Whole-body diffusion-weighted magnetic resonance imaging with apparent diffusion coefficient mapping for staging patients with diffuse large B-cell lymphoma

Objective

To design a whole-body MR protocol using exclusively diffusion-weighted imaging (DWI) with respiratory gating and to assess its value for lesion detection and staging in patients with diffuse large B-cell lymphoma (DLBCL), with integrated FDG PET/CT as the reference standard.

Methods

Fifteen patients underwent both whole-body DWI (b?=?50, 400, 800 s/mm²) and PET/CT for pretreatment staging. Lymph node and organ involvement were evaluated by qualitative and quantitative image analysis, including measurement of the mean apparent diffusion coefficient (ADC).

Results

A total of 296 lymph node regions in the 15 patients were analysed. Based on International Working Group size criteria alone, DWI findings matched PET/CT findings in 277 regions (94%) (kappa score?=?0.85, P?<?0.0001), yielding sensitivity and specificity for DWI lymph node involvement detection of 90% and 94%. Combining visual ADC analysis with size measurement increased DWI specificity to 100% with 81% sensitivity. For organ involvement, the two techniques agreed in all 20 recorded organs (100%). All involved organ lesions showed restricted diffusion. Ann Arbor stages agreed in 14 (93%) of the 15 patients.

Conclusion

Whole-body DWI with ADC analysis can potentially be used for lesion detection and staging in patients with DLBCL.     

18F-FDG PET/CT provides powerful prognostic stratification in the primary staging of large breast cancer when compared with conventional explorations

Purpose

The objective of this study was to assess the impact on management and the prognostic value of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT for initial staging of newly diagnosed large breast cancer (BC) when compared with conventional staging.

Methods

We prospectively included 142 patients with newly diagnosed BC and at least grade T2 tumour. All patients were evaluated with complete conventional imaging (CI) procedures (mammogram and/or breast ultrasound, bone scan, abdominal ultrasound and/or CT, X-rays and/or CT of the chest), followed by FDG PET/CT exploration, prior to treatment. The treatment plan based on CI staging was compared with that based on PET/CT findings. CI and PET/CT findings were confirmed by imaging and clinical follow-up and/or pathology when assessable. Progression-free survival (PFS) was analysed using the Cox proportional hazards regression model.

Results

According to CI staging, 79 patients (56 %) were stage II, 46 (32 %) stage III and 17 (12 %) stage IV (distant metastases). Of the patients, 30 (21 %) were upstaged by PET/CT, including 12 (8 %) from stage II or III to stage IV. On the other hand, 23 patients (16 %) were downstaged by PET/CT, including 4 (3 %) from stage IV to stage II or III. PET/CT had a high or medium impact on management planning for 18 patients (13 %). Median follow-up was 30 months (range 9–59 months); 37 patients (26 %) experienced recurrence or progression of disease during follow-up and 17 patients (12 %) died. The Cox model indicated that CI staging was significantly associated with PFS (p?=?0.01), but PET/CT staging provided stronger prognostic stratification (p?<?0.0001). Moreover, Cox regression multivariate analysis showed that only PET/CT staging remained associated with PFS (p?<?0.0001).

Conclusion

FDG PET/CT provides staging information that more accurately stratifies prognostic risk in newly diagnosed large BC when compared with conventional explorations alone.     

18F-FDG PET/CT imaging versus dynamic contrast-enhanced CT for staging and prognosis of inflammatory breast cancer

Purpose

Inflammatory breast cancer (IBC) is the most aggressive type of breast cancer with a poor prognosis. Locoregional staging is based on dynamic contrast-enhanced (DCE) CT or MRI. The aim of this study was to compare the performances of FDG PET/CT and DCE CT in locoregional staging of IBC and to assess their respective prognostic values.

Methods

The study group comprised 50 women (median age: 51?±?11 years) followed in our institution for IBC who underwent FDG PET/CT and DCE CT scans (median interval 5?±?9 days). CT enhancement parameters were net maximal enhancement, net early enhancement and perfusion.

