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L G Strauss

Publications and source records attributed to L G Strauss.

At least 19 recordsLinked to original sources
PubMed2005

Feasibility study of the use of similarity maps in the evaluation of oncological dynamic positron emission tomography images.

A preliminary study is presented on the potential role of similarity mapping (SM) in the evaluation of oncological dynamic 18F-fluorodeoxyglucose positron emission tomography studies, mainly in lesion localisation and detectability. Similarity maps were calculated using previously described (correlation coefficient (COR) and normalised correlation coefficient (NCOR)) and newly introduced similarity measures (sum of squares coefficient (SSQ), squared sum coefficient (SQS), sum of cubes coefficient (SC) and cubed sum coefficient (CS)). The results were evaluated using simulated and clinical data. The study revealed that the best-suited similarity measure for such applications was the CS similarity coefficient, which provided the best parametric images, delineating structures of interest and supporting the visual interpretation of data sets. It was shown that SM and standardised uptake value (SUV) images had comparable diagnostic performance, although SM was able to offer additional time-related information in a single image. For the case of colorectal recurrences (17 cases), the measured contrast values for the CS and SUV images were 2.36 +/- 0.47 and 4.12 +/- 0.42, respectively, whereas, for three cases of giant cell tumours, these values were 11.6 +/- 2.1 and 11.9 +/- 1.8, respectively.

Colorectal Neoplasms↗
PubMed2003

PET-FDG as predictor of therapy response in patients with colorectal carcinoma.

AIM: The purpose of this study was to evaluate the prognostic value of quantitative dynamic FDG PET studies in patients with metastastic colorectal cancer receiving FOLFOX (fluorouracil, folinic acid and oxaliplatin) chemotherapy. METHODS: The evaluation includes 28 patients with 55 metastases from primary colorectal cancer. Reference for the FDG studies was the clinical response data, according to the WHO classification. Three response groups were defined: progressive disease (PD), stable disease (SD) and partial response (PR). The FDG studies were accomplished as dynamic series for 60 min. The evaluation of the FDG kinetics was performed using the SUV, and fractal dimension (FD) of the time activity curves based on the box counting procedure (parameter for the inhomogeneity of the tumors). RESULTS: The median SUV as measured in the tumor lesions prior to onset to FOLFOX was 3.15, in comparison with 2.68 SUV after the first cycle and 2.61 SUV after the second cycle. Discriminant analysis (DA) was used for the classification of the data into the 3 categories. Both parameters SUV and FD provided 2 of the 3 "predicted" categories, namely PD and SD. It was possible to correctly classify PR in only 10% of the patients, using the FD of both studies. Generally, DA inclined to misclassify the data towards PD. Even the first PET study was predictive with respect to therapy outcome (96% for PD and 47% for SD using only the baseline SUV). Metastases with a baseline SUV lower than 4.6 did not respond to FOLFOX chemotherapy. The combination of SUV and FD of the first study lead to a correct classification of 93% of PD and 60% of SD. Best results were obtained for the FD of the initial PET study (90% for PD and 75% for SD) as well as for the FD of both studies (77% for PD, 73% for SD, 10% for PR). CONCLUSION: Quantitative, dynamic FDG-PET should be used preferentially for monitoring patients with metastatic colorectal cancer receiving chemotherapy. Even the first FDG study prior to onset to chemotherapy is predictive for the therapy outcome.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Quantitative evaluation of skeletal tumours with dynamic FDG PET: SUV in comparison to Patlak analysis.

