Stereotactic noninvasive volume measurement compared with geometric measurement for indications and evaluation of gamma knife treatment

Valle, Ramiro del; Pérez, Miguel; Ortiz, Juan; Ruiz, Salvador; Anda, Salvador de; Jaramillo, José; Martínez, Manuel; Corona, Roberto; Vivas, Isabel; Teresa, Małecka-Massalska; Olmos, Rosario; Arrieta, Arturo; Estrada, Josué

doi:10.3171/jns.2005.102.s_supplement.0140

Cited by 10 publications

(3 citation statements)

References 6 publications

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“…Error was estimated to be < 5%, as verified by phantom studies at another site. 1,2 We found the margin of error using this method to be ± 5% for lesions in our phantom studies (data not shown). Significant tumor expansion was defined as > 10% enlargement.…”

mentioning

confidence: 71%

Tumor shrinkage of vestibular schwannomas after Gamma Knife surgery: results after more than 5 years of follow-up

Nagano¹,

Serizawa

Higuchi

et al. 2010

JNS

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Object The authors prospectively analyzed volume changes in vestibular schwannomas (VSs) after Gamma Knife surgery (GKS). Methods Among 104 VSs treated by GKS at the Chiba Cardiovascular Center between 1998 and 2004, 87 consecutively treated unilateral VSs observed on follow-up MR imaging for at least 5 years were analyzed. These lesions were harbored by 31 men and 56 women, with a mean age of 58.6 years (range 29–80 years). The Gd-enhanced volume of each lesion was measured serially every 3 months during the 1st year and every 6 months thereafter using GammaPlan or SurgiPlan. The frequency and degree of volume shrinkage were documented and possible prognostic factors were analyzed. Results The mean tumor volume at GKS was 2.5 cm3 (range 0.1–13.2 cm3). The lesions were irradiated by directing a mean dose of 12.0 Gy (range 10.5–13.0 Gy) to the tumor margin, which was located at the mean 52.2% isodose line (range 50%–67% isodose line). The mean follow-up period was 7.5 years (range 5.0–11.1 years). Peak tumor volume expansion was most frequently observed at 8.6 months after GKS and averaged 58% (range 0%–613%). Five years after GKS, the mean reduction in tumor volume was 31%, and 9 tumors still remained larger than their initial volumes. Tumors that homogeneously enhanced on MR images displayed less shrinkage than other tumors. Conclusions Most VSs exhibit shrinkage 5 years after GKS. The mean volume reduction in this series was 31%. These results indicate that careful serial follow-up is necessary for patients who harbor tumors that display homogeneous enhancement on MR images and patients whose tumors continue to expand in size after GKS.

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mentioning

confidence: 71%

Tumor shrinkage of vestibular schwannomas after Gamma Knife surgery: results after more than 5 years of follow-up

Nagano¹,

Serizawa

Higuchi

et al. 2010

JNS

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“…Therefore, changes in the size of the VS are usually very subtle [9, 12]. In addition, the configuration of the VS often is heterogeneous and conventional mathematical methods are not always sufficient to calculate exact volumes in these tumours [10, 17–19]. Another imaging dilemma after radiation therapy is the phenomenon of transient tumour enlargement followed by subsequent tumour shrinkage, which is frequently observed and has been attributed to either true neoplastic growth, tumoral oedema or tumour expansion following central radiation-induced necrosis [9, 10, 37–39].…”

Section: Discussionmentioning

confidence: 99%

3D quantitative assessment of response to fractionated stereotactic radiotherapy and single-session stereotactic radiosurgery of vestibular schwannoma

et al. 2015

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Objectives To determine clinical outcome of patients with vestibular schwannoma (VS) after treatment with fractionated stereotactic radiotherapy (FSRT) and single-session stereotactic radiosurgery (SRS) by using 3D quantitative response assessment on MRI. Materials This retrospective analysis included 162 patients who underwent radiation therapy for sporadic VS. Measurements on T1-weighted contrast-enhanced MRI (in 2-year post-therapy intervals: 0–2, 2–4, 4–6, 6–8, 8–10, and 10–12 years) were taken for total tumour volume (TTV) and enhancing tumour volume (ETV) based on a semi-automated technique. Patients were considered non-responders (NRs) if they required subsequent microsurgical resection or developed radiological progression and tumour-related symptoms. Results Median follow-up was 4.1 years (range: 0.4–12.0). TTV and ETV decreased for both the FSRT and SRS groups. However, only the FSRT group achieved significant tumour shrinkage (p < 0.015 for TTV, p < 0.005 for ETV over time). The 11 NRs showed proportionally greater TTV (median TTV pre-treatment: 0.61 cm3, 8–10 years after: 1.77 cm3) and ETV despite radiation therapy compared to responders (median TTV pre-treatment: 1.06 cm3; 10–12 years after: 0.81 cm3; p = 0.001). Conclusion 3D quantification of VS showed a significant decrease in TTV and ETV on FSRT-treated patients only. NRs had significantly greater TTV and ETV over time.

