99mTc-DPD SPECT/CT for localisation of inflammatory and chronic osteoarthritis of the foot and ankle

Aim: The precise localisation of osteoarthritic and inflammatory changes is crucial for selective treatment planning of radiosynovectomy (RSV). The present study evaluated the diagnostic accuracy of planar bone imaging and SPECT for the detection of pathological bone metabolism and inflammation in joints of the foot and ankle, compared with SPECT/CT. Patients, methods: 39 patients (mean age 65.6 ± 11.1 years) with suspected inflammatory osteoarthritis underwent SPECT/CT of the feet. After injection of approximately 500 MBq 99mTc DPD, all patients had three-phase planar bone imaging and late-phase hybrid SPECT/CT. late-phase SPECT, and CT of the foot. Increased bone metabolism and blood-pool was assigned to the respective joint of the fore-, mid-, and hindfoot, using SPECT/CT as the reference standard. Results: Overall, SPECT had a higher sensitivity than planar imaging (0.80 vs 0.68, n.s.). The advantage of SPECT was most obvious in the anatomically complex midfoot area (0.63 vs 0.26, p < 0.05) and less obvious in the forefoot (0.85 vs 0.79, n.s.) and hindfoot (0.89 vs 0.89, n.s.). The overall concordance (Cohen`s Kappa) between SPECT/CT and planar (late-phase) imaging and SPECT was high for the forefoot and the hindfoot (planar: 0.78/0.81; SPECT 0.86/0.88) and comparatively low for the midfoot (planar: 0.27; SPECT 0.61). Conclusion: SPECT was significantly superior to planar bone imaging for the detection of joint lesions in the midfoot. The differences between SPECT and planar imaging in the fore- and hindfoot were not significant, most likely due to the inherently less complex anatomy. Compared with SPECT alone, a benefit from the use of SPECT/CT can be observed in the midfoot region where it facilitates the identification of the correct joint for RSV.

Lesion concordance, image quality and artefacts in PET/CT

Aim: This study had three major objectives: 1.) to record the number of concordant (both in PET and CT) pathological lesions in different body regions/organs, 2.) to evaluate the image quality and 3.) to determine both, the quantity and the quality of artefacts in whole body FDG PET/CT scans. Patients, methods: Routine whole body scans of 353 patients referred to FDG-PET/ CT exams at 4 university hospitals were employed. All potentially malignant lesions in 13 different body regions/organs were classified as either concordant or suspicious in FDG-PET or CT only. In the latter case the diagnostic relevance of this disparity was judged. The image quality in PET and CT was rated as a whole and separately in 5 different body regions. Furthermore we investigated the frequency and site of artefacts caused by metal implants and oral or intravenous contrast media as well as the subjective co-registration quality (in 4 body regions) and the diagnostic impact of such artefacts or misalignment. In addition, the readers rated the diagnostic gain of adding the information from the other tomographic method. Results: In total 1941 lesions (5.5 per patient) were identified, 1094 (56%) out of which were concordant. 602 (71%) out of the 847 remaining lesions were detected only with CT, 245 (29%) were only PET-positive. As expected, CT particularly depicted the majority of lesions in the lungs and abdominal organs. However, the diagnostic relevance was greater with PET-only positive lesions. Most of the PET/CT scans were performed with full diagnostic CT including administration of oral and intravenous contrast media (> 80%). The image quality in PET and CT was rated excellent. Artefacts occurred in more than 60% of the scans and were mainly due to (dental) metal implants and contrast agent. Nevertheless there was almost no impact on diagnostic confidence if reading of the non attenuation corrected PET was included. The co-registration quality in general was also rated as excellent. Misalignment mostly occurred due to patient motion and breathing and led to diagnostic challenges in about 4% of all exams. The diagnostic gain of adding PET to a CT investigation was rated higher than vice versa. Conclusions: As the image quality in both PET and CT was more than satisfying, CT-artefacts almost never led to diagnostic uncertainties and serious misalignment rarely occurred, PET/CT can be considered as suitable for routine use and may replace single PET- and CT-scans. However, additional reading of the non attenuation corrected PET is mandatory to assure best possible diagnostic confidence in PET. Since approximately half of all lesions found in PET/CT were not concordant, at least in a setting with a diagnostic CT the exams need to be reported by both a nuclear medicine physician and a radiologist in consensus.