This study was carried out to evaluate bone lesions using fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) and to explore whether dynamic and quantitative PET data may help to differentiate benign lesions from malignant masses. Forty patients with primary bone lesions were studied. The final diagnosis was confirmed by histopathology. A 60-min dynamic FDG PET acquisition was undertaken in all subjects. From the dynamic PET images, indices such as the average and maximal standardised uptake values (SUVs), the tumour SUV-to-muscle SUV ratio (T/M) and the SUV at 60 min-to-SUV at 30 min ratio (averSUV60/30 min and maxSUV60/30 min) were produced. Patlak graphical analysis was used to obtain the influx constant (Ki), and the metabolic rate of FDG (MRFDG) was calculated. Based on the receiver operator characteristic curve, the sensitivity and specificity for each parameter in differentiating between malignant and benign lesions were evaluated. The histological results revealed 21 malignant tumours and 19 benign lesions in this group. The MRFDG and SUV indices in malignant lesions were significantly higher than those in benign lesions. However, each index showed a considerable overlap between benign and malignant lesions. Average SUV correlated positively with MRFDG (r=0.67). When a cut-off of 1.8 average SUV was used, the sensitivity and specificity for discrimination of malignancy from benign disease were 85% and 82.4%, respectively. MRFDG showed a similar sensitivity (82.4%) and a better specificity (92.9%). A combination consisting of a cut-off of average SUV (1.8) and averSUV60/30 min (1.1) resulted in an improvement of specificity to 93.3%, with a small reduction in sensitivity (81.3%) as compared with exclusive use of SUV. The results of this study indicate that a detectable difference in glucose metabolism exists between malignant and benign skeletal lesions. The static FDG uptake indices alone may not enable adequate differentiation between benign and malignant lesions. Quantitative dynamic imaging may provide more helpful information, but will not permit a definite diagnosis. The use of uptake indices may represent an alternative and interesting approach to the evaluation of bone lesions.

Adolescent↗
PubMed2001

Quantitative PET studies in pretreated melanoma patients: a comparison of 6-[18F]fluoro-L-dopa with 18F-FDG and (15)O-water using compartment and noncompartment analysis.

UNLABELLED: The purpose of the study was to evaluate the 6-[18F]fluoro-L-dopa (FDOPA) kinetics with PET in patients with treated melanoma metastases and to compare it with the standard tracer 18F-FDG as well as with the perfusion tracer (15)O-water in selected cases. METHODS: The study included 11 patients (22 lesions) with pretreated metastatic melanomas. Dynamic studies with FDG and in selected cases with (15)O-water (eight patients) preceded the FDOPA study. A one-tissue-compartment model was used for the evaluation of the FDOPA and (15)O-water studies, and a two-tissue-compartment model and Patlak analysis were used for the FDG data. A noncompartment model based on chaos theory was used for calculating fractal dimension, which is a parameter for heterogeneity. RESULTS: The FDG studies showed a 1.5-fold increased uptake in comparison with surrounding tissue in 19 of 22 metastatic lesions (sensitivity of 86.4%). False-negative FDG results were obtained in 2 patients (three lesions). FDOPA uptake was enhanced in 14 of 22 metastatic lesions (sensitivity of 64%). FDG uptake was 1.5-fold higher than FDOPA uptake in 18 of 22 metastases from melanoma, whereas FDOPA uptake was 1.5-fold higher than FDG uptake in 2 patients with liver metastases. The data did not show a statistically significant correlation between the transport constant (K1) for FDOPA and that for FDG or between the standardized uptake value for FDOPA and FDG in metastases. No statistically significant correlation was found between K1 for FDOPA and that for (15)O-water. The data show that FDOPA uptake is not perfusion dependent and provides different information from FDG. The fractal dimension was similar for all tracers within the tumor region. Detectability of metastases was enhanced when both tracers were used (sensitivity of 95%). CONCLUSION: In patients with negative FDG findings, FDOPA can help to identify viable melanoma metastases and thus may help to select patients who would benefit from further treatment.

Dihydroxyphenylalanine↗
PubMed2001

Dynamic PET 18F-FDG studies in patients with primary and recurrent soft-tissue sarcomas: impact on diagnosis and correlation with grading.

