Radiation Oncology/Stereotactic radiosurgery

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Stereotactic Radiosurgery (SRS)


Clinical Sites[edit]

Overview

Malignant

Benign:


Treatment planning indices[edit]

  • Yomo; 2010 (PMID 19809786): Energy Index
    • EI = ID / (TV x PD)
    • ID = integral dose within target volume
    • PD = prescribed dose
    • Measure of dose homogeneity within target volume
  • Oliver; 2007 (PMID 17194494): Radical Dose Homogeneity Index
    • rDHI = Dmin / Dmax
    • Dmin = minimum dose within target volume
    • Dmax = maximum dose within target volume
  • Oliver; 2007 (PMID 17194494): Moderate Dose Homogeneity Index
    • mDHI = D95% / D5%
    • D95% = dose to 95% of target volume
    • D5% = dose to 5% of target volume
  • Paddick; 2006 (PMID 18503356): Dose Gradient Index
    • GI = PIVhalf / PIV
    • PIVhalf = Prescription isodose volume, at half the prescription isodose (e.g. at 25%)
    • PIV = Prescription isodose volume (e.g. at 50%)
    • Simplified UF Gradient Index
  • Wagner; 2003 (PMID 14575847): Conformity Gradient Index
    • CGI = (CGIc + CGIg) / 2
    • CGIc = TV / PIV * 100
    • CGIg = UF Gradient Index (see below)
  • Wagner; 2003 (PMID 14575847): UF Gradient Index
    • CGIg = 100 - (100 * ((REff,50%Rx - REff,Rx) - 0.3 cm))
    • REff,50%Rx = Effective radius of the isodose line that is equal to one-half of the prescription isodose volume
    • REff,Rx = Effective radius of the prescription volume
    • Evaluates the steepness of the gradient between prescription isodose line (e.g 50%) and half prescription isodose line (e.g. 25%)
  • Nakamura; 2001 (PMID 11728692): New Conformity Index
    • NCI = (TV x PIV) / (TVPIV)2
    • Inverse Paddick Conformity Index
  • Paddick; 2000 (PMID 11143252): Paddick Conformity Index
    • Paddick CI = (TVPIV)2 / (TV x PIV)
    • TVPIV = Target Volume covered by Prescription Isodose Volume
    • TV = Target Volume
    • PIV = Prescription Isodose Volume
    • This is two separate ratios multiplied together:
      • Undertreatment ratio: TVPIV / TV
      • Overtreatment ratio: TVPIV / PIV
  • ICRU; 1999 (ICRU Report): Conformity Index
    • CI = TV / PTV
    • TV: Treated volume = volume eclosed by a given isodose surface (e.g. 50%, 95%)
    • PTV: Planning target volume = CTV + IM + SM
    • RTOG conformity index with ICRU terminology
  • Knoos; 1998 (PMID 9869245): Radiation Conformity Index
    • RCIi = PTV / PIV
    • PTV: Planning target volume = CTV + IM + SM
    • PIV = Prescription Isodose Volume
    • Inverse of RTOG Conformity Index
  • RTOG; 1993 (PMID 8262852): Conformity Index
    • Conformity Index PITV = PIV / TV
    • PI = prescription isodose volume
    • TV = target volume
    • Normal 1.0-2.0, minor deviation if >2.0 or <1.0, major deviation if >2.5 or <0.9
  • RTOG; 1993 (PMID 8262852): Homogeneity
    • Homogeneity MDPD = MD / PD
    • MD = maximum dose within target volume
    • PD = prescribed dose
    • Minor deviation if >2.0, major deviation if >2.5
  • RTOG; 1993 (PMID 8262852): Coverage
    • Coverage = Dmin / PD
    • Dmin = minimum dose within target volume
    • PD = prescribed dose
    • Minor deviation if <0.9, major deviation if <0.8
  • Wu; 1988 (PMID 3352544): Dose Homogeneity Index
    • DHI: (VTDR - VHDR) / VTDR
    • VTDR = total treatment volume enclosed by prescribed treatment dose rate (PIV)
    • VHDR = volume enclosed by high-dose rate which is 1.5x TDR or greater (PIV1.5x)
    • Used for high dose rate brachytherapy implants, but applicable to SRS


Other literature

Dose overview[edit]

Doses are prescribed to the 50% isodose line unless stated otherwise

  • Brain metastases: 24 Gy, 18 Gy, 15 Gy for tumors <2 cm, 2.1-3cm, and 3.1-4 cm.
  • Trigeminal neuralgia: 40 Gy (80 Gy Dmax), using 4mm collimator
  • Acoustic neuroma (vestibular schwannoma): 12.5 Gy
  • Meningioma: 12-14 Gy
  • Arteriovenous malformation: 18-20 Gy

Gamma Knife Machines[edit]

  • Hopital Timone, Marseille (2006) -- GKS 4C vs PerfeXion
    • Randomized. 200 patients. Arm 1) GammaKnife 4C vs Arm 2) GammaKnife PerfeXion
    • 2009 PMID 19190462 -- "Radiosurgery with the world's first fully robotized Leksell Gamma Knife PerfeXion in clinical use: a 200-patient prospective, randomized, controlled comparison with the Gamma Knife 4C." (Regis J, Neurosurgery. 2009 Feb;64(2):346-55; discussion 355-6.)
      • Outcome: No technical failures. Median # of collimator sizes 4C 1 vs PerfeXion 2. Median treatment time 60 min vs 40 min (SS), but median beam-on time 33.4 vs 34.0 minutes (NS). Single run 42% vs. 99%. Collision risk requiring gamma angle 24% vs 0%.
      • Toxicity: Less dose with PerfeXion to vertex (8x), thyroid (10x), sternum (13x), and gonads (15X)
      • Conclusion: Technological advances with PerfeXion

Toxicity[edit]

  • Please see the toxicity page for further information