FDG PET and CT in locally advanced adenocarcinomas of the distal oesophagus

Aim: The incidence of adenocarcinomas of the distal oesophagus (ADE) has dramatically increased in Western countries. The clinical importance of a FDG PET finding discordant with CT was determined in patients with locally advanced ADE. In addition, tumour standardized uptake values (SUV) were correlated with patient survival. Patients, methods: 40 consecutive patients were analyzed retrospectively. All patients underwent an attenuation corrected FDG PET scan (neck, chest, abdomen) and contrast enhanced helical CT of the chest and abdomen. PET and CT scans were reviewed independently and concomitantly with respect to metastases in predefined lymph node sites and organs. Any discordance between PET and CT was assessed for clinical relevance. Clinical relevance was defined as a change in the overall therapeutic concept (curative vs. palliative). Follow-up imaging and histological evaluation served as the gold standard. Mean tumour SUVs were determined by 1.5 cm regions of interest placed over the tumour’s maximum. Results: When read independently from the CT scan FDG PET indicated a clinically relevant change in tumour stage in 9/40 patients (23%) and a non-relevant change in 11/40 patients (28%). PET was correct in 5/9 patients (56%) with clinically relevant discordances. In 4/9 patients PET was incorrect (3 false positive due to suspicion of M1-lymph nodes or lung metastases, 1 false negative in disseminated liver metastases). With concomitant reading, PET indicated a clinically relevant change in tumour stage in 6/40 patients (15%) and a non-relevant change in 5/40 patients (13%). PET was correct in 5/6 patients (83%) with clinically relevant discordances. The patient with disseminated liver disease remained the single false negative. Overall, the benefit from PET was based on its higher diagnostic accuracy at organ sites. Tumour SUV did not correlate with patient survival. Conclusion: About half of discordances between FDG PET and CT are clinically relevant. Concomitant reading of PET and CT is advisable as it reduces the overall rate of discordances and enhances the accuracy of PET in clinical relevant discordances (from 56% to 83%).

11C-choline PET/CT and whole-body MRI including diffusion-weighted imaging for patients with recurrent prostate cancer

Purpose

To compare the detection efficacy of 11C-choline positron emission tomography and computed tomography (PET/CT) with whole-body magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) in patients with suspected recurrent prostate cancer.

Materials and Methods

Fifty-seven patients (mean age 68, range 54-80 years) underwent 11C-choline PET/CT and MRI using T1-weighted (T1w), short-tau inversion recovery (STIR), and DWI. Two readers visually rated suspicious lesions on a 5-point scale in 20 different regions. Clinical follow-up and histopathology served as the standard of reference (SOR).

Results

Fifty patients (mean PSA 29.9, range 1.0-670 ng/mL) had at least one positive lesion according to the SOR. Twenty-four patients had local recurrence (LR), 27 had lymph node (LN) involvement, and 22 had bone metastases. The overall detection rates for PET/CT and MRI on a patient basis were 94% and 88%, respectively (p = 0.07). The PSA level (>2 ng/mL vs ≤2 ng/mL) significantly influenced the overall performance of PET/CT (p = 0.003) and MRI (p = 0.03). PET/CT was significantly superior to MRI in detecting LR (p = 0.03) and bone metastasis (p = 0.02). We found no difference with respect to the detection of LN metastasis (p = 0.65).

Conclusion

11C-choline PET/CT was superior in the detection of local recurrence and bone metastasis on a regional basis. Whole-body MRI including DWI showed similar diagnostic accuracy only for detecting lymph node metastases. Compared with 11C-choline PET/CT, therefore, whole-body MRI including DWI cannot serve as alternative imaging modality for restaging prostate cancer.

Non-invasive imaging of implanted peritoneal carcinomatosis in mice using PET and bioluminescence imaging

BACKGROUND

Non-invasive imaging of peritoneal carcinomatosis remains challenging. The aim of this study was to compare positron emission tomography (PET) and bioluminescence imaging (BLI) for the early detection of peritoneal carcinomatosis in a mouse model.

