Correlation between heterogeneity index (HI) and gradient index (GI) for high dose stereotactic radiotherapy/radiosurgery (SRT/SRS)

Tas, B.; Durmuş, İsmail; Okumus, A.; Uzel, Ömer

doi:10.1063/1.4976462

Cited by 4 publications

(4 citation statements)

References 14 publications

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“…Heterogeneity index (HI) describes PTV dose variation, and can be calculated with the simpler Radiation Therapy Oncology Group (RTOG) calculation where <2 is ideal, or with a more strict calculation using D98 and D2 (this calculation reveals more heterogeneity; values will vary widely by plan although the ideal value is 0) 28 . Table 6 shows that all CI were reasonably close to unity (median CI = 0.81 and 1.10, based on two different equations, respectively 26,28 ), GI was similar to the Paddick study for stereotactic wherein GI values were 2.4 to 3.3 27 (median GI = 3.35 in the current study), all cases had acceptable RTOG HI (median HI = 1.12), and 7/8 cases had alternate HI values ≤15 suggesting some heterogeneity in the approved plans 29 . Values for CI, GI and HI were only evaluated retrospectively and were not used in plan approval.…”

Section: Resultssupporting

confidence: 80%

“…CI does not account for whether the dose is in the same location at the target 26‐28 . Gradient index (GI) describes how quickly the dose drops outside the PTV, with smaller values representing steeper gradients 29 . Heterogeneity index (HI) describes PTV dose variation, and can be calculated with the simpler Radiation Therapy Oncology Group (RTOG) calculation where <2 is ideal, or with a more strict calculation using D98 and D2 (this calculation reveals more heterogeneity; values will vary widely by plan although the ideal value is 0) 28 .…”

Section: Resultsmentioning

confidence: 99%

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Long‐term outcomes with conventional fractionated and stereotactic radiotherapy for suspected heart‐base tumours in dogs

Hansen

Théon

Willcox

et al. 2020

Vet Comparative Oncology

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Published radiotherapy results for suspected heart‐based tumours in dogs are limited. In this retrospective longitudinal study (3/2014‐2019), eight dogs with either clinical signs attributable to a heart‐base mass (6), or asymptomatic with a progressively larger mass on echocardiogram (2), received conventional fractionated radiotherapy (CFRT) or stereotactic body radiotherapy (SBRT). Clinical findings in symptomatic cases included one or more of the following: retching/coughing (4), exercise intolerance (2), collapse (1), pericardial effusion (2), rare ventricular premature contractions (2), abdominal effusion (1), or respiratory distress due to chylothorax (1). CFRT cases received 50 Gray (Gy) in 20 fractions and SBRT cases received 30 Gy in 5 or 24 Gy in three fractions. Two dogs received chemotherapy post‐radiation. At analysis, 7/8 dogs were deceased and one was alive 684 days post‐treatment. The estimated median overall survival (MOS) from first treatment was 785 days (95% CI 114‐868 days, [range 114‐1492 days]). Five dogs received CFRT (MOS 817 days; (95% CI 155 days‐not reached [range 155‐1492 days])). Three dogs received SBRT with one alive at analysis (MOS 414 days, (95% CI, 114 days‐not reached [range 114‐414 days])). No statistically significant difference was found between survival for CFRT and SBRT. Of the symptomatic patients, 5/6 showed improvement. Mass size reduced in 4/5 cases receiving follow‐up ultrasounds. Possible complications included asymptomatic radiation pneumonitis (4), atrial tachycardia/premature beats (4) and pericardial effusion with heart failure coincident with tumour progression (1). This study provides preliminary evidence that radiotherapy may impact clinically relevant or progressively enlarging heart‐base masses.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Long‐term outcomes with conventional fractionated and stereotactic radiotherapy for suspected heart‐base tumours in dogs

Hansen

Théon

Willcox

et al. 2020

Vet Comparative Oncology

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“…The conformity index describes how the volume of a stereotactic radiotherapy plan conforms to the size and shape of the planning target volume, with values <2 being recommended, and values closer to 1 being ideal . Gradient index describes how steep the dose gradient is outside of the planning target volume, with smaller values having steeper gradients . Heterogeneity index describes the dose heterogeneity existing within the planning target volume, and can be calculated with the simple Radiation Therapy Oncology Group calculation, or with a more complex calculation based on the D98 and D2 (available for three‐dimensional‐conformal/IMRT cases) .…”

Section: Resultsmentioning

confidence: 99%

Long‐term survival with stereotactic radiotherapy for imaging‐diagnosed pituitary tumors in dogs

