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.     

Fluorine-18 fluorodeoxyglucose positron emission tomography and iodine-131 whole-body scintigraphy in the follow-up of differentiated thyroid cancer

Metastases of differentiated thyroid cancer may show different uptake patterns for fluorine-18 fluorodeoxyglucose and [¹³¹I]NaI. FDG positron emission tomography (PET), iodine-131 whole-body scintigraphy (¹³¹I WBS) and magnetic resonance imaging were performed in 58 unselected patients, and spiral computed tomography (CT) of the lung in 25 patients. Thirty-eight patients presented with papillary carcinomas, 15 patients with follicular carcinomas and five patients with variants of follicular carcinoma. Primary tumour stage (pT) was pT1 in 3, pT2 in 19, pT3 in 11 and pT4 in 25 cases. For the detection of metastases, FDG PET was found to have a sensitivity of 50%, ¹³¹I WBS a sensitivity of 61%, and the two methods combined a sensitivity of 86%. When FDG PET was limited to patients with elevated thyroglobulin (Tg) levels and negative ¹³¹I WBS, the sensitivity of this algorithm was 82%. Of the 21 patients with lymph node metastases, seven presented with FDG uptake but no iodine uptake. In four of them, a second FDG hot spot appeared in a lymph node metastasis of normal size. Five of the seven patients underwent surgery. None of the eight patients with pulmonary metastases smaller than 1 cm exhibited FDG uptake, while five of them had iodine uptake. All had positive results on spiral CT. In conclusion, FDG PET cannot be substituted for ¹³¹I WBS. If the Tg level is elevated and ¹³¹I WBS is negative, FDG PET can be used to detect lymph node metastases and complements anatomical imaging. A spiral CT of the lung is useful to exclude pulmonary metastases before planning a dissection of iodine-negative lymph node metastases. Received 2 May and in revised form 8 July 1997     

Preoperative assessment of cervical lymph nodes in head and neck cancer with fluorine-18 fluorodeoxyglucose using a dual-head coincidence camera: a pilot study

The aim of this study was to investigate whether in patients with head and neck cancer, staging is possible with fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) using a dual-head positron emission tomography (PET) camera. Twenty patients (ten men, ten women; mean age: 60 years) were studied using 185 MBq (5 mCi) ¹⁸F-FDG. Two of these patients who were suspected of having recurrence in the neck were restaged 19 and 12 months, respectively, after the resection of the primary tumour. The images were visually analyzed and the results were correlated with computed tomography (CT) (n = 18), ultrasonography (n = 17) and pathological findings. With respect to the primary tumour, FDG dual-head PET and CT revealed a sensitivity of 100% and 59%, respectively (P<0.001). In seven patients lymph node metastases were found in the neck specimen. Two of them had bilateral metastases. FDG dual-head PET correctly identified all nine pathological neck sides whereas CT and ultrasonography depicted eight of nine and seven of eight pathological sides, respectively. In three patients, false-positive FDG uptake was seen, which was due to a preceding biopsy in two cases. The sensitivity of FDG dual-head PET, CT and ultrasonography in the identification of pathological neck sides was 100%, 89% and 87%, respectively, and the specificity was 90%, 93% and 50%, respectively. With knowledge of the preceding biopsies, the specificity of FDG dual-head PET would have been 97%. The smallest lymph node metastasis detected by FDG dual-head PET that was missed by CT had a diameter of 0.6 cm. Measurement of ¹⁸F-FDG with a dual-head PET camera is very sensitive in the detection of primary head and neck cancers and accurate in the preoperative assessment of lymph node metastases. The results justify a prospective study on the identification of metastases in patients with head and neck cancer. In addition, it is justified to start a study on the detection of unknown primary tumours in patients with cervical metastases. Received 19 October and in revised form 18 December 1998     

PET with [18F]fluorothymidine for imaging of primary breast cancer: a pilot study

