A Method for the Calculation of Dose in the Radiation Treatment of Hodgkin’s Disease

Cundiff, Jackson; Cunningham, Jack R.; Golden, Robert N.; LANZL, L. H.; Meurk, Mary Louise; Ovadia, J.; LAST, V. PAGE; Pope, R. A.; Sampiere, Vincent; Saylor, William L.; Shalek, Robert J.; Suntharalingham, N.

doi:10.2214/ajr.117.1.30

Cited by 37 publications

(5 citation statements)

References 10 publications

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“…The problem of estimating the effective field size equivalent to a clinical irregular field is most accurately handled by irregular field calculations (Cundiff et al 1973). …”

Section: Equivalent Field Sizementioning

confidence: 99%

“…Changes in the beam quality as a function of position in the radiation field should also be considered ). The general method used for irregular-field calculations consists of summation of the primary and scatter irradiation at each point of interest, with allowance for the off-axis change in intensity (off-axis factor) and SSD (Cundiff et al 1973). The MUs required to deliver a specified tumor dose at an arbitrary point in an irregular field can be calculated as follows:…”

Section: Monitor Unit Calculation For Irregular Fieldsmentioning

confidence: 99%

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Physics of Radiotherapy Planning and Delivery

et al. 2011

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“…The problem of estimating the effective field size equivalent to a clinical irregular field is most accurately handled by irregular field calculations (Cundiff et al 1973). …”

Section: Equivalent Field Sizementioning

confidence: 99%

Section: Monitor Unit Calculation For Irregular Fieldsmentioning

confidence: 99%

Physics of Radiotherapy Planning and Delivery

et al. 2011

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“…The use of scatter-air ratios (SAR) in calculating depth dose in irregular fields has been discussed in detail in the literature (4,5). In principle, the same method was adopted for the computer program used in this study.…”

Section: Computer Programmentioning

confidence: 99%

“…So far the scatter calculation method as described by Clarkson (3) and Johns and Cunningham (4) has proved to be most general in its application and may be considered as a standard of comparison for approximation. methods (5).…”

mentioning

confidence: 99%

Computer and Approximation Methods of Calculating Depth Dose in Irregularly Shaped Fields

Khan¹,

Levitt²,

Moore³

et al. 1973

Radiology

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A computer program was developed to calculate depth dose in irregularly shaped fields. The program is general for any shaped field and includes corrections for variations of exposure rate within the field, body contour, and non-nominal source-skin distances. Depth doses were calculated in several actual cases involving irregular fields such as mantle, split, L-shaped, and inverted Y fields. Data were examined to determine the degree of dose inhomogeneity in these fields. An approximation method used in the irregular field dosimetry was evaluated with regard to its accuracy and limitations. Comparison of depth dose determinations using both methods showed a discrepancy of only 2 to 3%. INDEX TERMS: Computers. Dosimetry. Therapeutic Radiology, treatment planning Radiology 106:433-436, February 1973 Radiation Physics I R R E GU LAR FIELDS are encountered in radiotherapy when radiation sensitive structures are shielded from the main beam or when the field extends beyond the irregularly shaped patient body contour.. In such fields, the calculation of depth dose is often accomplished by approximation methods. These methods fall into two main categories; (a) those based on phantom measurements with correction factors to accommodate variations in the actual treatment conditions from the phantom set-up (1, 2), and (b) those involving geometric approximations in which the given irregular field is approximated by a rectangular field. Whereas these methods are often helpful in routine dosage calculations, their validity must be checked for various treatment conditions. So far the scatter calculation method as described by Clarkson (3) and Johns and Cunningham (4) has proved to be most general in its application and may be considered as a standard of comparison for approximation. methods (5).A computer program was developed embodying Clarkson's principle of separating 'the primary and scattered components of dose at a point in a phantom. The program was written in Fortran for the CDC-3300 computer. Depth doses computed for several cases involving irregular fields were compared with those calculated by geometric approximations. The results were analyzed to evaluate the accuracy and limitations of these approximations. COMPUTER PROGRAMThe use of scatter-air ratios (SAR) in calculating depth dose in irregular fields has been discussed in detail in the literature (4, 5). In principle, the same method was adopted for the computer program used in this study. The computer divides the field into elementary sectors using the coordinates of the field contour and the point of dose calculation. The radii of the sectors are calculated using mathematical equations. The SAR values for the sectors are assigned by interpolation of the SAR table for circular fields stored in the computer. The values are summated to give average scatter-air ratio (SAR) for the field at the given point at depth.The computed SAR is converted to average tissue air ratio (TAR) by the equationwhere TAR (0) is the tissue-air ratio for 0 X 0 field, i.e., TAR (0) = ...

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“…For Cobalt 60 radiation, the problem of dosimetry in irregular fields has largely been solved by the introduction of Tissue-Air Ratios (TAR'S) and Scatter-& Ratios (SAR's) as discussed by Johns and Cunningham (1969). In particular, the application of SAR calculations to the calculation of dose in Hodgkins disease has been very successful (Cundiff et al, 1973).…”

Section: Introductionmentioning

confidence: 99%

The Concept of Modified Scatter-Phantom Ratio and its Application to Irregular Field Dosimetry at 8MV

Sherlock

Budge

1978

Australas Radiol

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SUMMARY The concept of Modified Scatter‐Phantom Ratio has been applied to the calculation of central axis depth dose for irregular fields. The results are in good agreement with data obtained by direct measurement. Comparisons between the scatter summation method and the ‘equivalent square’ procedure suggest the former is superior. However, the errors in the ‘equivalent square’ method are small, and may be compensated by the simplicity of performing the calculation. With the parallel between MSPR and SAR established, the calculation procedure may be extended to points off the central axis along the lines suggested by Cundiff et al, 1973, in mantle techniques. ABSTRACT Modified Scatter‐Phantom Ratios are introduced as a formal extension of the concept of Scatter‐Air Ratios for beam energies greater than 2MV. Central Axis depth dose measurements for rectangular and irregular fields at 8MV are compared with calculations based on summation of primary and scattered radiation. Comparisons are also made with calculations using the equivalent square formula pointed out by Worthley(1966).

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A Method for the Calculation of Dose in the Radiation Treatment of Hodgkin’s Disease

Cited by 37 publications

References 10 publications

Physics of Radiotherapy Planning and Delivery

Physics of Radiotherapy Planning and Delivery

Computer and Approximation Methods of Calculating Depth Dose in Irregularly Shaped Fields

The Concept of Modified Scatter-Phantom Ratio and its Application to Irregular Field Dosimetry at 8MV

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