Comparison of <Superscript>11</Superscript>C-choline PET and FDG PET for the differential diagnosis of malignant tumors

We prospectively assessed and compared the usefulness of ¹¹C-choline positron emission tomography (PET) with that of [¹⁸F]-2-fluoro-2-deoxy-d-glucose (FDG) PET for the differentiation between benign and malignant tumors. A total of 126 patients with 130 lesions were studied (25 brain tumors, 51 head and neck tumors, 15 bone tumors, 16 lung tumors, and 23 soft tissue tumors). ¹¹C-choline PET and FDG PET were performed from 5 and 40 min, respectively, after injection of 275–370 MBq tracer. PET data were evaluated using the standardized uptake value (SUV) and were analyzed in accordance with the pathologic data. The ¹¹C-choline uptake in malignancies was 3.9±2.3 (n=81), which was significantly higher than that in benign lesions (n=49) (2.6±1.7, P<0.005). The FDG uptake in malignancies was 5.9±3.8 (n=81) and was also significantly higher than that in benign lesions (2.8±2.0, P<0.0001). The ¹¹C-choline uptake in the lesions correlated with FDG uptake (r=0.65, P<0.003). According to an ROC analysis, the areas under the ROC curves (AUCs) for ¹¹C-choline PET were more than 0.8 in bone, head and neck, lung, and soft tissue tumors, while the AUC was 0.79 in brain tumors. The AUCs for FDG PET were similarly more than 0.8 in bone, head and neck, lung, and soft tissue tumors, but had a lower value of 0.585 in brain tumors. In brain, head and neck, bone, and soft tissue tumors, ¹¹C-choline showed higher contrast than FDG. In conclusion, it is feasible to use ¹¹C-choline PET for differentiation between malignant and benign tumours, especially of the brain, head and neck, bone, and soft tissue. However, attention needs to be drawn to the high uptake of ¹¹C-choline in some benign tumors and tumour-like lesions, as this will be of significance in clinical practice.     

<Superscript>11</Superscript>C-acetate PET imaging of lung cancer: comparison with <Superscript>18</Superscript>F-FDG PET and <Superscript>99m</Superscript>Tc-MIBI SPET

Recently carbon-11 acetate (AC) positron emission tomography (PET) has been reported to be of clinical value for the diagnosis of cancer that is negative on fluorine-18 fluorodeoxyglucoce (FDG) PET. We investigated the uptake of AC in lung cancer to determine whether this tracer is of potential value for tumour detection and characterisation, and to compare AC PET imaging with FDG PET and technetium-99m sestamibi (MIBI) single-photon emission tomography (SPET). Twenty-three patients with 25 lung cancers underwent AC and FDG PET. Twenty of 23 patients were also investigated with MIBI SPET. Dynamic images were acquired for 26 min after the injection of 555 MBq of AC. Standardised uptake values (SUVs) and/or tumour to non-tumour activity ratios (T/N) for each tumour were investigated at 10–20 min after AC administration, 40–60 min after administration of 185 MBq FDG and 15–45 min after administration of 555 MBq MIBI. Twenty lung cancers were resected surgically, and the degree of tracer uptake in the primary lesion was correlated with histopathological features (cell dedifferentiation and aggressiveness) and prognosis. Rapid uptake of AC followed by extremely slow clearance was observed. For the purpose of tumour identification, AC PET was inferior to FDG PET in 8 of 25 (32%) lung cancers, and the T/N of AC was lower than that of FDG. However, AC PET was superior to FDG PET in the identification of a slow-growing tumour (bronchiolo-alveolar carcinoma). There was a positive correlation between AC uptake (T/N) and MIBI uptake (T/N) (r=0.799, P<0.0001). A positive correlation was not observed between either AC or MIBI uptake and the degree of cell dedifferentiation in lung adenocarcinomas, whereas FDG uptake did correlate with the degree of cell dedifferentiation. In lung adenocarcinoma, there was a weak correlation between aggressiveness and FDG uptake, but no correlation was evident for AC and MIBI. In addition, a positive correlation was not observed between AC or MIBI uptake and postoperative recurrence in lung adenocarcinoma, whereas FDG uptake did correlate with postoperative recurrence. Thus, the greater the FDG uptake, the higher the malignant grade. In conclusion, for the purpose of tumour identification, AC PET was inferior to FDG PET but superior to MIBI SPET. Neither AC nor MIBI uptake reflects the malignant grade in lung adenocarcinoma, whereas FDG uptake does. AC PET is less diagnostically informative than FDG PET in patients with lung cancer. However, AC PET may play a complementary role in the identification of low-grade malignancies that are not FDG avid.     

