Use of GammaPlan convolution algorithm for dose calculation on CT and cone-beam CT images

Purpose@#The aim of this study was to assess the suitability of using cone-beam computed tomography images (CBCTs) produced in a Leksell Gamma Knife (LGK) Icon system to generate electron density information for the convolution algorithm in Leksell GammaPlan (LGP) Treatment Planning System (TPS). @*Materials and Methods@#A retrospective set of 30 LGK treatment plans generated for patients with multiple metastases was selected in this study. Both CBCTs and fan-beam CTs were used to provide electron density data for the convolution algorithm. Plan quality metrics such as coverage, selectivity, gradient index, and beam-on time were used to assess the changes introduced by convolution using CBCT (convCBCT) and planning CT (convCT) data compared to the homogeneous TMR10 algorithm. @*Results@#The mean beam-on time for TMR10 and convCBCT was found to be 18.9 ± 5.8 minutes and 21.7 ± 6.6 minutes, respectively. The absolute mean difference between TMR10 and convCBCT for coverage, selectivity, and gradient index were 0.001, 0.02, and 0.0002, respectively. The calculated beam-on times for convCBCT were higher than the time calculated for convCT treatment plans. This is attributed to the considerable variation in Hounsfield values (HU) dependent on the position within the field of view. @*Conclusion@#The artifacts from the CBCT’s limited field-of-view and considerable HU variation need to be taken into account before considering the use of convolution algorithm for dose calculation on CBCT image datasets, and electron data derived from the onboard CBCT should be used with caution.

Use of GammaPlan convolution algorithm for dose calculation on CT and cone-beam CT images

Purpose@#The aim of this study was to assess the suitability of using cone-beam computed tomography images (CBCTs) produced in a Leksell Gamma Knife (LGK) Icon system to generate electron density information for the convolution algorithm in Leksell GammaPlan (LGP) Treatment Planning System (TPS). @*Materials and Methods@#A retrospective set of 30 LGK treatment plans generated for patients with multiple metastases was selected in this study. Both CBCTs and fan-beam CTs were used to provide electron density data for the convolution algorithm. Plan quality metrics such as coverage, selectivity, gradient index, and beam-on time were used to assess the changes introduced by convolution using CBCT (convCBCT) and planning CT (convCT) data compared to the homogeneous TMR10 algorithm. @*Results@#The mean beam-on time for TMR10 and convCBCT was found to be 18.9 ± 5.8 minutes and 21.7 ± 6.6 minutes, respectively. The absolute mean difference between TMR10 and convCBCT for coverage, selectivity, and gradient index were 0.001, 0.02, and 0.0002, respectively. The calculated beam-on times for convCBCT were higher than the time calculated for convCT treatment plans. This is attributed to the considerable variation in Hounsfield values (HU) dependent on the position within the field of view. @*Conclusion@#The artifacts from the CBCT’s limited field-of-view and considerable HU variation need to be taken into account before considering the use of convolution algorithm for dose calculation on CBCT image datasets, and electron data derived from the onboard CBCT should be used with caution.

Dosimetric comparative study of 3DCRT, IMRT, VMAT, Ecomp, and Hybrid techniques for breast radiation therapy

Purpose@#To assess and compare the dosimetric parameters obtained between three-dimensional conformal radiotherapy (3DCRT), three-dimensional field-in-field (3DFIF), 5-field intensity-modulated radiotherapy (IMRT MF5), tangential IMRT (tIMRT), tangential volumetric modulated arc therapy (tVMAT), electronic tissue compensation (Ecomp), and Hybrid treatment plans. Material and Methods: Thirty planning computed tomography datasets obtained from patients previously treated with whole breast radiation therapy (WBRT) were utilized in this study. Treatment plans were created for 3DCRT, 3DFIF, IMRT MF5, tIMRT, tVMAT, Ecomp, and Hybrid techniques using Eclipse Treatment Planning System (version 13.6) with a prescribed dose of 42.5 Gy in 16 fractions. @*Results@#Techniques with tangential beams produced statistically significantly better organs-at-risk (OARs) dosimetry (p < 0.001). Planning target volume Homogeneity Index (HI) was found to be significantly different among all techniques (p < 0.001), with Ecomp resulting in better HI (1.061 ± 0.029). Ecomp was also observed to require relatively shorter planning time (p < 0.001). @*Conclusions@#Techniques using tangential fields arrangements produced improved OARs dosimetry. Of all the treatment planning techniques employed in this study, Ecomp was found to be relatively easy to plan and produce acceptable dosimetry for WBRT in a short time.

