Staging of neuroendocrine tumours: comparison of [68Ga]DOTATOC multiphase PET/CT and whole-body MRI.

PURPOSE: In patients with a neuroendocrine tumour (NET), the extent of disease strongly influences the outcome and multidisciplinary therapeutic management. Thus, systematic analysis of the diagnostic performance of the existing staging modalities is necessary. The aim of this study was to compare the diagnostic performance of 2 whole-body imaging modalities, [(68)Ga]DOTATOC positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging (MRI) in patients with NET with regard to possible impact on treatment decisions. MATERIALS AND METHODS: [(68)Ga]DOTATOC-PET/CT and whole-body magnetic resonance imaging (wbMRI) were performed on 51 patients (25 females, 26 males, mean age 57 years) with histologically proven NET and suspicion of metastatic spread within a mean interval of 2.4 days (range 0-28 days). PET/CT was performed after intravenous administration of 150 MBq [(68)Ga]DOTATOC. The CT protocol comprised multiphase contrast-enhanced imaging. The MRI protocol consisted of standard sequences before and after intravenous contrast administration at 1.5 T. Each modality (PET, CT, PET/CT, wbMRI) was evaluated independently by 2 experienced readers. Consensus decision based on correlation of all imaging data, histologic and surgical findings and clinical follow-up was established as the standard of reference. Lesion-based and patient-based analysis was performed. Detection rates and accuracy were compared using the McNemar test. P values <0.05 were considered significant. The impact of whole-body imaging on the treatment decision was evaluated by the interdisciplinary tumour board of our institution. RESULTS: 593 metastatic lesions were detected in 41 of 51 (80%) patients with NET (lung 54, liver 266, bone 131, lymph node 99, other 43). One hundred and twenty PET-negative lesions were detected by CT or MRI. Of all 593 lesions detected, PET identified 381 (64%) true-positive lesions, CT 482 (81%), PET/CT 545 (92%) and wbMRI 540 (91%). Comparison of lesion-based detection rates between PET/CT and wbMRI revealed significantly higher sensitivity of PET/CT for metastatic lymph nodes (100% vs 73%; P < 0.0001) and pulmonary lesions (100% vs 87%; P = 0.0233), whereas wbMRI had significantly higher detection rates for liver (99% vs 92%; P < 0.0001) and bone lesions (96% vs 82%; P < 0.0001). Of all 593 lesions, 22 were found only in PET, 11 only in CT and 47 only in wbMRI. The patient-based overall assessment of the metastatic status of the patient showed comparable sensitivity of PET/CT and MRI with slightly higher accuracy of PET/CT. Patient-based analysis of metastatic organ involvement revealed significantly higher accuracy of PET/CT for bone and lymph node metastases (100% vs 88%; P = 0.0412 and 98% vs 78%; P = 0.0044) and for the overall comparison (99% vs 89%; P < 0.0001). The imaging results influenced the treatment decision in 30 patients (59%) with comparable information from PET/CT and wbMRI in 30 patients, additional relevant information from PET/CT in 16 patients and from wbMRI in 7 patients. CONCLUSION: PET/CT and wbMRI showed comparable overall lesion-based detection rates for metastatic involvement in NET but significantly differed in organ-based detection rates with superiority of PET/CT for lymph node and pulmonary lesions and of wbMRI for liver and bone metastases. Patient-based analysis revealed superiority of PET/CT for NET staging. Individual treatment strategies benefit from complementary information from PET/CT and MRI.

[MR aspect of the prostate in CPPS patients (chronic pelvic pain syndrome)]. / MR-Befundmuster der Prostata bei Patienten mit CPP Syndrom (chronic pelvic pain syndrome).