METHODS

Female nude mice were inoculated intraperitoneally with 1×10(7) HSC45-M2-luc gastric cancer cells. The cells were stably transfected with the gene coding for firefly luciferase. Tumour development was monitored using PET and BLI and in two subgroups, on days 3 and 4 or on days 6 and 7 after tumour cell inoculation. Tumour nodules found on post mortem examination served as the reference standard for evaluating the images.

RESULTS

PET detected 58/82 lesions (sensitivity 71 %). This method detected all (100 %) nodules larger than 6 mm, 88 % of nodules in the range of >2-4 mm, and even 58 % of small nodules measuring only 1-2 mm. BLI identified a total of 40/82 lesions (sensitivity 49 %). The difference between PET and BLI was statistically significant at p < 0.05 (PET/BLI chi-square 8.2).

CONCLUSIONS

PET was more sensitive than BLI for the detection of early peritoneal carcinomatosis in our mouse model. The sensitivity of BLI largely depended on the site of the lesions in relation to the imaging device.

Computed tomography to estimate cardiac preload and extravascular lung water. A retrospective analysis in critically ill patients

Background

In critically ill patients intravascular volume status and pulmonary edema need to be quantified as soon as possible. Many critically ill patients undergo a computed tomography (CT)-scan of the thorax after admission to the intensive care unit (ICU). This study investigates whether CT-based estimation of cardiac preload and pulmonary hydration can accurately assess volume status and can contribute to an early estimation of hemodynamics.

Methods

Thirty medical ICU patients. Global end-diastolic volume index (GEDVI) and extravascular lung water index (EVLWI) were assessed using transpulmonary thermodilution (TPTD) serving as reference method (with established GEDVI/EVLWI normal values). Central venous pressure (CVP) was determined. CT-based estimation of GEDVI/EVLWI/CVP by two different radiologists (R1, R2) without analyzing software. Primary endpoint: predictive capabilities of CT-based estimation of GEDVI/EVLWI/CVP compared to TPTD and measured CVP. Secondary endpoint: interobserver correlation and agreement between R1 and R2.

Results

Accuracy of CT-estimation of GEDVI (< 680, 680-800, > 800 mL/m²) was 33%(R1)/27%(R2). For R1 and R2 sensitivity for diagnosis of low GEDVI (< 680 mL/m²) was 0% (specificity 100%). Sensitivity for prediction of elevated GEDVI (> 800 mL/m²) was 86%(R1)/57%(R2) with a specificity of 57%(R1)/39%(R2) (positive predictive value 38%(R1)/22%(R2); negative predictive value 93%(R1)/75%(R2)). Estimated CT-GEDVI and TPTD-GEDVI were significantly different showing an overestimation of GEDVI by the radiologists (R1: mean difference ± standard error (SE): 191 ± 30 mL/m², p < 0.001; R2: mean difference ± SE: 215 ± 37 mL/m², p < 0.001). CT GEDVI and TPTD-GEDVI showed a very low Lin-concordance correlation coefficient (ccc) (R1: ccc = +0.20, 95% CI: +0.00 to +0.38, bias-correction factor (BCF) = 0.52; R2: ccc = -0.03, 95% CI: -0.19 to +0.12, BCF = 0.42). Accuracy of CT estimation in prediction of EVLWI (< 7, 7-10, > 10 mL/kg) was 30% for R1 and 40% for R2. CT-EVLWI and TPTD-EVLWI were significantly different (R1: mean difference ± SE: 3.3 ± 1.2 mL/kg, p = 0.013; R2: mean difference ± SE: 2.8 ± 1.1 mL/kg, p = 0.021). Again ccc was low with -0.02 (R1; 95% CI: -0.20 to +0.13, BCF = 0.44) and +0.14 (R2; 95% CI: -0.05 to +0.32, BCF = 0.53). GEDVI, EVLWI and CVP estimations of R1 and R2 showed a poor interobserver correlation (low ccc) and poor interobserver agreement (low kappa-values).

Conclusions

CT-based estimation of GEDVI/EVLWI is not accurate for predicting cardiac preload and extravascular lung water in critically ill patients when compared to invasive TPTD-assessment of these variables.

