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Localization and quantification of the delivered dose to the spinal cord

Predicting actual delivered dose during daily MVCT image-guided tomotherapy

Lokalisation und Quantifizierung der applizierten Dosis im Rückenmark

Vorhersage der tatsächlich verabreichten Dosis unter täglicher bildgesteuerter MVCT-Tomotherapie

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Abstract

Purpose

The goal of the present work was to localize and quantify the actual delivered dose to the cervical spinal cord (SC) during head and neck cancer (H&N) treatment.

Materials and methods

A total of 20 H&N patients treated with bilateral nodal irradiation with helical tomotherapy (HT) were analyzed. Daily MVCTs were performed for image guidance. On every second MVCT, the SC was recontoured and the delivered dose for the given treatment fraction (12 fractions per patient) was recalculated. The magnitude and localization (CT slice, spinal cord quadrant) of the Dmax to the SC on the planning CT (PLAN-Dmax) and of the actual delivered Dmax (a-Dmax) were analyzed.

Results

A systematic deviation from the PLAN-Dmax was observed in 15 out of 20 patients. Large interpatient variability of the a-Dmax in the spinal cord was noted (4.5 ± 4 %). Intrapatient variability in a-Dmax was, generally, minimal (1.8 ± 2.7 %). Throughout the treatment course, the higher dose was located in the same CT slices and in the same quadrants (anterior right and anterior left) for the same patient.

Conclusion

Exact localization and quantification of the change of the a-Dmax can be made for most patients by recalculating the dose on the daily IGRT-MVCTs. This could be helpful in assessing whether replanning is necessary in patients with doses close to the known tolerance doses of the spinal cord.

Zusammenfassung

Ziel

Ziel der Arbeit ist es, die Dosis zu bestimmen, die während einer Strahlentherapie im Kopf-Hals-Bereich im Rückenmark wirklich ankam.

Material und Methoden

Es wurden insgesamt 20 Patienten mit Kopf-Hals-Tumoren ausgewertet, die eine beidseitige Bestrahlung mittels Tomotherapie erhalten hatten. Auf jedem zweiten der täglich gefahrenen Image-Guidance-MVCTs wurde das Rückenmark eingezeichnet und die applizierte Dosis neu berechnet (insgesamt 12 Fraktionen pro Patient). Die Höhe und die Lokalisation (CT-Schicht sowie Quadrant des Rückenmarks) des Dosismaximums im Rückenmark (Dmax) wurden sowohl für das Planungs-CT (PLAN-Dmax) und für die MVCTs (tatsächlich verabreichte Dosis [a-Dmax]) bestimmt.

Ergebnisse

Bei 15 der 20 Patienten wurde eine systematische Abweichung des PLAN-Dmax gefunden. Zwischen den Patienten ergaben sich Unterschiede von a-Dmax im Rückenmark von 4,5 ± 4 %, innerhalb eines Patienten allerdings nur von 1,8 ± 2,7 %. Die neuberechneten Dmax lagen je Patient über die gesamte Behandlungsserie in der gleichen Schicht des CTs sowie im gleichen Quadranten (anterior links und rechts).

Zusammenfassung

Durch eine Neuberechnung der täglichen IGRT-MVCTs kann für die meisten Patienten eine genaue Lokalisation und Absolutbestimmung des verabreichten a-Dmax erfolgen. Vor allem bei Patienten mit einer Rückenmarksdosis nahe an der Toleranzdosis ist dies für die Entscheidung bezüglich einer Umplanung hilfreich.

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Compliance with ethical guidelines

Conflict of interest. M.N. Duma, T. Schuster, N. Aswathanarayana, L.-S. Fromm, M. Molls, H. Geinitz, and S. Kampfer state that there are no conflicts of interest.

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Authors and Affiliations

  1. Department of Radiation Oncology, Klinik und Poliklinik für Strahlentherapie und Radiologische Onkologie, Technische Universität München, Klinikum rechts der Isar, Ismaninger Str. 22, 81675, Munich, Germany

    M.N. Duma M.D., M. Molls M.D. & S. Kampfer

  2. Institute of Medical Statistics and Epidemiology, Technische Universität München, Klinikum rechts der Isar, Munich, Germany

    T. Schuster M.Sc.

  3. Medical School, Technische Universität München, Munich, Germany

    N. Aswathanarayana & L.-S. Fromm

  4. Abteilung für Radio-Onkologie, Krankenhaus der Barmherzigen Schwestern Linz, Linz, Austria

    H. Geinitz M.D.

Authors
  1. M.N. Duma M.D.
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  2. T. Schuster M.Sc.
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  3. N. Aswathanarayana
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  4. L.-S. Fromm
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  5. M. Molls M.D.
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  6. H. Geinitz M.D.
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  7. S. Kampfer
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Corresponding author

Correspondence to M.N. Duma M.D..

Additional information

Part of this work was presented at the ESTRO Anniversary Congress, May 2011, London, U.K.

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Duma, M., Schuster, T., Aswathanarayana, N. et al. Localization and quantification of the delivered dose to the spinal cord. Strahlenther Onkol 189, 1026–1031 (2013). https://doi.org/10.1007/s00066-013-0436-9

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  • DOI: https://doi.org/10.1007/s00066-013-0436-9

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