Dynamische Magnetresonanztomographie (dMRT)

PURPOSE

With the help of dynamic magnetic resonance tomography (dMRT) the status of tissue microcirculation can be visualized.

METHODS

Dynamic MRI was performed in 13 patients with advanced, nonresectable oro- or hypopharynx carcinoma at the beginning and the end of therapy. Maximal signal intensity and exchange rate constant in the tissue of the tumor and the lymph node metastases were analyzed using a pharmacokinetic two-compartment model.

RESULTS

In all six patients with clinical complete response (CR), the maximal signal intensity increased after therapy in the tissue of the primary tumor and the lymph node metastases. Furthermore, a high decrease in the parameter k(21) was associated with a better prognosis and could be observed especially after combined radiochemotherapy.

CONCLUSION

Our first results indicate that contrast-enhanced dynamic MRI studies before and after radio- or combined radiochemotherapy offer important information about the changes of microcirculation in the tissue of the tumor and lymph node metastases. Furthermore, this information seems to be a promising predictor for clinical outcome of therapy.

[Detection of prostate carcinomas with T1-weighted dynamic contrast-enhanced MRI. Value of two-compartment model]

AIM

The suitability of dynamic parameters of the two-compartment model for detecting prostate carcinomas and its correlation with tumor microvascular density were evaluated.

METHODS

The study included 43 patients with biopsy-proven prostate carcinoma: 28 were examined by 1.0-T MRI (Turbo-FLASH) and 15 by 1.5-T MRI (FLASH) with infusion of 0.1 mmol/kg Gd-DTPA. Signal time curves were parametrized with an open two-compartment model in amplitude and exchange rate constants (k(ep)). The microvascular density of resected prostate carcinomas was determined.

RESULTS

The microvascular density in the tumors was significantly higher than in the adjacent healthy prostate tissue and correlated in both sequences with k(ep). Prostate carcinomas of the peripheral zone were demarcated by amplitude and k(ep). In the Turbo-FLASH sequence there was a significant difference between the tumor tissue and healthy peripheral zone in terms of k(ep) and in the FLASH sequence in terms of amplitude.

CONCLUSION

Prostate carcinomas can be visualized with dynamic T1-weighted MR sequences using a two-compartment model. Moreover, the parameter k(ep) reveals the microvascular density in the tumor and can thus provide valuable clinical information for characterizing the tumors.

[Hemodynamic and metabolic characterization of orthotopic rat prostate carcinomas using dynamic MRI and proton magnetic resonance spectroscopy]

AIM

The aim of this study was the noninvasive characterization of prostate carcinoma orthotopically implanted in rats using Gd-DTPA-assisted dynamic MRI (dMRI) and proton magnetic resonance spectroscopy ((1)H-MRS).

MATERIAL AND METHODS

After surgical exposure of the prostate, Dunning R3327 orthotopic prostate carcinoma was induced by injecting cells of the MAT-LyLu subline. Six rats were examined 5 and 14 days after tumor induction with dMRI and (1)H-MRS at 1.5 T. Six tumor-free rats served as controls. Using an open two-compartment model, the parameters A (amplitude) and k(ep) (exchange rate constants) were calculated from the signal time curves of the dMRI. The relative signal intensities (Cho/Cr) of the resonances of choline (Cho) and the creatine-phosphocreatine complex (Cr) were computed from the MR spectra.

RESULTS

Already after 5 days, the tumors in the prostate could be clearly identified based on the decrease in signal intensity to T2w and increase of A and k(ep). High Cho/Cr levels and resonances of two lipid fractions (Lip(1) at 0.8-1.5 ppm and Lip(2) at 2.0-2.2 ppm) were observed by MRS in the highly necrotic tumors.

CONCLUSIONS

The orthotopic rat prostate carcinoma model resembles human prostate carcinoma in regard to MR morphology, dMRI, and (1)H-MRS. The noninvasive characterization of perfusion and metabolism makes a comparative examination of different treatment modalities possible.

[Monitoring of irradiated brain metastases using MR perfusion imaging and 1H MR spectroscopy]

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.

