[18F]-FDG-PET in clinical stage I/II non-seminomatous germ cell tumours: results of the German multicentre trial.

PURPOSE: The aim of this study was to determine the predictive values of 2-[fluorine-18]fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) in primary staging in patients with newly diagnosed non-seminomatous germ cell tumour (NSGCT) clinical stage I/II. PATIENTS AND METHODS: The hypothesis was that FDG-PET would improve the negative predictive value (NPV) from 70% to 90%, thus requiring a total of 169 patients. All scans underwent visual analysis by a reference team of nuclear medicine physicians. Results were validated by histology following retroperitoneal lymph node dissection. RESULTS: Only 72 of the planned 169 patients were included, due to poor accrual. The prevalence of nodal involvement was 26%. Correct nodal staging by FDG-PET was achieved in 83% compared with correct computed tomography (CT) staging in 71%. CT had a sensitivity and specificity of 41% and 95%, respectively. Positive predictive value (PPV) and NPV were 87% and 67%, respectively. FDG-PET had a sensitivity and specificity of 66% and 98%, respectively. PPV was 95%. The primary end point was not reached, with an NPV of 78%. CONCLUSION: FDG-PET as a primary staging tool for NSGCT yielded only slightly better results than CT. Both methods had a high specificity while false-negative findings were more frequent with CT. FDG-PET is mostly useful as a diagnostic tool in case of questionable CT scan.

Radionuclide imaging of the painful hip arthroplasty: positron-emission tomography versus triple-phase bone scanning.

Two major complications of hip replacement are loosening and infection. Reliable differentiation between these pathological processes is difficult since both may be accompanied by similar symptoms. Our aim was to assess the diagnostic ability of triple-phase bone scanning (TPBS) and positron-emission tomography (PET) to detect and differentiate these complications in patients with a hip arthroplasty. Both TPBS and PET were performed in 63 patients (92 prostheses). The radiotracer for PET imaging was (18)F-fluorodeoxyglucose (FDG). Image interpretation was performed according to qualitative and quantitative criteria although the final diagnosis was based upon either surgical findings or clinical follow-up. The sensitivity, specificity and accuracy of PET was 0.94, 0.95 and 0.95 respectively, compared with 0.68, 0.76 and 0.74 for TPBS. We found that an image interpretation based exclusively upon quantitative criteria was inappropriate because of its low selectivity. The histological examination indicated that increased periprosthetic uptake of FDG in patients with aseptic loosening was caused by wear-induced polyethylene particles and the subsequent growth of aggressive granulomatous tissue.

Measurement of clinical and subclinical tumour response using [18F]-fluorodeoxyglucose and positron emission tomography: review and 1999 EORTC recommendations. European Organization for Research and Treatment of Cancer (EORTC) PET Study Group.

[18F]-fluorodeoxyglucose ([18F]-FDG) uptake is enhanced in most malignant tumours which in turn can be measured using positron emission tomography (PET). A number of small clinical trials have indicated that quantification of the change in tumour [18F]-FDG uptake may provide an early, sensitive, pharmacodynamic marker of the tumoricidal effect of anticancer drugs. This may allow for the introduction of subclinical response for anticancer drug evaluation in early clinical trials and improvements in patient management. For comparison of results from smaller clinical trials and larger-scale multicentre trials a consensus is desirable for: (i) common measurement criteria; and (ii) reporting of alterations in [18F]-FDG uptake with treatment. This paper summarises the current status of the technique and recommendations on the measurement of [18F]-FDG uptake for tumour response monitoring from a consensus meeting of the European Organization for Research and Treatment of Cancer (EORTC) PET study group held in Brussels in February 1998 and confirmed at a subsequent meeting in March 1999.

Fasting improves discrimination of grade 1 and atypical or malignant meningioma in FDG-PET.