PURPOSE: To describe typical morphological patterns of abacterial prostatitis using magnetic resonance imagine (MRI) in chronic pelvic pain syndrome patients including spectroscopy. MATERIALS AND METHODS: 18 patients (age range between 25 and 67 years, average 46.2 years) with recurrent chronic pelvic pain syndrome for at least 3 months were evaluated clinically in the urological department and included if there were no suspicious findings from endorectal digital palpation and if their PSA values were < 5 ng/ml. A retrospective analysis of these 18 patients with 30 contrast-enhanced MRI investigations with endorectal coils in 28 of 30 cases was performed with a 1.5T MRI. T 2w signal intensity (SI) and spectroscopy data (9 / 18 patients) were acquired for the normal peripheral zone, the central zone, for the peripheral zone suspected of inflammation and for the muscle including SI ratios for the unaltered and the suspicious inflammatory peripheral zone. RESULTS: Typical MR patterns of signal alterations suspected of inflammation of CPPS patients were able to be detected as T 2w hypointense triangular, stringy (n = 12, 66.6 %) contrast-enhancing signal alterations without a nodular shape with well circumscribed margins of the capsula and without pericapsular signal alterations. In 6 patients changes also had a triangular but more homogeneous aspect (33.3 %). Three patients had an additional periurethral uptake (16.6 %). T 2w SI measurements and T 2w SI ratios showed much lower values for the peripheral zone suspected of inflammation as compared to the normal peripheral zone of the prostate (277.29 STD 77.5 to 432.9 STD 112.02 and 4.94 STD 1.47 to 7.58 STD 2.01 respectively). The spectroscopic analysis of the signal alterations suspected of inflammation showed normal Cholin+Creatin/Citrate SI ratio values in 3 patients (SI < 0.5), ratios suspected of low grade cancer in 3 patients (SI 0.5 and < 0.7) and ratios suspected of intermediate grade prostate cancer in 3 patients (SI > 0.7 and < 3.0). CONCLUSIONS: We saw typical MR patterns in CPPS patients. However, spectroscopy can mimic findings of cancer so that the knowledge of typical morphological patterns and a solid clinical evaluation play a major role in the diagnosis of CPPS.

Image quality improvement of composed whole-spine MR images by applying a modified homomorphic filter--first results in cases of multiple myeloma.

To establish a modified homomorphic filter (BiFiC) for post-processing of composed MR images in clinical routine and to evaluate it in special regards to image quality and diagnostic safety. Twenty-three whole-spine examinations were post-processed with the filter. Qualitative image evaluation included documentation of lesions and their visualization at original and post-processed images. Variations of signal intensities were calculated pixel by pixel and visualized by color-coded maps. Quantitative data evaluation was conducted by region-by-region analysis with standardized regions of interests. The BiFiC filter could be implemented successfully on the scanner's software platform and used within clinical routine. Color-coded maps could demonstrate that the BiFiC filter improves the signal uniformity in all cases, including images with metallic artifacts caused by implants. The subjective image quality of the post-processed images was improved in 22 out of the 23 MR examinations; in one case it was rated as equal. All pathologies were visualized on post-processed images without the need of additional contrast adjustments. The implemented BiFiC filter significantly improves image signal homogeneity. The algorithm can consequently be integrated into clinical routine as an automatic image post-processing step.

[Detection of bone metastasis of prostate cancer - comparison of whole-body MRI and bone scintigraphy]. / Nachweis ossärer Metastasen des Prostatakarzinoms - Vergleich der Leistungsfähigkeit der Ganzkörper-MRT und der Skelettszintigrafie.

PURPOSE: Prostate cancer continues to be the third leading cancer-related mortality of western men. Early diagnosis of bone metastasis is important for the therapy regime and for assessing the prognosis. The standard method is bone scintigraphy. Whole-body MRI proved to be more sensitive for early detection of skeletal metastasis. However, studies of homogenous tumor entities are not available. The aim of the study was to compare bone scintigraphy and whole-body MRI regarding the detection of bone metastasis of prostate cancer. MATERIALS AND METHODS: 14 patients with histologically confirmed prostate cancer and a bone scintigraphy as well as whole-body MRI within one month were included. The mean age was 68 years. Scintigraphy was performed using the planar whole-body technique (ventral and dorsal projections). Suspect areas were enlarged. Whole-body MRI was conducted using native T 1w and STIR sequences in the coronary plane of the whole body, sagittal imaging of spine and breath-hold STIR and T 1w-Flash-2D sequences of ribs and chest. Bone scintigraphy and whole-body MRI were evaluated retrospectively by experienced radiologists in a consensus reading on a lesion-based level. RESULTS: Whole-body MRI detected significantly more bone metastasis (p = 0.024). 96.4 % of the demonstrated skeletal metastases in bone scintigraphy were founded in whole-body MRI while only 58.6 % of the depicted metastases in MRI were able to be located in scintigraphy. There was no significant difference regarding bone metastasis greater than one centimeter (p = 0.082) in contrast to metastasis less than one centimeter (p = 0.035). Small osteoblastic metastases showed a considerably higher contrast in T 1w sequences than in STIR imaging. Further advantages of whole-body MRI were additional information about extra-osseous tumor infiltration and their complications, for example stenosis of spinal canal or vertebral body fractures, found in 42.9 % of patients. CONCLUSION: Whole-body MRI using native STIR and T 1w sequences is superior to bone scintigraphy for the detection of small bone metastasis of prostate cancer. Simultaneous clarification of associated complications demonstrates further advantages.