Value of <Superscript>11</Superscript>C-choline PET and PET/CT in patients with suspected prostate cancer

Purpose: The value and limitations of ¹¹C-choline PET and PET/CT for the detection of prostate cancer remain controversial. The aim of this study was to investigate the diagnostic efficacy of ¹¹C-choline PET and PET/CT in a large group of patients with suspected prostate cancer. Methods: Fifty-eight patients with clinical suspicion of prostate cancer underwent ¹¹C-choline PET (25/58, Siemens ECAT Exact HR+) or PET/CT (33/58, Philips Gemini) scanning. On average, 500 MBq of ¹¹C-choline was administered intravenously. Studies were interpreted by raters blinded to clinical information and other diagnostic procedures. Qualitative image analysis as well as semiquantitative SUV measurement was carried out. The reference standard was histopathological examination of resection specimens or biopsy. Results: Prevalence of prostate cancer in this selected patient population was 63.8% (37/58). ¹¹C-choline PET and PET/CT showed a sensitivity of 86.5% (32/37) and a specificity of 61.9% (13/21) in the detection of the primary malignancy. With regard to metastatic spread, PET showed a per-patient sensitivity of 81.8% (9/11) and produced no false positive findings. Conclusion: Based on our findings, differentiation between benign prostatic changes, such as benign prostatic hyperplasia or prostatitis, and prostate cancer is feasible in the majority of cases when image interpretation is primarily based on qualitative characteristics. SUV_max may serve as guidance. False positive findings may occur due to an overlap of ¹¹C-choline uptake between benign and malignant processes. By providing functional information regarding both the primary malignancy and its metastases, ¹¹C-choline PET may prove to be a useful method for staging prostate cancer.     

Detection of gastric cancer using <Superscript>18</Superscript>F-FLT PET: comparison with <Superscript>18</Superscript>F-FDG PET

Purpose  We prospectively investigated the feasibility of 3′-deoxy-3′-¹⁸F-fluorothymidine (FLT) positron emission tomography (PET) for the detection of gastric cancer, in comparison with 2-deoxy-2-¹⁸F-fluoro-d-glucose (FDG) PET, and determined the degree of correlation between the two radiotracers and proliferative activity as indicated by Ki-67 index. Methods  A total of 21 patients with newly diagnosed advanced gastric cancer were examined with FLT PET and FDG PET. Tumour lesions were identified as areas of focally increased uptake, exceeding that of surrounding normal tissue. For semiquantitative analysis, the maximal standardized uptake value (SUV) was calculated. Results  For detection of advanced gastric cancer, the sensitivities of FLT PET and FDG PET were 95.2% and 95.0%, respectively. The mean (±SD) SUV for FLT (7.0 ± 3.3) was significantly lower than that for FDG (9.4 ± 6.3 p < 0.05). The mean FLT SUV and FDG SUV in nonintestinal tumours were higher than in intestinal tumours, although the difference was not statistically significant. The mean (±SD) FLT SUV in poorly differentiated tumours (8.5 ± 3.5) was significantly higher than that in well and moderately differentiated tumours (5.3 ± 2.1; p < 0.04). The mean FDG SUV in poorly differentiated tumours was higher than in well and moderately differentiated tumours, although the difference was not statistically significant. There was no significant correlation between Ki-67 index and either FLT SUV or FDG SUV. Conclusion  FLT PET showed as high a sensitivity as FDG PET for the detection of gastric cancer, although uptake of FLT in gastric cancer was significantly lower than that of FDG.     

Correlation of <Superscript>18</Superscript>F-FLT and <Superscript>18</Superscript>F-FDG uptake on PET with Ki-67 immunohistochemistry in non-small cell lung cancer

Purpose The nucleoside analogue 3′-deoxy-3′-¹⁸F-fluorothymidine (FLT) has recently been introduced for imaging cell proliferation with positron emission tomography (PET). We prospectively evaluated whether FLT uptake reflects proliferative activity as indicated by the Ki-67 index in non-small cell lung cancer (NSCLC), in comparison with 2-deoxy-2-¹⁸F-fluoro-D-glucose (FDG). Methods A total of 18 patients with newly diagnosed NSCLC were examined with both FLT PET and FDG PET. PET imaging was performed at 60 min after each radiotracer injection. Tumour lesions were identified as areas of focally increased uptake, exceeding background uptake in the lungs. For semi-quantitative analysis, the maximum standardised uptake value (SUV) was calculated. Proliferative activity as indicated by the Ki-67 index was estimated in tissue specimens. Immunohistochemical findings were correlated with SUVs. Results The sensitivity of FLT and FDG PET for the detection of lung cancer was 72% and 89%, respectively. Four of the five false-negative FLT PET findings occurred in bronchiolo-alveolar carcinoma. The mean FLT SUV was significantly lower than the mean FDG SUV. A significant correlation was observed between FLT SUV and Ki-67 index (r = 0.77; p < 0.0002) and for FDG SUV (r = 0.81; p < 0.0001). Conclusion The results of this preliminary study suggest that, compared with FDG, FLT may be less sensitive for primary staging in patients with NSCLC. Although FLT uptake correlated significantly with proliferative activity in NSCLC, the correlation was not better than that for FDG uptake.     

