title: The role of diffusion tensor imaging tractography for Gamma Knife thalamotomy planning.
abstract: OBJECTIVE The role of tractography in Gamma Knife thalamotomy (GK-T) planning is still unclear. Pyramidal tractography might reduce the risk of radiation injury to the pyramidal tract and reduce motor complications. METHODS In this study, the ventralis intermedius nucleus (VIM) targets of 20 patients were bilaterally defined using Iplannet Stereotaxy Software, according to the anterior commissure-posterior commissure (AC-PC) line and considering the localization of the pyramidal tract. The 40 targets and tractography were transferred as objects to the GammaPlan Treatment Planning System (GP-TPS). New targets were defined, according to the AC-PC line in the functional targets section of the GP-TPS. The target offsets required to maintain the internal capsule (IC) constraint of < 15 Gy were evaluated. In addition, the strategies available in GP-TPS to maintain the minimum conventional VIM target dose at > 100 Gy were determined. RESULTS A difference was observed between the positions of both targets and the doses to the IC. The lateral (x) and the vertical (z) coordinates were adjusted 1.9 mm medially and 1.3 mm cranially, respectively. The targets defined considering the position of the pyramidal tract were more medial and superior, based on the constraint of 15 Gy touching the object representing the IC in the GP-TPS. The best strategy to meet the set constraints was 90° Gamma angle (GA) with automatic shaping of dose distribution; this was followed by 110° GA. The worst GA was 70°. Treatment time was substantially increased by the shaping strategy, approximately doubling delivery time. CONCLUSIONS Routine use of DTI pyramidal tractography might be important to fine-tune GK-T planning. DTI tractography, as well as anisotropy showing the VIM, promises to improve Gamma Knife functional procedures. They allow for a more objective definition of dose constraints to the IC and targeting. DTI pyramidal tractography introduced into the treatment planning may reduce the incidence of motor complications and improve efficacy. This needs to be validated in a large clinical series.
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.|Department of Neurosurgery, Real Hospital Português, Recife-PE, Brazil.
authors.forename: João Gabriel Ribeiro
authors.initials: JG
authors.lastname: Gomes
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.
authors.forename: Alessandra Augusta
authors.initials: AA
authors.lastname: Gorgulho
authors.affiliation: Department of Neurosurgery, Real Hospital Português, Recife-PE, Brazil.
authors.forename: Amanda
authors.initials: A
authors.lastname: de Oliveira López
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.
authors.forename: Crystian Wilian Chagas
authors.initials: CW
authors.lastname: Saraiva
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.
authors.forename: Lucas Petri
authors.initials: LP
authors.lastname: Damiani
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.
authors.forename: Anderson Martins
authors.initials: AM
authors.lastname: Pássaro
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.
authors.forename: João Victor
authors.initials: JV
authors.lastname: Salvajoli
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.
authors.forename: Ludmila
authors.initials: L
authors.lastname: de Oliveira Siqueira
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.
authors.forename: Bernardo Peres
authors.initials: BP
authors.lastname: Salvajoli
authors.affiliation: Department of Neurosurgery and Radiotherapy of the Hospital do Coração (HCOR Neurosciences), Gamma Knife Unit, São Paulo-SP, Brazil; and.
authors.forename: Antônio Afonso Ferreira
authors.initials: AA
authors.lastname: De Salles
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001927:Brain Diseases / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010347:Patient Care Planning; D016634:Radiosurgery / Q000379:methods*; D013788:Thalamus / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: AC-PC = anterior commissure–posterior commissure; AST = adjust shaped target; AT = adjusted target; DSF = dynamic shaping function; DTI = diffusion tensor imaging; GA = Gamma angle; GK-T = Gamma Knife thalamotomy; GP-TPS = GammaPlan Treatment Planning System; Gama Knife; IC = internal capsule; OT = original target; VIM = venetralis intermedius nucleus; anisotropy; stereotactic radiosurgery; thalamotomy; thalamus; tractography; tremor