[Cost considerations for whole-body MRI and PET/CT as part of oncologic staging]. / Kostenüberlegungen zur Ganzkörper-MRT und PET-CT im Rahmen des onkologischen Stagings.

PURPOSE: The aim of this study was to evaluate and discuss economic aspects of whole-body MRI and PET/CT in oncologic staging. Considerations from the perspective of the health care system, the radiologist, and the patients are presented. MATERIALS AND METHODS: Costs of both whole-body techniques are compared with the conventional radiologic diagnostic recommendations of the AWFM (Arbeitsgemeinschaft Wissenschaftlich Medizinischer Fachgesellschaften) in oncologic staging of the five most frequent tumor entities. Temporal and monetary aspects are calculated. Invasive, endoscopic, and endosonographic techniques are regarded as essential and cannot be replaced by other techniques. Thus only the minimal potential for cost reduction is quantified. RESULTS: In the German system there is no cipher to correctly balance whole-body MRI and PET/CT. Using the frequently applied ciphers 5700-5730 and 5378, 5489 (factor 1.0) total costs were 440.45 euros, and adding the cipher for additional series 545.37 euros (60 min examination time) for whole-body MRI and 774.74 euros (879.66 euros) (60/90 min examination time) for whole-body PET/CT. Using the common factor 1.8 costs were 981.66 and 1583.38 euros. On the basis of a simple full cost analysis total costs of whole-body PET/CT were higher than of whole-body MRI by a factor of about 2.0 (about 1123 vs 575 euros). There were substantial monetary and temporal differences between tumor entities. In extended bronchial carcinoma 375.32 euros and 55 min can be saved using whole-body MRI in comparison to conventional recommended techniques and using whole-body PET/CT 88.14 euros and 45 min. In tumor entities of lower stages with thus less essential radiologic diagnostics the potential for cost reduction is substantially lower. CONCLUSION: Whole-body imaging techniques make it possible to reduce the number of necessary separate radiologic examinations and thus time in oncologic staging. A substantial reduction of health care costs seems to be possible in many tumor entities but differences between different tumor entities are decisive.

[The interdisciplinary approach to improve treatment quality of prostate cancer. Optimized nerve sparing in radical prostatectomy]. / Interdisziplinäre Untersuchungen zur Verbesserung der Behandlungsqualität des Prostatakarzinoms. Optimierung des Nervenerhalts bei radikaler Prostatektomie.

BACKGROUND: After sufficient oncological treatment of prostate cancer the life quality becomes most important. A multi disciplinary research network aims to optimize the diagnostics and the resulting treatment of prostate cancer. METHODS: Main characteristics of the interdisciplinary cooperation are the interlocked individual projects. A major research field is investigation of the whole mounted prostate sections to study the peripheral nerves and the comparison of histological tumor locations with the MRI. Using serial sections of prostate specimens, three-dimensional computer-animated models are created illustrating the tumors histological and immunohistochemical distributions. For nodal staging, a new methodology is investigated to demonstrate single tumor cells in lymphatic tissue lysates. A retrospective evaluation of life quality including the functional outcome is performed by using questionnaire surveys. RESULTS: Anatomical studies gave new insights into the exact localizations of peripheral nerves which may lead to an improvement of the surgical approach in nerve-sparing radical prostatectomy. For the preoperative planning the MRI imaging might need a different interpretation in relation to the topographic location. Studies using molecular markers and their relation and distribution patterns gave new insights regarding interpretation of histological biopsy results concerning the tumor extension. Numerical quantification of tumor cells in each lymph node demonstrated micro metastases in histological negative nodes contributing to the nodal staging. A close connection of the nerve-sparing technique was demonstrated with quality of life aspects and functional results. CONCLUSION: An interdisciplinary approach is mandatory for translational prostate cancer research. As a result, individualized diagnostic and therapeutic approaches improve oncological results and at the same time provide the best quality of life in these patients.

[Generating statements at whole-body imaging with a workflow-optimized software tool--first experiences with multireader analysis]. / Befunderstellung bei der Ganzkörperbildgebung mittels einer workflowoptimierten Befundungssoftware--Erste Erfahrungen einer Multireader-Analyse.

