Dosimetric Considerations in Cobalt 60 Rotational Therapy for Esophageal Lesions

Goldenberg, David B.; Rao, U. V. Gopala; Lott, S; Digel, Joseph

doi:10.2214/ajr.105.3.518

Cited by 3 publications

(6 citation statements)

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“…[78910] Goldenberg et al . [7] did a study to determine lung correction factors under actual treatment conditions in 8 patients treated for the middle third of the esophagus with cobalt-60 unit rotational therapy. Transit dose measurements by IC were related to direct measurements (temperature corrected) using intraluminal dosimeter and obtained results within 3%.…”

Section: Discussionmentioning

confidence: 99%

“…[6] Another method, as part of in vivo dosimetry, transmission of radiation flux/signal measurement at a point far away from the patient was used in the days of deep X-rays and telecobalt beam treatments when rotation therapy was introduced in radiotherapy. [7] A simple and practical method was devised to obtain the in vivo dose in 60 pelvic treatments on the beam central axis using the signal measured by a small air ion chamber positioned along with beam central axis at typical distance of the electronic portal imaging device (EPID) from the source. [8] In another work, an estimation of in vivo dose from back projection of transit signal (S t ) measurement with EPID along the central axis of photon beam in patients undergoing conformal radiotherapy for various localizations was presented.…”

Section: Introductionmentioning

confidence: 99%

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On-line estimations of delivered radiation doses in three-dimensional conformal radiotherapy treatments of carcinoma uterine cervix patients in linear accelerator

et al. 2016

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Transmission of radiation fluence through patient's body has a correlation to the planned target dose. A method to estimate the delivered dose to target volumes was standardized using a beam level 0.6 cc ionization chamber (IC) positioned at electronic portal imaging device (EPID) plane from the measured transit signal (St) in patients with cancer of uterine cervix treated with three-dimensional conformal radiotherapy (3DCRT). The IC with buildup cap was mounted on linear accelerator EPID frame with fixed source to chamber distance of 146.3 cm, using a locally fabricated mount. Sts were obtained for different water phantom thicknesses and radiation field sizes which were then used to generate a calibration table against calculated midplane doses at isocenter (Diso,TPS), derived from the treatment planning system. A code was developed using MATLAB software which was used to estimate the in vivo dose at isocenter (Diso,Transit) from the measured Sts. A locally fabricated pelvic phantom validated the estimations of Diso,Transit before implementing this method on actual patients. On-line dose estimations were made (3 times during treatment for each patient) in 24 patients. The Diso,Transit agreement with Diso,TPS in phantom was within 1.7% and the mean percentage deviation with standard deviation is −1.37% ±2.03% (n = 72) observed in patients. Estimated in vivo dose at isocenter with this method provides a good agreement with planned ones which can be implemented as part of quality assurance in pelvic sites treated with simple techniques, for example, 3DCRT where there is a need for documentation of planned dose delivery.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On-line estimations of delivered radiation doses in three-dimensional conformal radiotherapy treatments of carcinoma uterine cervix patients in linear accelerator

et al. 2016

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“…In some of the studies, the in vivo dose was measured by inserting an ionization chamber directly into the natural body cavity (e.g., esophagus, rectum, or vagina) with a protective cap which comes in the region of the treatment portals. [ 13 14 15 16 ] The temperature of the cavity (which is the surrogate of the body temperature) where the chamber is placed is taken into account for temperature correction factor that needs to be applied to the charge collected by the chamber. The dose is then calculated by application of all chamber-related correction factors (e.g., calibration factor, temperature, pressure, and beam quality) to the collected charge.…”

Section: Introductionmentioning

confidence: 99%

“…Few studies described methods to assess in vivo mid-plane dose in patients through transit signal measured by an ionization chamber positioned at the EPID level while actual treatment is going on. [ 3 13 14 16 17 18 19 ]…”

Section: Introductionmentioning

confidence: 99%

“…Simultaneous measurements of in vivo and mid-plane dose through transit method were performed using two ionization chambers, one placed intraluminally in patients who are undergoing esophagus treatment and the other one kept at a transit level, which was reported in the literature. [ 13 ] A method was described to estimate mid-plane dose by measuring transit signal (D iso-transit ) in pelvic and thorax patients which was correlated with TPS-calculated values. [ 3 20 ] In these studies, simultaneous measurements of in vivo and mid-plane dose were also carried out on pelvic and thorax phantoms using two ionization chambers, one kept at the mid-plane level and the another one at EPID level which were compared with the TPS-calculated values.…”

Section: Introductionmentioning

confidence: 99%

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Simultaneous measurement of In vivo and transit mid-plane doses with ionization chambers in gynecological malignancy patients undergoing three-dimensional conformal radiotherapy

Putha

Srinivas

Vadhiraja³

et al. 2020

J Med Phys

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Purpose: The aim of this study is to estimate delivered radiation doses inside planning tumor volume (PTV) using the in vivo (mid-plane dose) measurement and transit measurement methods in gynecological malignancy patients undergoing three-dimensional conformal radiotherapy (3DCRT) using calibrated ionization chambers. Materials and Methods: Six patients with histopathologically proven carcinoma of the cervix or endometrium were planned with four-field 3DCRT to the pelvic site. Isocenter was at the geometric mid-plane of PTV with a dose prescription of 50 Gy in 25 fractions. Clinical mid-plane dose (D iso, Transit ) estimates were done in one method (transit) using the FC-65 positioned at electronic portal imaging device level. In another method, a repeat computerized tomography scan was performed (at the 11 th fraction) using CC-13 having a protective cap in the vaginal cavity for in vivo measurements (D in vivo ). Simultaneous measurements were performed with the two chambers from the 11 th fraction onward at least 3–4 times during the remaining course of treatment. Results: The agreement of mean doses from these two described methods and treatment planning system reference doses was in the range of −4.4 ± 1.1% (minimum) to −0.3 ± 2.0% (maximum) and −4.0 ± 1.7% (minimum) to 1.9 ± 2.4% for D in vivo and D iso, Transit , respectively, which are an acceptable range of daily radiation dose delivery. Conclusion: The fundamental importance of this study lies in simultaneous validation of delivered dose in real time with two methods. A study in this small number of patients has given the confidence to apply transit measurements for quality assurance on a routine basis as an accepted clinical dosimetry for the selected patients.

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In vivo dose estimations through transit signal measured with thimble chamber positioned along the central axis at electronic portal imaging device level in medical linear accelerator in carcinoma of the middle-third esophagus patients undergoing three-dimensional conformal radiotherapy

Putha¹,

Banerjee²,

Kumar³

et al. 2018

Journal of Cancer Research and Therapeutics

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Dosimetric Considerations in Cobalt 60 Rotational Therapy for Esophageal Lesions

Cited by 3 publications

References 0 publications

On-line estimations of delivered radiation doses in three-dimensional conformal radiotherapy treatments of carcinoma uterine cervix patients in linear accelerator

On-line estimations of delivered radiation doses in three-dimensional conformal radiotherapy treatments of carcinoma uterine cervix patients in linear accelerator

Simultaneous measurement of In vivo and transit mid-plane doses with ionization chambers in gynecological malignancy patients undergoing three-dimensional conformal radiotherapy

In vivo dose estimations through transit signal measured with thimble chamber positioned along the central axis at electronic portal imaging device level in medical linear accelerator in carcinoma of the middle-third esophagus patients undergoing three-dimensional conformal radiotherapy

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