The aim of this study was to evaluate the use of [¹⁸F]fluorothymidine (FLT) as a positron emission tomography (PET) tracer for the diagnosis of breast cancer. To this end, 12 patients with 14 primary breast cancer lesions (T2–T4) were studied by FLT-PET. For comparison, [¹⁸F]fluorodeoxyglucose (FDG) PET scans were performed in six patients. Thirteen of the 14 primary tumours demonstrated focally increased FLT uptake (SUV_mean=3.4±1.1). Seven out of eight patients with histologically proven axillary lymph node metastases showed focally increased FLT uptake in the corresponding areas (SUV_mean=2.4±1.2). The lowest SUV (mean =0.7) was observed in one of two inflammatory cancers. The contrast between primary tumours or metastases and surrounding tissue was high in most cases. In direct comparison to FDG-PET, the SUVs of primary tumours (5/6) and axillary lymph node metastases (3/4) were lower in FLT-PET (SUV_FLT: 3.2 vs SUV_FDG: 4.7 in primary tumours and SUV_FLT: 2.9 vs SUV_FDG: 4.6 in lymph node metastases). Since FLT uptake in surrounding breast tissue was also lower, tumour contrast was comparable to that with FDG. It is of note that normal FLT uptake was very low in the mediastinum, resulting in a higher tumour-to-mediastinum ratio as compared to FDG (P=0.03). FLT-PET is suitable for the diagnosis of primary breast cancer and locoregional metastases. High image contrast may facilitate the detection of small foci, especially in the mediastinum.     

The usefulness of FDG positron emission tomography for the detection of mediastinal lymph node metastases in patients with non-small cell lung cancer: a comparative study with X-ray computed tomography

We evaluated the usefulness of fluorine-18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) in the detection of mediastinal lymph node metastases in patients with non-small cell lung cancer and then compared the findings with the results of X-ray CT by region based on the histological diagnoses. We examined 29 patients with non-small cell lung cancer. One hundred and thirty-two mediastinal lymph nodes were surgically removed and the histological diagnoses were confirmed. FDG PET images, including 146 mediastinal regions, were visually analysed and the mediastinal lymph nodes were scored as positive when the FDG uptake was higher than that in the other mediastinal structures. On the X-ray CT scans, any mediastinal lymph nodes with a diameter of 10 mm or larger were scored as positive. All three examinations were successfully performed on 71 regions. For FDG PET, we found a sensitivity of 76%, a specificity of 98% and an accuracy of 93%. On the other hand, for X-ray CT a sensitivity of 65%, a specificity of 87% and an accuracy of 82% were observed. A significant difference was observed in respect of both specificity and accuracy (P<0.05). Based on the above findings, FDG PET is suggested to be superior to X-ray CT when used for the detection of mediastinal lymph node metastases in patients with non-small cell lung cancer.     

Tumour assessment in advanced melanoma: value of FDG-PET/CT in patients with elevated serum S-100B

Purpose To evaluate the usefulness of PET/CT in melanoma patients with an elevated serum S-100B tumour marker level. Methods Out of 165 consecutive high-risk melanoma patients referred for PET/CT imaging, 47 had elevated (>0.2 μg/l) S-100B serum levels and a contemporaneous ¹⁸F-FDG PET/CT scan. PET/CT scans were evaluated for the presence of metastases. To produce a composite reference standard, we used cytological, histological, MRI and PET/CT follow-up findings as well as clinical and S-100B follow-up. Results Among the 47 patients with increased S-100B levels, PET/CT correctly identified metastases in 38 (30 distant metastases and eight lymph node metastases). In one patient with cervical lymph node metastases, PET/CT was negative. Eight patients had no metastases and PET/CT correctly excluded metastases in all of them. Overall sensitivity for metastases was 97% (38/39), specificity 100% (8/8) and accuracy 98% (46/47). S-100B was significantly higher in patients with distant metastases (mean 1.93 μg/l, range 0.3–14.3 μg/l) than in patients with lymph node metastases (mean 0.49 μg/l, range 0.3–1.6 μg/l, p = 0.003) or patients without metastases (mean 0.625 μg/l, range 0.3–2.6 μg/l, p = 0.007). However, 6 of 14 patients with a tumour marker level of 0.3 μg/l had no metastases. Conclusion In melanoma patients with elevated S-100B tumour marker levels, FDG-PET/CT accurately identifies lymph node or distant metastases and reliably excludes metastases. Because of the significant number of false positive S-100B tumour marker determinations (17%), we recommend repetition of tumour marker measurements if elevated S-100B levels occur before extensive imaging is used.     