UNLABELLED: We investigated the use of PET with 2[18F]fluoro-2-deoxy-D-glucose (FDG) to discriminate between atypical or malignant and grade 1 meningiomas. The influence of fasting state and high-dose corticosteroid medication was analyzed retrospectively. METHODS: Preoperative PET scans of 75 patients with suspected diagnosis of intracranial meningioma were evaluated using standardized uptake values (SUV) and tumor-to-contralateral gray matter ratios (TGR) of FDG uptake. Fifty-one of 75 patients fasted before the PET scan, and 27 of 75 patients were studied under high-dose corticosteroid medication. Eighteen tumors had recurred. PET results were compared to histopathological grading. RESULTS: PET correctly identified 8/9 atypical or malignant meningiomas and 58/66 grade 1 meningiomas using TGR and a threshold of 1.05 in primary meningioma and 0.85 in tumor recurrence. This corresponds to a specificity of 0.88 for the detection of higher tumor grading. Specificity was significantly higher in fasting compared to nonfasting subjects (0.96 versus 0.73; p < 0.025). SUV quantification lead to a reduced specificity of 0.77 at the same level of sensitivity. The only false-negative PET finding occurred in a recurrent meningioma, which had been operated on four times before. CONCLUSION: Overnight fasting before injection is needed to improve the diagnostic accuracy of FDG-PET for noninvasive metabolic grading of meningioma. Hyperglycemia in nonfasting patients and in diabetic patients may lead to overestimation of meningioma grading.

Regional cerebral blood flow and negative/positive symptoms in 24 drug-naive schizophrenics.

UNLABELLED: SPECT/PET studies in schizophrenia revealed inconsistent changes of regional cerebral blood flow (rCBF). Frontal hyperperfusion as well as hypoperfusion are described. This study was undertaken to investigate the relations between rCBF, psychopathology according to PANSS and effects of neuroleptic therapy. METHODS: Twenty-four drug-naive acute patients with a first manifestation of schizophrenia were examined with 99mTc-HMPAO brain SPECT and assessed according to PANSS. Of these, 22 were controlled again after neuroleptic treatment. Following attenuation correction, region-to-cerebellar count ratios were obtained from 98 irregular regions of interest drawn in all slices (6.25 mm). The ratios were compared to 20 control subjects, and changes lying outside of 2 s.d. were considered abnormal. RESULTS: In different drug-naive patients, hyperperfusion as well as hypoperfused patterns were found. In drug-naive patients, the seven subscores of positive symptoms (pos 1-7) in PANSS showed different correlations to rCBF: Formal thought disorders (pos 2) and grandiosity (pos 5) were positively correlated to bifrontal and bitemporal rCBF (r = +0.59 to +0.70). Delusional ideas (pos 1), hallucinatory behavior (pos 3) and suspiciousness (pos 6) demonstrated a negative correlation to bifrontal, cingulate, left temporal and left thalamic rCBF (r = -0.59 to -0.66). Stereotyped ideas (neg 7) as a negative symptom showed a negative correlation to left frontal, left temporal and left parietal rCBF (r = -0.59 to -0.65). No correlations were found between residual positive symptoms and rCBF after neuroleptic treatment and clinical improvement, but all negative symptoms (neg 1-7) had a negative correlation to bifrontal, bitemporal, cingulate, basal ganglia and thalamic rCBF (r = -0.59 to -0.74). CONCLUSION: Our results illustrate that different positive symptoms are accompanied by different rCBF values: some induce hyperperfusion, others hypoperfusion. After therapy (and reduction of positive symptoms), only negative symptoms correlate exclusively to hypoperfusion. This may be the crucial factor in explaining inconsistencies of past results in perfusion pattern in drug-naive schizophrenic patients.

FDG PET for detection and therapy control of metastatic germ cell tumor.

UNLABELLED: We investigated the use of PET and 2[18F]fluoro-2-deoxy-D-glucose (FDG) for detection and therapy control of metastatic germ cell cancer in comparison to CT. METHODS: Fifty-four PET studies were performed in addition to CT in 33 patients with histopathologically proven germ cell tumors (14 seminomas, 18 nonseminomas, 1 not classified). The scans were done either after initial diagnosis (Group 1; n = 12), within 2 wk after completion of chemotherapy (Group 2; n = 13) or 14-375 days after chemotherapy (Group 3; n = 29). PET and CT were validated either by histology (n = 19) or clinical follow-up for 182-1704 days (n = 35). Focal pathological uptake with PET was quantified using standardized uptake values (SUVs). RESULTS: PET was significantly more accurate than CT (0.86 versus 0.59; p < 0.025) for detection of residual viable tumor in Group 3. While sensitivities of PET and CT did not differ markedly, PET was significantly more specific than CT. No significant differences between PET and CT were found in Groups 1 and 2. PET scans after therapy resulted in false-negative findings in five of nine cases of Group 2 but only in two of nine cases of Group 3. False-positive PET findings occurred in three inflammatory processes. SUV of seminomas was significantly higher than in nonseminomas (p < 0.01). CONCLUSION: PET using FDG is superior to CT for assessment of residual tumor after chemotherapy of germ cell cancer and may thus have an increased effect on patient management in the future. PET must be performed at least 2 wk after completion of therapy. Further data are necessary to determine the role of FDG PET for initial staging of germ cell cancer.