INTRODUCTION: Due to technical innovations in sectional diagram methods, whole-body imaging has increased in importance for clinical radiology, particularly for the diagnosis of systemic tumor disease. Large numbers of images have to be evaluated in increasingly shorter time periods. The aim was to create and evaluate a new software tool to assist and automate the process of diagnosing whole-body datasets. MATERIAL AND METHODS: Thirteen whole-body datasets were evaluated by 3 readers using the conventional system and the new software tool. The times for loading the datasets, examining 5 different regions (head, neck, thorax, abdomen and pelvis/skeletal system) and retrieving a relevant finding for demonstration were acquired. Additionally a Student T-Test was performed. For qualitative analysis the 3 readers used a scale from 0 - 4 (0 = bad, 4 = very good) to assess dataset loading convenience, lesion location assistance, and ease of use. Additionally a kappa value was calculated. RESULTS: The average loading time was 39.7 s (+/- 5.5) with the conventional system and 6.5 s (+/- 1.4) (p < 0.01) with the new software tool. For the different regions (conventional system/new software tool), the time reduction for readers 1, 2, and 3 were as follows: in the head region 35.9 % (p < 0.01)/49.9 % (p < 0.01)/54.3 % (p < 0,01), in the neck region 48.5 % (p < 0.01)/52.6 % (p < 0.01)/59.4 % (p < 0.05), in the thorax region 59.1 % (p < 0.01)/56.2 % (p < 0.05)/62.1 % (p < 0.05), in the abdominal region 61.9 % (p < 0.01)/62.7 % (p < 0.05)/47.9 % (p < 0.01) and in the pelvis region 73.1 % (p < 0.01)/63.7 % (p < 0.05)/55 % (p < 0.01), respectively. 148.2 s (+/- 94.8) compared to 2.5 s (+/- 0.5) were required to retrieve a previously described finding (p < 0.01). With and without the new software tool the same number of metastases was found (p < 0.01, k > 0.9). The qualitative analysis showed a significant advantage with respect to convenience (p < 0.01, k > 0.9). CONCLUSION: Use of the new software can achieve a significant time savings when working with whole-body datasets with a constant quality of findings and a significant advantage with respect to convenience. As a result, the problem of evaluating examinations with thousands of images can be approached systematically.

Diagnostic performance of spectroscopic and perfusion MRI for distinction of brain tumors.

OBJECTIVE: To assess the value of spectroscopic and perfusion MRI for glioma grading and for distinguishing glioblastomas from metastases and from CNS lymphomas. METHODS: The authors examined 79 consecutive patients with first detection of a brain neoplasm on nonenhanced CT scans and no therapy prior to evaluation. Spectroscopic MRI; arterial spin-labeling MRI for measuring cerebral blood flow (CBF); first-pass dynamic, susceptibility-weighted, contrast-enhanced MRI for measuring cerebral blood volume; and T1-weighted dynamic contrast-enhanced MRI were performed. Receiver operating characteristic analysis was performed, and optimum thresholds for tumor classification and glioma grading were determined. RESULTS: Perfusion MRI had a higher diagnostic performance than spectroscopic MRI. Because of a significantly higher tumor blood flow in glioblastomas compared with CNS lymphomas, a threshold value of 1.2 for CBF provided sensitivity of 97%, specificity of 80%, positive predictive value (PPV) of 94%, and negative predictive value (NPV) of 89%. Because CBF was significantly higher in peritumoral nonenhancing T2-hyperintense regions of glioblastomas compared with metastases, a threshold value of 0.5 for CBF provided sensitivity, specificity, PPV, and NPV of 100%, 71%, 94%, and 100%. Glioblastomas had the highest tumor blood flow values among all other glioma grades. For discrimination of glioblastomas from grade 3 gliomas, sensitivity was 97%, specificity was 50%, PPV was 84%, and NPV was 86% (CBF threshold value of 1.4), and for discrimination of glioblastomas from grade 2 gliomas, sensitivity was 94%, specificity was 78%, PPV was 94%, and NPV was 78% (CBF threshold value of 1.6). CONCLUSION: Perfusion MRI is predictive in distinguishing glioblastomas from metastases, CNS lymphomas and other gliomas vs MRI and magnetic resonance spectroscopy.

