11C-Acetate as a new biomarker for PET/CT in patients with multiple myeloma: initial staging and postinduction response assessment

Purpose

We investigated the potential value of ¹¹C-acetate (ACT) PET/CT in characterizing multiple myeloma (MM) compared with ¹⁸F-FDG PET/CT. Bone marrow histological and whole-body (WB) MRI findings served as the reference standards.

Methods

In this prospective study, 15 untreated MM patients (10 men and 5 women, age range 48?69 years) underwent dual-tracer ¹¹C-ACT and ¹⁸F-FDG PET/CT and WB MRI for pretreatment staging, and 13 of them had repeated examinations after induction therapy. Diffuse and focal bone marrow uptake was assessed by visual and quantitative analyses, including measurement of the maximum standardized uptake value (SUV_max). Between-group differences and correlations were assessed with the Mann-Whitney U test and the Pearson test.

Results

At staging, all 15 patients had diffuse myeloma involvement upon bone marrow examination with 30–90 % of plasma cell infiltrates. Diffuse infiltration was detected in all of them (100 %) using ¹¹C-ACT with a positive correlation between bone marrow uptake values and percentages of plasma cell infiltrates (r = +0.63, p?=?0.01). In contrast, a diagnosis of diffuse infiltration could be established using ¹⁸F-FDG in only six patients (40 %). Focal lesions were shown in 13 patients on both ¹¹C-ACT PET/CT and WB MRI, and in 10 patients on ¹⁸F-FDG PET/CT. Focal lesions demonstrated ¹¹C-ACT uptake with a mean SUV_max of 11.4 ± 3.3 (range 4.6?19.6, n?=?59), which was significantly higher than the ¹⁸F-FDG uptake (mean SUV_max 6.6 ± 3.1, range 2.3?13.7, n?=?29; p?<?0.0001). After treatment, the diffuse bone marrow ¹¹C-ACT uptake showed a mean SUV_max reduction of 66 % in patients with at least a very good partial response versus 34 % in those with at most a partial response only (p?=?0.01).

Conclusion

PET/CT using ¹¹C-ACT as a biomarker showed a higher detection rate for both diffuse and focal myeloma lesions at diagnosis than using ¹⁸F-FDG, and may be valuable for response assessment.     

Metabolic patterns of the shoulder joint on 18F-fluorodeoxyglucose positron emission tomography/computed tomography in adhesive capsulitis

Objective

The purpose of our study was to demonstrate metabolic patterns on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in patients with adhesive capsulitis (AC).

Methods

We retrospectively reviewed ¹⁸F-FDG PET/CT performed on 22 shoulders of 21 patients diagnosed with AC: 2 shoulders with stage I, 14 with stage II, and 6 with stage III. A clinical diagnosis of AC was retrospectively made based on clinical examination, clinical course, and imaging. The pattern of radiotracer uptake was analyzed. Standardized uptake values in rotator interval (RI), anterior joint capsule (AJC), axillary recess (AR), and greater tuberosity were measured and compared to those of the contralateral side and the control group consisting of 40 shoulders in 20 subjects without shoulder pain.

Results

Four patterns of uptake were noted: (1) glenoid type I (n = 16), with uptake in RI, AJC, and AR; (2) glenoid type II (n = 2),with uptake in AJC and AR; (3) glenoid type III (n = 2), with uptake in RI and AJC; (4) focal type (n = 2), with uptake in RI or AR. Affected side SUV_max for RI, AJC, and AR was significantly higher compared with the unaffected side and the control group. Two shoulders with stage I AC had patterns similar to the ones with stage II or III.

Conclusion

Specific patterns of ¹⁸F-FDG uptake with dominant uptake in RI, AJC, or AR may be related to AC.     

Diagnostic usefulness of an amino acid tracer, α-[N-methyl-11C]-methylaminoisobutyric acid (11C-MeAIB), in the PET diagnosis of chest malignancies

Objectives

Although positron emission tomography (PET) using [¹⁸F]-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) is established as one of the first-choice imaging modalities in the diagnosis of chest malignancies, there are several problems to solve in clinical practice, such as false positive uptake in inflammatory diseases. The aim of this study was to evaluate the clinical usefulness of an amino acid tracer, α-[N-methyl-¹¹C]-methylaminoisobutyric acid (¹¹C-MeAIB), in the diagnosis of chest malignancies, in combination with ¹⁸F-FDG.

Setting

Fifty-nine cases (57 patients, 66 ± 12 years old) who consulted to our institution for the wish to receive differential diagnosis of chest diseases were included. Purpose of the studies were as follows: differential diagnosis of newly developed lung nodules, n = 22; newly developed mediastinal lesions, n = 20; and both, n = 17 (including lung cancer: n = 19, lymphoma: n = 1, other cancers: n = 2, sarcoidosis: n = 15, non-specific inflammation: n = 18, other inflammatory: n = 4, respectively). Whole-body static PET or PET/CT scan was performed 20 and 50 min after the IV injection of ¹¹C-MeAIB and ¹⁸F-FDG, respectively.