Correlation of neuropsychological, morphological and functional (regional cerebral blood flow and glucose utilization) findings in cerebral microangiopathy.

UNLABELLED: Cerebral microangiopathy, indicated in MRI by lacunar infarctions (LIs) and deep white matter lesions (DWMLs), is said to be accompanied by vascular dementia, which is reportedly caused by LI and DWML. METHODS: To confirm this assumption, 57 patients with cerebral microangiopathy were assessed for changes in regional cerebral blood flow (rCBF) and glucose utilization (rMRGlu) in both white matter and cortex, and these findings were correlated to the results of extensive neuropsychological testing (cognitive, mnestic and attentiveness tests), as well as to MRI findings. A special head holder ensured reproducibility of positioning during measurement of rCBF (99mTc-HMPAO SPECT) and rMRGlu (18F-FDG PET) and MRI. White matter and cortex were quantified with regions of interest defined on MRI and superimposed to corresponding PET/SPECT slices. The rMRGlu was calculated according to Sokoloff, and rCBF was determined from normalization to the cerebellum. LI and DWML were graded by number and extent. Brain atrophy was classified as no to slight inner and/or outer atrophy (Group A) or moderate-to-severe inner and outer atrophy (Group B). RESULTS: Even in severe DWMLs and in multiple LIs, rCBFs and rMRGlu values were not reduced. Analysis of variance identified atrophy and neuropsychological deficits as the main determinants for reduced rCBF and rMRGlu values (p < 0.05). However, 60% of patients (19 of 31) with neuropsychological deficits in attentiveness tests and 61% of patients (23 of 38) with mnestic deficits belonged to Group A and revealed decreased rCBF and rMRGlu values. Neuropsychological deficits correlated well with decreased rCBF and rMRGlu, whereas MRI patterns, such as LI and DWML, did not. CONCLUSION: We conclude that LI and DWML are epiphenomena that morphologically characterize cerebral microangiopathy. Dementia or neuropsychological deficits, however, are exclusively reflected by functional criteria (rCBF and rMRGlu), as long as cerebral atrophy does not occur.

Pre-transplant positron emission tomography (PET) using fluorine-18-fluoro-deoxyglucose (FDG) predicts outcome in patients treated with high-dose chemotherapy and autologous stem cell transplantation for non-Hodgkin's lymphoma.

We investigated the predictive value of sequential FDG PET before and after high-dose chemotherapy (HDT) and autologous stem cell transplantation (ASCT) in 24 patients suffering from non-Hodgkin's lymphoma (NHL). FDG PET was performed at baseline, after three cycles of induction therapy, before and after HDT with ASCT. Response assessment from sequential PET scans using standardized uptake values (SUV) was available in 22 patients at the time of transplantation. Partial metabolic response (PMR) was defined as a >25% decrease of SUV between successive PET scans [corrected]. Six of seven patients who did not achieve a PMR after complete induction therapy developed lymphoma progression, while 10 of 15 patients with complete metabolic response (CMR) or PMR remained in continuous remission. Four of seven patients with less than PMR after induction therapy died vs two of 15 patients with CMR/PMR. Median progression-free and overall survival of patients with less than PMR after HDT and ASCT was 9 and 29 months, respectively. In contrast, neither conventional re-staging nor the International Prognostic Index were predictive. These data suggest that sequential quantitative PET imaging does enlarge the concept of chemosensitivity used to select patients with high-risk NHL for HDT and ASCT or to route them to alternative treatments.

Monosomy 1p is correlated with enhanced in vivo glucose metabolism in meningiomas.

