No abstract

Data from the literature on normal-tissue complication probability (rectal bleeding) refer to different rectal contours. When applying dose restrictions to the rectum, contouring becomes a significant factor that determines the risk of rectal toxicity. The results of this study show that different ways of rectal contouring significantly influence doses to the rectum. The influence of organ at risk contouring should be considered thoroughly in conformal radiotherapy of prostate cancer patients, especially in dose escalation studies. It is recommended to calculate the doses for absolute rectal volumes and correlate these data with toxicity in order to be able to achieve comparable results among different institutions.

The aim of the study was to assess the clinical value of combined SPECT/CT imaging using L: -3-[123I]iodine-alpha-methyl tyrosine (IMT) for the differential diagnosis of recurrences in patients pre-treated for head and neck cancer. Thirty-four consecutive patients with biopsy-proven carcinomas, who had previously been treated by surgery and/or radio/chemotherapy, were examined at our clinic by IMT-SPECT using a dual-head system with integrated low-dose CT. SPECT results were correlated with histopathology, clinical and CT/MRI follow-up data. In the follow-up after SPECT examination, the final diagnosis of recurrent tumour was established in 26 patients; the remaining eight patients were recurrence-free (follow-up >6 months). IMT-SPECT/CT correctly detected recurrent disease and/or neck lymph node metastases in 22 patients. In addition, distant metastases were displayed in two patients. The study was false-negative in four patients (sensitivity 85%). True-negative results were registered in seven patients, and false-positive in one patient. Image fusion with coregistered low-dose CT facilitates the localisation and interpretation of IMT-SPECT findings. IMT-SPECT using integrated low-dose CT is a promising non-invasive imaging tool for the detection of head and neck cancer recurrences and their differentiation from treatment-induced changes.

Assessing response to radiation therapy in patients with high grade gliomas is needed upon making decisions toward further therapy strategies. Currently used standard imaging tools such as CT and MRI are not sensitive enough to detect early therapy effects. We prospectively investigated if single photon emission computed tomography (SPECT) using radiolabelled amino acid derivate (123)I-methyltyrosine (IMT) would be useful for this aim. 10 patients with histologically proven high grade gliomas, who were candidates for radiation therapy, were enrolled in this investigation. All patients were examined by IMT SPECT before radiation therapy and 4 weeks after the initiation of the hypofractionated application of 40 Gy. Patients were followed up for 39 months; the tumours to background ratios (T/B) for IMT under/before radiation therapy were correlated to survival times. Initially, SPECT depicted an abnormal intratumoural IMT uptake in all patients (mean T/B ratios 1.37-1.87). In four out of 10 patients, the mean T/B ratios decreased by more than 10% under radiation therapy. In six other patients, the BQ decreased by less than 10% or increased. There were no significant correlations between the degree of changes in T/B and survival (r = -0.1, p = 0.973). Serial IMT SPECT measurements allow detection of changes in amino acid accumulation in high-grade gliomas under radiation therapy. However, these changes seem to possess no prognostic value in respect to survival prediction.

According to our data, image fusion is crucial for the interpretation of positive I-123 IMT SPECT findings.