Usefulness of <Superscript>11</Superscript>C-methionine PET in the evaluation of brain lesions that are hypo- or isometabolic on <Superscript>18</Superscript>F-FDG PET

The fact that some brain tumors show hypo- or isometabolism on fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) has caused problems in the detection of primary or recurrent tumors and in the differentiation from benign lesions. We investigated the usefulness of carbon-11 methionine PET in characterizing brain lesions under these conditions. 11C-methionine PET was performed in 45 patients with brain lesions (in 34 for initial diagnosis and in 11 for detection of recurrence) that showed hypo- or isometabolism compared with normal brain tissue on FDG PET. Ten minutes after the injection of 555-740 MBq of 11C-methionine, attenuation-corrected brain images were obtained with a dedicated PET scanner. The brain lesions comprised 24 gliomas, five metastatic brain tumors, four meningiomas, two other brain tumors and ten benign lesions (including three cases of cysticercosis, two cases of radiation necrosis, one tuberculous granuloma, one hemangioma, one benign cyst, and one organizing infarction). Proliferative activity was measured using the Ki-67 immunostaining method in glioma tissues. Thirty-one of 35 brain tumors (89% sensitivity) showed increased 11C-methionine uptake despite iso- or hypometabolism on FDG PET. By contrast, all ten benign lesions showed decreased or normal 11C-methionine uptake (100% specificity). Twenty-two of 24 gliomas (92%) showed increased 11C-methionine uptake, the extent and degree of which exceeded 18F-FDG uptake, and the 11C-methionine uptake correlated with the proliferation index (r=0.67). The mean (+/-SD) uptake ratios of glioma to normal brain on FDG and 11C-methionine PET were 0.92+/-0.34 and 2.54+/-1.25, respectively. All metastatic tumors except one showed intense 11C-methionine uptake in the entire tumor or in the peripheral margin of the tumor. In meningiomas, 11C-methionine uptake showed a variable increase. In conclusion, brain lesions that show hypo- or isometabolism on FDG PET can be detected and differentiated with high sensitivity and good contrast using 11C-methionine PET. 11C-methionine PET can provide additional information when used in combination with FDG PET in the evaluation of these patients.     

Positron emission tomography with [<Superscript>18</Superscript>F]FDOPA and [<Superscript>18</Superscript>F]FDG in the imaging of small cell lung carcinoma: preliminary results

Small cell lung carcinomas (SCLC) express neuroendocrine markers, and dihydroxyphenylalanine (DOPA) is known to accumulate in neuroendocrine tumours. This study was performed with the aim of evaluating the uptake of 3,4-dihydroxy-6-¹⁸F-fluoro-phenylalanine ([¹⁸F]FDOPA) by SCLC, based on comparison with the results of fluorine-18 fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography (PET) and standard imaging procedures. [¹⁸F]FDG PET and [¹⁸F]FDOPA PET were performed on four patients with newly diagnosed SCLC. There was agreement between the results of [¹⁸F]FDOPA PET and [¹⁸F]FDG PET in four tumoural sites out of 11, whereas [¹⁸F]FDG PET and standard imaging procedures were in full agreement. A semi-quantitative analysis based on standardised uptake values (SUVs) was performed in order to compare [¹⁸F]FDG and [¹⁸F]FDOPA tumour uptake. The median [¹⁸F]FDG SUV_max was 5.9 (with a 95% confidence interval from 4.4 to 9.2), while the median [¹⁸F]FDOPA SUV_max was 1.9 (with a 95% confidence interval from 1.6 to 3.8). The difference between [¹⁸F]FDG SUV_max and [¹⁸F]FDOPA SUV_max was significant (P<0.01). [¹⁸F]FDOPA PET appeared less sensitive than [¹⁸F]FDG PET and standard imaging procedures in the staging of SCLC. No clear relation between [¹⁸F]FDOPA uptake and positivity of neuroendocrine markers on immunohistochemistry emerged from these preliminary results; however, since [¹⁸F]FDOPA uptake may reflect better differentiation of the tumour, and possibly a better prognosis, this point warrants clarification in a larger study.     

