Treatment planning issues related to prostate movement in response to differential filling of the rectum and bladder

Haken, Randall K. Ten; Forman, Jeffrey D.; Heimburger, D.K.; Gerhardsson, A.; McShan, Daniel L.; Perez-Tamayo, Claudia; Schoeppel, Sonja L.; Lichter, Allen S.

doi:10.1016/0360-3016(91)90244-x

Cited by 291 publications

(113 citation statements)

References 17 publications

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“…However, the true accuracy of the treatment can only be judged in this way if the assumption that the position of the prostate and/or the bladder within the pelvis is more or less fixed is correct. The question of to what extent the bony structures of the pelvis repre sent the true position of the prostate or the bladder in the field, has been addressed by several authors (4,5,15,20,28), using l25I seed implants or CT scans to compare the position of the prostate to that of the bony pelvis. Results of these studies have been summarized in Table 5.…”

Section: Small Pelvic Fields For Urological Cancermentioning

confidence: 99%

A quality control study of the accuracy of patient positioning in irradiation of pelvic fields

Creutzberg

Althof

Hoog

et al. 1996

International Journal of Radiation Oncology*Biology*Physics

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Section: Small Pelvic Fields For Urological Cancermentioning

confidence: 99%

A quality control study of the accuracy of patient positioning in irradiation of pelvic fields

Creutzberg

Althof

Hoog

et al. 1996

International Journal of Radiation Oncology*Biology*Physics

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“…Despite use of image guidance, rectal distension can significantly influence rectal doses and consequent toxicities 8,25,29 and potentially impact on intrafractional prostate motion, especially for hypofractionated protocols with prolonged treatment times. Rectal distension may also result in additional radiation exposure from extra CBCTs performed if the patient is required to empty their bowels after having an overfilled rectum at initial set-up.…”

Section: Discussionmentioning

confidence: 99%

“…Studies using implanted fiducial markers, 4,5 serial CT scans 6 and ultrasound 7 demonstrate prostatic displacements of up to 20 mm. 8 The position of the prostate gland in relation to bony landmarks is also seen to change in an unpredictable way. 9 To ensure adequate dose coverage of the tumour, a safety margin is added to the clinical target volume (CTV) to accommodate for positional uncertainties called the planning target volume (PTV).…”

mentioning

confidence: 99%

Image-guided radiotherapy of the prostate using daily CBCT: the feasibility and likely benefit of implementing a margin reduction

Maund¹,

Benson²,

Fairfoul³

et al. 2014

The British Journal of Radiology

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Objective: To investigate whether planning target volume (PTV) margins may be safely reduced in radiotherapy of localized prostate cancer incorporating daily online tube potential-cone beam CT (CBCT) image guidance and the anticipated benefit in predicted rectal toxicity. Methods: The prostate-only clinical target volume (CTV2) and rectum were delineated on 1 pre-treatment CBCT each week in 18 randomly selected patients. By transposing these contours onto the original plan, dose–volume histograms (DVHs) for CTV2 and the rectum were each calculated and combined, for each patient, to produce a single mean DVH representative of the dose delivered over the treatment course. Plans were reoptimized using reduced CTV2 to PTV2 margins and the consequent radiobiological impact modelled by the tumour control probability (TCP) and normal tissue complication probability (NTCP) of the rectum. Results: All CBCT images were deemed of sufficient quality to identify the CTV and rectum. No loss of TCP was observed when plans using the standard 5-mm CTV2 to PTV2 margin of the centre were reoptimized with a 4- or 3-mm margin. Margin reduction was associated with a significant decrease in rectal NTCP (5–4 mm; p < 0.05 and 5–3 mm; p < 0.01). Conclusion: Using daily online image guidance with CBCT, a reduction in CTV2 to PTV2 margins to 3 mm is achievable without compromising tumour control. The consequent sparing of surrounding normal tissues is associated with reduced anticipated rectal toxicity. Advances in knowledge: Margin reduction is feasible and potentially beneficial. Centres with image-guided radiotherapy capability should consider assessing whether margin reduction is possible within their institutes.

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“…This phenomenon has been reported by various authors. 5,[15][16][17][18][19][20][21][22][23] It has been suggested that the implantation of marker seeds directly into the prostate, may help circumvent this problem. 5,18,24 The main advantage of this technique in our view, would be to allow corrections to the treatment or field set up prior to each fraction as suggested by Vigneault.…”

Section: Discussionmentioning

confidence: 99%

CT slice index and thickness: Impact on organ contouring in radiation treatment planning for prostate cancer

Berthelet¹

2003

J. Appl. Clin. Med. Phys.

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Objective: To assess the impact of CT slice index and thickness ͑3 mm versus 5 mm͒ on ͑i͒ prostate volume, dimensions, and isocenter coordinates, ͑ii͒ bladder and rectal volumes, and ͑iii͒ DRR quality, in the treatment of prostate cancer. Methods: 16 patients with prostate cancer underwent two planning CT-scans using 3 and 5 mm slice index/thickness. Prostate, bladder, and rectum were outlined on all scans. Prostate isocenter coordinates, maximum dimensions, and volumes were compared along with bladder and rectal volumes. Bladder volumes and maximum diameters were further investigated using a second observer. A comparative analysis of DRR quality was conducted as well as a dosimetric analysis using DVH. Results: The differences in measurements of prostate volume, isocenter coordinates and maximum dimensions between the 3 and 5 mm scans, were small and not statistically significant. Similar finding was seen for rectal volume. However, bladder volume was always larger on the 3 mm scan ͑mean differenceϭ27.9 cc; SEϭ4.8 cc; 95% CI: 17.7-38.2 cc; pϽ0.001) and the findings were reproduced with the second observer ͑mean differenceϭ31.9 cc; SEϭ4.7 cc; 95% CI: 21.9-41.9 cc; p Ͻ0.001). The differences in volume are caused by a slight increase in ͑1͒ the measurement of the longitudinal dimensions on the 3 mm scans, and ͑2͒ the slice by slice measured bladder area on the 3 mm scans. The latter is due to partial volume effect. The 3 mm DRR were slightly better than the 5 mm DRR. The bladder DVH differed significantly in some patients. Conclusion: Bladder volume is significantly larger on the 3 mm scans. Differences in contoured areas may be accounted for, in part, by the partial volume effect.

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Treatment planning issues related to prostate movement in response to differential filling of the rectum and bladder

Cited by 291 publications

References 17 publications

A quality control study of the accuracy of patient positioning in irradiation of pelvic fields

A quality control study of the accuracy of patient positioning in irradiation of pelvic fields

Image-guided radiotherapy of the prostate using daily CBCT: the feasibility and likely benefit of implementing a margin reduction

CT slice index and thickness: Impact on organ contouring in radiation treatment planning for prostate cancer

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