Gadoxetate-enhanced versus diffusion-weighted MRI for fused Ga-68-DOTANOC PET/MRI in patients with neuroendocrine tumours of the upper abdomen

Objectives

To compare fused gadoxetate-enhanced Ga-68-DOTANOC PET/MRI and Ga-68-DOTANOC PET/DWI (diffusion-weighted imaging) for the assessment of abdominal neuroendocrine tumours (NETs).

Methods

Eighteen patients with suspected or histologically proven NETs of the abdomen were enrolled in this retrospective study. All patients underwent Ga-68-DOTANOC PET/CT for a primary search, staging, or restaging, and received an additional MRI, including dynamic gadoxetate-enhanced T1-weighted sequences and DWI (b-values 50, 300 and 600). Co-registered gadoxetate-enhanced PET/MRI and PET/DWI were separately analysed for NET lesions by a nuclear medicine physician and a radiologist in consensus. Sensitivity and specificity were calculated on a per-region, per-organ and per-patient basis.

Results

Eighty-seven out of 684 anatomical regions, and 23 out of 270 organs, were NET-positive in 14 out of 18 patients. Region-based sensitivities and specificities were 97.7 % and 99.7 % for gadoxetate-enhanced PET/MRI and 98.9 % and 99.7 % for PET/DWI. Organ-based sensitivities and specificities were 91.3 % and 99.6 % for gadoxetate-enhanced PET/MRI and 95.7 % and 99.6 % for PET/DWI. Finally, patient-based sensitivities and specificities were 100 % and 100 % for gadoxetate-enhanced PET/MRI and 100 % and 75 % for PET/DWI. Sensitivities and specificities of the two methods did not differ significantly.

Conclusions

Gadoxetate-enhanced Ga-68-DOTANOC PET/MRI and Ga-68-DOTANOC PET/DWI are equally useful for the assessment of abdominal NETs.

Key Points

? Positron emission tomography and magnetic resonance imaging can both assess neuroendocrine tumours. ? Fusion of PET/MR imaging provides helpful information. ? Gadoxetate-enhanced Ga-68-DOTANOC PET/MRI and Ga-68-DOTANOC PET/DWI assess neuroendocrine tumours equally well. ? PET/DWI is inherently simpler than gadoxetate-enhanced PET/MRI. ? Only benign hepatic lesions pose a potential diagnostic dilemma for PET/DWI.     

Comparison of <Superscript>18</Superscript>F–FDG PET/MRI and MRI alone for whole-body staging and potential impact on therapeutic management of women with suspected recurrent pelvic cancer: a follow-up study

Purpose

To evaluate the diagnostic performance of ¹⁸F–FDG PET/MRI for whole-body staging and potential changes in therapeutic management of women with suspected recurrent pelvic cancer in comparison with MRI alone.

Methods

Seventy-one consecutive women (54?±?13 years, range: 25–80 years) with suspected recurrence of cervical (32), ovarian (26), endometrial (7), vulvar (4), and vaginal (2) cancer underwent PET/MRI including a diagnostic contrast-enhanced MRI protocol. PET/MRI and MRI datasets were separately evaluated regarding lesion count, localization, categorization (benign/malignant), and diagnostic confidence (3-point scale; 1–3) by two physicians. The reference standard was based on histopathology results and follow-up imaging. Diagnostic accuracy and proportions of malignant and benign lesions rated correctly were retrospectively compared using McNemar’s chi² test. Differences in diagnostic confidence were assessed by Wilcoxon test.

Results

Fifty-five patients showed cancer recurrence. PET/MRI correctly identified more patients with cancer recurrence than MRI alone (100% vs. 83.6%, p?<?0.01). In contrast to PET/MRI, MRI alone missed 4/15 patients with pelvic recurrence and miscategorized 8/40 patients with distant metastases as having local recurrence only. Based on the reference standard, 241 lesions were detected in the study cohort (181 malignant, 60 benign). While PET/MRI provided correct identification of 181/181 (100%) malignant lesions, MRI alone correctly identified 135/181 (74.6%) malignant lesions, which was significantly less compared to PET/MRI (p?<?0.001). PET/MRI offered superior diagnostic accuracy (99.2% vs. 79.3%, p?<?0.001) and diagnostic confidence in the categorization of malignant lesions compared with MRI alone (2.7?±?0.5 vs. 2.4?±?0.7, p?<?0.001).