A comparative study of 11C-choline PET and [18F]fluorodeoxyglucose PET in the evaluation of lung cancer

The purpose of this study was to compare the diagnostic value of 11C-choline positron emission tomography (PET) and [18F]fluorodeoxyglucose (FDG) PET imaging in the detection of primary lung cancer and mediastinal lymph node metastases. Seventeen patients with histologically proven primary lung cancer were examined with both 11C-choline and FDG PET within a week of each study. Lung cancers were analysed visually and semiquantitatively using the ratio of tumour-to-normal radioactivity (T/N ratio) and standardized uptake value (SUV). Mediastinal lymph node metastases were analysed visually. Although both techniques delineated focal lesions with an increase in tracer accumulation in 13 patients, FDG PET identified three additional patients in whom 11C-choline PET did not visualize any lesion. In the detection of lung cancer <2 cm in size, FDG PET provided higher sensitivity (six of seven, 85.7%) than 11C-choline PET (four of seven, 57.1%). The T/N ratio and SUV were significantly higher with FDG PET (T/N ratio, 7.43+/-6.22; SUV, 4.05+/-3.05) than these were with 11C-choline PET (T/N ratio, 2.93+/-1.19; SUV, 2.93+/-0.79) (P<0.001). There was a significant positive correlation between the T/N ratios and SUVs of FDG and 11C-choline. In the assessment of mediastinal lymph node involvement, FDG PET detected lymph node metastases in two patients who were negative on 11C-choline PET, whereas both techniques could not detect tumour involvement in one patient. Both techniques have clinical value for the non-invasive detection of primary lung cancer that is 2 cm or greater in size. However, FDG PET is superior to 11C-choline PET in the detection of lung cancer that is less than 2 cm in diameter and in mediastinal lymph node metastases.     

[<Superscript>18</Superscript>F]FLT PET for diagnosis and staging of thoracic tumours

The nucleoside analogue 3'-deoxy-3'-[¹⁸F]fluorothymidine (FLT) has been introduced for imaging of tumour cell proliferation by positron emission tomography (PET). This study evaluated the use of FLT in patients with thoracic tumours prior to treatment. Whole-body FLT PET was performed in 16 patients with 18 tumours [17 thoracic tumours (nine non-small cell lung cancers, five oesophageal carcinomas, two sarcomas, one Hodgkin's lymphoma) and one renal carcinoma] before treatment. Fluorine-18 fluorodeoxyglucose (FDG) PET was performed for comparison except in those patients with oesophageal carcinoma. For semi-quantitative analysis, the average and maximum standardised uptake values (avgSUV and maxSUV, respectively) (FLT, 114±20 min p.i.; FDG, 87±8 min p.i.; 50% isocontour region of interest) was calculated. All 17 thoracic tumours and 19/20 metastases revealed significant FLT accumulation, resulting in easy delineation from surrounding tissue. The additional small grade 1 renal carcinoma was not detected with either FLT or FDG. In most lung tumours (avgSUV 1.5–8.2) and metastases, FLT showed intense uptake. However, one of two spinal bone metastases was missed owing to the high physiological FLT uptake in the surrounding bone marrow. Oesophageal carcinoma primaries (avgSUV 2.7–10.0) and occasional metastases showed particularly favourable tumour/non-tumour contrast. Compared with FDG, tumour uptake of FLT was lower (avgSUV, P=0.0006; maxSUV, P=0.0001), with a significant linear correlation (avgSUV, r²=0.45; maxSUV, r²=0.49) between FLT and FDG. It is concluded that FLT PET accurately visualises thoracic tumour lesions. In the liver and the bone marrow, high physiological FLT uptake hampers detection of metastases. On the other hand, FLT may be favourable for imaging of brain metastases owing to the low physiological uptake.     

11C-choline PET for the detection of bone and soft tissue tumours in comparison with FDG PET

We assessed and compared the usefulness of C-choline positron emission tomography (PET) with that of 2-[ F]fluoro-2-deoxy-D-glucose (FDG) PET for the differentiation between benign and malignant bone and soft tissue tumours. A total of 43 patients with 45 lesions were included. C-choline PET and FDG PET were performed from 5 and 40 min, respectively, after injection of 275-370 MBq tracer. PET data were evaluated by using the standardized uptake value (SUV) and were analysed according to the pathological data. C-choline uptake in malignancies was 4.9+/-2.1 (n=14), which was significantly higher than that in benign lesions (2.5+/-1.7, n=31) (P <0.0001). The sensitivity, specificity and accuracy of C-choline PET were 100%, 64.5% and 75.6%, respectively, when 2.59 of the SUV was used as the cut-off value. The FDG uptake in malignancies was 5.1+/-4.2 (n=14) and was also significantly larger than that in benign lesions 2.9+/-2.9 (n=31) (P<0.003). The sensitivity, specificity and accuracy of FDG PET were 85.7%, 41.9% and 55.6%, respectively (cut-off=1.83). The C-choline uptake in the lesions correlated with FDG uptake ( r=0.61, P<0.003). In receiver operating characteristic (ROC) analysis, the area under the ROC curve for C-choline PET (area=0.847) was higher than that for FDG PET (area=0.717). This study showed that C-choline PET was superior to FDG PET in differentiation between malignant and benign lesion in bone and soft tissue tumours. C-choline PET might be useful as a screening method for malignant bone and soft tissue tumours.     