Results

The PET/CT scans showed intense FDG uptake in all primary tumours. Concordance rate between PET/CT and DCE CT for breast tumour localization was 92 %. No significant correlation was found between SUVmax and CT enhancement parameters in primary tumours (p?>?0.6). PET/CT and DCE CT results were poorly correlated for skin infiltration (kappa?=?0.19). Ipsilateral foci of increased axillary FDG uptake were found in 47 patients (median SUV: 7.9?±?5.4), whereas enlarged axillary lymph nodes were observed on DCE CT in 43 patients. Results for axillary node involvement were fairly well correlated (kappa?=?0.55). Nineteen patients (38 %) were found to be metastatic on PET/CT scan with a significant shorter progression-free survival than patients without distant lesions (p?=?0.01). In the primary tumour, no statistically significant difference was observed between high and moderate tumour FDG uptake on survival, using an SUVmax cut-off of 5 (p?=?0.7 and 0.9), or between high and low tumour enhancement on DCE CT (p?>?0.8).

Conclusion

FDG PET/CT imaging provided additional information concerning locoregional involvement to that provided by DCE CT on and allowed detection of distant metastases in the same whole-body procedure. Tumour FDG uptake or CT enhancement parameters were not correlated and were not found to have any prognostic value.     

Whole-body FDG PET/CT is more accurate than conventional imaging for staging primary breast cancer patients

Purpose

This retrospective study aimed (1) to compare the diagnostic accuracy of whole-body FDG PET/CT for initial breast cancer staging with the accuracy of a conventional, multimodal imaging algorithm, and (2) to assess potential alteration in patient management based on the FDG PET/CT findings.

Methods

Patients with primary breast cancer (106 women, mean age 57?±?13?years) underwent whole-body FDG PET/CT and conventional imaging (X-ray mammography, MR mammography, chest plain radiography, bone scintigraphy and breast, axillary and liver ultrasonography). The diagnostic accuracies of FDG PET/CT and a conventional algorithm were compared. Diagnostic accuracy was assessed in terms of primary tumour detection rate, correct assessment of primary lesion focality, T stage and the detection rates for lymph node and distant metastases. Histopathology, imaging or clinical follow-up served as the standards of reference.

Results

FDG PET/CT was significantly more accurate for detecting axillary lymph node and distant metastases (p?=?0.0125 and p?Conclusion Full-dose, intravenous contrast-enhanced FDG PET/CT was more accurate than conventional imaging for initial breast cancer staging due to the higher detection rate of metastases and synchronous tumours, although the study had several limitations including a retrospective design, a possible selection bias and a relevant false-positive rate for the detection of axillary lymph node metastases. FDG PET/CT resulted in a change of treatment in a substantial proportion of patients.     

Use of diffusion-weighted imaging (DWI) in PET/MRI for head and neck cancer evaluation

Objective

The purpose of this study was to analyze whether diffusion-weighted imaging (DWI) adds significant information to positron emission tomography/magnetic resonance imaging (PET/MRI) on lesion detection and characterization in head and neck cancers.

Methods

Seventy patients with different head and neck cancers were enrolled in this prospective study. All patients underwent sequential contrast-enhanced (ce) PET/computed tomography (CT) and cePET/MRI using a tri-modality PET/CT-MR setup either for staging or re-staging. First, the DWI alone was evaluated, followed by the PET/MRI with conventional sequences, and in a third step, the PET/MRI with DWI was evaluated. McNemar’s test was used to evaluate differences in the accuracy of PET/MRI with and without DWI compared to the standard of reference.

Results

One hundred eighty-eight (188) lesions were found, and of those, 118 (62.8 %) were malignant and 70 (37.2 %) were benign. PET/MRI without DWI had a higher accuracy in detecting malignant lesions than DWI alone (86.8 % vs. 60.6 %, p?Conclusion The use of DWI as part of PET/MRI to evaluate head and neck cancers does not provide remarkable information. Thus, the use of DWI might not be needed in clinical PET/MRI protocols for the staging or restaging of head and neck cancers.     

Whole-body [18F]FDG PET/MRI vs. PET/CT in the assessment of bone lesions in oncological patients: initial results

Objectives

To compare [¹⁸?F]FDG PET/MRI with PET/CT for the assessment of bone lesions in oncologic patients.

Methods

This prospective study included 67 patients with solid tumours scheduled for PET/CT with [¹⁸?F]FDG who also underwent a whole-body PET/MRI scan. The datasets (PET/CT, PET/MRI) were rated by two readers regarding lesion conspicuity (four-point scale) and diagnostic confidence (five-point scale). Median scores were compared using the Wilcoxon test.