UNLABELLED: The purpose of this study was to evaluate (18)F-FDG PET studies of primary and recurrent sarcomas for diagnosis and correlation with grading. METHODS: The evaluation included 56 patients, 43 with histologically proven malignancies and 13 with benign lesions. Seventeen patients were referred with suspicion on a primary tumor, and the remaining 39 were referred with suspicion on a recurrent tumor. The FDG studies were accomplished as a dynamic series for 60 min. The evaluation of the FDG kinetics was performed using the following parameters: standardized uptake value (SUV), global influx, computation of the transport constants K1-k4 with consideration of the distribution volume (VB) according to a two-tissue-compartment model, and fractal dimension based on the box-counting procedure (parameter for the inhomogeneity of the tumors). RESULTS: Visual evaluation revealed a sensitivity of 76.2%, a specificity of 42.9%, and an accuracy of 67.9%. The vascular fraction VB and the SUV were higher in malignant tumors compared with benign lesions (t test, P < 0.05). Although the FDG SUV helped to distinguish benign and malignant tumors, there was some overlap, which limited the diagnostic accuracy. The SUV and fractal dimension accounted for significant differences in six of the nine diagnostic pairs. Whereas grade (G) II and G III tumors were differentiated from lipomas on the basis of the fractal dimension and some other kinetic parameters, no differences were found between G I tumors and lipomas. On the basis of the discriminant analysis, the differentiation of soft-tissue tumors was best for the use of six parameters of the FDG kinetics (SUV, VB, K1, k3, influx, and fractal dimension). Eighty-four percent of G III tumors, 37.5% of G II tumors, 80% of G I tumors, 50% of lipomas, and 14.3% of scars could be classified correctly, whereas inflammatory lesions were misclassified. CONCLUSION: FDG PET should be used preferentially for monitoring patients with G III sarcomas. Visual analysis provides a low specificity. In contrast, the evaluation of the full FDG kinetics provides superior information, particularly for the discrimination of G I and G III tumors (positive predictive value, >80%).

Diagnosis, Differential↗
PubMed2000

Sensitivity and specificity of positron emission tomography (PET) for the diagnosis of lymph node metastases.

The introduction of Positron Emission Tomography (PET) and the use of the glucose analog F-18-Deoxyglucose (FDG) can help to improve the sensitivity of the diagnosis of lymph node metastases. Sensitivity exceeding 90% can be achieved when advanced imaging protocols and image reconstruction methods are used for PET. Superior staging information is obtained with PET as compared to morphological imaging methods for the most frequent tumor types. The accuracy of N-staging can be significantly improved by adding PET to the pretherapeutic diagnostic procedures. Limitations exist with regard to false positive results. Acute or chronic inflammation as well as unspecific reactions following radiotherapy may mimic tumor tissue.

Breast Neoplasms↗
PubMed2000

Clinical value of [18-F]] fluorodeoxyglucose positron emission tomography imaging in soft tissue sarcomas.

OBJECTIVE: To evaluate positron emission tomography (PET) using 2-fluoro-2-deoxy-D-glucose (FDG) for clinical application in soft tissue sarcomas. SUMMARY AND BACKGROUND DATA: FDG PET is a promising noninvasive method for the preoperative assessment of soft tissue sarcomas and may complement radiologic tomography. METHODS: Data from 50 consecutive patients with 59 masses, either suspicious for primary or locally recurrent soft tissue sarcoma, were prospectively gathered. The semiquantitative FDG uptake (standardized uptake values [SUVs]) was calculated in tumor and normal tissue (muscle). Histopathology of surgical specimens and follow-up data were used as control criteria. RESULTS: In primary soft tissue sarcomas, PET displayed a sensitivity of 91% and a specificity of 88%. Local recurrence was detected with a sensitivity of 88% and a specificity of 92%. All intermediate-grade and high-grade soft tissue sarcomas (primary and locally recurrent) were visualized with a precise differentiation from muscle. Fifty percent of the low-grade sarcomas showed an FDG uptake equivalent to muscle (false-negative results in one primary and three recurrent soft tissue sarcomas). Benign soft tissue tumors (e.g., lipoma, leiomyoma, ganglion) did not accumulate FDG. Inflammation resulted in an increased FDG uptake. The semiquantitative FDG uptake (SUVs) correlated with tumor grade but not with size and histologic type. CONCLUSION: High-grade and intermediate-grade soft tissue sarcomas are amenable to PET imaging, whereas low-grade lesions may not be depicted. SUVs for FDG correlate with tumor grade in soft tissue sarcomas. Benign soft tissue tumors are differentiated from higher-grade soft tissue sarcomas. These data show that FDG-PET can complement preoperative radiologic assessment for soft tissue sarcomas and that FDG-PET is a powerful diagnostic tool for detecting high-grade and intermediate-grade local recurrence.

Adolescent↗
PubMed1999

Noninvasive determination of the arterial input function of an anticancer drug from dynamic PET scans using the population approach.