The incremental value of <Superscript>18</Superscript>F-FDG PET/CT in paediatric malignancies

PURPOSE: (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) imaging has been used in the assessment of paediatric malignancies. PET/CT increases the diagnostic accuracy in adult cancer patients. The present study assesses the incremental value of FDG PET/CT in paediatric malignancies. METHODS: A total of 118 (18)FDG PET/CT studies of 46 paediatric patients were reviewed retrospectively. PET and PET/CT results were classified as malignant, equivocal or benign, compared on a site- and study-based analysis, and also compared with the clinical outcome. RESULTS: Three hundred and twenty-four sites of increased FDG uptake were detected. Discordant PET and PET/CT interpretations were found in 97 sites (30%) in 27 studies (22%). PET yielded a statistically significant higher proportion of equivocal and a lower proportion of benign lesion and study results (p<0.001) than PET/CT. With PET there were 153 benign (47%), 84 (26%) equivocal and 87 (27%) malignant sites, while PET/CT detected 226 benign (70%), 10 (3%) equivocal and 88 (27%) malignant lesions. PET/CT mainly improved the characterisation of uptake in brown fat (39%), bowel (17%), muscle (8%) and thymus (7%). The study-based analysis showed that 17 equivocal and seven positive PET studies (20%) were interpreted as benign on PET/CT, while three equivocal studies were interpreted as malignant. The study-based sensitivity and specificity of PET/CT were 92% and 78% respectively. CONCLUSION: PET/CT significantly improved the characterisation of abnormal (18)FDG foci in children with cancer, mainly by excluding the presence of active malignancy in sites of increased tracer activity.     

[<Superscript>68</Superscript>Ga]DOTATATE PET/MRI and [<Superscript>18</Superscript>F]FDG PET/CT are complementary and superior to diffusion-weighted MR imaging for radioactive-iodine-refractory differentiated thyroid cancer

Purpose

The purpose of this study was to determine whether [⁶⁸Ga]DOTATATE PET/MRI with diffusion-weighted imaging (DWI) can replace or complement [¹⁸F]FDG PET/CT in patients with radioactive-iodine (RAI)-refractory differentiated thyroid cancer (DTC).

Methods

The study population comprised 12 patients with elevated thyroglobulin and a negative RAI scan after thyroidectomy and RAI remnant ablation who underwent both [¹⁸F]FDG PET/CT and [⁶⁸Ga]DOTATATE PET/MRI within 8 weeks of each other. The presence of recurrent cancer was evaluated on a per-patient, per-organ and per-lesion basis. Histology, and prior and follow-up examinations served as the standard of reference.

Results

Recurrent or metastatic tumour was confirmed in 11 of the 12 patients. [⁶⁸Ga]DOTATATE PET(/MRI) correctly identified the tumour burden in all 11 patients, whereas in one patient local relapse was missed by [¹⁸F]FDG PET/CT. In the lesion-based analysis, overall lesion detection rates were 79/85 (93 %), 69/85 (81 %) and 27/82 (33 %) for [¹⁸F]FDG PET/CT, [⁶⁸Ga]DOTATATE PET/MRI and DWI, respectively. [¹⁸F]FDG PET(/CT) was superior to [⁶⁸Ga]DOTATATE PET(/MRI) in the overall evaluation and in the detection of pulmonary metastases. In the detection of extrapulmonary metastases, [⁶⁸Ga]DOTATATE PET(/MRI) showed a higher sensitivity than [¹⁸F]FDG PET(/CT), at the cost of lower specificity. DWI achieved only poor sensitivity and was significantly inferior to [¹⁸F]FDG PET in the lesion-based evaluation in the detection of both extrapulmonary and pulmonary metastases.

Conclusion

[¹⁸F]FDG PET/CT was more sensitive than [⁶⁸Ga]DOTATATE PET/MRI in the evaluation of RAI-refractory DTC, mostly because of its excellent ability to detect lung metastases. In the evaluation of extrapulmonary lesions, [⁶⁸Ga]DOTATATE PET(/MRI) was more sensitive and [¹⁸F]FDG PET(/CT) more specific. Furthermore, DWI did not provide additional information and cannot replace [¹⁸F]FDG PET for postoperative monitoring of patients with suspected RAI-refractory DTC.