Results

¹¹C-MeAIB uptake of malignant and benign lesions was statistically different both in pulmonary nodules (p < 0.005) and in mediastinal lesions (p < 0.0005). In visual differential diagnosis, ¹¹C-MeAIB showed higher results (specificity: 73 %, accuracy: 81 %), compared to those in ¹⁸F-FDG (60, 73 %, respectively). In cases of sarcoidosis, ¹¹C-MeAIB showed higher specificity (80 %) with lower uptake (1.8 ± 0.7) in contrast to the lower specificity (60 %) with higher uptake of ¹⁸F-FDG (7.3 ± 4.5).

Conclusions

¹¹C-MeAIB PET/CT was useful in the differential diagnosis of pulmonary and mediastinal mass lesions found on CT. ¹¹C-MeAIB PET or PET/CT showed higher specificity than that of ¹⁸F-FDG PET/CT in differentiating between benign and malignant disease. Our data suggest that the combination of ¹⁸F-FDG and ¹¹C-MeAIB may improve the evaluation of chest lesions, when CT and ¹⁸F-FDG PET/CT are equivocal.     

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.     

Evaluation of intratumoural heterogeneity on 18F-FDG PET/CT for characterization of peripheral nerve sheath tumours in neurofibromatosis type 1

Purpose

The aim of the study was to evaluate the potential usefulness of intratumoural tracer uptake heterogeneity on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT as compared to a cut-off maximum standardized uptake value (SUV_max) for characterization of peripheral nerve sheath tumours (PNSTs) in neurofibromatosis type 1 (NF1).

Methods

Fifty patients suffering from NF1 were examined by ¹⁸F-FDG PET/CT. Intralesional tracer uptake was analysed qualitatively and semi-quantitatively by measuring the mean and maximum SUV. Uptake heterogeneity was graded qualitatively using a three-point scale and semi-quantitatively by calculating an SUV-based heterogeneity index (HI_SUV). Cohen’s κ was used to determine inter- and intra-rater agreement. Histopathological evaluation and clinical as well as radiological follow-up examinations served as the reference standards.

Results

A highly significant correlation between the degree of intratumoural uptake heterogeneity on ¹⁸F-FDG PET and malignant transformation of PNSTs was observed (p?<?0.0001). Semi-quantitative HI_SUV was significantly higher in malignant PNSTs (MPNSTs) than in benign tumours (p?=?0.0002). Both intralesional heterogeneity and SUV_max could be used to identify malignant tumours with a sensitivity of 100 %. Cohen’s κ was 0.86 for inter-rater agreement and 0.88 for intra-rater agreement on heterogeneity.

Conclusion

MPNSTs in patients with NF1 demonstrate considerable intratumoural uptake heterogeneity on ¹⁸F-FDG PET/CT. Assessment of tumour heterogeneity is highly reproducible. Both tumour heterogeneity and a cut-off SUV_max may be used to sensitively identify malignant PNSTs, but the specificity is higher for the latter. A combination of both methods leads to a non-significant improvement in diagnostic performance.     

Dual-time-point <Superscript>18</Superscript>F-FDG PET/CT in the diagnosis of solitary pulmonary lesions in a region with endemic granulomatous diseases

Objective

Granulomatous diseases (GDs) can be metabolically active and indistinguishable from lung cancer on ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) imaging. Evaluation of solitary pulmonary lesions remains a diagnostic challenge in regions with endemic GD. This study sought to determine the efficacy of dual-time-point (DTP) ¹⁸F-FDG PET/computed tomography (CT) imaging in diagnosing solitary pulmonary lesions from such regions.

Methods

A total of 50 patients with solitary pulmonary nodules or masses with confirmed histopathological diagnoses underwent DTP ¹⁸F-FDG PET/CT imaging at 1 and 3 h after tracer injection. The maximum standardized uptake value (SUV_max) on early and delayed scans (SUV_1h and SUV_3h, respectively) and retention index (RI) were calculated for each pulmonary lesion. Receiver operating characteristic analysis was performed to evaluate the discriminating validity of the parameters.

Results

There were 37 malignant and 13 benign solitary pulmonary lesions. Eight of the 13 (62 %) benign lesions were GDs. The sensitivity/specificity/accuracy of SUV_1h, SUV_3h and RI were 84/69/80 %, 84/85/84 %, and 81/54/74 %, respectively. SUV_3h had the best diagnostic performance, especially regarding specificity. The values of SUV_1h and SUV_3h were significantly different between malignant lesions and GD, while the RI values of malignant lesions and GD were both high (18.6 ± 19.5 and 18.7 ± 15.3 %, respectively; P = not significant).

Conclusion

SUV_3h appeared to improve the diagnostic specificity of ¹⁸F-FDG PET/CT in evaluating solitary pulmonary lesions from regions with endemic GD.

     

Anatomical and functional volume concordance between FDG PET,and T2 and diffusion-weighted MRI for cervical cancer: a hybrid PET/MR study

Purpose

To evaluate the concordance among ¹⁸F-FDG PET imaging, MR T2-weighted (T2-W) imaging and apparent diffusion coefficient (ADC) maps with diffusion-weighted (DW) imaging in cervical cancer using hybrid whole-body PET/MR.