For the application of a kinetic model to PET data, it is generally necessary to obtain the arterial input function (AIF). It was the aim of the present study to introduce a method suitable for the determination of the AIF of a substance that undergoes biochemical transformation from noisy PET data: the population approach. F-18 labeled 5-fluorouracil (5-[18F]FU) was administered i.v. to eight patients suffering from liver metastases of colorectal carcinoma. Radioactivity concentrations in liver and aorta were dynamically measured with PET over 120 min. Pharmacokinetic analysis was carried out by applying a five-compartment model to individual activity-time data for the eight patients or to the mean activity-time data among the eight patients. The mean values of all parameters describing 5-FU transport and catabolism, i.e., volumes of distribution and clearances, as well as interindividual coefficients of variation (CV) were calculated according to both approaches. With our model, we were able to separate the concentration-time course of 5-FU in plasma, i.e., the AIF, from that of its major catabolite alpha-fluoro-beta-alanine (FBAL). As far as the mean parameter estimates are concerned, the differences between both approaches are not significant. For the liver data, the CV's are almost the same for both approaches. For the parameters concerning the aorta, however, there is a decrease in the CV's by using the population approach. For example, the CV of the central distribution volume of 5-FU was 30% for the individual approach and 18% for the population approach. With the population approach, it is possible to determine the AIF of drugs that undergo metabolic conversion, such as anticancer drugs, from the abdominal aorta visualized on PET images. The population approach helps to overcome noise in individual data. Since no measurements are needed in addition to the PET examination, the suggested method helps to reduce risk and pain for the patients as well as cost and thus facilitates large scale patient studies.

Adenocarcinoma↗
PubMed1999

Pharmacokinetic imaging of 11C ethanol with PET in eight patients with hepatocellular carcinomas who were scheduled for treatment with percutaneous ethanol injection.

PURPOSE: To evaluate the carbon 11 ethanol kinetics with positron emission tomography after intratumoral injection of the tracer and assess its redistribution and dilution in patients who have hepatocellular carcinomas and who were scheduled for treatment with percutaneous ethanol injection. MATERIALS AND METHODS: The study included eight patients with hepatocellular carcinomas. 11C ethanol was administered via a puncture needle positioned with ultrasonographic guidance. Parametric images based on the Fourier transformation were created for further analysis of the local distribution patterns of the tracer. The ratio of the 45-minute postinjection standardized uptake value to the 5-minute postinjection standardized uptake value was used for the evaluation of ethanol dilution. RESULTS: Five of eight tumors demonstrated almost constant uptake values after the initial distribution phase. In contrast, a rapid elimination of the 11C ethanol from the tumor was documented in three of eight tumors. The 45 minute-to-5 minute ratio was 0.18-0.67 (median value, 0.56) in the tumors. The time-activity curves of the normal liver parenchyma increased slowly but steadily with time owing to a low ethanol elimination from the tumor. Fourier transformation demonstrated inhomogeneous parts on the amplitude images in seven of eight tumors and random redistribution on the phase images in six of eight tumors. CONCLUSION: Inhomogeneous drug distribution and drug dilution in the target area are likely to be the major limiting parameters for therapy response.

Aged↗
PubMed1998

18F-labeled fluorouracil positron emission tomography and the prognoses of colorectal carcinoma patients with metastases to the liver treated with 5-fluorouracil.

BACKGROUND: Although many factors have been investigated in connection with the prognoses of colorectal carcinoma patients with metastases to the liver, a means for evaluating response and prognosis prior to the administration of standard chemotherapy has not been available. Positron emission tomography (PET) is a noninvasive means of measuring the distribution of radiolabeled cytostatic agents in tumor regions. METHODS: Prior to the administration of 5-fluorouracil chemotherapy, the authors examined 14 colorectal carcinoma patients with unresectable liver metastases using a single PET scan and 18F-labeled fluorouracil (18F-FU). Clinical response and survival time were correlated with 18F-FU uptake values (SUV) measured in liver metastases 120 minutes after tracer infusion. RESULTS: Trapping of 18F-FU varied even among different metastases in the same patient. The range of SUV was 0.9-4.3 (mean, 2.20). Four patients with SUV exceeding 2.8 had stable disease for longer than 12 months and survived longer than 21 months. Three patients with SUV less than 1.2 had progressive disease and survived less than 12 months. The 6 patients with partial remission or stable disease had a mean SUV of 2.96 and a mean survival of 31.6 months. Eight patients with progressive disease had a mean SUV of 1.59 and a mean survival of 14.5 months (Student's t-test, P < 0.012). In scatterplot analysis, there was a statistically significant correlation between SUV and survival time. CONCLUSIONS: Patients with high 18F-FU uptake values are more likely to achieve at least stabilization of disease with planned chemotherapy. 18F-FU PET may be a valuable new tool for determining, prior to 5-FU-based chemotherapy, which patients are likely to have good responses and prolonged survival.

