Effect of skull contours on dose calculations in Gamma Knife Perfexion stereotactic radiosurgery. 2014

Hisato Nakazawa, and Masataka Komori, and Yoshimasa Mori, and Masahiro Hagiwara, and Yuta Shibamoto, and Takahiko Tsugawa, and Chisa Hashizume, and Tatsuya Kobayashi
Nagoya University Graduate School of Medicine, Nagoya Kyoritsu Hospital. hnakazawa@kaikou.or.jp.

In treatment planning of Leksell Gamma Knife (LGK) radiosurgery, the skull geometry defined by generally dedicated scalar measurement has a crucial effect on dose calculation. The LGK Perfexion (PFX) unit is equipped with a cone-shaped collimator divided into eight sectors, and its configuration is entirely different from previous model C. Beam delivery on the PFX is made by a combination of eight sectors, but it is also mechanically available from one sector with the remaining seven blocked. Hence the treatment time using one sector is more likely to be affected by discrepancies in the skull shape than that of all sectors. In addition, the latest version (Ver. 10.1.1) of the treatment planning system Leksell GammaPlan (LGP) includes a new function to directly generate head surface contouring from computed tomography (CT) images in conjunction with the Leksell skull frame. This paper evaluates change of treatment time induced by different skull models. A simple simulation using a uniform skull radius of 80 mm and anthropomorphic phantom was implemented in LGP to find the trend between dose and skull measuring error. To evaluate the clinical effect, we performed an interobserver comparison of ruler measurement for 41 patients, and compared instrumental and CT-based contours for 23 patients. In the phantom simulation, treatment time errors were less than 2% when the difference was within 3 mm. In the clinical cases, the variability of treatment time induced by the differences in interobserver measurements was less than 0.91%, on average. Additionally the difference between measured and CT-based contours was good, with a difference of -0.16% ± 0.66% (mean ±1 standard deviation) on average and a maximum of 3.4%. Although the skull model created from CT images reduced the dosimetric uncertainty caused by different measurers, these results showed that even manual skull measurement could reproduce the skull shape close to that of a patient's head within an acceptable range.