Results

Bone metastases were present in ten patients (15 %), and benign bone lesions in 15 patients (22 %). Bone metastases were predominantly localized in the pelvis (18 lesions, 38 %) and the spine (14 lesions, 29 %). Benign bone lesions were exclusively osteosclerotic and smaller than the metastases (mean size 6 mm vs. 23 mm). While PET/CT allowed identification of 45 of 48 bone metastases (94 %), PET/MRI allowed identification of all bone metastases (100 %). Conspicuity of metastases was high for both modalities with significantly better results using PET/MRI (p?<?0.05). Diagnostic confidence in lesion detection was high for both modalities without a significant difference. In benign lesions, conspicuity and diagnostic confidence were significantly higher with PET/CT (p?<?0.05).

Conclusions

[¹⁸?F]FDG PET/MRI shows high potential for the assessment of bone metastases by offering superior lesion conspicuity when compared to PET/CT. In hypersclerotic, benign bone lesions PET/CT still sets the reference.

Key Points

? PET/MRI and PET/CT are of equal value for the identification of disease-positive patients ? PET/MRI offers higher lesion conspicuity as well as diagnostic confidence ? PET/MRI is an attractive new alternative for the assessment of bone metastases     

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.     

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.     

Diagnostic and prognostic impact of 18F-FDG PET/CT in follicular lymphoma

Purpose

The aim of this study was to assess the usefulness of positron emission tomography/computed tomography in staging, prognosis evaluation and restaging of patients with follicular lymphoma.

Methods

A retrospective study was performed on 45 patients with untreated biopsy-proven follicular lymphoma who underwent ¹⁸F-fluorodeoxyglucose PET/CT (FDG PET/CT) and CT before and after chemoimmunotherapy induction treatment (rituximab combined with cyclophosphamide, doxorubicin, vincristine and prednisone).

Results

PET/CT detected more nodal (+51%) and extranodal (+89%) lesions than CT. PET/CT modified Ann Arbor staging in eight patients (18%). Five patients (11%) initially considered as being early stage (I/II) were eventually treated as advanced stage (III/IV). In this study, an initial PET/CT prognostic score was significantly more accurate than the Follicular Lymphoma International Prognostic Index score in identifying patients with poor prognosis (i.e. patients with incomplete therapeutic response or early relapse). The accuracy of PET/CT for therapeutic response assessment was higher than that of CT (0.97 vs 0.64), especially due to its ability to identify inactive residual masses. In addition, post-treatment PET/CT was able to predict patients’ outcomes. The median progression-free survival was 48 months in the PET/CT-negative group as compared with 17.2 months for the group with residual uptake (p?<?10^?4).

Conclusion

FDG PET/CT is useful for staging and assessing the prognosis and therapeutic response of patients with follicular lymphoma.     

18F-fluorodeoxyglucose positron emission tomography and computed tomography in anaplastic thyroid cancer

Purpose

Our aim was to evaluate in anaplastic thyroid carcinoma (ATC) patients the value of ¹⁸F-FDG PET/CT compared with total body computed tomography (CT) using intravenous contrast material for initial staging, prognostic assessment, therapeutic monitoring and follow-up.

Methods

Twenty consecutive ATC patients underwent PET/CT for initial staging. PET/CT was performed again during follow-up. The gold standard was progression on imaging follow-up (CT or PET/CT) or confirmation with another imaging modality.

Results

A total of 265 lesions in 63 organs were depicted in 18 patients. Thirty-five per cent of involved organs were demonstrated only with PET/CT and one involved organ only with CT. In three patients, the extent of disease was significantly changed with PET/CT that demonstrated unknown metastases. Initial treatment modalities were modified by PET/CT findings in 25% of cases. The volume of FDG uptake (≥300 ml) and the intensity of FDG uptake (SUV_max ≥18) were significant prognostic factors for survival. PET/CT permitted an earlier assessment of tumour response to treatment than CT in 4 of the 11 patients in whom both examinations were performed. After treatment with combined radiotherapy and chemotherapy, only the two patients with a negative control PET/CT had a confirmed complete remission at 14 and 38 months; all eight patients who had persistent FDG uptake during treatment had a clinical recurrence and died.

Conclusion

FDG PET/CT appears to be the reference imaging modality for ATC at initial staging and seems promising in the early evaluation of treatment response and follow-up.     

Incidental pituitary uptake on whole-body 18F-FDG PET/CT: a multicentre study

Purpose

The purpose of this study was to determine the incidence of incidental pituitary uptake on whole-body ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and to investigate its clinical significance.

