization chambers are modeled using the EGSnrc and PENELOPE Monte Carlo codes based on the blueprints provided by the manufacturers.

Suitability of microDiamond detectors for the determination of absorbed dose to water around high-dose-rate Ir brachytherapy sources.

Purpose: Experimental dosimetry of high-dose-rate (HDR) Ir brachytherapy (BT) sources is complicated due to high dose and dose-rate gradients, and softening of photon energy spectrum with depth. A single crystal synthetic diamond detector microDiamond (PTW 60019, Freiburg, Germany) has a small active volume, high sensitivity, direct readout, and nearly water-equivalent active volume. The purpose of this study was to evaluate the suitability of microDiamond detectors for the determination of absorbed dose to water around HDR Ir BT sources.

Adaptive hypofractionated gamma knife radiosurgery in the acute management of large thymic carcinoma brain metastases.

Background: Brain metastases often lead to serious neurological impairment and life threatening states. Their acute management remains complex, particularly in the case of rare malignancies with aggressive evolution. In large single lesions, open surgery followed by radiation to the surgical cavity is widely regarded as the best approach; yet in many cases, microsurgery is not feasible due to the lesion's critical location and/or the number of brain metastases present.

Role of the density, density effect and mean excitation energy in solid-state detectors for small photon fields.

A number of recent publications on small photon beam dosimetry aim at contributing to the understanding of the response of solid-state detectors in small fields. Some of them assign the difference in response to the mass density, or to the electron density, of the sensitive detector material relative to that of water. This work analyses the role of the mass and electron density ([Formula: see text]), density effect (δ) and mean excitation energy (I-value) of some detector materials in a 6 MV photon beam of 0.

Spectral distribution of particle fluence in small field detectors and its implication on small field dosimetry.

Purpose: Correction factors for the relative dosimetry of narrow megavoltage photon beams have recently been determined in several publications. These corrections are required because of the several small-field effects generally thought to be caused by the lack of lateral charged particle equilibrium (LCPE) in narrow beams. Correction factors for relative dosimetry are ultimately necessary to account for the fluence perturbation caused by the detector.

On the Monte Carlo simulation of small-field micro-diamond detectors for megavoltage photon dosimetry.

Monte Carlo (MC) calculated detector-specific output correction factors for small photon beam dosimetry are commonly used in clinical practice. The technique, with a geometry description based on manufacturer blueprints, offers certain advantages over experimentally determined values but is not free of weaknesses. Independent MC calculations of output correction factors for a PTW-60019 micro-diamond detector were made using the EGSnrc and PENELOPE systems.

Increased survival using delayed gamma knife radiosurgery for recurrent high-grade glioma: a feasibility study.

Objective: The current study retrospectively assessed delayed gamma knife radiosurgery (GKRS) in the management of high-grade glioma recurrences.

Methods: A total of 55 consecutive patients with high-grade glioma comprising 68 World Health Organization (WHO) III and WHO IV were treated with GKRS for local recurrences between 2001 and 2007. All patients had undergone microsurgery and radiochemotherapy, considered as standard therapy for high-grade glioma.

Output correction factors for nine small field detectors in 6 MV radiation therapy photon beams: a PENELOPE Monte Carlo study.

Purpose: To determine detector-specific output correction factors,[Formula: see text], in 6 MV small photon beams for air and liquid ionization chambers, silicon diodes, and diamond detectors from two manufacturers.

Methods: Field output factors, defined according to the international formalism published byAlfonso et al. [Med.

Influence of phantom thickness and material on the backscatter factors for diagnostic x-ray beam dosimetry.

Most of the existing backscatter factors for the dosimetry of clinical diagnostic x-ray beams have been calculated for 15 cm thick phantoms; these data are used for skin dose determinations which in general ignore the influence of phantom material and thickness. The former should strictly be required whenever dosimetry measurements are made on phantom materials different from those used for the backscatter factor calculations. The phantom or patient thickness is of special importance when skin dose determinations are made for infants or paediatric patients.

Backscatter factors and mass energy-absorption coefficient ratios for diagnostic radiology dosimetry.

Backscatter factors, B, and mass energy-absorption coefficient ratios, (μ(en)/ρ)(w, air), for the determination of the surface dose in diagnostic radiology were calculated using Monte Carlo simulations. The main purpose was to extend the range of available data to qualities used in modern x-ray techniques, particularly for interventional radiology. A comprehensive database for mono-energetic photons between 4 and 150 keV and different field sizes was created for a 15 cm thick water phantom.