Methods

This study prospectively included 35 patients with cervical cancer who underwent pretreatment ¹⁸F-FDG PET/MR imaging. ¹⁸F-FDG PET and MR images were fused using standard software. The percent of the maximum standardized uptake values (SUV_max) was used to contour tumours on PET images, and volumes were calculated automatically. Tumour volumes measured on T2-W and DW images were calculated with standard techniques of tumour area multiplied by the slice profile. Parametric statistics were used for data analysis.

Results

FDG PET tumour volumes calculated using SUV_max (14.30?±?4.70) and T2-W imaging volume (33.81?±?27.32 cm³) were similar (P?>?0.05) at 35 % and 40 % of SUV_max (32.91?±?18.90 cm³ and 27.56?±?17.19 cm³ respectively) and significantly correlated (P?<?0.001; r?=?0.735 and 0.766). The mean DW volume was 30.48?±?22.41 cm³. DW volumes were not significantly different from FDG PET volumes at either 35 % SUV_max or 40 % SUV_max or from T2-W imaging volumes (P?>?0.05). PET subvolumes with increasing SUV_max cut-off percentage showed an inverse change in mean ADC values on DW imaging (P?<?0.001, ANOVA).

Conclusion

Hybrid PET/MR showed strong volume concordance between FDG PET, and T2-W and DW imaging in cervical cancer. Cut-off at 35 % or 40 % of SUV_max is recommended for ¹⁸F-FDG PET/MR SUV-based tumour volume estimation. The linear tumour subvolume concordance between FDG PET and DW imaging demonstrates individual regional concordance of metabolic activity and cell density.     

Role of 18F-FDG PET/CT in the prediction of gastric cancer recurrence after curative surgical resection

Purpose

The study evaluated the role of preoperative ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in the prediction of recurrent gastric cancer after curative surgical resection.

Methods

A total of 271 patients with gastric cancer who underwent ¹⁸F-FDG PET/CT and subsequent curative surgical resection were enrolled. All patients underwent follow-up for cancer recurrence with a mean duration of 24?±?12?months. ¹⁸F-FDG PET/CT images were visually assessed and, in patients with positive ¹⁸F-FDG cancer uptake, the maximum standardized uptake value (SUV_max) of cancer lesions was measured. ¹⁸F-FDG PET/CT findings were tested as prognostic factors for cancer recurrence and compared with conventional prognostic factors. Furthermore, ¹⁸F-FDG PET/CT findings were assessed as prognostic factors according to histopathological subtypes.

Results

Of 271 patients, 47 (17?%) had a recurrent event. Positive ¹⁸F-FDG cancer uptake was shown in 149 patients (55?%). Tumour size, depth of invasion, presence of lymph node metastasis, positive ¹⁸F-FDG uptake and SUV_max were significantly associated with tumour recurrence in univariate analysis, while only depth of invasion, positive ¹⁸F-FDG uptake and SUV_max had significance in multivariate analysis. The 24-month recurrence-free survival rate was significantly higher in patients with negative ¹⁸F-FDG uptake (95?%) than in those with positive ¹⁸F-FDG uptake (74?%; p?18F-FDG uptake was a significant prognostic factor in patients with tubular adenocarcinoma (p?=?0.003) or poorly differentiated adenocarcinoma (p?=?0.0001). However, only marginal significance was shown in patients with signet-ring cell carcinoma and mucinous carcinoma (p?=?0.05).

Conclusion

¹⁸F-FDG uptake of gastric cancer is an independent and significant prognostic factor for tumour recurrence. ¹⁸F-FDG PET/CT could provide effective information on the prognosis after surgical resection of gastric cancer, especially in tubular adenocarcinoma and poorly differentiated adenocarcinoma.     

Prospective evaluation of solitary thyroid nodule on 18F-FDG PET/CT and high-resolution ultrasonography

Purpose

The utility of 18F-FDG PET/CT in the assessment of thyroid nodules is unclear as there are several conflicting reports on the usefulness of SUV as an indicator to distinguish benign from malignant thyroid lesions. This study incorporated an additional parameter, namely dual time point imaging, to determine the diagnostic accuracy of PET/CT imaging. The performance of 18F-FDG PET/CT was compared to that of high-resolution ultrasound which is routinely used for the evaluation of thyroid nodules.

Methods

Two hundred patients with incidentally detected solitary thyroid nodules were included in the study. Each patient underwent ultrasound and PET/CT evaluation within 7 days of each other, reported by an experienced radiologist and nuclear medicine specialist, respectively, in a blinded manner. The PET/CT criteria employed were maximum SUV (SUV_max) at 60 min and change in SUV_max at delayed (120 min) imaging. Final diagnosis was based on pathological evaluation and follow-up.

