MRI prostate contouring is not impaired by the use of a radiotherapy image acquisition set-up. An intra- and inter-observer paired comparative analysis with diagnostic set-up images

PURPOSE

The use of MRI for radiotherapy planning purposes is growing but image acquisition using radiotherapy set-ups has impaired image quality. Whether differences in image acquisition set-up could modify organ contouring has not been evaluated. Therefore, we aimed to evaluate differences in contouring between paired of image sets that were acquired in the same scanning session using different parameters.

MATERIAL AND METHODS

Ten patients underwent RT treatment planning with MRI co-registration. MRI was carried out using two different set-ups during the same session, MRI radiotherapy set-ups and MRI diagnostic set-ups. Prostates and rectums were retrospectively contoured in both image sets by 5 radiation oncologists and 4 radiologists. Intra-observer analysis was carried out comparing organ volumes, the Dice coefficient and hausdorff distance values between two contouring rounds. Inter-observer analysis was carried out by comparing individual contours to a generated STAPLE consensus contour, which is considered the gold standard reference.

RESULTS

No significant differences were observed between MRI acquisition set-ups. Significant differences were observed for the dice and hausdorff parameters, comparing individual contours to the STAPLE consensus contour, when analysing diagnostic images between rounds, although raw values were similar.

CONCLUSION

Prostate and rectum contours did not differ significantly when using diagnostic or radiotherapy MRI acquisition set-ups.

Vaginal cuff brachytherapy in endometrial cancer - a technically easy treatment?

Endometrial cancer (EC) is one of the most common gynecological cancers among women in the developed countries. Vaginal cuff is the main location of relapses after a curative surgical procedure and postoperative radiation therapy have proven to diminish it. Nevertheless, these results have not translated into better survival results. The preeminent place of vaginal cuff brachytherapy (VCB) in the postoperative treatment of high- to intermediate-risk EC was given by the PORTEC-2 trial, which demonstrated a similar reduction in relapses with VCB than with external beam radiotherapy (EBRT), but VCB induced less late toxicity. As a result of this trial, the use of VCB has increased in clinical practice at the expense of EBRT. A majority of the clinical reviews of VCB usually address the risk categories and patient selection but pay little attention to technical aspects of the VCB procedure. Our review aimed to address both aspects. First of all, we described the risk groups, which guide patient selection for VCB in clinical practice. Then, we depicted several technical aspects that might influence dose deposition and toxicity. Bladder distension and rectal distension as well as applicator position or patient position are some of those variables that we reviewed.

Rectal contrast increases rectal dose during vaginal cuff brachytherapy

PURPOSE

To evaluate the impact of rectal dose on rectal contrast use during vaginal cuff brachytherapy (VCB).

METHODS AND MATERIALS

A retrospective review of gynecology patients who received some brachytherapy fractions with and without rectal contrast was carried out. Rectal contrast was instilled at the clinician's discretion to increase rectal visibility. Thirty-six pairs of CT scans in preparation for brachytherapy were analyzed. Pairs of CTs were segmented and planned using the same parameters. The rectum was always defined from 1 cm above the cylinder tip up to 1.5 cm below the last activated dwell source position. An individual plan was computed at every VCB fraction. A set of values (Dmax, D(0.1cc), D(1cc), and D(2cc)) derived from dose-volume histograms were extracted and compared according to the rectal status.

RESULTS

Rectal volume was 26.7% larger in the fractions with rectal contrast. Such an increase in volume represented a significant increase from 7.7% to 10.4% in all parameters analyzed except Dmax dose-volume histogram.

CONCLUSIONS

Avoiding rectal contrast is a simple way of decreasing the rectal dose parameters of VCB, which would mean a better therapeutic ratio. Results also suggest that action directed at maintaining the rectum empty might have the same effect.

Scintigraphy and Doppler ultrasonography for the evaluation of obstructive urinary calculi

Forty-seven patients with unilateral obstructive calculi (12 males and 35 females) were submitted to 99mTc-diethylene triamine pentaacetic acid (DTPA) or 99mTc-dimercaptosuccinic acid (DMSA) scans for assessment of renal function. The scans revealed unilateral functional deficit in 68 and 66% of the patients, respectively. A calculus size of 1.1 to 2.0 cm was significantly associated with deficit detected by DTPA, but duration of obstruction and calculus localization were not. After relief of the obstruction, the mean percent renal function of the affected kidney was found to be significantly increased from 25 +/- 12% to 29 +/- 12% in DTPA and from 21 +/- 15% to 24 +/- 12% in DMSA. Initial Doppler ultrasonography performed in 35 patients detected an increased resistive index in 10 (29%). In the remaining patients with a normal resistive index, ureteral urinary jet was observed, indicating partial obstruction. The high frequency of renal function impairment detected by DTPA and of tubulointerstitial damage detected by DMSA as well as the slight amelioration of unilateral renal function after relief of obstruction suggest that scintigraphy assessment may help evaluate the unilateral percentage of renal function and monitor renal function recovery when it occurs. The presence of a urinary jet detected by Doppler ultrasonography further indicates the severity of obstruction and the recovery prognosis.