[Application of (1)H MR spectroscopic imaging in radiation oncology: choline as a marker for determining the relative probability of tumor progression after radiation of glial brain tumors]. / Einsatz der (1)H-MR-spektroskopischen Bildgebung in der Strahlentherapie: Cholin als Marker für die Bestimmung der relativen Wahrscheinlichkeit eines Tumorprogresses nach Bestrahlung glialer Hirntumoren.

PURPOSE: To determine the relative signal intensity ratios of choline (Cho), phosphocreatine (CR) and N-acetyl-aspartate (NAA) in MR spectroscopic imaging (proton-MRSI) for differentiating progressive tumors (PT) from non-progressive tumors (nPT) in follow-up and treatment planning of gliomas. Threshold values to indicate the probability of a progressive tumor were also calculated. MATERIAL AND METHODS: Thirty-four patients with histologically proven gliomas showing a suspicious brain lesion in MRI after stereotactic radiotherapy were evaluated on a 1.5 Tesla unit (Magnetom Vision, Siemens, Erlangen, Germany) using 2D proton MRSI (repetition time/echo time = 1500/135 msec, PRESS; voxel size 9 x 9 x 15 mm (3)). A total of 274 spectra were analyzed (92 voxel were localized within the suspicious brain lesion). Relative signal intensities Cho, Cr and NAA were measured and their ability to discern between PT and nPT was assessed using the linear discrimination method, logistic regression, and the cross-validation method. PT and nPT were differentiated between on the basis of clinical course and follow-up by MRI, CT and positron emission tomography. RESULTS: The Cho parameter and the relative signal intensity ratios of Cr and NAA were most effective in differentiating between PT and nPT. The logistic regression method using the parameter ln(Cho/Cr) and ln(Cho/NAA) had the best predictive results in cross-validation. A sensitivity of 93.8 % and specificity of 85.7 % were achieved in the differentiation of PT from nPT by proton-MRSI. CONCLUSION: (1)H-MRSI has a high sensitivity and specificity for differentiating between therapy-related effects and the relapse of irradiated gliomas. This method allows for assessment of the probability of radiotherapy response or failure.

Optimal classification of long echo time in vivo magnetic resonance spectra in the detection of recurrent brain tumors.

We describe the optimal high-level postprocessing of single-voxel (1)H magnetic resonance spectra and assess the benefits and limitations of automated methods as diagnostic aids in the detection of recurrent brain tumor. In a previous clinical study, 90 long-echo-time single-voxel spectra were obtained from 52 patients and classified during follow-up (30/28/32 normal/non-progressive tumor/tumor). Based on these data, a large number of evaluation strategies, including both standard resonance line quantification and algorithms from pattern recognition and machine learning, were compared in a quantitative evaluation. Results from linear and non-linear feature extraction, including ICA, PCA and wavelet transformations, and also the data from resonance line quantification were combined systematically with different classifiers such as LDA, chemometric methods (PLS, PCR), support vector machines and ensemble methods. Classification accuracy was assessed using a leave-one-out cross-validation scheme and the area under the curve (AUC) of the receiver operator characteristic (ROC). A regularized linear regression on spectra with binned channels reached 91% classification accuracy compared with 83% from quantification. Interpreting the loadings of these regressions, we find that lipid and lactate signals are too unreliable to be used in a simple machine rule. Choline and NAA are the main source of relevant information. Overall, we find that fully automated pattern recognition algorithms perform as well as, or slightly better than, a manually controlled and optimized resonance line quantification.

[Metabolic imaging to follow stereotactic radiation of gliomas -- the role of 1H MR spectroscopy in comparison to FDG-PET and IMT-SPECT]. / Metabolische Bildgebung zur Verlaufskontrolle stereotaktisch bestrahlter Gliome -- Wertigkeit der 1H-MR-Spektroskopie im Vergleich zur FDG-PET und IMT-Spect.