Results

Of the 200 patients, 26 had malignant and 174 had benign nodules. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of ultrasound were 80.8, 81.6, 39.6, 96.6 and 81.5%, respectively. Using SUV_max at 60 min as the diagnostic criterion, the above indices were 80.8, 84.5, 43.8, 96.7 and 84%, respectively, for PET/CT. The SUV_max of malignant thyroid lesions was significantly higher than benign lesions (16.2 ± 10.6 vs. 4.5 ± 3.1, respectively; p = 0.0001). Incorporation of percentage change in SUV_max at delayed imaging as the diagnostic criterion yielded a slightly improved sensitivity, specificity, PPV, NPV and accuracy of 84.6, 85.6, 46.8, 97.4 and 85.5%, respectively. There was a significant difference in percentage change in SUV_max between malignant and benign thyroid lesions (14.9 ± 11.4 vs. ?1.6 ± 13.7, respectively; p = 0.0001). However, there was no statistically significant difference (95% confidence interval) between the diagnostic performance of PET/CT and ultrasound.

Conclusions

Routine use of 18F-FDG PET/CT with SUV_max at 60 min as the sole diagnostic criterion does not appear to have a significant advantage over high-resolution ultrasound in the evaluation of thyroid nodules. Incorporation of dual time point imaging enhances image interpretation, and yields a higher diagnostic performance, yet it is not statistically significant. Bearing in mind the cost, limited availability and radiation exposure, routine use of 18F-FDG PET/CT for distinguishing benign from malignant thyroid nodules cannot be recommended.     

<Superscript>18</Superscript>F-FDG and <Superscript>18</Superscript>F-FLT PET/CT imaging in the characterization of mediastinal lymph nodes

Purpose

There is currently no single modality for accurate characterization of enlarged mediastinal lymph nodes into benign or malignant. Recently ¹⁸F-fluorothymidine (FLT) has been used as a proliferation marker. In this prospective study, we examined the role of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) and ¹⁸F-FLT PET/CT in categorizing mediastinal lymph nodes as benign or malignant.

Materials and methods

A total of 70 consecutive patients with mediastinal lymphadenopathy detected on computed tomography (CT) or chest radiograph underwent whole body ¹⁸F-FLT PET/CT and ¹⁸F-FDG PET/CT (within 1 week of each other). Lymph nodal tracer uptake was determined by calculation of standardized uptake value (SUV) with both the tracers. Results of PET/CT were compared with histopathology of the lymph nodes.

Results

Histopathology results showed thirty-seven patients with sarcoidosis, seven patients with tuberculosis, nine patients with non-small cell lung cancer, five patients with Hodgkin’s lymphoma and twelve patients with non-Hodgkin’s lymphoma. The mean FDG SUV_max of sarcoidosis, tuberculosis, Hodgkin’s and non-Hodgkin’s lymphoma was 12.7, 13.4, 8.2, and 8.8, respectively, and the mean FLT SUV_max was 6.0, 5.4, 4.4, and 3.8, respectively. It was not possible to characterize mediastinal lymphadenopathy as benign or malignant solely based on FDG SUV_max values (p > 0.05) or FLT SUV_max values (p > 0.05). There was no significant difference in FDG uptake (p > 0.9) or FLT uptake (p > 0.9) between sarcoidosis and tuberculosis. In lung cancer patients, the FDG SUV_max and FLT SUV_max of those lymph nodes with tumor infiltration on biopsy was 6.7 and 3.9, respectively, and those without nodal infiltration was 6.4 and 3.7, respectively, and both the tracers were not able to characterize the nodal status as malignant or benign (p > 0.05).

Conclusion

Though ¹⁸F-FLT PET/CT and ¹⁸F-FDG PET/CT reflect different aspects of biology, i.e., proliferation and metabolism, respectively, neither tracer could provide satisfactory categorization of benign and malignant lymph nodes. The results of this study clearly suggest that differentiation of mediastinal nodes into benign and malignant solely based on SUV_max values cannot be relied upon, especially in settings where tuberculosis and sarcoidosis are common.

     

Factors affecting intrapatient liver and mediastinal blood pool 18F-FDG standardized uptake value changes during ABVD chemotherapy in Hodgkin’s lymphoma

Purpose

The aim of our study was to assess the intrapatient variability of 2-deoxy-2-(¹⁸F)-fluoro-D-glucose (¹⁸F-FDG) uptake in the liver and in the mediastinum among patients with Hodgkin’s lymphoma (HL) treated with doxorubicin (Adriamycin), bleomycin, vinblastine and dacarbazine (ABVD) chemotherapy (CHT).

Methods

The study included 68 patients (30 men, 38 women; mean age 32?±?11 years) with biopsy-proven HL. According to Ann Arbor criteria, 6 were stage I, 34 were stage II, 12 were stage 3 and 16 were stage 4. All of them underwent a baseline (PET0) and an interim (PET2) ¹⁸F-FDG whole-body positron emission tomography (PET)/CT. All patients were treated after PET0 with two ABVD cycles for 2 months that ended 15?±?5 days prior to the PET2 examination. All patients were further evaluated 15?±?6 days after four additional ABVD cycles (PET6). None of the patients presented a serum glucose level higher than 107 mg/dl. The mean and maximum standardized uptake values (SUV) of the liver and mediastinum were calculated using the same standard protocol for PET0, PET2 and PET6, respectively. Data were examined by means of the Wilcoxon matched pairs test and linear regression analysis.

