A stationary wavelet transform based approach to registration of planning CT and setup cone beam-CT images in radiotherapy.

Image registration between planning CT images and cone beam-CT (CBCT) images is one of the key technologies of image guided radiotherapy (IGRT). Current image registration methods fall roughly into two categories: geometric features-based and image grayscale-based. Mutual information (MI) based registration, which belongs to the latter category, has been widely applied to multi-modal and mono-modal image registration. However, the standard mutual information method only focuses on the image intensity information and overlooks spatial information, leading to the instability of intensity interpolation. Due to its use of positional information, wavelet transform has been applied to image registration recently. In this study, we proposed an approach to setup CT and cone beam-CT (CBCT) image registration in radiotherapy based on the combination of mutual information (MI) and stationary wavelet transform (SWT). Firstly, SWT was applied to generate gradient images and low frequency components produced in various levels of image decomposition were eliminated. Then inverse SWT was performed on the remaining frequency components. Lastly, the rigid registration of gradient images and original images was implemented using a weighting function with the normalized mutual information (NMI) being the similarity measure, which compensates for the lack of spatial information in mutual information based image registration. Our experiment results showed that the proposed method was highly accurate and robust, and indicated a significant clinical potential in improving the accuracy of target localization in image guided radiotherapy (IGRT).

[Comparison of two different chemotherapy regimens for concurrent chemoradiotherapy in stage Ib2 to IVa squamous cell carcinoma of the uterine cervix].

OBJECTIVE: To compare the clinical efficacy and safety of two chemotherapy regimens for concurrent chemoradiotherapy in patients with stage Ib2 to IVa squamous cell carcinoma of the uterine cervix. METHODS: Between November 2007 and November 2011, 146 patients with stage Ib2 to IVa squamous cell carcinoma of the uterine cervix who received concurrent chemoradiotherapy in Peking University Cancer Hospital were analyzed. All cases were divided into two groups according to the different chemotherapy regimens during radiation therapy, the group receiving radiotherapy concomitant with weekly cisplatin or nedaplatin alone (platinum alone group, n = 59), the group receiving radiotherapy concomitant with cisplatin plus fluorouracil or nedaplatin plus tegafur every 3 weeks (combined group, n = 87). There were no statistical difference in the clinical and pathological characteristics between the two groups. RESULTS: Patients were evaluated by pelvic examination and pelvic MRI after chemoradiotherapy for 3 months according to WHO criteria. The response rate were respectively 97% (57/59) and 93% (81/87) in platinum alone group and combined group, in which there was no significant difference (P = 0.249). The five-year overall survival and the five-year progression-free survival of platinum alone group and combined group were respectively 61.2% versus 69.5% (P > 0.05) and 43.3% versus 24.4% (P > 0.05). There were also no statistically significant differences between platinum alone group and combined group in the five-year local recurrence rate and five-year distant metastasis (11.8% versus 9.8%, 29.4% versus 38.7%; all P > 0.05). Acute gastrointestinal toxicities (nausea and vomiting) in combined group were exactly higher than that in the other group [78% (68/87) versus 51% (30/59), P < 0.01]. Moreover, anaemia was slightly more common in combined group [53% (46/87) versus 25% (15/59), P = 0.019]. However, the occurrence rate of the acute or late proctitis and cystitis did not reveal difference between two groups (P > 0.05). CONCLUSIONS: Both concurrent chemoradiotherapy regimens had similar efficacy on cervical cancer patients with stage Ib2 to IVa. But the toxicity was lower in patients with weekly platinum than those with platinum-based combined regimens during radiation therapy.