Aged↗
PubMed1998

[Biologic characterization of soft tissue sarcomes by positron emission tomography (initial results)].

Positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (FDG), carbon-11-labeled aminoisobutyric acid (AIB) and oxygen-15-labeled water (15O-labeled water) was evaluated for imaging soft tissue sarcomas (STS). Eleven pathologically confirmed STS were evaluated by PET using FDG, AIB and 15O-labeled water. All radiotracers showed an increased activity in viable tumor with a significant differentiation from normal tissue (muscle). An increased glucose metabolism in STS allowed a differentiation from normal tissue (muscle) with FDG. Furthermore, STS showed an increased AIB activity suggesting an increased "A-type" aminoacid transport. AIB therefore can be used for evaluation of STS. 15O-labeled water demonstrated an increased uptake with an overlap with blood vessel activity. These radiotracers supply information about biological properties of STS. Five patients with suspicious lesions in conventional radiodiagnostic but negative PET scans were free of local recurrence, diagnosed either by surgery or by follow-up. Two patients with PET findings suggesting local failure, ultimately demonstrated local recurrence. The differentiation of local recurrence from benign postoperative tissue alterations is encouraging and requires further evaluation.

Amino Acid Transport System A↗
PubMed1998

Intravenous and intra-arterial oxygen-15-labeled water and fluorine-18-labeled fluorouracil in patients with liver metastases from colorectal carcinoma.

UNLABELLED: Intra-arterial chemotherapy can potentially increase drug delivery at the tumor sites and has therefore been used for the therapy of metastatic colorectal cancer. METHODS: Dynamic PET and [18F]fluorouracil (18F-FU) were used in patients with liver metastases from colorectal cancer to examine the pharmacokinetics of the drug up to 120 min after intravenous and intra-arterial injection of the same dose of fluorouracil (FU). All patients included in the study (n = 15) had surgically implanted catheters in the gastroduodenal artery. Dynamic PET studies (up to 5 min) with 15O-labeled water were performed for the evaluation of the access to the lesions immediately before the 18F-FU study using both administration routes. The final evaluation included 24 metastases, obtained from 15 patients. RESULTS: Of 24 lesions, 21 (87.5%) showed an improved access using the intra-arterial approach, and 20 (83.3%) demonstrated a better FU influx after intra-arterial 18F-FU infusion. Metastases reached the highest 18F-FU concentrations after intra-arterial administration, with a maximum standardized uptake values of 18.75 for the FU influx and of 5.03 for FU trapping. Of 24 metastases, eight (33.3%) demonstrated enhanced FU trapping after the intra-arterial administration. Cluster analysis revealed a group of metastases (n = 6) with a nonperfusion-dependent FU transport using the intravenous application. Of these six lesions, five (83.3%) did not show any enhancement of the 18F-FU trapping after intra-arterial application. The data gave evidence for at least one different, energy-dependent transport system, which can be saturated even after intravenous administration of the drug. CONCLUSION: The data show that the main limiting factor for a therapy response is the very high and rapid elimination of the cytostatic agent out of the tumor cells. Furthermore, it was not possible to predict the pharmacokinetics of FU after intra-arterial application using an intravenous PET study. It may be possible, using intravenous PET double-tracer studies, to identify metastases having a nonperfusion-dependent transport system and exclude them from an intra-arterial treatment protocol.

Antimetabolites, Antineoplastic↗
PubMed1998

Fluorine-18-fluorouracil to predict therapy response in liver metastases from colorectal carcinoma.