Comparison of <Superscript>18</Superscript>F-FLT PET and <Superscript>18</Superscript>F-FDG PET for preoperative staging in non-small cell lung cancer

Purpose The nucleoside analog 3′-deoxy-3′-¹⁸F-fluorothymidine (FLT) has been introduced for imaging cell proliferation with positron emission tomography (PET). We prospectively compared the diagnostic efficacy of FLT PET with that of 2-deoxy-2-¹⁸F-fluoro-d-glucose (FDG) PET for the preoperative nodal and distant metastatic staging of non-small cell lung cancer (NSCLC). Methods A total of 34 patients with NSCLC underwent FLT PET and FDG PET. PET imaging was performed at 60 min after each radiotracer injection. The PET images were evaluated qualitatively for regions of focally increased metabolism. For visualized primary tumors, the maximum standardized uptake value (SUV) was calculated. Nodal stages were determined by using the American Joint Committee on Cancer staging system and surgical and histologic findings reference standards. Results For the depiction of primary tumor, sensitivity of FLT PET was 67%, compared with 94% for FDG PET (P = 0.005). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for lymph node staging on a per-patient basis were 57, 93, 67, 89, and 85%, respectively, with FLT PET and 57, 78, 36, 91, and 74%, respectively, with FDG PET (P > 0.1 for all comparisons). Two of the three distant metastases were detected with FLT and FDG PET. Conclusion In NSCLC, FLT PET showed better (although not statistically significant) specificity, positive predictive value and accuracy for N staging on a per-patient basis than FDG PET. However, FDG PET was found to have higher sensitivity for depiction of primary tumor than FLT PET.     

Diagnostic value of full-dose FDG PET/CT for axillary lymph node staging in breast cancer patients

Purpose

The aims of this study were (1) to evaluate FDG PET/CT and CT for the detection of axillary lymph node metastases in breast cancer (BC) patients and (2) to evaluate FDG PET/CT as a pre-test for the triage to sentinel lymph node biopsy (SLNB) versus axillary lymph node dissection (ALND).

Methods

The sensitivity, specificity, positive and negative predictive value (PPV, NPV), and accuracy of FDG PET/CT and CT for axillary lymph node metastases were determined in 61 patients (gold standard: histopathology). According to the equation “NPV = specificity ? (1-prevalence) / [specificity ? (1-prevalence) + (1-sensitivity) ? prevalence]” FDG PET/CT was evaluated as a triage tool for SLNB versus ALND.

Results

The sensitivity, specificity, PPV, NPV and accuracy of FDG PET/CT was 58, 92, 82, 77 and 79% and of CT 46, 89, 72, 71 and 72%, respectively. Patients with an up to ~60% risk for axillary lymph node metastases appear to be candidates for SLNB provided that the axilla is unremarkable on FDG PET/CT.

Conclusion

FDG PET/CT cannot replace invasive approaches for axillary staging but may extend the indication for SLNB.     

Comparison of FDG PET/CT and MRI in lymph node staging of endometrial cancer

Objective

Endometrial cancer is the most frequent cancer occurring in the female genital tract in the Western countries. Because surgical staging is currently the standard, noninvasive techniques that accurately identify lymph node (LN) metastases would be beneficial by reducing costs and complications. The purpose of our study is to compare the diagnostic accuracy of 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) with that of magnetic resonance imaging (MRI) for detecting LN metastases in the preoperative staging of endometrial cancer.

Methods

Two hundred eighty-seven consecutive patients with endometrial cancer underwent preoperative PET/CT and MRI for staging. The malignancy criteria for LNs were a short diameter of 1 cm or more by MRI and focally increased ¹⁸F-FDG uptake by PET/CT. After evaluating PET/CT and MRI separately, morphologic and functional image findings were compared with the histological findings regarding LN metastasis for all patients. PET/CT and MRI images were classified on the basis of histological findings as true-positive, true-negative, false-positive, or false-negative. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated.

Results

Histologic examination revealed LN metastases in 51 patients (17.8 %). The maximal standardized uptake values (SUVmax) of the primary lesions by PET/CT ranged from 1.4 to 37.7, with a mean value of 9.3, whereas those of the metastatic LNs ranged from 2.0 to 22.5 with a mean of 7.3. On a per-patient basis, node staging resulted in sensitivities of 70.0 % with ¹⁸F-FDG PET/CT and 34.0 % with MRI, and specificities of 95.4 % with PET/CT and 95.0 % with MRI. The NPV of PET/CT was 94.3 %, and that of MRI was 87.2 %. On a lesion base analysis, sensitivity of PET/CT was 79.4 % while that of MRI was 51.6 %. In detecting distant metastasis, the sensitivity, specificity, accuracy, PPV, and NPV of PET/CT were 92.9, 98.9, 98.6, 81.3, and 99.6 %, respectively.