Differentiation of radiation necrosis from tumor progression using proton magnetic resonance spectroscopy

We report on a young woman who was treated by stereotactic radiotherapy for recurrence of an initially resected low-grade astrocytoma. MRI follow-up examination 7 months after radiotherapy showed a gadolinium-DTPA-enhancing mass lesion indicative of high-grade tumor progression. This assumption was also supported by positron emission tomography with [2-18F]fluoro-2-deoxy-D-glucose (FDG-PET). In contrast, proton MR spectroscopy (1H-MRS) indicated radiation necrosis, which was confirmed histopathologically in surgical specimens. Subsequent follow-up examinations up to 19 months after surgery showed no evidence of tumor recurrence.

Proton MR spectroscopic evaluation of suspicious brain lesions after stereotactic radiotherapy

BACKGROUND AND PURPOSE

The radiologic assessment of suspicious brain lesions after stereotactic radiotherapy of brain tumors is difficult. The purpose of our study was to define parameters from single-voxel proton MR spectroscopy that provide a probability measure for differentiating neoplastic from radiation-induced, nonneoplastic lesions.

METHODS

Seventy-two lesions in 56 patients were examined using a combined MR imaging and MR spectroscopy protocol (point-resolved spectroscopy, TE = 135 ms). Signal intensities of cholines, creatines, N-acetyl aspartate, and the presence of lactate and lipid resonances were correlated to final diagnoses established by clinical and MR imaging follow-up, positron emission tomography studies, or biopsy/surgery. Statistical analysis was performed using the t test, linear discriminant analysis, and k nearest-neighbor method.

RESULTS

Significantly increased signal intensity ratios I(tCho)/I(tCr) (P <.0001) and I(tCho)/I(NAA) (P <.0001) were observed in neoplastic (n = 34) compared with nonneoplastic lesions (n = 32) and contralateral normal brain (n = 33). Analysis of I(tCho)/I(tCr) and I(tCho)/I(NAA) data yielded correct retrospective classification as neoplastic and nonneoplastic in 82% and 81% of the lesions, respectively. Neither I(NAA)/I(tCr) nor signal intensitities of lactate or lipids were useful for differential diagnosis.

CONCLUSION

Metabolic information provided by proton MR spectroscopy is useful for the differentiation of neoplastic and nonneoplastic brain lesions after stereotactic radiotherapy of brain tumors.

Fluid-attenuated inversion-recovery MR imaging of gliomatosis cerebri

Magnetic resonance imaging has been shown to be the most sensitive imaging modality in the assessment of gliomatosis cerebri. Recent studies have shown that fluid-attenuated inversion-recovery (FLAIR) is a valuable MR sequence in the delineation of cerebral pathologies including intra-axial tumors. However, no data are available about the role of this novel technique in the assessment of gliomatosis lesions. The purpose of this study was therefore to evaluate the diagnostic potential of FLAIR MR imaging in patients with suspected gliomatosis cerebri. Seven patients suspected of having lesions of gliomatosis cerebri were examined by T1-weighted spin echo (SE), T2-weighted fast spin echo (FSE), and FLAIR MR imaging with identical slice parameters. T1 and FLAIR were repeated after contrast media administration. Delineation and extent of gliomatosis were the primary parameters of the image analysis. The FLAIR imaging clearly delineated the extent of gliomatosis lesions in all patients. Due to the suppression of cerebrospinal fluid, the delineation was superior to conventional T2-weighted FSE images. Especially the detection and delineation of cortical spread and the infiltration of the corpus callosum was best seen on FLAIR images. The FLAIR MR imaging is a valuable diagnostic modality in the assessment of patients with gliomatosis cerebri. Due to its better delineation of tumor spread, it was found to be the imaging method of choice and should therefore be integrated into the MR imaging protocol of these patients.

Locoregional late effects of paravascular thorotrast deposits: results of the german thorotrast study

PURPOSE

The aim of this study was to assess late effects of long-term exposure to alpha irradiation caused by paravascular Thorotrast deposits.

SUBJECTS AND METHODS

899 patients, who had received the radioactive contrast medium Thorotrast for angiography in the 1930s and 1940s, and 662 controls were followed-up since 1968 every two years by standardized clinical and laboratory examinations. Initially, X-ray plain films of the thorax, upper abdomen and the former injection site were performed. In selected patients the sites of paravascular Thorotrast deposits were evaluated by ultrasonography, CT and MRI.