UNLABELLED: Prediction of chemotherapy response is still a problem in oncological patients. METHODS: Studies with PET and 18F-fluorouracil (FU) were used for measurements of drug concentrations in patients with liver metastases from colorectal carcinoma. The PET data obtained before onset of FU chemotherapy were correlated to the growth rate of the metastases after therapy. The final evaluation included 25 metastases obtained in 17 patients. CT preceded the first chemotherapeutic cycle and was repeated within 3-11 mo after onset of treatment. The uptake of the cytostatic agent was evaluated in the liver metastases using the SUV at 120 min after tracer infusion. Tumor growth rate of the metastases was calculated based on CT volumetric data. RESULTS: The trapping of 18F-FU was highly variable even for multiple metastases in the same patients. Six metastases with high 18F-FU uptake values exceeding 3.0 SUV correlated with negative growth rate values, 5 of 25 metastases with intermediate uptake values ranging from 2.0-3.0 SUV were associated with almost stable growth rate values nearly zero and 14 of 25 metastases with low uptake values <2.0 SUV demonstrated positive growth rate values. Only metastases with a 18F-FU uptake exceeding 3.0 SUV at 120 min postinjection demonstrated a response to therapy. A significant correlation of 0.86 (p < 0.001) was found between the 18F-FU uptake values in the metastases measured before chemotherapy and the growth rate of the lesions after treatment. CONCLUSION: The data show, that FU chemotherapy outcome can be predicted using a single PET study with 18F-FU before onset to therapy.

Antimetabolites, Antineoplastic↗
PubMed1997

Pharmacokinetic analysis of 5-[18F]fluorouracil tissue concentrations measured with positron emission tomography in patients with liver metastases from colorectal adenocarcinoma.

The purpose of our study was to develop a pharmacokinetic model to quantify the intracellular 5-fluorouracil (5-FU) concentration in liver metastases, which is expected to be closely correlated to therapy response. In addition, the influence of the biomodulator folinic acid on the action of 5-FU in the metastases was investigated. After i.v. application of 5-FU labeled with the positron emitter fluorine-18 (5-[18F]FU), the kinetics of the regional 5-[18F]FU/uptake was measured dynamically with positron emission tomography over 120 min in 14 patients with a total of 27 liver metastases from colorectal adenocarcinoma. Activity-time curves were evaluated in the metastases, the normal liver tissue, as well as in the aorta and analyzed by a six-compartment model. The catabolic breakdown of 5-FU to alpha-fluoro-beta-alanine (FBAL) in the normal liver tissue was modeled to separate the catabolites from the cytostatic agent 5-[18F]FU and the active 5-[18F]fluorodeoxyuridine nucleotides. With our model, all measured activity-time courses could be described adequately with only small interindividual variations in parameters connected with liver and blood. Extrahepatic clearance of 5-FU was estimated as 0.66 +/- 0.33 liters/min, whereas the hepatic clearance was 0.52 +/- 0.25 liters/min. The Michaelis-Menten parameters describing the nonlinear conversion of 5-FU to FBAL were Km = 11.3 +/- 6.4 micromol and Vmax = 147.1 +/- 130.7 micromol/min. The maximum FBAL concentration in the liver was reached between 35 and 65 min after i.v. 5-FU infusion. The most sensitive parameters for therapy monitoring were k(in) and k(out), which characterize the transport in and out of the intracellular volume of the metastases, respectively. Tumor response can only be expected if k(in) is high and k(out) is low ("trapping"). These criteria were met by 6 of the 27 metastases, which were identical to those with high values for the area under the intracellular 5-FU concentration curve (AUC[meta,IC]5-FU). The parameters k(in) and k(out) were also used to investigate the influence of the biomodulating agent folinic acid on drug effect. Five of the six metastases that showed trapping belonged to patients who received folinic acid. With the exception of one patient, however, all patients who received folinic acid had multiple metastases, of which only one was able to trap 5-FU. Because patient response can only be expected when all metastases trap 5-FU, folinic acid showed no effect on the overall clinical response. With the quantitative modeling approach used, trapping of 5-FU can be assessed noninvasively and on an individual basis. This makes it possible to adjust the dose for each individual patient to optimize the treatment schedule.

Adult↗
PubMed1997

[Positron emission tomography (PET) in diagnosis and therapy planning of malignant lymphoma].