Conclusion

Diagnostic performance of FDG PET/CT was better than MRI for detecting metastatic lymph nodes in patients with endometrial cancer both by patient basis and lesion basis analyses. Due to high NPV, FDG PET-CT could aid in selecting candidates for lymphadenectomy.

     

Assessment of lymph node metastases using 18F-FDG PET in patients with advanced gastric cancer

Purpose The aim of this study was to assess the diagnostic accuracy of ¹⁸F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) with respect to lymph node (LN) metastasis in patients with advanced gastric cancer, and to ascertain the factors that affect this accuracy.Methods Seventy-three patients with advanced gastric cancer, verified in all cases by endoscopic biopsy, were enrolled in this prospective study. We conducted FDG PET and other routine preoperative studies, including abdominal computed tomography (CT). Patients underwent either curative-intent gastrectomy and lymphadenectomy (n=67) or exploratory laparotomy. The Japanese system for the classification of gastric cancer was used for LN assessment.Results FDG PET was able to detect primary lesions in 70 of the 73 cases. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value of FDG PET for LN metastasis were 40%, 95%, 91% and 56%, respectively. Signet-ring cell carcinoma was associated with the lowest sensitivity (15%), whereas other cell types could be detected with moderate sensitivity (30–71%) and high specificity (93–100%). According to multiple logistic regression, the standardised uptake value for primary tumours was the only independent variable to be significantly related to sensitivity for LN metastasis (p=0.02, odds ratio=1.14). CT was superior to PET in terms of sensitivity (p<0.0001), and PET was superior to CT in terms of specificity (p<0.0001) and PPV (p=0.05).Conclusion FDG PET exhibits good specificity for LN staging of gastric cancer, and FDG uptake in the primary tumour is significantly related to the accuracy of FDG PET. Despite some clear limitations, FDG PET proved useful in the LN staging of FDG-avid gastric cancer.Seok-Ki Kim and Keon Wook Kang contributed equally to this paper.     

Preoperative lymph node staging in patients with primary prostate cancer: comparison and correlation of quantitative imaging parameters in diffusion-weighted imaging and 11C-choline PET/CT

Purpose

To compare the diagnostic performance of DWI and 11C-choline PET/CT in the assessment of preoperative lymph node status in patients with primary prostate cancer.

Material and methods

Thirty-three patients underwent DWI and 11C-choline PET/CT prior to prostatectomy and extended pelvic lymph node dissection. Mean standardised uptake value (SUV_mean) and mean apparent diffusion coefficient (ADC) of 76 identified lymph nodes (LN) were measured and correlated with histopathology. ADC values and SUVs were compared using linear regression analysis.

Results

A significant difference between benign and malignant LN was observed for ADC values (1.17 vs. 0.96?×?10^-3 mm²/s; P?<?0.001) and SUV_mean (1.61 vs. 3.20; P?<?0.001). ROC analysis revealed an optimal ADC threshold of 1.01?×?10^-3 mm²/s for differentiating benign from malignant LN with corresponding sensitivity/specificity of 69.70 %/78.57 % and an area under the curve (AUC) of 0.785. The optimal threshold for SUV_mean was 2.5 with corresponding sensitivity/specificity of 69.72 %/90.48 % and with an AUC of 0.832. ADC values and SUV_mean showed a moderate significant inverse correlation (r?=?-0.63).

Conclusion

Both modalities reveal similar moderate diagnostic performance for preoperative lymph node staging of prostate cancer, not justifying their application in routine clinical practice at this time. The only moderate inverse correlation between ADC values and SUV_mean suggests that both imaging parameters might provide complementary information on tumour biology.

Key Points

? Conventional imaging shows low performance for lymph node staging in prostate cancer. ? DWI and 11C-choline PET/CT both provide additional functional information ? Both functional modalities reveal only moderate diagnostic performance.     