     

Positron emission tomographic imaging with<Superscript>11</Superscript>C-choline in differential diagnosis of head and neck tumors: comparison with<Superscript>18</Superscript>F-FDG PET

The aim of this study was to evaluate the clinical value of positron emission tomography (PET) with¹¹C-labeled choline (CHOL) for the differential diagnosis of malignant head and neck tumors from benign lesions as compared with¹⁸F-fluorodeoxyglucose PET.Methods: We studied 45 patients (28 males, 17 females, age range, 29-84 years) with suspected lesions in the head and neck region using both CHOL and FDG PET within a 2-week period on each patient. All patients fasted for at least 6 hours for both the CHOL and FDG studies. PET imaging was performed 5 min and 50-60 min after intravenous injection of CHOL and FDG, respectively. After data acquisition, PET images were corrected for attenuation, and the reconstructed images were analyzed by visual interpretation. Then, the standardized uptake value (SUV) was calculated for semiquantitative evaluation of tumor tracer uptake. Finally the results of PET scans were compared with the histological diagnoses from surgical specimens or biopsies.Results: With CHOL PET, malignant tumors were correctly detected in 24 (96%) of 25 patients, and benign lesions in 14 (70%) of 20 patients with an accuracy of 84.4%. With FDG PET, malignancy was correctly diagnosed in 23 (92%) of 25 patients, and benign lesions in 13 (65%) of 20 patients resulting an accuracy of 80%. A significant positive correlation between CHOL and FDG SUVs was found for all lesions (r = 0.677, p = 0.004, n = 45). Malignant tumors showed significantly higher tracer accumulation than the benign lesions in both CHOL and FDG studies (5.69 ± 1.61, n = 25 vs. 2.98 ± 2.13, n = 20, p < 0.0001; 9.21 ± 4.23, n = 25 vs. 3.60 ± 2.57, n = 20, p < 0.0001). The cutoff SUV for differentiating malignant and benign lesions was 3.5 for CHOL and 3.9 for FDG. CHOL showed slightly better differentiation between malignant and benign lesions than FDG although some overlap existed on both studies. But the difference was not statistically significant.Conclusion: The results of this study indicate that CHOL PET may be feasible clinically for head and neck tumor imaging. PET imaging with CHOL seems to be able to detect malignant head and neck tumors as effectively as FDG PET. The advantages of CHOL PET were shorter examination period and low uptake in the muscle. However, both CHOL and FDG have some limitations in the evaluation of salivary gland lesions.     

<Superscript>11</Superscript>C-methionine uptake in cerebrovascular disease: A comparison with<Superscript>18</Superscript>F-FDG PET and<Superscript>99m</Superscript>Tc-HMPAO SPECT

OBJECTIVES: Carbon-11-L-methyl-methionine (11C-methionine) has been reported to be useful for evaluating brain tumors, but several other brain disorders have also shown signs of high methionine uptake. We retrospectively evaluated the significance of 11C-methionine uptake in cerebrovascular diseases, and also compared our results with those for 18F-FDG PET and 99mTc-HMPAO SPECT. METHODS: Seven patients, including 3 patients with a cerebral hematoma and 4 patients with a cerebral infarction, were examined. All 7 patients underwent both 11C-methionine PET and 99mTc-HMPAO SPECT, and 6 of them underwent 18F-FDG PET. RESULTS: A high 11C-methionine uptake was observed in all 3 patients with cerebral hematoma. Increased 99mTc-HMPAO uptake was observed in 2 out of 3 patients, and all 3 patients had decreased 18F-FDG uptake. Of 4 patients with a cerebral infarction, high 11C-methionine uptake was observed in 3. Increased 99mTc-HMPAO uptake was also observed in one patient, whereas 3 patients had decreased 18F-FDG uptake. CONCLUSIONS: We should keep in mind that high 11C-methionine uptake is frequently observed in cerebrovascular diseases. CVD should therefore be included in the differential diagnosis when encounting patients with a high 11C-methionine uptake.     

Imaging of adenosine A<Subscript>1</Subscript> receptors in the human brain by positron emission tomography with [<Superscript>11</Superscript>C]MPDX

We report the first clinical PET study using [1-methyl-11C]8-dicyclopropylmethyl-1-methyl-3-propylxanthine ([11C]MPDX) for imaging adenosine A1 receptors in the human brain. The binding of [11C]MPDX evaluated quantitatively as the distribution volume by a graphical analysis was high in the striatum and thalamus, and low in the cerebellum. The distribution pattern of [11C]MPDX was coincident with that of adenosine A1 receptors in vitro reported previously, and was different from those of blood flow and [18F]FDG. The [11C]MPDX PET has the potential for mapping adenosine A1 receptors in the human brain.     