T-cell lymphoproliferative disorder potentially induced by imatinib in a patient with GIST

BACKGROUND

A 71-year-old male patient was diagnosed as having a KIT-positive gastrointestinal stromal tumor located at the gastric antrum. With no signs of distant metastasis, the patient primarily underwent gastric surgery with antrectomy and Billroth-I-reconstruction. Owing to tumor size and mitotic index, the patient was considered at high risk of tumor relapse and thus was entered into a clinical trial to receive adjuvant imatinib treatment. 4 months after initiation of imatinib treatment, the patient presented with several newly discovered subcutaneous and intra-abdominal tumor lesions. Imatinib treatment had been tolerated well until then.

INVESTIGATIONS

Physical examination, blood tests, biopsies of the subcutaneous tumor lesions, tumor morphology and immunohistochemistry, PCR for the T-cell receptor gamma genes, sequential CT and PET-CT.

DIAGNOSIS

Monoclonal T-cell lymphoproliferative disorder, potentially induced by imatinib.

MANAGEMENT

Imatinib was stopped, after which the tumor lesions spontaneously regressed and, eventually, complete remission was achieved.

[(11)C]Choline positron emission tomography/computed tomography for staging and restaging of patients with advanced prostate cancer

INTRODUCTION

To evaluate [(11)C]Choline positron emission tomography (PET)/computed tomography (CT) for staging and restaging of patients with advanced prostate cancer and to compare the diagnostic performance of PET, CT and PET/CT.

METHODS

Forty-five consecutive patients with advanced prostate cancer underwent [(11)C]Choline-PET/CT between 5/2004 and 2/2006.

RESULTS

Overall, 295 lesions were detected: PET alone, 178 lesions; diagnostic CT, 221 lesions; PET/CT (low-dose CT), 272 lesions; PET/CT (diagnostic CT), 295 lesions. Two thirds of the lesions were located in the bone; one third in the prostate, lymph nodes, periprostatic tissue and soft tissue (lung, liver). The use of diagnostic CT did not result in a statistically significant difference with respect to lesion localization certainty and lesion characterization (P=.063, P=.063). PET-negative but PET/CT-positive lesions were mostly localized in the bone (78%, 91/117) as were PET-positive and CT-negative lesions (72%, 53/74). Of the latter, 91% (48/53) represented bone marrow and 9% (5/53) cortical involvement.

CONCLUSIONS

Staging and restaging with [(11)C]Choline PET/CT in patients with advanced prostate cancer improve the assessment of local and regional recurrent as well as metastatic disease including skeletal manifestations. [(11)C]Choline PET/CT (with a low-dose CT) results in improved localization and lesion characterization. [(11)C]Choline PET/CT provides an added value for skeletal manifestations. [(11)C]Choline PET/CT changed disease management in 11 (24%) of 45 patients with advanced prostate cancer.

PET imaging with [18F]3′-deoxy-3′-fluorothymidine for prediction of response to neoadjuvant treatment in patients with rectal cancer

PURPOSE

Positron emission tomography (PET) using 18F-labelled 3'-deoxy-3'-fluorothymidine (FLT) was assessed for therapy monitoring in patients with rectal cancer undergoing neoadjuvant chemoradiotherapy.

METHODS

Ten patients with locally advanced rectal cancer were included and underwent long-course preoperative chemoradiotherapy (total dose 45 Gy, 1.8 Gy/day, concomitant 250 mg/m2 5-fluorouracil) followed by surgery. FLT-PET was performed prior to chemoradiotherapy, 2 weeks after initiation of chemoradiotherapy and preoperatively (3-4 weeks post chemoradiotherapy). FLT uptake was correlated with histopathological tumour regression and changes in T stage.

RESULTS

Mean tumour FLT uptake was 4.2+/-1.0 SUV before therapy and decreased significantly to 2.9+/-0.6 SUV 14 days after initiation of chemoradiotherapy (-28.6%+/-10.7%, p=0.005). The preoperative scan showed a further decrease to 1.9+/-0.4 SUV (-54.7%+/-7.6%, p=0.005). However, the degree of change in FLT uptake 2 weeks after initiation and after completion of neoadjuvant therapy did not correlate with histopathological tumour regression.