Advantages and limitations of FDG PET in the follow-up of breast cancer

18F-Fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) has been evaluated in breast cancer for the characterisation of primary tumours, lymph node staging and the follow-up of patients after surgery, chemotherapy and/or external radiotherapy. In contrast to both the low sensitivity and moderate specificity of FDG PET in the initial detection and characterisation of breast cancer and the low lesion-based sensitivity for lymph node staging, the results from use of FDG PET in re-staging breast cancer patients are very promising. A major advantage of FDG PET imaging compared with conventional imaging is that it screens the entire patient for local recurrence, lymph node metastases and distant metastases during a single whole-body examination using a single injection of activity, with a reported average sensitivity and specificity of 96% and 77%, respectively. In most studies the sensitivity of FDG PET is higher than that of a combination of conventional imaging methods. Limitations of FDG PET in the follow-up of breast cancer patients include the relatively low detection rate of bone metastases, especially in case of the sclerotic subtype, and the relatively high rate of false positive results. The rather low specificity of FDG PET can be improved/increased by utilising combined anatomical-molecular imaging techniques, such as a PET/CT tomograph. First results using PET/CT imaging in the follow-up of breast cancer patients demonstrate increased specificity compared with FDG PET alone. Both imaging modalities, however, offer to detect recurrent and metastatic breast cancer disease at an early stage and thus continue to demonstrate the efficacy of molecular imaging in patient management, despite the limited therapeutic options in recurrent and metastatic breast cancer.     

Accuracy of integrated FDG-PET/contrast-enhanced CT in detecting pelvic and paraaortic lymph node metastasis in patients with uterine cancer

The purpose is to evaluate the accuracy of integrated ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography ((CT) with intravenous contrast medium in detecting pelvic and paraaortic lymph node metastasis in patients with uterine cancer, with surgical and histopathological findings used as the reference standard. Forty-five patients with endometrial or uterine cervical cancer underwent radical hysterectomy, including pelvic lymphadenectomy with or without paraaortic lymphadenectomy, after PET/CT. PET/CT findings were interpreted by two experienced radiologists in consensus. The criterion for malignancy on PET/CT images was increased tracer uptake by the lymph node, independent of node size. The overall node-based sensitivity, specificity, PPV, NPV and accuracy of PET/CT for detecting nodal metastases were 51.1% (23/45), 99.8% (1,927/1,931), 85.2% (23/27), 98.9% (1,927/1,949) and 98.7% (1,950/1,976), respectively. The sensitivity for detecting metastatic lesions 4 mm or less in short-axis diameter was 12.5% (2/16), that for between 5 and 9 mm was 66.7% (16/24), and that for 10 mm or larger was 100.0% (5/5). The overall patient-based sensitivity, specificity, positive predictive value ((PPV), negative predictive value (NPV), and accuracy were 50% (6/12), 90.9% (30/33), 66.7% (6/9), 83.3% (30/36) and 80.0% (36/45), respectively. Integrated FDG-PET/contrast-enhanced CT is superior to conventional imaging, but only moderately sensitive in predicting lymph node metastasis preoperatively in patients with uterine cancer.     

Preoperative PET/CT FDG standardized uptake value of pelvic lymph nodes as a significant prognostic factor in patients with uterine cervical cancer

Purpose

Using integrated PET/CT, we evaluated the prognostic relevance in uterine cervical cancer of preoperative pelvic lymph node (LN) [¹⁸F]FDG uptake.

Methods

Patients with FIGO stage IB to IIA uterine cervical cancer were imaged with FDG PET/CT before radical surgery. We used Cox proportional hazards regression to examine the relationship between recurrence and the FDG maximum standardized uptake value (SUV_max) in the pelvic LN (SUV_LN) on PET/CT.