Usefulness of <Superscript>18</Superscript>F-FDG PET in intrahepatic cholangiocarcinoma

Surgical resection is the only curative treatment strategy for intrahepatic cholangiocarcinoma (CC). Therefore, accurate staging is essential for appropriate management of patients with CC. We assessed the usefulness of 2-[¹⁸F]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) in the staging of CC. We undertook a retrospective review of FDG PET images in 21 patients (10 female, 11 male; mean age 57 years) diagnosed with CC. Ten patients had hilar CC and 11, peripheral CC. Patients underwent abdominal magnetic resonance imaging (MRI) (n=20) and computed tomography (CT) (n=12) for the evaluation of primary tumours, and chest radiography and whole-body bone scintigraphy for work-up of distant metastases. For semi-quantitative analysis, the maximum voxel standardised uptake value (SUV_max) was obtained from the primary tumour. All peripheral CCs showed intensely increased FDG uptake, and some demonstrated ring-shaped uptake corresponding to peripheral rim enhancement on CT and/or MRI. In nine of the ten patients, hilar CCs demonstrated increased FDG uptake of a focal nodular or linear branching appearance. The remaining case was false negative on FDG PET. One patient with a false negative result on MRI demonstrated increased uptake on FDG PET. Among the ten hilar CCs, FDG uptake was intense in only two patients and was slightly higher than that of the hepatic parenchyma in the remaining patients. For the detection of lymph node metastasis, FDG PET and CT/MRI were concordant in 16 patients, and discordant in five (FDG PET was positive in three, and CT and MRI in two). FDG PET identified unsuspected distant metastases in four of the 21 patients; all of these patients had peripheral CC. FDG PET is useful in detecting the primary lesion in both hilar and peripheral CC and is of value in discovering unsuspected distant metastases in patients with peripheral CC. FDG PET could be useful in cases of suspected hilar CC with non-confirmatory biopsy and radiological findings.     

[<Superscript>11</Superscript>C]choline PET/CT imaging in occult local relapse of prostate cancer after radical prostatectomy

Purpose The aim of this study was to assess the accuracy and clinical impact of [¹¹C]choline PET/CT for localizing occult relapse of prostate adenocarcinoma after radical prostatectomy. Methods Fourty-nine patients with prostate adenocarcinoma, radical prostatectomy, no evidence of metastatic disease, and occult relapse underwent [¹¹C]choline PET/CT. Thirty-six of the patients had biochemical evidence and histological evaluation of local recurrence. Thirteen patients had PSA < 0.3 ng/ml and no evidence of active disease after 1 year follow-up. Focal nodular [¹¹C]choline uptake in the prostatic fossa was visually assessed and graded on a five point scale. Maximum standardized radioactivity uptake value (SUV_max) and the lesion size were measured. A receiver operating characteristic (ROC) analysis was performed and the clinical impact of the PET/CT study was determined. Results [¹¹C]choline PET/CT was true positive in 23/33 patients and true negative in 12/13 controls. SUV_max of local recurrence was 3.0 (median, range 0.6–7.4) and 1.1 (0.4–1.6) in controls (p = 0.0002). Lesion size was 1.7 cm (range 0.9–3.7). Area under the ROC curve for detecting relapse was 0.90 ± 0.05 and 0.83 ± 0.06 for visual evaluation and SUV_max, respectively. Sensitivity and specificity of [¹¹C]choline PET/CT were 0.73 and 0.88, respectively. [¹¹C]choline PET/CT identified 12/17 (71%) patients with a favourable biochemical response to local radiotherapy at 2 year (median, 0.8–3.2 range) follow-up. Conclusions Focally increased [¹¹C]choline uptake in the prostatic bed reliably predicted local low volume occult relapsing prostate adenocarcinoma after radical prostatectomy and identified 71% of patients with a favourable biochemical response to local radiotherapy.     

Pheochromocytomas: imaging with 2-[fluorine-18]fluoro-2-deoxy-D-glucose PET.