CONCLUSION

FLT-PET did not seem to be a promising method for assessment of tumour response in the studied chemoradiotherapy regimen in patients with rectal cancer.

Comparison of 16-MDCT and MRI for Characterization of Kidney Lesions

OBJECTIVE

The objective of our study was to compare the diagnostic performance of 16-MDCT with that of MRI in the characterization of kidney lesions.

SUBJECTS AND METHODS

Twenty-eight patients with kidney lesions detected with sonography and requiring further evaluation were examined. MDCT was performed in the unenhanced, arterial, and portal venous phases. MRI was performed at 1.5 T with T2- and T1-weighted and dynamic gadolinium-enhanced sequences. Consensus reading was done by two radiologists. Image quality was rated on a four-point scale. Classification of lesions as surgical or nonsurgical was done with five levels of confidence, and it was required that a definite diagnosis be assigned to each lesion. The 1997 TNM classification was used for staging. Statistical analysis was done by receiver operating characteristic analysis or paired Student's t test. Histologic or follow-up findings at least 12 months after the primary diagnosis served as the standard of reference.

RESULTS

The image quality of MDCT (mean grade, 2.79 on a 0-3 scale) was superior to that of MRI (1.93; p < 0.01). The area under the curve for differentiating surgical from nonsurgical lesions was 0.979 for MDCT and 0.957 for MRI with resulting sensitivity and specificity values of 92.3% and 96.3% for MDCT and 92.3% and 91.3% for MRI. Sensitivity and specificity for definite classification of the lesions were 93.8% and 68.4% for MDCT and 93.8% and 71.4% for MRI.

CONCLUSION

Both MDCT and MRI are excellent for differentiating surgical from nonsurgical kidney lesions. Both methods have low specificity for the differentiation of benign from malignant lesions.

Adenocarcinomas of Esophagogastric Junction: Multi–Detector Row CT to Evaluate Early Response to Neoadjuvant Chemotherapy

PURPOSE

To prospectively evaluate multi-detector row computed tomography (CT) in the assessment of early response during neoadjuvant chemotherapy for adenocarcinoma of the esophagogastric junction (AEG).

MATERIALS AND METHODS

The study protocol was approved by the local ethics committee. Written informed consent was obtained from all patients. Thirty-one patients with an AEG (stage T3 N0/1 M0 or T4 N0/1 M0) were examined with multi-detector row CT before and 2 weeks after the initiation of chemotherapy. There were seven women and 24 men with a mean age of 62 years +/- 8.1 (standard deviation). The maximal transverse tumor diameter was measured and tumor volumetry was performed by three independent readers. The resulting changes were correlated with the histopathologic grade of regression in 21 patients. The differentiation of responders from nonresponders was assessed with receiver operating characteristic analysis in these 21 patients. Interobserver variability was determined in all 31 patients with the Spearman rank correlation. Survival without disease progression was estimated in all patients according to the Kaplan-Meier method. Statistical comparisons between different groups of patients were performed with the log-rank test.

RESULTS

The interobserver variability for the diameter measurements (R = 0.13-0.20) was higher than that for the volumetric measurements (R = 0.70-0.82). The correlation of histopathologic grades of regression with changes in diameter was not statistically significant for the three readers, whereas the correlation of volume changes with histopathologic grades of regression was statistically significant for two of the three readers (P = .01, .05, and .08). Results of receiver operating characteristic analysis revealed an optimal cutoff level for tumor volumetry at a reduction of volume of 14.8%, which resulted in a sensitivity of 100% (six of six patients) and a specificity of 53% (eight of 15 patients). Although the probability of progression was higher in the nonresponder group than in the responder group (61% vs 40%, respectively), the differences were not statistically significant.

CONCLUSION

Tumor volumetry based on multi-detector row CT can help predict early response to treatment 2 weeks after the initiation of neoadjuvant chemotherapy in patients with AEG; however, the classic approach of tumor diameter measurement failed to show significant correlation with histopathologic tumor regression.