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“…Hence, repeat imaging follow-up is mandatory to evaluate the radiosurgical outcome. The most reliable and valid method in the evaluation of tumor response is assessment of changes in volumes [4][5][6] . The expected volume measurement errors implied by segmental errors, the size and morphology of the tumors, and thickness and number of tomographic slices must be carefully considered.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Factors Associated with Volumetric Data Errors in Gamma Knife Radiosurgery

Yang¹,

Sheehan

Liu

et al. 2009

Stereotact Funct Neurosurg

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Object: Gamma knife (GK) surgery is an important part of the treatment armamentarium for benign and malignant brain tumors. In general, quantitative volumetrical analysis of the tumor on neuroimaging studies is the most reliable method of assessment of the tumor’s response and is critical for accurate dose planning. This study evaluated various factors contributing to volumetric data error of tumors treated with GK radiosurgery. Method: Three differently shaped phantoms (spherical, rectangular, and irregular morphology) were created by immersing like shaped objects into 2% agarose gel. The volumes of phantoms were measured by laser scanning with errors <1%. MRI sequence and parameters including time of flight (TOF), T₁, T₂, different slice thickness, size of field of view (FOV), phase FOV as well as different position and axis of phantoms were retrieved and transferred to a Perfexion Gamma Knife Workstation (PGK-WS) and Picture Archiving and Communication System (PACS) for data analysis. The volumetric data errors were presented as the volume difference between those computed on the PGK-WS and actual volume measured by laser scanning divided by the actual laser scanning volume. The systemic error was defined as volume discrepancy between Perfexion and PACS over that in Perfexion. One-way ANOVA was used for evaluation of data errors between different methods as well as for factor analysis. Results: The MRI-computed volume of the various phantoms approached the laser-scanned volume within 2% when the slice number was ≥30. The volumetrical data errors (10/5 slices) associated with various MRIs for phantoms were 6.94 ± 0.04%/9.45 ± 0.35% (spherical phantom), 12.3 ± 0.2%/ 20.06 ± 0.7% (rectangular phantom), and 9.29 ± 0.078%/ 15.67 ± 0.6% (irregular phantom) (p < 0.001 and p < 0.001), respectively. The system errors (10/5 slices) associated with various MRIs for the phantoms were 3.17 ± 0.11%/3.9 ± 0.13% (spherical phantom), 3.61 ± 0.12%/4.01 ± 0.12% (rectangular phantom), and 4.39 ± 0.07%/4.75 ± 0.13% (irregular phantom) (p < 0.001 and p = 0.01), respectively. The volumetric data errors were related to the number of slices and the shape of phantom, but the systemic errors were only related to the irregularity of phantom morphology. The volumetrical data errors were not related to size of the FOV, phase FOV, sequence of T₁, T₂, TOF, and position of phantom. For the rectangular phantom, the data error was related to slice orientation of imaging acquisition (p < 0.001). Conclusion: Volume discrepancies existed between those volumes computed by the PGK-WS and volumes determined by laser scanning. The volumetric data errors were reduced through the acquisition of more slices through the phantom and a more spherical morphology of the phantom. Relatively few system volume errors were observed between those by the PGK-WS and PACS except for a significant discrepancy for the irregular surface phantom. For the rectangular-shaped phantom, the volumetric data errors were significantly ...

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Stereotactic noninvasive volume measurement compared with geometric measurement for indications and evaluation of gamma knife treatment

Abstract: The use of stereotactic volume calculation is highly recommended in planning, follow up, and determination of the outcome in patients participating in radiosurgical treatment and should lead to more uniform reports of the response to treatment.

Cited by 10 publications

References 6 publications

Tumor shrinkage of vestibular schwannomas after Gamma Knife surgery: results after more than 5 years of follow-up

Tumor shrinkage of vestibular schwannomas after Gamma Knife surgery: results after more than 5 years of follow-up

3D quantitative assessment of response to fractionated stereotactic radiotherapy and single-session stereotactic radiosurgery of vestibular schwannoma

Analysis of Factors Associated with Volumetric Data Errors in Gamma Knife Radiosurgery

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