Hansen

Zwingenberger

Théon

et al. 2018

Vet Radiology Ultrasound

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Published studies on the use of stereotactic radiotherapy for dogs with pituitary tumors are limited. This retrospective observational study describes results of stereotactic radiotherapy for 45 dogs with imaging-diagnosed pituitary tumors. All dogs were treated at a single hospital during the period of December 2009-2015. The stereotactic radiotherapy was delivered in one 15 Gray (Gy) fraction or in three 8 Gy fractions. At the time of analysis, 41 dogs were deceased.Four were alive and censored from all survival analyses; one dog received 8 Gy every other day and was removed from protocol analyses. The median overall survival from first treatment was 311 days (95% confidence interval 226-410 days [range 1-2134 days]). Thirty-two dogs received 15 Gy (median overall survival 311 days; 95% confidence interval [range 221-427 days]), and 12 received 24 Gy on three consecutive days (median overall survival 245 days, 95% confidence interval [range 2-626 days]). Twenty-nine dogs had hyperadrenocorticism (median overall survival 245 days), while 16 had nonfunctional masses (median overall survival 626 days). Clinical improvement was reported in 37/45 cases. Presumptive signs of acute adverse effects within 4 months of stereotactic radiotherapy were noted in 10/45, and most had improvement spontaneously or with steroids. Late effects versus tumor progression were not discernable, but posttreatment blindness (2), hypernatremia (2), and progressive neurological signs (31) were reported.There was no statistical difference in median overall survival for different protocols. Patients with nonfunctional masses had longer median overall survival than those with hyperadrenocorticism (P = 0.0003). Survival outcomes with stereotactic radiotherapy were shorter than those previously reported with definitive radiation, especially for dogs with hyperadrenocorticism. K E Y W O R D SCushing's disease, hyperadrenocorticism, photon therapy, SRS, stereotaxis three-dimensional-conformal fields, or with a cone-based system for beam collimation. 17,18,25 There is one study of 51 dogs with

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“…Other groups have reported reduction in GI with increasing HI. 11,12 GI as a function of the dose HI for all PTVs ≥0.8 cm 3 is shown in Fig. 2.…”

Section: Ma Et Al Published a Planning Study Comparing Plans For Gammamentioning

confidence: 99%

Institutional experience with SRS VMAT planning for multiple cranial metastases

Ballangrud

Kuo

Happersett

et al. 2018

J Applied Clin Med Phys

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Background and PurposeThis study summarizes the cranial stereotactic radiosurgery (SRS) volumetric modulated arc therapy (VMAT) procedure at our institution.Materials and MethodsVolumetric modulated arc therapy plans were generated for 40 patients with 188 lesions (range 2–8, median 5) in Eclipse and treated on a TrueBeam STx. Limitations of the custom beam model outside the central 2.5 mm leaves necessitated more than one isocenter pending the spatial distribution of lesions. Two to nine arcs were used per isocenter. Conformity index (CI), gradient index (GI) and target dose heterogeneity index (HI) were determined for each lesion. Dose to critical structures and treatment times are reported.ResultsLesion size ranged 0.05–17.74 cm3 (median 0.77 cm3), and total tumor volume per case ranged 1.09–26.95 cm3 (median 7.11 cm3). For each lesion, HI ranged 1.2–1.5 (median 1.3), CI ranged 1.0–2.9 (median 1.2), and GI ranged 2.5–8.4 (median 4.4). By correlating GI to PTV volume a predicted GI = 4/PTV0.2 was determined and implemented in a script in Eclipse and used for plan evaluation. Brain volume receiving 7 Gy (V 7 Gy) ranged 10–136 cm3 (median 42 cm3). Total treatment time ranged 24–138 min (median 61 min).ConclusionsVolumetric modulated arc therapy provide plans with steep dose gradients around the targets and low dose to critical structures, and VMAT treatment is delivered in a shorter time than conventional methods using one isocenter per lesion. To further improve VMAT planning for multiple cranial metastases, better tools to shorten planning time are needed. The most significant improvement would come from better dose modeling in Eclipse, possibly by allowing for customizing the dynamic leaf gap (DLG) for a special SRS model and not limit to one DLG per energy per treatment machine and thereby remove the limitation on the Y‐jaw and allow planning with a single isocenter.

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Correlation between heterogeneity index (HI) and gradient index (GI) for high dose stereotactic radiotherapy/radiosurgery (SRT/SRS)

Cited by 4 publications

References 14 publications

Long‐term outcomes with conventional fractionated and stereotactic radiotherapy for suspected heart‐base tumours in dogs

Long‐term outcomes with conventional fractionated and stereotactic radiotherapy for suspected heart‐base tumours in dogs

Long‐term survival with stereotactic radiotherapy for imaging‐diagnosed pituitary tumors in dogs

Institutional experience with SRS VMAT planning for multiple cranial metastases

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