Phase II study of weekly oxaliplatin plus infusional fluorouracil and folinic acid (FUFOX regimen) as first-line treatment in metastatic gastric cancer

Oxaliplatin plus fluorouracil/folinic acid (5-FU/FA) every 2 weeks has shown promising activity in advanced gastric cancer. This study assessed the efficacy and safety of weekly oxaliplatin plus 5-FU/FA (FUFOX regimen) in the metastatic setting. Patients with previously untreated metastatic gastric cancer received oxaliplatin (50 mg m⁻²) plus FA (500 mg m⁻², 2-h infusion) followed by 5-FU (2000 mg m⁻², 24-h infusion) given on days 1, 8, 15 and 22 of a 5-week cycle. The primary end point of this multicentre phase II study was the response rate according to RECIST criteria. A total of 48 patients were enrolled. Median age was 62 years and all patients had metastatic disease, with a median number of three involved organs. The most common treatment-related grade 3/4 adverse events were diarrhoea (17%), deep vein thrombosis (15%), neutropenia (8%), nausea (6%), febrile neutropenia (4%), fatigue (4%), anaemia (4%), tumour bleeding (4%), emesis (2%), cardiac ischaemia (2%) and pneumonia (2%). Grade 1/2 sensory neuropathy occurred in 67% of patients but there were no episodes of grade 3 neuropathy. Intent-to-treat analysis showed a response rate of 54% (95% CI, 39–69%), including two complete responses. At a median follow-up of 18.1 months (range 11.2–26.2 months), median survival is 11.4 months (95% CI, 8.0–14.9 months) and the median time to progression is 6.5 months (95% CI, 3.9–9.2 months). The weekly FUFOX regimen is well tolerated and shows notable activity as first-line treatment in metastatic gastric cancer.

FDG PET and CT in locally advanced adenocarcinomas of the distal oesophagus. Clinical relevance of a discordant PET finding

AIM

The incidence of adenocarcinomas of the distal oesophagus (ADE) has dramatically increased in Western countries. The clinical importance of a FDG PET finding discordant with CT was determined in patients with locally advanced ADE. In addition, tumour standardized uptake values (SUV) were correlated with patient survival.

PATIENTS, METHODS

40 consecutive patients were analyzed retrospectively. All patients underwent an attenuation corrected FDG PET scan (neck, chest, abdomen) and contrast enhanced helical CT of the chest and abdomen. PET and CT scans were reviewed independently and concomitantly with respect to metastases in predefined lymph node sites and organs. Any discordance between PET and CT was assessed for clinical relevance. Clinical relevance was defined as a change in the overall therapeutic concept (curative vs. palliative). Follow-up imaging and histological evaluation served as the gold standard. Mean tumour SUVs were determined by 1.5 cm regions of interest placed over the tumour's maximum.

RESULTS

When read independently from the CT scan FDG PET indicated a clinically relevant change in tumour stage in 9/40 patients (23%) and a non-relevant change in 11/40 patients (28%). PET was correct in 5/9 patients (56%) with clinically relevant discordances. In 4/9 patients PET was incorrect (3 false positive due to suspicion of M1-lymph nodes or lung metastases, 1 false negative in disseminated liver metastases). With concomitant reading, PET indicated a clinically relevant change in tumour stage in 6/40 patients (15%) and a non-relevant change in 5/40 patients (13%). PET was correct in 5/6 patients (83%) with clinically relevant discordances. The patient with disseminated liver disease remained the single false negative. Overall, the benefit from PET was based on its higher diagnostic accuracy at organ sites. Tumour SUV did not correlate with patient survival.

CONCLUSION

About half of discordances between FDG PET and CT are clinically relevant. Concomitant reading of PET and CT is advisable as it reduces the overall rate of discordances and enhances the accuracy of PET in clinical relevant discordances (from 56% to 83%).

[PET/CT for colorectal and hepatic tumors]

This contribution presents clinical and technical aspects of combining positron emission tomography (PET) and computed tomography (CT) for patients with colorectal tumors and characterization of unclear liver foci. In which manner and for which patients combined PET/CT is superior to PET or CT alone is also discussed. PET/CT can fulfil most prerequisites for imaging in pre- and postoperative management of patients with colorectal tumors and best meets the desire for optimal imaging procedures. Some of the disadvantages encountered in frequently employed CT can be overcome by the combination of PET and CT while increasing both sensitivity in detecting lesions and specificity in their characterization. Questions regarding treatment response offer an opportunity for devising novel study concepts and initiating research on new PET tracers. Although few publications are available, we are of the opinion that the combination of functional and anatomical imaging provided by PET/CT can improve both preoperative management and aftercare. To this end, however, optimum cooperation between practitioners of nuclear medicine and radiology is imperative.