Methods

The files of 40,967 patients who underwent whole-body FDG PET/CT were retrospectively reviewed. Quantification of pituitary metabolic activity was obtained by using the maximum standardized uptake value (SUV_max). Hormone assays and pituitary MRIs were performed to assess pituitary lesions.

Results

Focally increased pituitary FDG uptake on PET/CT was found in 30 of 40,967 patients, accounting for an incidence of 0.073%. The mean SUV_max of 30 patients was 8.9?±?6.6 (range: 3.2–32.6). Histological diagnosis was obtained in three patients and included two growth hormone-secreting adenomas and one non-functioning adenoma. Hormone assays were performed on serum samples from 11 patients, 2 of whom were shown to have hypersecretion of pituitary hormone. MRI was performed on 19 patients. Abnormal MRI findings suggesting a pituitary mass were found in 18 of 19 cases (94.7%). The mean SUV_max calculated without correction for partial volume effect for macroadenomas was significantly higher than the SUV_max for microadenomas (11.5?±?8.4 vs 4.8?±?1.3; p?<?0.05). There were no cases diagnosed with metastasis to the pituitary gland during clinical follow-up.

Conclusion

Incidental pituitary FDG uptake was a very rare finding. Cases with incidental pituitary FDG uptake were diagnosed primarily with clinically non-functioning adenomas, and there were also a few functioning adenomas. Further evaluations, including hormone assays and pituitary MRI, are warranted when pituitary uptake is found on FDG PET/CT.     

Direct comparison of [18F]FDG PET/CT with PET alone and with side-by-side PET and CT in patients with malignant melanoma

Purpose

The purpose of this retrospective, blinded study was to evaluate the additional value of [¹⁸F]FDG PET/CT in comparison with PET alone and with side-by-side PET and CT in patients with malignant melanoma (MM).

Methods

A total of 127 consecutive studies of patients with known MM referred for a whole-body PET/CT examination were included in this study. PET alone, side-by-side PET and CT and integrated PET/CT study were independently and separately interpreted without awareness of the clinical information. One score each was applied for certainty of lesion localisation and for certainty of lesion characterisation. Verification of the findings was subsequently performed using all available clinical, pathological (n?=?30) and follow-up information.

Results

The number of lesions with an uncertain localisation was significantly (p?p?p?=?0.057) compared versus PET alone. Respectively, PET, side-by-side PET and CT and PET/CT showed a sensitivity of 86%, 89% and 91%, a specificity of 94%, 94% and 94%, a positive predictive value of 96%, 96% and 96% and a negative predictive value of 80%, 83% and 87%.

Conclusion

Integrated PET/CT offers a significant benefit in lesion localisation and an improvement in lesion characterisation compared with PET alone or with side-by-side PET and CT. The benefit is not as great as that reported for other tumour entities, which may be due to the high avidity of MM for [¹⁸F]FDG.     

Protocol requirements and diagnostic value of PET/MR imaging for liver metastasis detection

Purpose

To compare the accuracy of PET/MR imaging with that of FDG PET/CT and to determine the MR sequences necessary for the detection of liver metastasis using a trimodality PET/CT/MR set-up.

Methods

Included in this single-centre IRB-approved study were 55 patients (22 women, age 61?±?11 years) with suspected liver metastases from gastrointestinal cancer. Imaging using a trimodality PET/CT/MR set-up (time-of-flight PET/CT and 3-T whole-body MR imager) comprised PET, low-dose CT, contrast-enhanced (CE) CT of the abdomen, and MR with T1-W/T2-W, diffusion-weighted (DWI), and dynamic CE imaging. Two readers evaluated the following image sets for liver metastasis: PET/CT (set A), PET/CECT (B), PET/MR including T1-W/T2-W (C), T1-W/T2-W with either DWI (D) or CE imaging (E), and a combination (F). The accuracy of each image set was determined by receiver-operating characteristic analysis using image set B as the standard of reference.