The management of patients who have malignant lymphomas requires functional methods to differentiate residual soft tissue masses. Positron emission tomography (PET) was performed in patients with histologically proven malignant lymphomas prior to the onset of second-line chemotherapy to examine tumor viability. Twenty patients (68 malignant lesions and 3 benign lesions) with Hodgkin lymphomas (HL) as well as 26 patients (46 malignant lesions and 1 benign lesion) with non-Hodgkin lymphomas (NHL) were studied with fluorine-18-deoxyglucose (FDG). Oxygen-15-labelled water was used in addition in 14 patients with 25 lesions to obtain information on the tissue perfusion. PET with FDG is highly sensitive for the detection of viable tumor tissue, all malignant lesions being correctly classified in this study. We noted no statistically significant difference in FDG metabolism for Hodgkin and non-Hodgkin lymphomas. Even normal-sized lymph-node metastases (< 1 cm) were detected with PET and FDG. The possible limitations are inflammatory processes, which may obscure tumor detection because of the increased FDG uptake, as well as malignant lesions with low FDG uptake as a result of reduced perfusion. Comparison of tumor perfusion and FDG uptake showed a significant nonlinear correlation of r = 0.78 between the two parameters. Two patients with scar tissue and no evidence of malignancy were excluded from blood stem-cell support therapy as a result of the PET study. The data demonstrate that PET is a useful tool for making a diagnosis and deciding on therapy for malignant lymphomas.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Fluorine-18 deoxyglucose and false-positive results: a major problem in the diagnostics of oncological patients.

Fluorine-18 deoxyglucose (FDG) is not a very tumour-specific substance, and its accumulation in benign lesions with increased glucose metabolism may give rise to false-positive results and hence cause FDG positron emission tomography (PET) to display relatively low specificity (frequently below 85%). Correct interpretation of FDG PET studies is predicated upon detailed knowledge of morphological abnormalities, and the importance of the correlation of functional and morphological information, as derived from computed tomography or magnetic resonance imaging, is discussed. It is emphasized that image fusion programs cannot substitute for understanding of functional and morphological methods. The reconstruction of PET cross-sections is considered, and it is concluded that an iterative image reconstruction method is to be favoured, given its advantages in reducing image artefacts and improving quantification of radioactivity concentrations. The differentiation of malignant and benign lesions when using FDG PET is then reviewed; false-positive findings may be obtained, for example, in patients with acute inflammatory lesions, chronic pancreatitis, retroperitoneal fibrosis or salivary gland tumours. It is suggested that these problems may be alleviated by means of multitracer studies, e.g. using carbon-11 labelled aminoisobutyric acid for quantification of A-type amino acid transport. Finally, the effects of radiotherapy and chemotherapy on FDG uptake and the problems that accrue from these effects are reviewed. Both radiotherapy and chemotherapy can cause increased FDG uptake, complicating diagnosis and evaluation. Knowledge of the effects of different treatment procedures on regional FDG metabolism is therefore necessary for correct interpretation of the PET data.

Artifacts↗
PubMed1996

[PET studies with C-11 ethanol in intratumoral therapy of hepatocellular carcinomas].

Positron emission tomography (PET) is a noninvasive functional method for the study of solid tumor perfusion, metabolism and interaction with different therapeutic agents. The aim of the study was the investigation of the metabolism of hepatocellular carcinomas (HCC) and the kinetics during a treatment with intratumoral ethanol by PET. The ongoing study includes seven patients with child. A cirrhosis and HCC (UICC stage III-IVA; tumor size 3-6 cm). Dynamic PET studies (60 min) with 18F-fluordeoxyglucose (FDG) were performed prior to therapy to assess tumor viability. The evaluation of the FDG data demonstrated a liver-equivalent uptake in six of the tumors (well and moderately differentiated HCC), which were poorly delineated against the normal liver parenchyma. One moderately differentiated HCC showed an increased FDG metabolism, indicating no correlation between histology and metabolism. A dose of 37-80 MBq 11C-ethanol was applied together with a nonlabelled therapeutic dose of the drug via a puncture needle positioned under sonography. Five out of seven tumors demonstrated a high 11C uptake shortly after the end of the ethanol injection followed by constant 11C-ethanol concentration during the whole study period of 45 min. The PET data demonstrated no significant elimination of the 11C-ethanol from the tumor and no accumulation in the surrounding liver tissue. One case showed a decrease of the intra-tumoral 11C-ethanol concentration due to a punkture of a tumor vein, and in another case the surrounding liver parenchyma demonstrated significant 11C uptake in the early phase following paratumoral injection of the drug. In conclusion, PET is a useful tool for the study of the mechanism and the kinetics of percutaneous intratumoral ethanol injection of HCC.

Aged↗