Results

The main results of our study were an increased liver SUV_mean in PET2 (1.76?±?0.35) as compared with that of PET0 (1.57?±?0.31; p?<?0.0001) and PET6 (1.69?±?0.28; p?=?0.0407). The same results were obtained when considering liver SUV_max in PET2 (3.13?±?0.67) as compared with that of PET0 (2.82?±?0.64; p?<?0.0001) and PET6 (2.96?±?0.52; p?=?0.0105). No significant differences were obtained when comparing mediastinum SUV_mean and SUV_max in PET0, PET2 and PET6 (p?>?0.05). Another finding is a relationship in PET0 between liver SUV_mean and SUV_max with the stage, which was lower in those patients with advanced disease (r ²?=?0.1456 and p?=?0.0013 for SUV_mean and r ²?=?0.1277 and p?=?0.0028 for SUV_max).

Conclusion

The results of our study suggest that liver ¹⁸F-FDG uptake is variable in patients with HL during the CHT treatment and the disease course and should be considered carefully when used to define the response to therapy in the interim PET in HL.     

Diagnostic accuracy of 68Ga-DOTANOC PET/CT imaging in pheochromocytoma

Purpose

The purpose of the present study was to evaluate the diagnostic accuracy of ⁶⁸Ga-DOTANOC positron emission tomography (PET)/CT in patients with suspicion of pheochromocytoma.

Methods

Data of 62 patients [age 34.3?±?16.1 years, 14 with multiple endocrine neoplasia type 2 (MEN2)] with clinical/biochemical suspicion of pheochromocytoma and suspicious adrenal lesion on contrast CT (n?=?70), who had undergone ⁶⁸Ga-DOTANOC PET/CT, were retrospectively analyzed. PET/CT images were analyzed visually as well as semiquantitatively, with measurement of maximum standardized uptake value (SUV_max), SUV_mean, SUV_max/SUV_liver, and SUV_mean/SUV_liver. Results of PET/CT were compared with ¹³¹I-metaiodobenzylguanidine (MIBG) imaging, which was available in 40 patients (45 lesions). Histopathology and/or imaging/clinical/biochemical follow-up (minimum 6 months) was used as reference standard.

Results

The sensitivity, specificity, and accuracy of ⁶⁸Ga-DOTANOC PET/CT was 90.4, 85, and 88.7 %, respectively, on patient-based analysis and 92, 85, and 90 %, respectively, on lesion-based analysis. ⁶⁸Ga-DOTANOC PET/CT showed 100 % accuracy in patients with MEN2 syndrome and malignant pheochromocytoma. On direct comparison, lesion-based accuracy of ⁶⁸Ga-DOTANOC PET/CT for pheochromocytoma was significantly higher than ¹³¹I-MIBG imaging (91.1 vs 66.6 %, p?=?0.035). SUV_max was higher for pheochromocytomas than other adrenal lesions (p?=?0.005), MEN2-associated vs sporadic pheochromocytoma (p?=?0.012), but no difference was seen between benign vs malignant pheochromocytoma (p?=?0.269).

Conclusion

⁶⁸Ga-DOTANOC PET/CT shows high diagnostic accuracy in patients with suspicion of pheochromocytoma and is superior to ¹³¹I-MIBG imaging for this purpose. Best results of ⁶⁸Ga-DOTANOC PET/CT are seen in patients with MEN2-associated and malignant pheochromocytoma.     

PET/CT studies of multiple myeloma using 18 F-FDG and 18 F-NaF: comparison of distribution patterns and tracers’ pharmacokinetics

Objective

The aim of this prospective study is to evaluate the combined use of fluorine-18 fluorodeoxyglucose (¹⁸?F-FDG) and fluorine-18 sodium fluoride (¹⁸?F-NaF) PET/CT in the skeletal assessment of patients with multiple myeloma (MM) and to compare the efficacy of these two PET tracers regarding detection of myeloma-indicative osseous lesions.

Patients and methods

The study includes 60 patients with multiple myeloma (MM) diagnosed according to standard criteria. All patients underwent dynamic (dPET/CT) scanning of the pelvis as well as whole body PET/CT studies with both tracers. The interval between the two exams was one day. Sites of focal increased ¹⁸?F-FDG uptake were considered as highly suspicious of myelomatous involvement. The lesions detected on the ¹⁸?F-NaF PET/CT scans were then correlated with those detected on ¹⁸?F-FDG PET/CT, which served as a reference. Moreover, the ¹⁸?F-FDG PET/CT results were also correlated with the low-dose CT findings. The evaluation of dPET/CT studies was based on qualitative evaluation, SUV calculation, and quantitative analysis based on a 2-tissue compartment model and a non-compartmental approach.