UI MeSH Term Description Entries
D008279 Magnetic Resonance Imaging Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques. Chemical Shift Imaging,MR Tomography,MRI Scans,MRI, Functional,Magnetic Resonance Image,Magnetic Resonance Imaging, Functional,Magnetization Transfer Contrast Imaging,NMR Imaging,NMR Tomography,Tomography, NMR,Tomography, Proton Spin,fMRI,Functional Magnetic Resonance Imaging,Imaging, Chemical Shift,Proton Spin Tomography,Spin Echo Imaging,Steady-State Free Precession MRI,Tomography, MR,Zeugmatography,Chemical Shift Imagings,Echo Imaging, Spin,Echo Imagings, Spin,Functional MRI,Functional MRIs,Image, Magnetic Resonance,Imaging, Magnetic Resonance,Imaging, NMR,Imaging, Spin Echo,Imagings, Chemical Shift,Imagings, Spin Echo,MRI Scan,MRIs, Functional,Magnetic Resonance Images,Resonance Image, Magnetic,Scan, MRI,Scans, MRI,Shift Imaging, Chemical,Shift Imagings, Chemical,Spin Echo Imagings,Steady State Free Precession MRI
D009464 Neuroma, Acoustic A benign SCHWANNOMA of the eighth cranial nerve (VESTIBULOCOCHLEAR NERVE), mostly arising from the vestibular branch (VESTIBULAR NERVE) during the fifth or sixth decade of life. Clinical manifestations include HEARING LOSS; HEADACHE; VERTIGO; TINNITUS; and FACIAL PAIN. Bilateral acoustic neuromas are associated with NEUROFIBROMATOSIS 2. (From Adams et al., Principles of Neurology, 6th ed, p673) Acoustic Neuroma,Melanocytic Vestibular Schwannoma,Schwannoma, Acoustic,Schwannoma, Vestibular,Acoustic Neuroma, Cerebellopontine Angle,Acoustic Tumor,Angle Tumor,Cerebellopontine Angle Acoustic Neuroma,Cerebellopontine Angle Tumor,Neurilemmoma, Acoustic,Neurilemoma, Acoustic,Neurinoma of the Acoustic Nerve,Neurinoma, Acoustic,Neuroma, Acoustic, Unilateral,Vestibular Schwannoma,Acoustic Neurilemmoma,Acoustic Neurilemmomas,Acoustic Neurilemoma,Acoustic Neurilemomas,Acoustic Neurinoma,Acoustic Neurinomas,Acoustic Neuromas,Acoustic Schwannoma,Acoustic Schwannomas,Acoustic Tumors,Angle Tumor, Cerebellopontine,Angle Tumors,Angle Tumors, Cerebellopontine,Cerebellopontine Angle Tumors,Melanocytic Vestibular Schwannomas,Neurilemmomas, Acoustic,Neurilemomas, Acoustic,Neurinomas, Acoustic,Neuromas, Acoustic,Schwannoma, Melanocytic Vestibular,Schwannomas, Acoustic,Schwannomas, Melanocytic Vestibular,Schwannomas, Vestibular,Tumor, Acoustic,Tumor, Angle,Tumor, Cerebellopontine Angle,Tumors, Acoustic,Tumors, Angle,Tumors, Cerebellopontine Angle,Vestibular Schwannoma, Melanocytic,Vestibular Schwannomas,Vestibular Schwannomas, Melanocytic
D011874 Radiometry The measurement of radiation by photography, as in x-ray film and film badge, by Geiger-Mueller tube, and by SCINTILLATION COUNTING. Geiger-Mueller Counters,Nuclear Track Detection,Radiation Dosimetry,Dosimetry, Radiation,Geiger Counter,Geiger-Mueller Counter Tube,Geiger-Mueller Probe,Geiger-Mueller Tube,Radiation Counter,Counter Tube, Geiger-Mueller,Counter Tubes, Geiger-Mueller,Counter, Geiger,Counter, Radiation,Counters, Geiger,Counters, Geiger-Mueller,Counters, Radiation,Detection, Nuclear Track,Dosimetries, Radiation,Geiger Counters,Geiger Mueller Counter Tube,Geiger Mueller Counters,Geiger Mueller Probe,Geiger Mueller Tube,Geiger-Mueller Counter Tubes,Geiger-Mueller Probes,Geiger-Mueller Tubes,Probe, Geiger-Mueller,Probes, Geiger-Mueller,Radiation Counters,Radiation Dosimetries,Tube, Geiger-Mueller,Tube, Geiger-Mueller Counter,Tubes, Geiger-Mueller,Tubes, Geiger-Mueller Counter
D011879 Radiotherapy Dosage The total amount of radiation absorbed by tissues as a result of radiotherapy. Dosage, Radiotherapy,Dosages, Radiotherapy,Radiotherapy Dosages
D011880 Radiotherapy Planning, Computer-Assisted Computer-assisted mathematical calculations of beam angles, intensities of radiation, and duration of irradiation in radiotherapy. Computer-Assisted Radiotherapy Planning,Dosimetry Calculations, Computer-Assisted,Planning, Computer-Assisted Radiotherapy,Calculation, Computer-Assisted Dosimetry,Calculations, Computer-Assisted Dosimetry,Computer Assisted Radiotherapy Planning,Computer-Assisted Dosimetry Calculation,Computer-Assisted Dosimetry Calculations,Dosimetry Calculation, Computer-Assisted,Dosimetry Calculations, Computer Assisted,Planning, Computer Assisted Radiotherapy,Radiotherapy Planning, Computer Assisted
D001921 Brain The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM. Encephalon
D001932 Brain Neoplasms Neoplasms of the intracranial components of the central nervous system, including the cerebral hemispheres, basal ganglia, hypothalamus, thalamus, brain stem, and cerebellum. Brain neoplasms are subdivided into primary (originating from brain tissue) and secondary (i.e., metastatic) forms. Primary neoplasms are subdivided into benign and malignant forms. In general, brain tumors may also be classified by age of onset, histologic type, or presenting location in the brain. Brain Cancer,Brain Metastases,Brain Tumors,Cancer of Brain,Malignant Primary Brain Tumors,Neoplasms, Intracranial,Benign Neoplasms, Brain,Brain Neoplasm, Primary,Brain Neoplasms, Benign,Brain Neoplasms, Malignant,Brain Neoplasms, Malignant, Primary,Brain Neoplasms, Primary Malignant,Brain Tumor, Primary,Brain Tumor, Recurrent,Cancer of the Brain,Intracranial Neoplasms,Malignant Neoplasms, Brain,Malignant Primary Brain Neoplasms,Neoplasms, Brain,Neoplasms, Brain, Benign,Neoplasms, Brain, Malignant,Neoplasms, Brain, Primary,Primary Brain Neoplasms,Primary Malignant Brain Neoplasms,Primary Malignant Brain Tumors,Benign Brain Neoplasm,Benign Brain Neoplasms,Benign Neoplasm, Brain,Brain Benign Neoplasm,Brain Benign Neoplasms,Brain Cancers,Brain Malignant Neoplasm,Brain Malignant Neoplasms,Brain Metastase,Brain Neoplasm,Brain Neoplasm, Benign,Brain Neoplasm, Malignant,Brain Neoplasms, Primary,Brain Tumor,Brain Tumors, Recurrent,Cancer, Brain,Intracranial Neoplasm,Malignant Brain Neoplasm,Malignant Brain Neoplasms,Malignant Neoplasm, Brain,Neoplasm, Brain,Neoplasm, Intracranial,Primary Brain Neoplasm,Primary Brain Tumor,Primary Brain Tumors,Recurrent Brain Tumor,Recurrent Brain Tumors,Tumor, Brain
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012886 Skull The SKELETON of the HEAD including the FACIAL BONES and the bones enclosing the BRAIN. Calvaria,Cranium,Calvarium,Skulls
D013997 Time Factors Elements of limited time intervals, contributing to particular results or situations. Time Series,Factor, Time,Time Factor

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