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Purpose: To evaluate rectal dose-volume relations during three-dimensional conformal radiotherapy of patients with prostate cancer by means of different rectal volume contours., Patients and Methods: 55 patients with prostate cancer underwent three-dimensional conformal external-beam radiotherapy. Rectal dose-volume histograms were calculated for four separately contoured rectal volumes in all patients resulting in four groups. In group 1 the outer rectal wall was contoured two CT slices above and below the planning target volume. The rectal contour of group 2 was drawn from the anal verge up to the sigmoid. Furthermore, the posterior half of the rectum was contoured for both volumes mentioned above (groups 1a and 2a). Statistical analysis was then performed using nonparametric Wilcoxon tests., Results: The mean target dose was 72.9 Gy (standard deviation [SD] +/- 2.1 Gy). The minimum target dose was 70.2 Gy. Mean rectum dose (+/- SD) over all patients was 50.7 Gy (+/- 4.6 Gy), 45.2 Gy (+/- 5.4 Gy), 43.2 Gy (+/- 4.2 Gy), and 38.7 Gy (+/- 5.5 Gy) for group 1, 2, 1a, and 2a, respectively. The corresponding volumes receiving > or = 70 Gy for groups 1 and 2 were 14.0% (+/- 5.3%) and 11.9% (+/- 4.5%). These differences were statistically significant. Comparison of minimum and mean rectal dose also revealed a statistically significant difference toward higher doses in groups 1 and 1a (p < 0.001). Maximum rectal doses for groups 1 and 2 as well as for groups 1a and 2a revealed no statistically significant difference (p = 1.0)., Conclusion: 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.

Purpose: The aim of the study was to investigate the impact of MR/SPECT image fusion on the interpretation of I-123 iodo-methyl-tyrosine (IMT) SPECT examinations in patients with pretreated brain tumors., Material and Methods: In this retrospective study, 45 consecutive patients with suspected recurrent/residual gliomas (n = 41) or cerebral metastases (n = 4) were included. SPECT studies were performed using a triple-head gamma-camera system 10 minutes after injection of 300 to 370 MBq (8.1-10 mCi) I-123 IMT. Concerning MR, T1-, T2-, and FLAIR-weighted sequences as well as contrast-enhanced T1-weighted sequences were acquired by 1.5-T or 3.0-T scanners. For image fusion, the MPI-tool software package was used. SPECT and MR/SPECT fusion images were anonymized and then independently evaluated by 3 observers aware of the clinical data. Tumor localization and extent were evaluated and correlated with histopathology or clinical follow up, including MR imaging., Results: In 10 of 45 (22%) patients, image fusion had a significant impact on the interpretation of scans: 5 suspected SPECT findings were correctly classified as physiological or therapy-related; in another 5 patients, image fusion added relevant clinical information on tumor extent (infiltration of the contralateral hemisphere n = 3, infiltration of the brain stem n = 2)., Conclusions: According to our data, image fusion is crucial for the interpretation of positive I-123 IMT SPECT findings.

Background: Nuclear medicine imaging is increasingly used in the evaluation of tumors of the head and neck. In the current study, we assess the value of single-photon emission tomography (SPECT) using the amino acid tracer L-3-[123I]iodine-alpha-methyl-tyrosine (IMT) for the detection of recurrent head and neck cancer., Patients and Methods: 45 consecutive patients with suspected recurrence of previously treated head and neck cancer were examined by IMT-SPECT using a dual head system with integrated low-dose computed tomography (CT). The accuracy of the IMT-SPECT was evaluated by correlating the findings with results of histology or clinical and CT/MRI (magnetic resonance imaging) follow-up examinations., Results: The sensitivity, specificity and accuracy of IMT-SPECT in the detection of recurrent/persistent tumors were 83, 89 and 84.5%, respectively. The positive and negative predictive value amounted to 96.5 and 60%, respectively., Conclusion: IMT-SPECT using integrated low-dose CT appears to be a helpful complementary imaging tool for the detection of local recurrences and lymph node metastases of head and neck cancer and their differentiation from treatment-induced changes. The advantage of the method is the high positive predictive value in the diagnosis of relapsed tumors. However, a negative IMT-SPECT result does not exclude a recurrence.

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.