Results

Whole body ¹⁸?F-FDG PET/CT revealed approximately 343 focal lesions while ¹⁸?F-NaF PET/CT revealed 135 MM-indicative lesions (39 % correlation). CT demonstrated 150 lesions that correlated with those in ¹⁸?F-FDG PET/CT (44 % correlation). Six patients demonstrated a diffuse pattern of disease with ¹⁸?F-FDG, while 15 of them had a mixed (diffuse and focal) pattern of skeletal ¹⁸?F-FDG uptake. A high number of degenerative, traumatic and arthritic disease lesions were detected with ¹⁸?F-NaF PET/CT. In three patients with multiple focal ¹⁸?F-FDG-uptake, ¹⁸?F-NaF PET/CT failed to demonstrate any bone lesion. The dPET/CT scanning of the pelvic area with ¹⁸?F-FDG and ¹⁸?F-NaF revealed 77 and 24 MM-indicative lesions, respectively. Kinetic analysis of ¹⁸?F-FDG revealed the following mean values: SUV_aver?=?5.1, k₁?=?0.37 (1/min), k₃?=?0.10 (1/min), V_B?=?0.06, influx?=?0.04 (1/min), FD?=?1.28; the respective values for ¹⁸?F-NaF were SUV_average?=?10.7, k₁?=?0.25 (1/min), k₃?=?0.34 (1/min), V_B?=?0.02, influx?=?0.10 (1/min), FD?=?1.37. Apart from the correlation between V_B of ¹⁸?F-FDG and k₁ of ¹⁸?F-NaF (r?=?0.54), no other significant correlation was observed between the two tracers’ kinetic parameters. We found a significant correlation between FD and SUV_average (r?=?0.93), FD and SUV_max (r?=?0.80), FD and influx ( r?=?0.85), as well as between influx and SUV_average (r?=?0.74) for ¹⁸?F-FDG. In ¹⁸?F-NaF we observed the most significant correlations between FD and SUV_average (r?=?0.97), FD and SUV_max (r?=?0.87), and between influx and k₁ (r?=?0.72).

Conclusion

The combined use of ¹⁸?F-FDG PET/CT and ¹⁸?F-NaF PET/CT provides different molecular information regarding the biological processes that take place in a MM osseous lesion. ¹⁸?F-FDG PET/CT proved to be a more specific biomarker than ¹⁸?F-NaF PET/CT in multiple myeloma skeletal assessment.     

18F-FDG uptake in breast cancer correlates with immunohistochemically defined subtypes

Objectives

To determine whether a correlation exists between maximum standardized uptake value (SUV_max) on ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) and the subtypes of breast cancer.

Methods

This retrospective study involved 548 patients (mean age 51.6 years, range 21–81 years) with 552 index breast cancers (mean size 2.57 cm, range 1.0–14.5 cm). The correlation between ¹⁸F-FDG uptake in PET/CT, expressed as SUV_max, and immunohistochemically defined subtypes (luminal A, luminal B, human epidermal growth factor receptor 2 (HER2) positive and triple negative) was analyzed.

Results

The mean SUV_max value of the 552 tumours was 6.07?±?4.63 (range 0.9–32.8). The subtypes of the 552 tumours were 334 (60 %) luminal A, 66 (12 %) luminal B, 60 (11 %) HER2 positive and 92 (17 %) triple negative, for which the mean SUV_max values were 4.69?±?3.45, 6.51?±?4.18, 7.44?±?4.73 and 9.83?±?6.03, respectively. In a multivariate regression analysis, triple-negative and HER2-positive tumours had 1.67-fold (P?<?0.001) and 1.27-fold (P?=?0.009) higher SUV_max values, respectively, than luminal A tumours after adjustment for invasive tumour size, lymph node involvement status and histologic grade.

Conclusion

FDG uptake was independently associated with subtypes of invasive breast cancer. Triple-negative and HER2-positive breast cancers showed higher SUV_max values than luminal A tumours.

Key Points

? ¹⁸ F-FDG PET demonstrates increased tissue glucose metabolism, a hallmark of cancers. ? Immunohistochemically defined subtypes appear significantly associated with FDG uptake (expressed as SUV _max ). ? Triple-negative tumours had 1.67-fold higher SUV _max values than luminal A tumours. ? HER2-positive tumours had 1.27-fold higher SUV _max values than luminal A tumours.     

Detection of internal mammary lymph node metastasis with 18F-fluorodeoxyglucose positron emission tomography/computed tomography in patients with stage III breast cancer

Purpose

The present study assessed the positive predictive value (PPV) of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for the detection of internal mammary node (IMN) metastasis in patients with clinical stage III breast cancer.

Methods

Patients who were diagnosed with clinical stage III breast cancer and underwent pretreatment ¹⁸F-FDG PET/CT were retrospectively analyzed. The ¹⁸F-FDG PET/CT scans were prospectively reviewed by two board-certified nuclear medicine physicians in a blinded manner. The intensities of IMNs were graded into four categories (no activity and lower, similar, and higher activities than that of the mediastinal blood pool). IMNs were measured from the combined CT (largest diameter of the short axis). Histologic data of the IMNs were obtained by ultrasonography-guided fine-needle aspiration biopsy or surgical excision. The PPV was calculated for pathologically confirmed IMNs. Visual grade, maximum standardized uptake values (SUV_max), and sizes were analyzed according to the pathology results.