Results

Of 120 liver lesions in 21/55 patients (38 %), 79 (66 %) were considered malignant, and 63/79 (80 %) showed abnormal FDG uptake. Accuracies were 0.937 (95 % CI 89.5 – 97.9 %) for image set A, 1.00 (95 % CI 99.9 – 100.0 %) for set C, 0.998 (95 % CI 99.4 – 100.0 %) for set D, 0.997 (95 % CI 99.3 – 100.0 %) for set E, and 0.995 (95 % CI 99.0 – 100.0 %) for set F. Differences were significant for image sets D – F (P?<?0.05) when including lesions without abnormal FDG uptake. As shown by follow-up imaging after 50 – 177 days, the use of image sets D and both sets E and F led to the detection of metastases in one and three patients, respectively, and further metastases in the contralateral lobe in two patients negative on PET/CECT (P?=?0.06).

Conclusion

PET/MR imaging with T1-W/T2-W sequences results in similar diagnostic accuracy for the detection of liver metastases to PET/CECT. To significantly improve the characterization of liver lesions, we recommend the use of dynamic CE imaging sequences. PET/MR imaging has a diagnostic impact on clinical decision making.     

Value of a Dixon-based MR/PET attenuation correction sequence for the localization and evaluation of PET-positive lesions

Purpose

In this study, the potential contribution of Dixon-based MR imaging with a rapid low-resolution breath-hold sequence, which is a technique used for MR-based attenuation correction (AC) for MR/positron emission tomography (PET), was evaluated for anatomical correlation of PET-positive lesions on a 3T clinical scanner compared to low-dose CT. This technique is also used in a recently installed fully integrated whole-body MR/PET system.

Methods

Thirty-five patients routinely scheduled for oncological staging underwent ¹⁸F-fluorodeoxyglucose (FDG) PET/CT and a 2-point Dixon 3-D volumetric interpolated breath-hold examination (VIBE) T1-weighted MR sequence on the same day. Two PET data sets reconstructed using attenuation maps from low-dose CT (PET_{AC_CT}) or simulated MR-based segmentation (PET_{AC_MR}) were evaluated for focal PET-positive lesions. The certainty for the correlation with anatomical structures was judged in the low-dose CT and Dixon-based MRI on a 4-point scale (0?C3). In addition, the standardized uptake values (SUVs) for PET_{AC_CT} and PET_{AC_MR} were compared.

Results

Statistically, no significant difference could be found concerning anatomical localization for all 81 PET-positive lesions in low-dose CT compared to Dixon-based MR (mean 2.51?±?0.85 and 2.37?±?0.87, respectively; p?=?0.1909). CT tended to be superior for small lymph nodes, bone metastases and pulmonary nodules, while Dixon-based MR proved advantageous for soft tissue pathologies like head/neck tumours and liver metastases. For the PET_{AC_CT}- and PET_{AC_MR}-based SUVs (mean 6.36?±?4.47 and 6.31?±?4.52, respectively) a nearly complete concordance with a highly significant correlation was found (r?=?0.9975, p?Conclusion Dixon-based MR imaging for MR AC allows for anatomical allocation of PET-positive lesions similar to low-dose CT in conventional PET/CT. Thus, this approach appears to be useful for future MR/PET for body regions not fully covered by diagnostic MRI due to potential time constraints.     

Diffusion-weighted MRI of lymphoma: prognostic utility and implications for PET/MRI?

Purpose

With the recent introduction of PET/MRI, we investigated whether diffusion-weighted imaging (DWI) can complement PET for predicting local treatment response in Hodgkin lymphoma.

Methods

This retrospective study included 39 patients selected from a hospital database with a histological diagnosis of Hodgkin lymphoma undergoing whole-body MRI (supplemented by DWI) and PET/CT before and after two cycles of vincristine, etoposide, prednisolone and doxorubicin (OEPA). The pretreatment volume, MRI apparent diffusion coefficient (ADC) and PET maximum standardized uptake value (SUV_max) of the largest nodal mass were determined quantitatively for evaluation of the local response following two cycles of OEPA. Quantitative pretreatment imaging biomarkers (disease volume, ADC, SUV_max) were compared between sites with an adequate and those with an inadequate response using Fisher’s exact test and Mann Whitney statistics. Multivariate models predictive of an inadequate response based on demographic/clinical features, pretreatment disease volume and SUV_max without (model 1) and with (model 2) the addition of ADC were derived and crossvalidated. The ROC area under curve (AUC) was calculated for both models using the full dataset (training) and the crossvalidation (test) data.