PET imaging with [11C]methyl- L-methionine for therapy monitoring in patients with rectal cancer

In this study we evaluated whether positron emission tomography (PET) using the amino acid [11C]methyl- L-methionine (MET) may be used for therapy monitoring in patients with rectal cancer who are undergoing preoperative chemoradiotherapy. A total of 41 MET-PET scans were performed in 26 patients with locally advanced rectal cancers. All patients were examined prior to chemoradiotherapy. In 15 patients, MET-PET was repeated after preoperative chemoradiotherapy (45 Gy radiation dose, 250 mg 5-fluorouracil as continuous infusion). MET uptake prior to and after the completion of chemoradiotherapy was correlated with changes in T stage and histopathological regression. All tumours were visualised with high contrast and had a significantly higher SUV (5.7+/-2.2) than normal rectum (2.7+/-0.9) and all other organs in the field of view except the small intestine (3.9+/-1.7). In all tumours studied prior to and after chemoradiotherapy, MET uptake decreased during therapy (SUV before therapy, 6.2+/-2.3; SUV after therapy, 2.6+/-1.2; P=0.0007). However, the degree of change in MET uptake was not correlated with histopathological tumour response. In conclusion, primary rectal cancer can be imaged with MET-PET. However, for the studied chemoradiotherapy regimen, MET-PET did not allow an assessment of the response to therapy.

Preoperative evaluation of pancreatic masses with positron emission tomography using 18F-fluorodeoxyglucose: diagnostic limitations

Identification of pancreatic cancer in patients presenting with an enlarged pancreatic mass is a major diagnostic problem. Positron emission tomography (PET) using the radiolabeled glucose analogue 18F-fluorodeoxyglucose (FDG) has been suggested to provide excellent accuracy for noninvasive determination of suspicious pancreatic masses. We conducted a prospective study to verify these results. Forty-two patients admitted for pancreatic surgery underwent PET scanning. Image analysis was based on visual film evaluation and quantification of regional tracer uptake. PET imaging was visually analyzed by three observers blinded for the results of other diagnostic tests; they qualitatively graded the scans using a five-point scale (I = low to V = high) for the presence and intensity of focal FDG uptake. Diagnosis was proven by histology (n = 38) or follow-up (n = 4). Furthermore, the results of PET were compared with helical computed tomography (CT) and conventional ultrasonography (US), done during the routine diagnostic workup before pancreatic cancer surgery. Regarding only the results with scores of IV and V as positive for representing definite malignancy yielded a sensitivity of 71% and a specificity of 64% for film reading. Quantification of regional tracer uptake contributed no significant diagnostic advantage for differentiation between benign and malignant tumors. Helical CT revealed a sensitivity of 74% and a specificity of 45.5% and abdominal US 56% and 50%, respectively. We concluded that PET imaging provides only fair diagnostic accuracy (69%) for characterizing enlarged pancreatic masses. PET does not allow exclusion of malignant tumors. In doubtful cases, the method must be combined with other imaging modalities, such as helical CT. The results indicate that the number of invasive procedures is not significantly reduced by PET imaging.

Diagnosis of pancreatic cancer by 2[18F]-fluoro-2-deoxy-D-glucose positron emission tomography