Results

Clinical data, treatment modalities, and results in 130 eligible patients were reviewed. The median postsurgical follow-up was 34 months (range 6 to 109 months). Receiver operating characteristic analysis identified SUV_LN 2.36 as the most significant cut-off value for predicting recurrence. SUV_LN was correlated with SUV_tumour (P?=?0.002), primary tumour size (P?=?0.004), and parametrial invasion (P?=?0.013). Univariate analyses showed significant associations between recurrence and SUV_LN (P?=?0.001), SUV_tumour (P?=?0.007), pelvic LN metastasis (P?=?0.002), parametrial invasion (P?<?0.001), primary tumour size (P?=?0.007), suspected LN metastasis on MRI (P?=?0.024), and FIGO stage (P?=?0.026). Multivariate analysis identified SUV_LN (P?=?0.013, hazard ratio, HR, 4.447, 95 % confidence interval, CI, 1.379 – 14.343) and parametrial invasion (P?=?0.013, HR 6.728, 95 % CI 1.497 – 30.235) as independent risk factors for recurrence. Patients with SUV_LN ≥2.36 and SUV_LN <2.36 differed significantly in terms of recurrence (HR 15.20, P?<?0.001).

Conclusion

Preoperative pelvic LN FDG uptake showed a strong significant association with uterine cervical cancer recurrence.     

Imaging of lung cancer with fluorine-18 fluorodeoxyglucose: comparison of a dual-head gamma camera in coincidence mode with a full-ring positron emission tomography system

Dual-head gamma cameras operated in coincidence mode are a new approach for tumour imaging using fluorine-18 fluorodeoxyglucose (FDG). The aim of this study was to assess the diagnostic accuracy of such a camera system in comparison with a full-ring positron emission tomography (PET) system in patients with lung cancer. Twenty-seven patients (1 female, 26 males, age 62±9 years) with lung cancer or indeterminate pulmonary nodules were studied on the same day with a full-ring PET scanner (Siemens ECAT EXACT) and a coincidence gamma camera system (ADAC Vertex MCD). Sixty minutes after injection of 185–370 MBq FDG, a scan of the chest was performed with the full-ring system. Approximately 2 h p.i., the coincidence camera study was performed. Coincidence gamma camera (CGC) and PET images with (PETac) and without attenuation correction (PETnac) were analysed independently by two blinded observers. In addition, FDG uptake in primary tumours and involved lymph nodes was quantified relative to normal contralateral lung (T/L ratios). All primary tumours were histologically proven. The lymph node status was histologically determined in 23 patients. In four patients, no lymph node sampling was performed because of extensive disease or concurrent illnesses. In the 27 patients, 25 primary lung cancers and two metastatic lesions were histologically diagnosed. The number of coincidences per centimetre axial field of view was 3.33±0.93×10⁵ for the CGC and 1.09±0.36×10⁶ for the dedicated PET system. All primary tumours (size: 4.6±2.6 cm) were correctly identified in the CGC and dedicated PET studies. T/L ratios were 4.7±2.5 for CGC and 6.9±2.8 for PETnac (P <0.001). Histopathological evaluation revealed lymph node metastases in 11 of 88 sampled lymph node stations (size: 2.3±1.0 cm). All lymph node metastases were identified in the PETac studies, while PETnac detected 10/11 and CGC 8/11. For positive lymph nodes that were visible in CGC and PETnac studies, T/L ratios were 3.7±2.3 for CGC and 6.6±3.1 for PETnac (P=0.02). The diameters of false-negative lymph nodes in the CGC studies were 0.75, 1.5 and 2 cm. False-positive FDG uptake in lymph nodes was found in two patients with all three imaging methods. For all lesions combined, T/L ratios in CGC relative to PETnac studies decreased significantly with decreasing lesion size (r=0.62; P<0.001). In conclusion, compared with a full-ring PET system the sensitivity of CGC imaging for detection of lung cancer is limited by a lower image contrast which deteriorates with decreasing lesion size. Nevertheless, the ability of CGC imaging to detect pulmonary lesions with a diameter of at least 2 cm appears to be similar to that of a full-ring system. Both systems provide a similar specificity for the evaluation of lymph node involvement. Received 29 August and in revised form 7 December 1998     

Preoperative PET/CT standardized FDG uptake values of pelvic lymph nodes as a significant prognostic factor in patients with endometrial cancer

Purpose

Using integrated PET/CT, we evaluated the prognostic relevance of preoperative pelvic lymph node (LN) ¹⁸F-FDG uptake in endometrioid endometrial cancer.

Methods

We retrospectively reviewed patients with pathologically proven endometrial cancer who underwent preoperative ¹⁸F-FDG PET/CT scans to evaluate the prognostic significance of PET/CT parameters and other clinicopathological variables. We used Cox proportional hazards regression to examine the relationship between recurrence and the maximum standardized uptake value (SUV_max) in pelvic LNs (SUV_LN) on FDG PET/CT.