PURPOSE: To assess the sensitivity of positron emission tomography (PET) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) in pheochromocytomas and, secondarily, to compare images obtained with FDG PET to those obtained with metaiodobenzylguanidine (MIBG) scintigraphy. MATERIALS AND METHODS: Twenty-nine patients with one or more known or subsequently proved pheochromocytomas underwent FDG PET (35 scans) and MIBG scintigraphy (35 scans). Tumor uptake of FDG was quantified on positive PET scans. RESULTS: Tumor uptake of FDG was detected in 22 of 29 patients. Most benign (seven of 12 patients) and most malignant (15 of 17 patients) pheochromocytomas and their metastases avidly concentrated FDG. In four patients whose pheochromocytomas failed to accumulate MIBG, uptake of FDG in the tumors was intense. For the majority of the 16 patients whose tumors concentrated both agents, however, ratings for MIBG images compared to FDG PET images for delineation of the tumor in comparison to background and normal organ accumulation were superior for nine patients (56%) and as good or better for 14 (88%). CONCLUSION: Most pheochromocytomas accumulate FDG. Uptake is found in a greater percentage of malignant than benign pheochromocytomas. FDG PET is especially useful in defining the distribution of those pheochromocytomas that fail to concentrate MIBG.     

<Superscript>18</Superscript>F-choline in experimental soft tissue infection assessed with autoradiography and high-resolution PET

For each oncological tracer it is important to know the uptake in non-tumorous lesions. The purpose of this study was to measure the accumulation of fluorine-18 choline (FCH), a promising agent for the evaluation of certain tumour types, in infectious tissue. Unilateral thigh muscle abscesses were induced in five rats by intramuscular injection of 0.1 ml of a bacterial suspension (Staphylococcus aureus, 1.2×10⁹ CFU/ml). In all animals, FCH accumulation was measured with high-resolution positron emission tomography (PET) on day 6. Autoradiography of the abscess and ipsilateral healthy muscle was performed on day 7 (three animals) and day 11 (two animals) and correlated with histology. In addition, ¹⁸F-fluorodeoxyglucose (FDG) PET was performed on day 5. Increased FCH uptake was noted in specific layers of the abscess wall which contained an infiltrate of mainly granulocytes on day 7 and mainly macrophages on day 11. The autoradiographic standardised uptake values in the most active part of the abscess wall were 2.99 on day 7 (n=3) and 4.05 on day 11 (n=2). In healthy muscle the corresponding values were 0.99 and 0.64. The abscesses were clearly visualised on the FCH and FDG PET images. In conclusion, this study demonstrated avid FCH accumulation in inflammatory tissue, which limits the specificity of FCH for tumour detection. Future studies are now needed to determine the degree of this limitation in human cancer patients.     

Intraindividual comparison of <Superscript>68</Superscript>Ga-DOTA-TATE and <Superscript>18</Superscript>F-DOPA PET in patients with well-differentiated metastatic neuroendocrine tumours

Aim  To compare the diagnostic impact of ⁶⁸Ga-DOTA-TATE and ¹⁸F-DOPA PET in the diagnosis of well-differentiated metastatic neuroendocrine tumours (NET). Methods  PET/CT using both ⁶⁸Ga-DOTA-TATE and ¹⁸F-DOPA was performed in 25 patients with histologically proven metastatic NET (nine gut, five pancreas, six lung, one paranasal sinus, four with unknown primary). Analyses of PET examinations were patient-based (pathological uptake: yes/no), and based on tumour regions (primary tumour if present and metastases of liver, lung, bones and lymph nodes). The results were compared with the results of contrast enhanced CT, and with plasma serotonin levels, which were available in 24 of the 25 patients. Results  Patient-based sensitivities were 96% for ⁶⁸Ga-DOTA-TATE PET and 56% for ¹⁸F-DOPA PET. ⁶⁸Ga-DOTA-TATE PET delineated metastases in 54 of 55 positive metastatic tumour regions in contrast to 29 of 55 delineated by ¹⁸F-DOPA PET. Overall, ⁶⁸Ga-DOTA-TATE was superior to ¹⁸F-DOPA in 13 patients (two patients showed fewer positive tumour regions with ¹⁸F-DOPA PET). The results were comparable in 12 patients. In 13 of 24 patients, plasma serotonin levels were elevated, and 11 of these 13 patients showed pathological uptake of ¹⁸F-DOPA. Of the 11 patients with normal levels of serotonin, 3 also showed positive ¹⁸F-DOPA uptake. In patients positive for ¹⁸F-DOPA uptake the maximum tumour SUVs were correlated with the levels of serotonin (r=0.66, p=0.01). Conclusion  In this study ⁶⁸Ga-DOTA-TATE PET proved clearly superior to ¹⁸F-DOPA PET for detection and staging of NET. ¹⁸F-DOPA uptake tended to be increased in those patients with elevated plasma serotonin. We conclude that ¹⁸F-DOPA PET should be employed in patients with NET with negative ⁶⁸Ga-DOTA-TATE PET and elevated plasma serotonin.