The 2-[18F]fluoro-2-deoxy-D-glucose (FDG) uptake of 25 human meningiomas was preoperatively evaluated in vivo by positron-emission tomography (PET). After surgery, meningioma biopsies were analyzed cytogenetically. Five meningiomas showed partial monosomy for chromosome 1p additional to other typical chromosome aberrations. This aberrant karyotype was correlated with increased FDG uptake. Three of five meningiomas with monosomy 1p were classified as grade II according to WHO, while only one of 20 tumors without monosomy 1p was classified as grade II. Thus, monosomy 1p and elevated FDG uptake in PET are to be regarded as cytogenetic and metabolic parameters for the aggressiveness of meningiomas.

Correlation of histology, cytogenetics and proliferation fraction (Ki-67 and PCNA) quantitated by image analysis in meningiomas.

Sixty meningiomas were classified histologically according to the WHO criteria and analyzed cytogenetically. The Ki-67 and PCNA proliferation fractions (PRFs) were assessed by immunhistochemistry. The staining results were quantified by TV-image analysis (Miamed, Leica, Germany). Within meningiomas of WHO-grade II/III and those with complete or partial deletion of # 1p, we found a significantly higher mean and maximal Ki-67 PRFs than in those of WHO-grade I and those with all other karyotypes. This was not the case for PCNA PRFs. No differences in PRFs were detectable between histological subtypes. Although these results were obtained after measurement of five high power fields (HPFs) only, the heterogeneity of PRF distribution within the tumors was high. Even after the measurement of 100 HPFs, the 95% confidence intervals were in a range of 18% to 34.3% PRF. This finding seems to be responsible for the moderate interobserver reproducibility of image analytical determination of PRF (r = 0.74). Nevertheless, there was a good correlation between subjective and objective image analytical assessment of PRF (r = 0.83). The significance of the maximum Ki-67 PRF per specimen implies the possibility of selecting those areas which show the highest fraction of positively stained nuclei for measurement, avoiding the problem of intraslide heterogeneity. Thus the time needed for image analytical quantification may be reduced.

[Bone scintigraphy and rhenium radioisotope management in the course of metastatic prostatic cancer]. / Skelettszintigraphie und Radio-Rhenium-Behandlung im Verlauf eines metastasierenden Prostatakarzinoms.

A 78-year-old patient with prostate cancer and osseous metastases had a pain symptomatic. In the Urology he was treated with antiandrogenes. The outcome of the bone scintigraphy showed a super bone scan with normalization after antiandrogene-therapy which seemed to be a sign of remission, before he showed a progressive form with multiple osseous metastases. Pain could not be treated with non steroidal antiphlogistics and opiates, so the indication for treatment with Rhenium-186-HEDP was given in this case.

[Analysis of (18)F-FDG uptake patterns in PET for diagnosis of septic and aseptic loosening after total hip arthroplasty]. / Analyses des (18)F-FDG Speichermusters in der PET zur Diagnostik von septischer und aseptischer Lockerung bei Totalendoprothesen des Hüftgelenks.

AIM: Identification of typical patterns for fluorodeoxy-glucose (FDG) uptake in positron emission tomography (PET) to detect aseptic loosening of hip prosthesis (ace-tabular and/or femoral component) and prosthetic infection. METHODS: 18 patients with painful hip prosthesis underwent PET using a dedicated full ring scanner after application of 200-300 MBq FDG. The interface between bone and surrounding soft tissue or bone as displayed on coronal slices was divided into 12 segments in accordance with the classifications of Delee and Gruen. FDG uptake in each of the segments was scored (0-3) by two independent observers. Intraoperative findings were regarded as the gold standard. RESULTS: After surgical revision 14 acetabular components and 9 femoral components were found to be loose and prosthetic infection was present in 7 prostheses. Loosening of the acetabular component was correlated to enhanced uptake in the middle of the acetabular interface, while loosening of the femoral component was correlated to enhanced uptake in the proximal and middle segment of the lateral femoral interface and the proximal segment of the medial femoral interface. A similar pattern was found in prosthetic infection with high uptake along the middle portion of the lateral femoral interface. In 6 of 7 infected prostheses loosening of the acetabular and of the femoral component was present. Taking the typical uptake patterns as criteria for loosening and grade 3 uptake as an additional criterion for septic loosening the accuracy of PET imaging in the detection of loosening of the acetabular or the femoral component and of prosthetic infection was 72, 78 and 89%, respectively. CONCLUSION: This pilot study presents FDG-PET as a promising diagnostic tool for patients with painful hip prostheses. Its clinical value should be evaluated in a larger patient population.