Results

Sites with an adequate response had a significantly lower median pretreatment ADC (1.0?×?10^?3mm²s^?1) than those with an inadequate response (1.26?×?10^?3mm²s^?1; p?<?0.01). There were no significant differences in patient demographic/clinical parameters, pretreatment SUV_max or pretreatment nodal volume between sites with inadequate and adequate response. The ROC-AUCs for prediction of an inadequate response for the training and test data for model 1 were 0.90 and 0.53, and for model 2 were 0.84 and 0.71, respectively.

Conclusion

DWI complements PET for prediction of site-specific interim response to chemotherapy.     

Whole-body MR-DWIBS vs. [18F]-FDG-PET/CT in the study of malignant tumors: a retrospective study

Purpose

Our aim was to assess the overall diagnostic accuracy of magnetic resonance diffusion-weighted whole-body imaging with background signal suppression (MR-DWIBS) compared with ([¹⁸F]-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT), considered the reference standard of whole-body tumour imaging modalities, in a series of consecutive patients with malignant tumour.

Materials and methods

Thirty-eight patients diagnosed with a malignant tumour over a 4-month period were enrolled in this retrospective, observational study. PET/CT and MR-DWIBS images were reviewed in double-blind manner by a nuclear medicine physician and radiologists with 4 years experience. Lesion size, standard uptake value (SUV) and apparent diffusion coefficient (ADC) were measured and calculated for each lesion.

Results

The qualitative analysis of MR-DWIBS and [¹⁸F]-FDG-PET/CT showed that two patients were negative at both techniques. MR-DWIBS was positive in 36 patients, 34 of whom were positive and two negative at [¹⁸F]-FDG-PET/CT, respectively. Two hundred and fifty-five lesions were identified by MR-DWIBS and 184 by [¹⁸F]-FDG-PET/CT, which was a significative discordance. Correlation between SUV and ADC of lesions positive at both techniques was not statistically significant. The mean difference between lesion size in [¹⁸F]-FDG-PET/CT and MR-DWIBS was not statistically significant. No correlation was found between glucose metabolism and water motion.

Conclusions

MR-DWIBS may be used to evaluate localisation of parenchymal neoplasms but is less efficacious in characterising lymph-node and skeletal lesions. [¹⁸F]-FDG-PET/CT remains the best whole-body technique to identify lymph-node and skeletal lesions, but its limitation is identifying tumours with low glucose metabolism as in mucinous neoplasms. MR-DWIBS evaluation must be integrated with morphological images to increase MR diagnostic accuracy.     

Evaluation of Wegener’s granulomatosis using 18F-fluorodeoxyglucose positron emission tomography/computed tomography

Objective

Wegener’s granulomatosis (WG) is a relatively rare disease characterized by granulomatous necrotizing vasculitis that primarily involves small- and medium-sized vessels. Systemic findings observed on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) have not been well reported. The purpose of this study was to evaluate the FDG PET/CT imaging in the diagnosis and follow-up of patients with WG.

Materials and methods

Thirteen FDG PET/CT images obtained for 8 patients (2 men and 6 women) with WG were retrospectively analyzed. Of these, 6 were performed for diagnosis, 2 for restaging and follow-up, and 5 for assessment of treatment efficacy. Maximum standardized uptake values (max SUVs) and visual analyses were used to interpret the FDG PET/CT images. In addition, nonenhanced CT findings obtained during FDG PET/CT were described.

Results

WG lesions of the upper respiratory tract and lung were more clearly detected by FDG PET/CT fusion imaging than by nonenhanced CT alone, and all of the active lesions showed decreased FDG uptake after treatment. In addition, FDG PET/CT can provide complementary information to indicate biopsy site based on FDG uptakes.

Conclusions

FDG PET/CT is a feasible modality for evaluating lesion activities, therapeutic monitoring, and follow-up of WG. Furthermore, biopsy sites of WG lesions may be determined by FDG PET/CT.     

Whole body MRI with qualitative and quantitative analysis of DWI for assessment of bone marrow involvement in lymphoma

Aim

Our study aimed to investigate the role of qualitative and quantitative whole body MRI with DWI for assessment of bone marrow involvement (BMI) in newly diagnosed lymphoma using FDG PET–CT and bone marrow biopsy (BMB) as reference standard.

Materials and methods

We retrospectively evaluated 56 patients with newly diagnosed lymphoma (21 Hodgkin’s lymphoma and 35 non-Hodgkin’s lymphoma) who underwent random unilateral BMB, FDG PET–CT and Wb-MRI-DWI for initial staging. In a patient-based analysis, results of Wb-MRI-DWI were compared with FDG PET–CT and BMB. For quantitative analysis, mean ADC values of posterior iliac crest were correlated with BMI and bone marrow cellularity.