Results

There were 249 clinical stage III breast cancer patients (age 48.0?±?10.1 years, range 26–79 years) who had undergone initial ¹⁸F-FDG PET/CT prior to treatment. Excluding 33 cases of stage IV breast cancer, 62 of 216 patients had visible IMNs on ¹⁸F-FDG PET/CT, and histologic confirmation was obtained in 31 patients. There were 27 metastatic and four nonmetastatic nodes (PPV 87.1 %). Metastatic nodes mostly presented with visual grade 3 (83.9 %), and SUV_max and size were 3.5?±?4.3 and 5.6?±?2.0 mm, respectively.

Conclusion

¹⁸F-FDG PET/CT has a high PPV for IMN metastasis in clinical stage III breast cancer, indicating the possibility of metastasis in IMNs with FDG uptake similar to/lower than that of the blood pool or small-sized nodes.     

Assessment of aortitis by semiquantitative analysis of 180-min 18F-FDG PET/CT acquisition images

Purpose

The aim of this study was to evaluate the contribution of semiquantitative analysis of 180-min ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT images for the assessment of aortitis in cases of suspected large vessel vasculitis (LVV) and to establish a threshold index for application in the clinical setting.

Methods

This prospective study included 43 patients (mean age 67.5?±?12.9?years) with suspicion of LVV (25 with a final diagnosis of aortitis). ¹⁸F-FDG PET/CT scan was acquired 180 min after injection of 7 MBq/kg of ¹⁸F-FDG. A semiquantitative analysis was performed calculating the aortic wall maximum standardized uptake value (SUV_max) (T), the lumen SUV_max (B) and the target to background ratio (TBR). These results were also compared with those obtained in a control population.

Results

The mean aortic wall SUV_max was 2.00?±?0.62 for patients with aortitis and 1.45?±?0.31 for patients without aortitis (p?p?max (0.997 vs 0.871). The highest sensitivity and specificity was obtained for a TBR of 1.34 (sensitivity 100 %, specificity 94.4 %).

Conclusion

Semiquantitative analysis of PET/CT images acquired 180 min after ¹⁸F-FDG injection and the TBR index of 1.34 show very high accuracy and, therefore, are strongly recommended for the diagnosis of aortitis in the clinical setting.     

Quantitative assessment of atherosclerotic plaques on <Superscript>18</Superscript>F-FDG PET/MRI: comparison with a PET/CT hybrid system

Purpose

PET with ¹⁸F-FDG has the potential to assess vascular macrophage metabolism. ¹⁸F-FDG is most often used in combination with contrast-enhanced CT to localize increased metabolism to specific arterial lesions. Novel ¹⁸F-FDG PET/MRI hybrid imaging shows high potential for the combined evaluation of atherosclerotic plaques, due to the superior morphological conspicuity of plaque lesions. The purpose of this study was to evaluate the reliability and accuracy of ¹⁸F-FDG PET/MRI uptake quantification compared to PET/CT as a reference standard in patients with carotid atherosclerotic plaques.

Methods

The study group comprised 34 consecutive oncological patients with carotid plaques who underwent both PET/CT and PET/MRI with ¹⁸F-FDG on the same day. The presence of atherosclerotic plaques was confirmed by 3 T MRI scans. Maximum standardized uptake values (SUV_max) for carotid plaque lesions and the average SUV of the blood pool within the adjacent internal jugular vein were determined and target-to-blood ratios (TBRs, plaque to blood pool) were calculated.

Results

Atherosclerotic lesions with maximum colocalized focal FDG uptake were assessed in each patient. SUV_max values of carotid plaque lesions were significantly lower on PET/MRI than on PET/CT (2.3?±?0.6 vs. 3.1?±?0.6; P?<?0.01), but were significantly correlated between PET/CT and PET/MRI (Spearman’s r?=?0.67, P?<?0.01). In contrast, TBR_max values of plaque lesions were similar on PET/MRI and on PET/CT (2.2?±?0.3 vs. 2.2?±?0.3; P?=?0.4), and again were significantly correlated between PET/MRI and PET/CT (Spearman’s r?=?0.73, P?<?0.01). Considering the increasing trend in SUV_max and TBR_max values from early to delayed imaging time-points on PET/CT and PET/MRI, respectively, with continuous clearance of radioactivity from the blood, a slight underestimation of TBR_max values may also be expected with PET/MRI compared with PET/CT.

Conclusion

SUV_max and TBR_max values are widely accepted reference parameters for estimation of the radioactivity of atherosclerotic plaques on PET/CT. However, due to a systematic underestimation of SUV_max and TBR_max with PET/MRI, the optimal cut-off values indicating the presence of inflamed plaque tissue need to be newly defined for PET/MRI.

     

Correlation of FDG PET/CT Findings with Long-Term Growth and Clinical Course of Abdominal Aortic Aneurysm

Purpose

Herein, we report characteristics of ¹⁸F–fluorodeoxyglucose (FDG) uptake in abdominal aortic aneurysms (AAAs) during a long-term follow-up. In addition, we investigated the association between FDG uptake and the physician decision to perform an intervention.

