Skull phantom-based methodology to validate MRI co-registration accuracy for Gamma Knife radiosurgery.

Purpose: Target localization, for stereotactic radiosurgery (SRS) treatment with Gamma Knife, has become increasingly reliant on the co-registration between the planning MRI and the stereotactic cone-beam computed tomography (CBCT). Validating image registration between modalities would be particularly beneficial when considering the emergence of novel functional and metabolic MRI pulse sequences for target delineation. This study aimed to develop a phantom-based methodology to quantitatively compare the co-registration accuracy of the standard clinical imaging protocol to a representative MRI sequence that was likely to fail co-registration.

Single-Fraction Stereotactic Radiosurgery Versus Hippocampal-Avoidance Whole Brain Radiation Therapy for Patients With 10 to 30 Brain Metastases: A Dosimetric Analysis.

Purpose: To compare normal tissue dosimetry between hippocampal-avoidance whole brain radiation therapy (HA-WBRT) and stereotactic radiosurgery (SRS) in patients with 10 to 30 brain metastases, and to describe a novel SRS strategy we term Spatially Partitioned Adaptive RadiosurgEry (SPARE).

Methods And Materials: A retrospective review identified SRS treatment plans with >10 brain metastases located >5 mm from the hippocampi. Our Gamma Knife Icon (GKI) SPARE (GKI-Spr) technique treats multiple metastases with single-fraction SRS partitioned over consecutive days while limiting the total treatment time to ≤60 minutes per day.

A realistic phantom for validating MRI-based synthetic CT images of the human skull.

Purpose: To introduce a new realistic human skull phantom for the validation of synthetic CT images of cortical bone from ultra-short echo-time (UTE) sequences.

Methods: A human skull of an adult female was utilized as a realistic representation of skull cortical bone. The skull was stabilized in a special acrylic container and was filled with contrast agents that have T and T relaxation times similar to human brain.

Measurement of time delays in gated radiotherapy for realistic respiratory motions.

Purpose: Gated radiotherapy is used to reduce internal motion margins, escalate target dose, and limit normal tissue dose; however, its temporal accuracy is limited. Beam-on and beam-off time delays can lead to treatment inefficiencies and/or geographic misses; therefore, AAPM Task Group 142 recommends verifying the temporal accuracy of gating systems. Many groups use sinusoidal phantom motion for this, under the tacit assumption that use of sinusoidal motion for determining time delays produces negligible error.

Robust method for 3D arterial spin labeling in mice.

Arterial spin labeling is a versatile perfusion quantification methodology, which has the potential to provide accurate characterization of cerebral blood flow (CBF) in mouse models. However, a paucity of physiological data needed for accurate modeling, more stringent requirements for gradient performance, and strong artifacts introduced by magnetization transfer present special challenges for accurate CBF mapping in the mouse. This article describes robust mapping of CBF over three-dimensional brain regions using amplitude-modulated continuous arterial spin labeling.

Measurement of cerebral blood volume in mouse brain regions using micro-computed tomography.

Micro-computed tomography (micro-CT) is an X-ray imaging technique that can produce detailed 3D images of cerebral vasculature. This paper describes the development of a novel method for using micro-CT to measure cerebral blood volume (CBV) in the mouse brain. As an application of the methodology, we test the hypotheses that differences in CBV exist over anatomical brain regions and that high energy demanding primary sensory regions of the cortex have locally elevated CBV, which may reflect a vascular specialization.