Results

Clinical data, treatment modalities and results were reviewed in 70 eligible patients. The median postsurgical follow-up was 29 months (range 6 to 95 months). Receiver-operating characteristic analysis identified the significant SUV_LN cut-off value as 15. The SUV_LN correlated with FIGO stage (P?<?0.001), LN metastasis (P?<?0.001), lymphovascular space invasion (P?<?0.001), SUV_tumour (P?=?0.001), metastatic LN size (P?=?0.004), primary tumour size (P?=?0.012), tumour grade (P?=?0.015) and depth of tumour invasion (P?=?0.035). Regression analysis showed a statistically significant association between recurrence and SUV_LN (P?=?0.002). Recurrence differed significantly (P?<?0.001) between patients with SUV_LN >15 and those with SUV_LN ≤15.

Conclusion

Preoperative pelvic LN FDG uptake exhibited a strong significant association with recurrence of endometrioid endometrial cancer.     

Comparison of 3′-deoxy-3′-[18F]fluorothymidine positron emission tomography (FLT PET) and FDG PET/CT for the detection and characterization of pancreatic tumours

Purpose

Despite recent advances in clinical imaging modalities, differentiation of pancreatic masses remains difficult. Here, we tested the diagnostic accuracy of molecular-based imaging including 3′-deoxy-3′-[¹⁸F]fluorothymidine (FLT) positron emission tomography (PET) and [¹⁸F]fluorodeoxyglucose (FDG) PET/CT in patients with suspected pancreatic masses scheduled to undergo surgery.

Methods

A total of 46 patients with pancreatic tumours suspicious for malignancy and scheduled for resective surgery were recruited prospectively. In 41 patients, FLT PET and FDG PET/CT scans were performed. A diagnostic CT performed on a routine basis was available in 31 patients. FLT PET and FDG PET/CT emission images were acquired according to standard protocols. Tracer uptake in the tumour [FDG and FLT standardized uptake value (SUV)] was quantified by the region of interest (ROI) technique. For FDG PET/CT analysis, correct ROI placement was ensured via side-by-side reading of corresponding CT images.

Results

Of 41 patients, 33 had malignancy, whereas 8 patients had benign disease. Visual analysis of FDG and FLT PET resulted in sensitivity values of 91% (30/33) and 70% (23/33), respectively. Corresponding specificities were 50% (4/8) for FDG PET and 75% (6/8) for FLT PET. In the subgroup of patients with contrast-enhanced CT (n?=?31), sensitivities were 96% (PET/CT), 88% (CT alone), 92% (FDG PET) and 72% (FLT PET), respectively. Mean FLT uptake in all malignant tumours was 3.0 (range SUV_max 1.1–6.5; mean FDG SUV_max 7.9, range 3.3–17.8; p?Conclusion For differentiation of pancreatic tumours, FDG PET and FDG PET/CT showed a higher sensitivity but lower specificity than FLT PET. Interestingly, visual analysis of FLT PET led to two false-positive findings by misinterpreting physiological bowel uptake as pathological FLT uptake in the pancreas. Due to the limited number of patients, the clinical value of adding FLT PET to the diagnostic workup of pancreatic tumours remains to be determined.     

Value of<Superscript> 18</Superscript>F-FDG PET in the detection of peritoneal carcinomatosis

Purpose Peritoneal carcinomatosis can be difficult to diagnose using computed tomography (CT). The purpose of this study was to evaluate the role of 2-(fluorine 18) fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) in the detection of peritoneal carcinomatosis.Methods We reviewed the CT and FDG PET radiological reports and clinical charts of 18 patients with peritoneal carcinomatosis and 17 cancer patients without peritoneal carcinomatosis. We also assessed FDG PET scans from 20 healthy volunteers as a baseline study. The maximum standardised uptake values (SUV_max) over peritoneal lesions in cancer patients and over the area of most intense intestinal uptake in healthy volunteers and cancer patients without peritoneal carcinomatosis were measured.Results The sensitivity and positive predictive value (PPV) of combined FDG PET and CT were superior to those of CT alone for the detection of peritoneal lesions (sensitivity: 66.7% vs 22.2%, p<0.025; PPV: 92.3% vs 50.0%, p<0.05). The most frequent pattern of FDG uptake in patients with peritoneal carcinomatosis was abnormally intense focal uptake near the abdominal wall. An SUV_max threshold of 5.1 produced a diagnostic accuracy of combined FDG PET and CT of 78%. The additional information provided by FDG PET allowed a more accurate diagnosis in 14 patients (40.0%), and led to alteration of the therapeutic strategy in five (14.3%) of the enrolled cancer patients.Conclusion We found that use of an intra-abdominal FDG uptake cut-off value for SUV_max of >5.1 assists in the diagnosis of peritoneal carcinomatosis. FDG PET may play an important role in the clinical management of patients with suspected peritoneal carcinomatosis.     