Results

WB-MR-DWI obtained excellent concordance with FDG PET–CT both in HL (k = 1.000; 95% CI 1.000–1.000) and in DLBCL (k = 1.000; 95% CI 1.000–1.000). In other NHL, WB-MRI-DWI obtained a good correlation with BMB (k = 0.611; 95% CI 0.295–0.927) while FDG PET–CT had poor concordance (k = 0.067; 95% CI 0.372–0.505). WB-MR-DWI has no false negative errors but 4 false positive results consisting in focal lesions consensually reported by FDG PET–CT and resolved after therapy. No significant correlation between ADC mean value and BMI was found (p = 0.0586).

Conclusion

Our data suggest that Wb-MRI-DWI is a valid technique for BMI assessment in lymphoma patients, thanks to its excellent concordance with FDG PET–CT and good concordance with BMB (superior than FDG PET–CT). If further investigations will confirm our results on larger patient groups, it could become a useful tool in the clinical workup.

     

PET/CT for staging and follow-up of pediatric nasopharyngeal carcinoma

Purpose

While FDG PET/CT for the evaluation of nasopharyngeal carcinoma (NPC) in adult patients has documented advantages and disadvantages compared with conventional imaging, to our knowledge, no studies of FDG PET/CT for the evaluation of NPC in pediatric patients have been performed. In this investigation, we studied the utility of FDG PET/CT in children with NPC.

Methods

The study group comprised 18 children with biopsy-proven NPC who underwent FDG PET/CT and MRI (total 38 pairs of images). All baseline and follow-up FDG PET/CT and MRI studies were independently reviewed for restaging of disease.

Results

The concordance between FDG PET/CT and MRI in T, N, and overall staging was 29%, 64%, and 43%, respectively. Compared with MRI, FDG PET/CT yielded lower T and overall staging and showed less cervical and retropharyngeal lymphadenopathy. The concordance between follow-up FDG PET/CT and MRI was 79% overall and 100% 9?months after therapy. In patients who achieved complete remission, FDG PET/CT showed disease clearance 3–6?months earlier than MRI. There were no false-positive or false-negative FDG PET/CT scans during follow-up.

Conclusion

FDG PET/CT may underestimate tumor extent and regional lymphadenopathy compared with MRI at the time of diagnosis, but it helps to detect metastases and clarify ambiguous findings. FDG PET/CT is sensitive and specific for follow-up and enables earlier determination of disease remission. FDG PET/CT is a valuable imaging modality for the evaluation and monitoring of NPC in pediatric patients.     

18F-FDG PET as a single imaging modality in pediatric neuroblastoma: comparison with abdomen CT and bone scintigraphy

Objective

The purpose of this study was to evaluate the diagnostic performance of ¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) as a single imaging agent in neuroblastoma in comparison with other imaging modalities.

Methods

A total of 30 patients with pathologically proven neuroblastoma who underwent FDG PET for staging were enrolled. Diagnostic performance of FDG PET and abdomen CT was compared in detecting soft tissue lesions. FDG PET and bone scintigraphy (BS) were compared in bone metastases. Maximal standardized uptake value (SUVmax) of primary or recurrent lesions was calculated for quantitative analysis.

Results

Tumor FDG uptake was detected in 29 of 30 patients with primary neuroblastoma. On initial FDG PET, SUVmax of primary lesions were lower in early stage (I–II) than in late stage (III–IV) (3.03 vs. 5.45, respectively, p = 0.019). FDG PET was superior to CT scan in detecting distant lymph nodes (23 vs. 18 from 23 lymph nodes). FDG PET showed higher accuracy to identify bone metastases than BS both on patient-based analyses (100 vs. 94.4 % in sensitivity, 100 vs. 77.8 % in specificity), and on lesion-based analyses (FDG PET: 203 lesions, BS: 86 lesions). Sensitivity and specificity of FDG PET to detect recurrence were 87.5 % and 93.8, respectively.

Conclusion

FDG PET was superior to CT in detecting distant LN metastasis and to BS in detecting skeletal metastasis in neuroblastoma. BS might be eliminated in the evaluation of neuroblastoma when FDG PET is performed.