RESULTS

Paravascular Thorotrast deposits were detected in 245 patients. Clinical symptoms related to deposits appeared 10 to 30 years after Thorotrast administration. The severity of symptoms depended on the location and extension of granulomas and were mainly caused by fibrosis, nerve paralysis and vascular changes. Four malignant tumors adjacent to granulomas were observed (one soft tissue sarcoma in the groin, two squamous cell carcinomas of the parotid gland and one lymphoepithelial carcinoma of the nasopharynx). MRI including MRA allowed an accurate determination of tissue damage, whereas the utility of US and CT was restricted due to strong sound attenuation and streak artefacts caused by the high X-ray absorption of Thorotrast.

DISCUSSION AND CONCLUSION

Locoregional late effects of paravascular Thorotrast deposits mainly comprise radiation induced, fibrotic tissue destruction. The incidence of malignant tumors, in particular sarcomas, adjacent to deposits, however, is much lower than initially expected.

[Functional magnetic resonance tomography in neuroradiology]

The assessment of cerebral functions has long been the domain of positron-emission tomography and single photon emission computed tomography. The use of rapid imaging sequences and contrast agents enables physiological and pathophysiological cerebral processes to be assessed and monitored by magnetic resonance imaging. Both T1- and T2-weighted contrast-enhanced fast imaging sequences can be used to assess tissue perfusion, vascularity, and microcirculation by applying models developed in nuclear medicine. The diffusion of water molecules and hemodynamic aspects of the macrovasculature can also be monitored. Functional magnetic resonance (MR) imaging enables the visualization of neuronal function and activity, and MR spectroscopy makes possible the metabolic mapping of lesions and surrounding tissue. The advantages of MR techniques includes their low invasiveness, multiplanar imaging ability, and lack of radiation. This contribution discusses the clinical use of functional MR imaging methods and their role in neuroradiological diseases. Measuring perfusion and diffusion allows detailed insight into the pathophysiology of cerebral ischemia and is already being used routinely in acute ischemic stroke. Dynamic MR angiography enables the hemodynamic assessment of vascular malformations. In CNS neoplasms these imaging techniques can improve lesion characterization and the selecting, planning, and monitoring of therapy. Functional MR imaging techniques have also revolutionized the study of psychiatric illness; however, their clinical utility here is still limited. Initial results in patients with dementia and schizophrenia have provided insight into the pathophysiological changes of these diseases.

[Improved tumor contrast and delineation in the stereotactic radiotherapy planning of cerebral gliomas and metastases with contrast media-supported FLAIR imaging]

BACKGROUND

FLAIR MR imaging has shown to be a valuable imaging modality in pathologic lesions of the brain including intra-axial brain tumors. The aim of the study was to assess the value of a FLAIR technique in the planning process of stereotactic radiotherapy in patients with cerebral gliomas and metastases.

PATIENTS AND METHODS

Thirty-five patients with cerebral gliomas and 12 patients with a total of 39 cerebral metastases were examined by T2/PD-weighted fast spin-echo, fast FLAIR prior and after contrast and contrast enhanced T1-weighted spin-echo using identical slice parameters. The images were evaluated by using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid contrast and contrast-to-noise. The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation and image artifacts.

RESULTS

In the qualitative evaluation (Table 3 and 6), all readers found the fast FLAIR images to be superior to fast spin-echo in the exact delineation of cerebral tumors (p < 0.001) and the delineation of enhancing and non enhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contrast and tumor-to-CSF contrast-to-noise (p < 0.001) (Tables 1, 2a, 2b, 4, 5). The tumor-to-background contrast and tumor-to-background contrast-to-noise of the fast FLAIR images were lower than that of T2-weighted spin-echo images but were significantly increased after the application of contrast media. FLAIR images had more image artifacts, but the image interpretation was not influenced.

CONCLUSIONS

FLAIR MR imaging was found to be a valuable sequence in the planning protocol of stereotactic radiotherapy. The concurrent presentation of enhancing and non enhancing tumor tissue on contrast enhanced fast FLAIR imaging enables to use a single imaging sequence in the treatment protocol. This enables to load a reduced image amount into the radiotherapy planning software, is therefore time saving and reduces potential errors.