PURPOSE: To evaluate the clinical value of 1H MR spectroscopy (1H MRSI) for follow-up of irradiated glioma compared to positron emission tomography (PET) with [18F]-2-fluoro-deoxy-D-glucose (FDG-PET) and single photon emission tomography with [123I]-a-methyl-L-tyrosine (IMT-SPECT). MATERIALS AND METHODS: Twenty-four patients with irradiated gliomas were examined using 1H MRSI (2D spectroscopic imaging; PRESS; TE = 135 msec; 1.5T Magnetom Vision, Siemens; Voxel size 9 x 9 x 15 mm (3)). MR spectra (n = 233) were evaluated in areas suspicious of tumor (n = 86) as well as in healthy appearing brain tissue (n = 147). Relative signal intensity ratios of choline (Cho), creatine (Cr) and N-acetyl-aspartate (NAA) were calculated. PET scans (n = 19) were performed with 200 - 250 MBq FDG, IMT-SPECT examinations (n = 14) with 200 - 250 mBq IMT. Based on clinical and MRI/CT, follow-up lesions were classified as either neoplastic [PT] or non-neoplastic [nPT]. RESULTS: True positive results for the diagnosis of PT/nPT were 88/89 % (1H MRSI), 73/100 % (PET) and 100/75 % (SPECT). Cho/Cr showed highly significant changes for PT. Determinating a correlation between Cho, Cr, NAA and IMT-SPECT as well as FDG-PET was not possible because of different location of maximum tracer uptake and acquired 2D 1H MRSI. CONCLUSION: IMT-SPECT seems to be superior to detect tumor progression in irradiated gliomas. 1H MRSI was more suitable than FDG-PET to differentiate between recurrence and radiation-induced changes. FDG-PET plays a role as sensitive method for detecting high-grade tumors. PET and SPECT allowed the examination of the entire tumor including surrounding brain tissue with higher spatial resolution than the acquired 2D 1H MRSI. A main limitation of our study was that only 2D 1H MRSI was used, with only parts of the tumor evaluated. The use of 3D MR spectroscopic imaging may further increase the diagnostic accuracy.

[Magnetic resonance spectroscopy. Part 2: Application in diagnosis and clinical research]. / Magnetresonanzspektoskopie. Teil 2: Anwendung in Diagnostik und klinischer Forschung.

MR spectroscopy creates a noninvasive window into the metabolism of normal and diseased tissue in vivo. The physics and the measurement techniques being described in part I, this contribution presents the potential use of MRS in patient healthcare and clinical research. We discuss applications of MRS to neurooncology, to oncology outside the central nervous system and to nononcological diseases.

Monitoring individual response to brain-tumour chemotherapy: proton MR spectroscopy in a patient with recurrent glioma after stereotactic radiotherapy.

Since antineoplastic activity varies, sensitive methods for individual assessment of efficacy are needed. We demonstrate the clinical value of MR spectroscopy in monitoring chemotherapy in a patient with recurrent glioma after stereotactic radiotherapy. Diagnostic imaging before and after chemotherapy included contrast-enhanced MRI, single-voxel proton MR spectroscopy ((1)H MRS), (1)H MR spectroscopic imaging ((1)H SI), and fluorodeoxyglucose (FDG) positron-emission tomography (PET). A significant decrease in choline signal intensity was observed 2 months after chemotherapy indicating tumour chemosensitivity, in line with tumour shrinkage on MRI and decreased uptake of FDG. Assessment of early response by MRS may help to improve treatment protocols in other patients.

[Monitoring of irradiated brain metastases using MR perfusion imaging and 1H MR spectroscopy]. / Verlaufsbeobachtung bestrahlter Hirnmetastasen mittels MR-Perfusionsbildgebung und 1H-MR-Spektroskopie.

PURPOSE: In follow-up examinations of irradiated brain metastases conventional contrast-enhanced morphological MR imaging is often unable to distinguish between transient radiation effects, radionecrosis,and tumor recurrence. To evaluate changes of relative cerebral blood flow (rCBF) in irradiated brain metastases arterial spin-labeling techniques (ASL) were applied and compared to the outcome of (1)H MR spectroscopy and spectroscopic imaging ((1)H MRS, SI). PATIENTS AND METHODS: In 2 patients follow-up examinations of irradiated brain metastases were performed on a 1.5-T tomograph (average single dose: 20 Gy/80% isodose). Relative CBF values of gray matter (GM), white matter (WM),and metastases (Met) were measured by means of the ASL techniques ITS-FAIR and Q2TIPS. (1)H MRS was performed with PRESS 1500/135. RESULTS: In both patients with initially hyperperfused metastases (Met/GM >1) the reduction of rCBF after stereotactic radiosurgery indicated response to treatment--even if the contrast-enhancing region increased--while increasing rCBF values indicated tumor progression. The findings were confirmed by (1)H MRS, SI and subsequent follow-up. CONCLUSION: The ASL techniques ITS-FAIR and Q2TIPS are able to monitor changes of rCBF in irradiated brain metastases. The two cases imply a possible role for ASL-MR perfusion imaging and (1)H MR spectroscopy in differentiating radiation effects from tumor progression.