Methods

We performed a retrospective review of 42 patients with AAAs who underwent FDG positron emission tomography (PET)/computed tomography (CT). The size of the AAA was measured in serial CT or PET/CT images. The long-term growth rate of AAAs was calculated by linear regression of the size change. Maximal SUV of the AAA (SUV_AAA) and mean SUV of the blood pool (SUV_Blood) were measured in PET/CT fusion images. To assess the FDG uptake of AAAs, the target-to-background ratio (TBR) was defined as the ratio of SUV_AAA to SUV_Blood. We compared FDG uptake of AAAs with the long-term growth rate of AAAs and clinical data.

Results

TBR was not significantly different between patients with and without significant growth (1.55 ± 0.20 vs. 1.57 ± 0.14; P = 0.5599). However, in patients with significant growth, TBR exhibited a significant positive correlation with the growth rate (r ²  = 0.2601, P = 0.0306). TBR also exhibited a significant difference between patients with and without intervention (P = 0.0228).

Conclusion

FDG uptake of AAA is associated with long-term growth of AAAs in a specified group that exhibits growth. FDG PET/CT may only be effective in predicting the long-term growth of AAAs in specific subgroups of patients. It is also suggested that FDG PET is potentially related to the clinical conditions of AAA patients who need surgical or interventional treatment.

     

Current generation time-of-flight <Superscript>18</Superscript>F-FDG PET/CT provides higher SUVs for normal adrenal glands,while maintaining an accurate characterization of benign and malignant glands

Objective

Modern PET/CT scanners have significantly improved detectors and fast time-of-flight (TOF) performance and this may improve clinical performance. The aim of this study was to analyze the impact of a current generation TOF PET/CT scanner on standardized uptake values (SUV), lesion-background contrast and characterization of the adrenal glands in patients with suspected lung cancer, in comparison with literature data and commonly used SUV cut-off levels.

Methods

We included 149 adrenal glands from 88 patients with suspected lung cancer, who underwent ¹⁸F-FDG PET/CT. We measured the SUV_max in the adrenal gland and compared this with liver SUV_mean to calculate the adrenal-to-liver ratio (AL ratio). Results were compared with literature derived with older scanners, with SUV_max values of 1.0 and 1.8 for normal glands [1, 2]. Final diagnosis was based on histological proof or follow-up imaging. We proposed cut-off values for optimal separation of benign from malignant glands.

Results

In 127 benign and 22 malignant adrenal glands, SUV_max values were 2.3 ± 0.7 (mean ± SD) and 7.8 ± 3.2 respectively (p < 0.01). Corresponding AL ratios were 1.0 ± 0.3 and 3.5 ± 1.4 respectively (p < 0.01). With a SUV_max cut-off value of 3.7, 96 % sensitivity and 96 % specificity was reached. An AL ratio cut-off value of 1.8 resulted in 91 % sensitivity and 97 % specificity. The ability of both SUV_max and AL ratio to separate benign from malignant glands was similar (AUC 0.989 vs. 0.993, p = 0.22).

Conclusions

Compared with literature based on the previous generation of PET scanners, current generation TOF ¹⁸F-FDG PET/CT imaging provides higher SUVs for benign adrenal glands, while it maintains a highly accurate distinction between benign and malignant glands. Clinical implementation of current generation TOF PET/CT requires not only the use of higher cut-off levels but also visual adaptation by PET readers.

     

Role of 68Ga-DOTATOC PET/CT in initial evaluation of patients with suspected bronchopulmonary carcinoid

Purpose

The objective of this study was to evaluate the role of ⁶⁸Ga-DOTATOC positron emission tomography (PET)/CT scan in patients with suspected pulmonary carcinoid tumour and to compare its results with ¹⁸F-fluorodeoxyglucose (FDG) PET/CT scan.

Methods

In this prospective study, 32 patients (age 34.22?±?12.03 years; 53.1 % female) with clinical suspicion of bronchopulmonary carcinoid were evaluated with ⁶⁸Ga-DOTATOC PET/CT and ¹⁸F-FDG PET/CT. The two imaging modalities were compared, considering the tissue diagnosis as the reference standard.

Results

Based on the reference standard 26 cases were carcinoid tumours [21 typical carcinoids (TC) and 5 atypical carcinoids (AC)] and 6 cases were non-carcinoid tumours. The sensitivity, specificity and accuracy of ⁶⁸Ga-DOTATOC PET/CT in the diagnosis of pulmonary carcinoid tumour were 96.15, 100 and 96.87 % respectively, whereas those of ¹⁸F-FDG PET/CT were 78.26, 11.1 and 59.37 % respectively. The maximum standardised uptake value (SUV_max) of TC on ⁶⁸Ga-DOTATOC PET/CT scan ranged from 3.58 to 55, while that of AC ranged from 1.1 to 32.5. ¹⁸F-FDG PET/CT was true-positive in all cases of AC and false-negative in eight cases of TC (sensitivity for TC 61.9 % and for AC 100 %).

Conclusion

⁶⁸Ga-DOTATOC PET/CT is a useful imaging investigation for the evaluation of pulmonary carcinoids. ¹⁸F-FDG PET/CT scan suffers from low sensitivity and specificity in differentiating the pulmonary carcinoids from other tumours.