Pathology-based validation of FDG PET segmentation tools for volume assessment of lymph node metastases from head and neck cancer

Purpose

FDG PET is increasingly incorporated into radiation treatment planning of head and neck cancer. However, there are only limited data on the accuracy of radiotherapy target volume delineation by FDG PET. The purpose of this study was to validate FDG PET segmentation tools for volume assessment of lymph node metastases from head and neck cancer against the pathological method as the standard.

Methods

Twelve patients with head and neck cancer and 28 metastatic lymph nodes eligible for therapeutic neck dissection underwent preoperative FDG PET/CT. The metastatic lymph nodes were delineated on CT (Node_CT) and ten PET segmentation tools were used to assess FDG PET-based nodal volumes: interpreting FDG PET visually (PET_VIS), applying an isocontour at a standardized uptake value (SUV) of 2.5 (PET_SUV), two segmentation tools with a fixed threshold of 40 % and 50 %, and two adaptive threshold based methods. The latter four tools were applied with the primary tumour as reference and also with the lymph node itself as reference. Nodal volumes were compared with the true volume as determined by pathological examination.

Results

Both Node_CT and PET_VIS showed good correlations with the pathological volume. PET segmentation tools using the metastatic node as reference all performed well but not better than PET_VIS. The tools using the primary tumour as reference correlated poorly with pathology. PET_SUV was unsatisfactory in 35 % of the patients due to merging of the contours of adjacent nodes.

Conclusion

FDG PET accurately estimates metastatic lymph node volume, but beyond the detection of lymph node metastases (staging), it has no added value over CT alone for the delineation of routine radiotherapy target volumes. If FDG PET is used in radiotherapy planning, treatment adaptation or response assessment, we recommend an automated segmentation method for purposes of reproducibility and interinstitutional comparison.     

Correlation of apparent diffusion coefficients measured by 3T diffusion-weighted MRI and SUV from FDG PET/CT in primary cervical cancer

Purpose  Diffusion-weighted magnetic resonance imaging (DWI) and fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) are oncological feasible techniques. Currently, apparent diffusion coefficient (ADC) measured by DWI and standard uptake value (SUV) from FDG PET/CT have similar applications in clinical oncology. The aim of this study was to assess the correlation between ADC and SUV in primary cervical cancer. Materials and methods  Patients with documented primary cervical cancer were recruited. All participants underwent abdominopelvic DWI at 3T and FDG PET/CT within 2 weeks. For the primary tumor, ADC was measured as minimum ADC (ADC_min) and mean ADC (ADC_mean) within the whole tumor by DWI. Maximum SUV (SUV_max) and mean SUV (SUV_mean) were measured by FDG PET/CT. Results  A total of 33 patients were included. There was no significant correlation either between ADC_min and SUV_max or between ADC_mean and SUV_mean. The relative ADC_min (rADC_min) defined as ADC_min/ADC_mean ratio was significantly inversely correlated with the relative SUV_max (rSUV_max) defined as SUV_max/SUV_mean ratio (r = –0.526, P = 0.0017) in all study patients. A significantly inverse correlation between rADC_min and rSUV_max was observed in patients with adenocarcinoma/adenosquamous carcinoma (r = –0.685, P = 0.0012) and those with well-to-moderate differentiated tumor (r = –0.631, P = 0.0050). No significant correlation was demonstrated in patients with squamous cell carcinoma or poorly differentiated tumor. Conclusions  The significantly inverse correlation between rADC_min and rSUV_max in primary cervical tumor suggests that DWI and FDG PET/CT might play a complementary role for the clinical assessment of this cancer type.