Optimizing ventilation-perfusion lung scintigraphy: parting with planar imaging.

AIM: Of the study was to introduce and verify a ventilation-perfusion (V/Q) acquisition protocol that incorporates new developments in scintigraphy in order to allow for a more balanced comparison with other diagnostic procedures. METHODS: In 103 patients suspect of having pulmonary embolism, V/Q scans were acquired exclusively with SPECT technique. Ventilation was done with ultrafine aerosol. Planar images in eight directions were reconstructed through addition of three consecutive SPECT projections. Three referees examined the scans in regard to type, localization, and extent of V/Q defects. RESULTS: Using this protocol, significantly more defects, especially of subsegmental size, were detected (p < 0.01). Sensitivity, and diagnostic accuracy were also significantly improved (p < 0.01) to 0.96, and 0.99, respectively. Furthermore, kappa values were increased up to 0.82--a relevant enhancement in the ability to precisely localize V/Q defects. CONCLUSION: In conclusion this protocol provides high-resolution tomographic scans as well as high-quality planar images within a short acquisition time. Due to the significant increase in lesion detection, sensitivity, diagnostic accuracy, and anatomical localization of defects, it is a substantial improvement in the diagnosis of pulmonary embolism that will put V/Q scintigraphy on a par with other tomographic methods.

Prognostic significance of positron emission tomography using fluorine-18-fluorodeoxyglucose in patients treated for malignant lymphoma.

AIM: To evaluate the prognostic significance of positron emission tomography (PET) using fluorine-18-[2]-fluoro-2-deoxyglucose (FDG) in patients treated for Hodgkin's disease (HD) or non-Hodgkin's lymphoma (NHL) compared to conventional restaging (CRS). METHODS: Fifty-six patients with either HD (n = 22), high-grade NHL (n = 26) or centrocytic-centroblastic NHL (n = 8) were included. PET was performed in 41 patients for treatment reevaluation up to three months after therapy and in patients with persisting residual masses (n = 10) or suspected relapse (n = 5) four to twelve months after treatment. The scans were evaluated qualitatively and quantitatively using standardised uptake values (SUV). Progression-free survival (PFS) was estimated to assess the prognostic value of FDG PET and clinical follow-up was taken as gold standard. RESULTS: PET was positive in nineteen of 41 patients studied for treatment reevaluation. Progression was observed after a median interval of two months (range 0-15) in sixteen of 19 patients after a positive PET scan and in three of 22 patients after a negative scan (p < .001). Median duration of follow-up in progression-free patients was 21 months (range 6-72). In patients with a partial remission in CRS progression was more common in PET-positive than in PET-negative patients (5 of 7 vs. 1 of 14; p < .01) and positivity with PET was associated with poorer PFS (p < .0025). PET studies performed four to twelve months after treatment were true negative in seven, true positive in five and false-positive in three patients. SUV > 11.35 of lymphoma lesions was associated with poorer PFS than SUV < 11.35 (p < 0.025). CONCLUSION: We conclude that FDG PET after treatment of malignant lymphoma has a high prognostic value and should be recommended in patients with persistence of residual masses.

Combined image interpretation of computed tomography and hybrid PET in head and neck cancer.

AIM: Evaluation of potential synergistic effects of combined image interpretation of FDG PET using a gamma camera modified for coincidence detection (hybrid PET) and computed tomography (CT) and comparison of the diagnostic accuracy of hybrid PET and dedicated PET in patients with head and neck cancer. METHODS: Forty-two patients with suspected primary or recurrent cancer were included. Twenty-four patients underwent dedicated PET in addition to attenuation-corrected hybrid PET using a one-day protocol. RESULTS: Sensitivity, specificity and accuracy for detection of primary or recurrent head and neck cancer were 74, 73, and 74% for hybrid PET, 52, 82, and 60% for CT and 77, 82, and 79% for combined reading. With the combination of CT and hybrid PET all cases of recurrent disease were detected. The largest tumour not detected was 1.7 cm in diameter. Sensitivity, specificity and accuracy for the detection of neck sides with lymph node metastases were 69, 88, and 85% for hybrid PET, 62, 88, and 84% for CT, 69, 99, and 94% for combined image interpretation. With combined interpretation four involved neck sides were missed including two cases of microscopic metastases. Hybrid PET revealed concordant results to dedicated PET in all patients with respect to the detection of primary or recurrent tumour and in 45 of 48 neck sides (94%) with the same number of false negative findings. CONCLUSION: The combination of functional information of hybrid PET and morphological information of CT by the simple approach of combined image interpretation improves the sensitivity for the detection of primary/recurrent head and neck cancer and increases the specificity of lymph node staging compared to CT alone. The accuracy of hybrid PET and dedicated PET was almost identical.