[Distal choledochal cyst in hydro-spiral CT]

Bile duct cysts are rare abnormalities of the biliary tract. Surgical therapy has been recommended because of possible complications such as cholestasis with jaundice and the risk of bile duct carcinoma. Accurate preoperative radiological imaging is available for surgical planning. In addition to direct imaging of the biliary system in ERCP, high-resolution axial computerized imaging techniques are necessary. The use of MRCP is becoming more frequent in diagnostic imaging of the biliary tract. Similar to the diagnosis of pancreatic tumors with hydro-spiral CT technique, we demonstrate the benefits of hydro-CT in imaging of a distal choledochal cyst, the problems of differential diagnosis and the classification in the generally accepted Todani system in a case in which accurate clarification with MRCP and ERCP was not possible.

[Multiphase, contrast-enhanced 3D-MR angiography for morphological and functional focal lesion detection. Initial results]

PURPOSE

To investigate the value of multiphase breath-hold 3D gadolinium (Gd)-enhanced MR angiography (MRA) for lesion detection and characterization of focal liver lesions.

MATERIALS AND METHODS

Breath-hold 3D Gd-enhanced MRA was performed in 25 patients with benign and malignant hepatic lesions on a 1.5-T MR system using an ultrafast 3D spoiled gradient echo sequence (TR/TE =5/2 ms, FOV=300-450 mm, matrix=256x168, voxel volume=1.8x2.3 x2.5 mm, 64 partitions, central k-space reordering; acquisition time=27 s). Three measurements were done in the arterial, portal venous, and late venous phase.

RESULTS

The analysis of the spatial and temporal evolution of contrast enhancement of the 3D-MRA improved significantly (P<0.01) lesion detection and characterization if compared with T1 precontrast, T2-weighted, and T1 postcontrast images.

CONCLUSION

Multiphase breath-hold 3D Gd-enhanced MRA imaging is a robust new technique to significantly improve morphological detection of benign and malignant lesions during the early arterial phase and further improves functional characterization of liver lesions by a combination of an arterial, a portal venous, and a late venous phase. Schlüssselwörter Multiphasisch. MR-Angiographie. Leberläsionen

Alterations of intratumoral pharmacokinetics of 5-fluorouracil in head and neck carcinoma during simultaneous radiochemotherapy

The kinetics of local drug uptake and metabolism of the anticancer drug 5-fluorouracil (5-FU) has been monitored by means of 19F nuclear magnetic resonance spectroscopy in 17 patients with neck tumors during concurrent radiochemotherapy. All of the patients underwent an accelerated hyperfractionated, concomitant-boost radiochemotherapy with 5-FU [600 or 1000 mg/m2 of body surface (b.s.)] and carboplatin (70 mg/m2 of b.s.). Serial 19F nuclear magnetic resonance spectra were obtained during and after the administration of 5-FU in a 15-T scanner with the use of a 5-cm diameter surface coil positioned on a cervical lymph node metastasis. Examinations were performed at day 1 of therapy and, in 13 patients, also after 43.5 Gy of irradiation at day 1 of the second chemotherapy cycle. Resonances of 5-FU and the catabolites 5,6-dihydro-5-fluorouracil (DHFU) and alpha-fluoro-beta-alanine (FBAL) were resolved in the tumor spectra. The median of the 5-FU and FBAL levels was significantly higher (more than 2-fold) at the second compared with the first examination, whereas the level of DHFU did not change. This effect could indicate an increased delivery of 5-FU into the interstitial space of the tumor in the course of the combined treatment, which would result in an enhanced exposure of the tumor cells to the drug. A potential mechanism for synergy between radio- and chemotherapy is discussed, but alternative mechanisms are also being considered. The findings indicate that a method is available to rationally address the design of dosing schedules in concurrent therapy regimens.

[1H-MR spectroscopy in anorexia nervosa: reversible cerebral metabolic changes]

PURPOSE

By using localized 1H-MR spectroscopy in the brain of patients with anorexia nervosa we wanted to verify our preliminary results and to look for a reversibility of the metabolic changes under therapy.

METHODS

In 22 patients and 17 healthy volunteers (11 follow-up examinations) single voxel 1H-MR spectroscopy (TE = 50 ms, TM = 30 ms, TR = 1500 ms, voxel (2 cm)3, acq.: 256) was used in two different localizations (thalamus and parieto-occipital region). The first examination of the patients was performed before therapy, the follow-up examination at the end of therapy.