Dosimetric comparative study of 3DCRT, IMRT, VMAT, Ecomp, and Hybrid techniques for breast radiation therapy

Purpose@#To assess and compare the dosimetric parameters obtained between three-dimensional conformal radiotherapy (3DCRT), three-dimensional field-in-field (3DFIF), 5-field intensity-modulated radiotherapy (IMRT MF5), tangential IMRT (tIMRT), tangential volumetric modulated arc therapy (tVMAT), electronic tissue compensation (Ecomp), and Hybrid treatment plans. Material and Methods: Thirty planning computed tomography datasets obtained from patients previously treated with whole breast radiation therapy (WBRT) were utilized in this study. Treatment plans were created for 3DCRT, 3DFIF, IMRT MF5, tIMRT, tVMAT, Ecomp, and Hybrid techniques using Eclipse Treatment Planning System (version 13.6) with a prescribed dose of 42.5 Gy in 16 fractions. @*Results@#Techniques with tangential beams produced statistically significantly better organs-at-risk (OARs) dosimetry (p < 0.001). Planning target volume Homogeneity Index (HI) was found to be significantly different among all techniques (p < 0.001), with Ecomp resulting in better HI (1.061 ± 0.029). Ecomp was also observed to require relatively shorter planning time (p < 0.001). @*Conclusions@#Techniques using tangential fields arrangements produced improved OARs dosimetry. Of all the treatment planning techniques employed in this study, Ecomp was found to be relatively easy to plan and produce acceptable dosimetry for WBRT in a short time.

Granulocytic sarcoma masquerading as Ewing's sarcoma: a diagnostic dilemma.

An eleven-year-old boy presented with a swelling in his left elbow. Radiologically the features were that of an Ewing's sarcoma involving the ulna. Histopathology showed small round cell tumor strongly positive for Monoclonal Imperial Cancer research fund 2 (MIC2) antigen. Similar cells in the bone marrow were involved with MIC2 positivity. The patient developed skin lesions, which on biopsy were found to be chloromas. The initial biopsies were reevaluated with special stains revealing granulocytic sarcomas in acute myeloid leukemia masquerading as Ewing's due to its MIC2 positivity. The possibility of myeloid neoplasms should be considered routinely with known MIC2 positive round cell tumors.

Execution of mantle field with multileaf collimator: a simple approach.

BACKGROUND: Until very recently mantle field radiotherapy remained the gold standard for the treatment of favorable early-stage Hodgkin's lymphoma. The classic mantle includes all the major lymph nodes above the diaphragm and extends from the inferior portion of the mandible to the level of the insertion of the diaphragm. AIMS: To describe a simple technique that has been devised to treat the mantle field with the help of multileaf collimator and using computed tomography (CT)-based treatment planning. MATERIALS AND METHODS: CT scan was performed with the patient in the supine position and the datasets were transferred to the Eclipse treatment planning system. Elekta Precise linear accelerator equipped with 40 pairs of multileaf collimator (MLC) was used for the execution of the mantle field. The MLC's shapes were designed to take the shape of the conventional customized blocks used for treatment of mantle field. The anterior mantle field was divided into three separate MLC segments with the collimator kept at 0 degrees. The first MLC segment was shaped to cover the neck, clavicular regions, and mediastinum. The second and the third MLC segments covered the right and left axilla, respectively. The posterior fields were opposed to the anterior subfields in a similar fashion. The dose was prescribed at the midplane, using reference points. RESULTS AND CONCLUSION: The technique described in this study is very simple, easy to implement, and avoids unnecessary delay in the execution of the mantle field. The mantle field can be easily shaped with the multileaf collimators, without any collimator rotation.

Radiation injury to the spinal cord in head and neck cancers: does field arrangement have a role.

STUDY DESIGN: A study of eight cases of head and neck cancers, to see if the cord was getting a higher dose in the antero-posterior (A-P) fields, compared to the bilateral (B/L) fields. OBJECTIVE: Radiation damage to the spinal cord is a critical issue for the radiation oncologists. This study was conducted to evaluate, if the dose to the spinal cord is higher by the antero-posterior (A-P) fields, compared to the bilateral (B/L) fields. MATERIALS AND METHODS: Eight cases of head and neck cancer were taken in our study. Two beam arrangements were placed in the treatment planning system, the B/L and the A-P fields. The DVH's for the cord dose were recorded and compared in both plans, with a standard fraction size of 200 cGy/fraction. RESULTS: The mean dose to the spinal cord was 168.06 cGy in A-P arrangement, while it was 133.75 cGy in the B/L arrangement. CONCLUSION: A-P field arrangement in head and neck malignancies delivers a higher dose to the spinal cord. Therefore, we need to spare the cord at an earlier dose limit.