[18F-fluorodeoxyglucose PET in ovarian carcinoma: methodology and preliminary results]. / 18F-Fluordeoxyglukose PET beim Ovarialkarzinom: Methodik und erste Ergebnisse.

AIM: Of the present study was to evaluate 18FDG PET as a diagnostic tool in primary and recurrent ovarian cancer. METHODS: PET of the abdomen and the pelvis was performed in 26 patients suspected for primary (n = 17) or recurrent (n = 9) ovarian cancer with an ECAT 953/15 scanner 45 min after intravenous administration of 245 MBq 18F-FDG (mean). PET findings were validated by surgery, histology and/or cytology. RESULTS: Ovarian malignancies or recurrent ovarian cancer were demonstrated by PET in 16 out of 19 cases. Malignancy was excluded in six out of seven cases. False negative findings were obtained in two cases of low malignant potential tumors (LMP) and in one case of low grade serous/mucinous ovarian cystadenocarcinoma. PET yielded one false positive result in a case of salpingoophoritis. Quantitative analysis revealed a mean SUV of 6.8 +/- 2.3 in primary ovarian carcinoma vs. 2.6 +/- 1.2 in benign masses (p < 0.05). CONCLUSION: These preliminary data show 18FDG PET to be useful in diagnosis of recurrent ovarian cancer. PET is of limited use in differentiating LMP from benign tumors and ovarian cancer from inflammatory processes. Concerning this differentiation, quantitative analysis does not improve diagnostic accuracy.

F-18-FDG positron imaging in oncological patients: gamma camera coincidence detection versus dedicated PET.

AIM: Of the present study was to investigate the feasibility of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) imaging in oncological patients with a dual head gamma camera modified for coincidence detection (MCD). METHODS: Phantom studies were done to determine lesion detection at various lesion-to-background ratios, system sensitivity and spatial resolution. Thirty-two patients with suspected or known malignant disease were first studied with a dedicated full-ring PET system (DPET) applying measured attenuation correction and subsequently with an MCD system without attenuation correction. MCD images were first interpreted without knowledge of the DPET findings. In a second reading, MCD and DPET were evaluated simultaneously. RESULTS: The phantom studies revealed a comparable spatial resolution for DPET and MCD (5.9 x 6.3 x 4.2 mm vs. 5.9 x 6.5 x 6.0 mm). System sensitivity of MCD was less compared to DPET (91 cps/Bq/ml/cmFOV vs. 231 cps/Bq/ml/cmFOV). At a lesion-to-background ratio of 4:1, DPET depicted a minimal phantom lesion of 1.0 cm in diameter, MCD a minimal lesion of 1.6 cm. With DPET, a total of 91 lesions in 27 patients were classified as malignant. MCD without knowledge of DPET results revealed increased FDG uptake in all patients with positive DPET findings. MCD detected 72 out of 91 DPET lesions (79.1%). With knowledge of the DPET findings, 11 additional lesions were detected (+12%). MCD missed lesions in six patients with relevance for staging in two patients. All lesions with a diameter above 18 mm were detected. CONCLUSION: MCD FDG imaging yielded results comparable to dedicated PET in most patients. However, a considerable number of small lesions clearly detectable with DPET were not detected by MCD alone. Therefore, MCD cannot yet replace dedicated PET in all oncological FDG studies. Further technical refinement of this new method is needed to improve image quality (e.g. attenuation correction).

[Quantification of repositioning errors in PET studies through superimposition of emission and transmission scans. Comparison between acquisition with and without repositioning]. / Quantifizierung von Repositionierungsfehlern bei PET-Studien durch Uberlagerung von Emissions- und Transmissionsscan. Ein Vergleich zwischen Akquisitionen mit und ohne Repositionierung.