RESULTS

In both regions of the brain we found a statistically significant elevation of the Cho/Cr-ratio in comparison to normal controls. The follow-up examinations revealed reversibility of the metabolic changes under successful therapy.

CONCLUSIONS

1H-MR spectroscopy reveals metabolic changes in the brain of patients with anorexia nervosa, which are reversible under successful therapy. These metabolic changes can be conclusively explained using a biochemical model.

[1H-MR spectroscopy in anorexia nervosa: the characteristic differences between patients and healthy subjects]

PURPOSE

The neurophysiological and neuromorphological changes in patients with anorexia nervosa (AN) are well-known but the reason of both is still unknown. We have evaluated the usefulness of hydrogen (H1) magnetic resonance spectroscopy in anorexia nervosa.

METHOD

We investigated 15 patients with clinically diagnosed AN (ICD F50.0) and 17 controls without eating disorders. The body mass index (BMI) was 15.8 and 21, respectively. The spectroscopy was recorded on two voxels in the parieto-occipital white matter or in the thalamus with a water-suppressed STEAM-sequence. The metabolites were recorded with respect to phosphocreatine (PCr).

RESULTS

The ratio of NAA/PCr in both voxels were not significantly different when comparing patients vs. controls. Patients showed significantly higher ratios of choline-containing components (Cho) or, respectively Cho/PCr and NAA/PCr in the white matter. Distinct, but not significant differences were detected both for m-Ino and m-Ino/PCr in the parieto-occipital region and for the Cho- and m-Ino contained ratios in the thalamus.

CONCLUSION

AN is not associated with neuronal damage. The ratio of Cho/PCr and NAA/Cho may reflect the disturbance of membrane-turnover. It is possible that the increase of membrane catabolism leads to a hyperosmolar state. The change of m-Ino/PCr ratio may reflect the regulation of osmolarity.

[Ultrafast MRI phlebography of the lungs]

AIM

Improved detection of pulmonary-venous pathologies by imaging the pulmonary veins without arterial overlay.

MATERIAL AND METHODS

Sequential 3D imaging of the pulmonary arterial and arteriovenous phase was performed with an ultrafast 3D FLASH sequence successively acquiring eight 3D data sets every 2.9 s within a single breathhold. For an 8 cm thick 3D slab an interpolated spatial resolution of about 1.4 x 1.9 x 3.3 mm could be achieved. Different protocols for contrast media dose and infusion rate were used. For selective visualization of the pulmonary veins, the pulmonary arterial phase was subtracted from a subsequent arteriovenous phase with the highest venous signal. 5 healthy volunteers, 8 patients with history of a cerebrovascular accident (CVA) of unknown etiology an suspected pulmonary-venous thrombosis and 9 patients with compression of the pulmonary vasculature by centrally growing malignancies were evaluated.

RESULTS

With higher infusion rate and lower contrast media dose, arteries and veins could be better separated by their enhancement kinetics. In all cases a complete visualization of the main pulmonary veins, segmental and subsegmental veins up to the fourth order of each lung segment was achieved without any overlay of pulmonary arteries. No thrombi of the pulmonary veins were found in patients with CVA. The obstruction of pulmonary arteries and veins due to vessel compression could be selectively visualized.

CONCLUSION

Ultrafast multiphase 3D-Gd-MRA is a new reliable method for selective 3D visualization of pulmonary veins.

Proton magnetic resonance spectroscopy in acute, juvenile anorexia nervosa

Anorexia nervosa is usually associated with a shrinkage of the brain that is at least partially reversible with weight gain. The pathogenesis of this brain abnormality is unclear. The purpose of this study was to investigate potential alterations in localized proton magnetic resonance (1H MR) spectra of anorectic patients immediately after an interval of excessive weight loss. Twelve patients and seventeen control subjects were examined. Water suppressed 1H MR spectra were recorded from two voxels placed in the thalamus and in the parieto-occipital white matter. The spectra of ten patients could be evaluated. Comparing patients and control subjects, significantly higher signal intensity ratios of choline containing compounds (Cho) relative to total creatine (Cr) as well as significantly lower ratios of N-acetyl-aspartate (NAA) relative to Cho were found in the white matter region. We hypothesize that these results indicate an abnormal starvation, associated membrane turnover, which predominantly takes place in the white matter. No evidence for neuronal degeneration was found in the thalamus or in the white matter region.