The detection of pancreatic cancer or the discrimination between pancreatic cancer and chronic pancreatitis remains an important diagnostic problem. The increased glucose metabolism in malignant tumours formed the basis for this investigation, which focused on the role of positron emission tomography (PET) with 2[18F]-fluoro-2-deoxy-D-glucose (FDG) in the detection of pancreatic cancer and its differentiation from chronic pancreatitis. Eighty patients admitted for elective pancreatic surgery received preoperatively 250-350 mBq FDG intravenously and emission scans were recorded 45 minutes later. Intense focal activity in the pancreatic region was taken at the time of scanning as showing the presence of pancreatic cancer. The presence of cancer was later confirmed by histological examination of the surgical specimens and histological findings were compared with the preoperative PET results. Forty one patients with pancreatic cancer (group I: n = 42) had a focally increased FDG uptake in the pancreatic region. Two patients with a periampullary carcinoma (group II: n = 6) failed to develop FDG accumulation. In 28 patients with chronic pancreatitis (group III: n = 32) no FDG accumulation occurred. Overall sensitivity and specificity of PET for malignancy (group I + II) were 94% (45 of 48) and 88% (28 of 32), respectively. The standard uptake value of the patients with pancreatic carcinoma was significantly higher than in patients with chronic pancreatitis (3.09 (2.18) v 0.87 (0.56); p < 0.001; median (interquartile range)). These findings show that FDG-PET represents a new and non-invasive diagnostic procedure for the diagnosis of pancreatic cancer and to differentiate pancreatic cancer from chronic pancreatitis. However, the diagnostic potential of this technique requires further evaluation.

[The noninvasive determination of resting myocardial blood flow in patients using 82 Rb in comparison with the argon method]

Resting myocardial blood flow in absolute units was determined in 11 patients without known heart disease using dynamic PET with 82Rb. Based on a modified Fick's approach to measuring myocardial blood flow, originally developed and validated in canine studies by Herrero and coworkers (Circulation 1990; 82: 1377-86), a global flow value of 0.60 +/- 0.10 ml/min/gr myocardium (MV +/- SD, N = 11) was obtained. With the exception of the apex, segmental blood flow was not significantly different in 12 left ventricular myocardial segments, indicating homogenous myocardial blood flow distribution. In 5 patients global myocardial blood flow was determined simultaneously both by 82Rb PET and argon as inert gas method. 82Rb flow did not differ significantly from argon flow (0.60 +/- 0.05 vs. 0.68 +/- 0.15, MV +/- SD, N.S.). These results show that correct quantitation of resting myocardial blood flow with dynamic 82Rb PET is feasible also in patients.

Diagnostic tests in enzyme allergy

BACKGROUND

Allergies to enzymes occur frequently in enzyme manufacturing plants. In epidemiologic studies the number of exposed subjects with symptoms is considerably higher than the number of sensitizations as assessed by skin tests or RAST. It was the aim of this study to evaluate the sensitivity and specificity of skin prick tests, enzyme allergosorbent test, and immunoprint with enzymes by using the results of bronchial provocation tests as the "gold standard."

METHODS

We performed 82 bronchial provocation tests with nine different enzymes in 42 chemical plant workers, all of whom had reported work-related symptoms. All tests with the exception of bronchial provocation tests were also performed in 10 atopic and 10 healthy control subjects.

RESULTS

Thirteen workers showed positive results to bronchial provocation tests (50% or greater fall in specific airway conductance) with an enzyme at a maximal concentration of 10 mg/ml. Equivocal test results, that is, tests with a 30% or greater and less than 50% fall in specific airway conductance were seldom. Skin prick tests with nondialyzed aqueous enzyme extracts at a concentration of 10 mg/ml yielded a sensitivity of 100% and a specificity of 93%. Control subjects had no cutaneous reactions to enzymes. Discrepancies between skin tests and bronchial provocation tests occurred in 5 of 82 tests, all with a positive skin test and a negative bronchial provocation test. False-positive skin tests were considered more likely in four subjects and a false-negative bronchial challenge more likely in one case. Enzyme allergosorbent test was 62% sensitive and 96% specific, and atopic control subjects showed positive results in two cases. Results of immunoprint with amylase showed one main band at pH 3.4; this band was also found in exposed subjects without further signs of sensitization, but was not found in control subjects. All but one person with positive results to bronchial provocation tests with enzymes showed bronchial hyperresponsiveness. We identified 13 subjects with bronchial hyperresponsiveness, but without occupational allergy: five of these had sensitizations to nonoccupational allergens and the remainder showed bronchial hyperresponsiveness without any detectable cause.

CONCLUSIONS

Occupation-related symptoms were not indicative of occupational allergy. Bronchial provocation tests and skin prick tests with nondialyzed aqueous enzyme extracts were appropriate techniques for the diagnosis of enzyme allergy.