AIM: The purpose of this study was to quantify positioning discrepancies between emission (E) and transmission (T) scan using image fusion. A direct comparison of one-step and two-step acquisitions was performed where all studies were analyzed in respect to artifacts caused by inaccurate positioning. In addition, phantom measurements were conducted to estimate the consequences of repositioning errors on standardized uptake value calculations (SUV). METHODS: 40 patients were examined by two-step whole-body scans using PET and 15 patients were subject to one-step examinations in the head/neck area. Repositioning between the scans was achieved by a laser matrix positioning system in combination with external body markings. After reconstruction and image fusion of the scans, the positioning discrepancies were measured as the distances between the outer boundaries of E and T in four different body regions. Additional evaluations of the SUV by increasing E-T dislocation were performed using a Jaszczak phantom containing hollow spheres. RESULTS: For the two-step acquisitions, the mean spatial deviations along the three orthogonal axes x, y, and z were between 8.9 mm and 13.8 mm, whereas for the one-step examinations mean values between 3.5 mm and 4.3 mm were determined (level of significance in each direction p < 0.0001). Artifacts were found in 47.5% of the whole body scans, but in none of the head/neck studies. The development of image artifacts was simulated by phantom studies. In contrast, the deviations of the computed SUV caused by increasing positioning discrepancies were minimal because of the minimal differences between the attenuation coefficients of the media involved. CONCLUSION: The presented data show that an artifactfree reconstruction of attenuation-corrected studies requires a precise positioning of the patient. One-step examination protocols without repositioning are advantageous due to the significantly lower positioning discrepancies. The additional reconstruction of nonattenuation-corrected studies has proven to be useful in discovering image artifacts and is therefore recommended.

[Clinical value of FDG PET for therapy monitoring of malignant lymphoma--results of a retrospective study in 72 patients]. / Klinische Wertigkeit der FDG-PET zur Therapiekontrolle bei malignen Lymphomen--Ergebnisse einer retrospektiven Studie an 72 Patienten.

AIM: Of the present retrospective study was to validate the clinical value of FDG-PET for therapy control of malignant lymphoma. METHOD: 72 patients (41 non-Hodgkin lymphomas, 29 Hodgkin's disease, 2 unclassified) received static FDG-PET scans of initially involved regions (n = 53) or of the entire neck and trunk (n = 19) after therapy. CT imaging (n = 70) and serum LDH measurement (n = 64) were also performed. Results were validated either by biopsy (n = 7) or by clinical follow-up (n = 65). The predictive value of PET was analysed in relation to different prognostic factors (stage, recurrence status, number of prior therapy regimen). RESULTS: PET obtained a sensitivity of 88%, a specificity of 83% and an overall accuracy of 85% for detection of residual disease. The values for CT were 84%, 31% resp. 54%, and for serum LDH 50%, 92% and 73%. The predictive value of PET was related to the prevalence of residual disease. PET predicted complete remission in more than 90% of patients with moderate risk (stage I-III, no relapse, no more than two different therapy regimens). In high risk patients, however, the negative predictive value of PET was 50-67%. CONCLUSION: FDG-PET is more accurate than CT imaging and LDH measurement for therapy monitoring of malignant lymphoma. Therapy success can be reliably predicted in patients with moderate risk.

[18FDG-PET in intracranial meningiomas versus grading, proliferation index, cellular density and cytogenetic analysis]. / 18FDG-PET bei intrakraniellen Meningeomen versus Grading, Proliferationsindex, Zelldichte und zytogenetische Analyse.

62 intracranial meningiomas in 60 patients were studied with 18FDG-PET prior to neurosurgery in order to evaluate the relationship between 18FDG uptake and biological aggressiveness of the tumors. Histopathological grading, cellular density, Ki-67 proliferation index and evidence of chromosomal aberrations were used to assess tumor aggressiveness. Significantly elevated 18FDG uptake was found in grade 2- and 3- compared to grade 1-meningiomas, in tumors of high cellularity compared with those of low cellularity, and in meningiomas with an elevated Ki-67 proliferation index (above 2%). The two meningiomas with the most pronounced chromosomal aberrations revealed the highest 18FDG uptake of all cytogenetically studied meningiomas. We conclude that 18FDG-PET is useful for estimating the biological aggressiveness of intracranial meningiomas.