Pharmacokinetic analysis of sparse in vivo NMR spectroscopy data using relative parameters and the population approach

NMR spectroscopy in vivo when applied to studying drugs and their metabolites usually measures relative concentration in a tissue over time. Only ratios of clearance and volume parameters can be estimated from these data. Low drug dosages (relative to the sensitivity of in vivo NMR) or rapid drug elimination create the additional problem of data sparsity where a pharmacokinetic model cannot be fitted individually. We have investigated whether relative and absolute pharmacokinetic parameters can be estimated from such data by applying a population model. The data analysed were relative concentrations of 5-fluorouracil (FU) and of the sum of its catabolites alpha-fluoro-beta-ureido-propanoic acid (FUPA) and alpha-fluoro-beta-alanine (FBAL) in the liver, as monitored in 16 cancer patients by [19F]-NMR spectroscopy during and after a 10-min intravenous infusion of 650 mg FU.m-2. The "structural" part of the population model was a non-linear, two-compartment model featuring one FU compartment with volume VFU, a saturable clearance of FU by conversion into the catabolites where CL = vmax/(kM+CFU), a catabolite compartment with volume Vcat, and a concentration-independent clearance of the catabolites, CLcat. The parameters actually fitted were: gamma, vmax, kM.VFU, Vcat/VFU, and CLcat/Vcat where gamma is a proportionality factor relating the NMR signal intensity of FU to the amount of FU in the body and, therefore, has no purely pharmacokinetic interpretation. All parameters were checked for random interindividual variation: gamma and vmax were also tested for inter-occasion variation. The program system NONMEM was used for model fitting.(ABSTRACT TRUNCATED AT 250 WORDS)

[TOF-MR angiography in radiotherapy treated cerebral arteriovenous malformations]

Intracerebral arteriovenous malformations represent congenital anomalies with an arteriovenous shunt (nidus). The therapeutic goal is to eliminate the risk of bleeding and to improve the clinical symptoms. The exact localization of the nidus and the identification of the feeding arteries are critical for therapy planning. Up to now conventional brain angiograms have been used for treatment planning and for the assessment of therapy response. We studied whether 3D time-of-flight (TOF) MR angiography can be used for therapy planning and monitoring. MRI and TOF-MRA studies of 28 patients undergoing radiotherapy were evaluated. They were compared to conventional angiography to assess the MRA study. A Correct identification of the arterial feeder and the nidus was possible in about 75% of the patients. In combination with the MRI study, an important 3D dataset for treatment planning could be obtained that includes therapeutically relevant information on the localization and spatial structure of the AVM as well as the adjacent brain tissue. As a noninvasive technique, close-meshed follow-up studies could be performed with MRA.

Drug monitoring of 5-fluorouracil: in vivo 19F NMR study during 5-FU chemotherapy in patients with metastases of colorectal adenocarcinoma

The metabolism of 5-fluorouracil (5-FU) is complex and the reason for the low response rate of tumor patients to 5-FU is currently unknown. The aim of this study was to evaluate whether spectral parameters obtained noninvasively by in vivo 19F nuclear magnetic resonance (NMR) spectroscopy can be used to assess individual response to 5-FU chemotherapy. Eighteen patients with metastases of colorectal carcinoma treated with 5-FU were examined by 19F NMR at 1.5 T. The NMR signal intensity versus time curves were observed for the cytostatic and its catabolite alpha-fluoro-beta-alanine (FBAL). Clinical response to treatment was monitored by CT/MR imaging of the liver and carcinoembryonic antigen (CEA) levels in the serum. 5-FU levels observed in IV-treated patients correlate with volumes of metastases in the liver region examined with the 19F NMR coil (k = 0.77, p < .0001). 5-FU levels in patients at their initial 5-FU chemotherapy were related with clinical response determined after three cycles of treatment. In the group of patients with extensive liver involvement and IV treatment, responders (n = 3) had enhanced 5-FU levels compared to nonresponders (n = 3). FBAL data indicate an apparent saturation of 5-FU catabolism in the liver for 5-FU doses > 1 g infused during 10 min. Mean absolute concentrations of FBAL were about 1 mumol per gram liver tissue. 19F NMR spectroscopy could be used to guide dose escalation schemes or to assess the modulation of 5-FU metabolism by other drugs in combined chemotherapy.