Conclusion

PET/MRI demonstrates excellent diagnostic performance and outperforms MRI alone for whole-body staging of women with suspected recurrent pelvic cancer, indicating potential changes in therapy management based on evaluation of local recurrence and distant metastatic spread.

     

Diagnostic value of diffusion-weighted magnetic resonance imaging (DWI) compared to FDG PET/CT for whole-body breast cancer staging

Purpose

The aim of the study was to prospectively compare the diagnostic value of whole-body diffusion-weighted imaging (DWI) and FDG PET/CT for breast cancer (BC) staging.

Methods

Twenty BC patients underwent whole-body FDG PET/CT and 1.5-T DWI. Lesions with qualitatively elevated signal intensity on DW images (b?=?800 s/mm²) were rated as suspicious for tumour and mapped to individual lesions and different compartments (overall 552 lesions). The apparent diffusion coefficient (ADC) value was determined for quantitative evaluation. Histopathology, MRI findings, bone scan findings, concordant findings between FDG PET/CT and DWI, CT follow-up scans and plausibility served as the standards of reference defining malignancy.

Results

According to the standards of reference, breasts harboured malignancy in 11, regional lymph nodes in 4, M1 lymph nodes in 3, bone in 7, lung in 2, liver in 3 and other tissues in 3 patients. On a compartment basis, the sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) for the detection of malignancies were 94, 99, 98, 97 and 98% for FDG PET/CT and 91, 72, 76, 50 and 96% for DWI, respectively. Of the lesions seen on DWI only, 348 (82%) turned out to be false-positive compared to 23 (11%) on FDG PET/CT. The average lesion ADC was 820?±?300 with true-positive lesions having 929?±?252 vs 713?±?305 in false-positive lesions (p?<?0.0001).

Conclusion

Based on these initial data DWI seems to be a sensitive but unspecific modality for the detection of locoregional or metastatic BC disease. There was no possibility to quantitatively distinguish lesions using ADC. DWI alone may not be recommended as a whole-body staging alternative to FDG PET(/CT). Further studies are necessary addressing the question of whether full-body MRI including DWI may become an alternative to FDG PET/CT for whole-body breast cancer staging.     

The usefulness of 18F-FDG PET/MRI fusion image in diagnosing pancreatic tumor: comparison with 18F-FDG PET/CT

Purpose

This study aimed at demonstrating the feasibility of retrospectively fused ¹⁸F FDG-PET and MRI (PET/MRI fusion image) in diagnosing pancreatic tumor, in particular differentiating malignant tumor from benign lesions. In addition, we evaluated additional findings characterizing pancreatic lesions by FDG-PET/MRI fusion image.

Methods

We analyzed retrospectively 119 patients: 96 cancers and 23 benign lesions. FDG-PET/MRI fusion images (PET/T1 WI or PET/T2WI) were made by dedicated software using 1.5 Tesla (T) MRI image and FDG-PET images. These images were interpreted by two well-trained radiologists without knowledge of clinical information and compared with FDG-PET/CT images. We compared the differential diagnostic capability between PET/CT and FDG-PET/MRI fusion image. In addition, we evaluated additional findings such as tumor structure and tumor invasion.

Results

FDG-PET/MRI fusion image significantly improved accuracy compared with that of PET/CT (96.6 vs. 86.6 %). As additional finding, dilatation of main pancreatic duct was noted in 65.9 % of solid types and in 22.6 % of cystic types, on PET/MRI-T2 fusion image. Similarly, encasement of adjacent vessels was noted in 43.1 % of solid types and in 6.5 % of cystic types. Particularly in cystic types, intra-tumor structures such as mural nodule (35.4 %) or intra-cystic septum (74.2 %) were detected additionally. Besides, PET/MRI-T2 fusion image could detect extra benign cystic lesions (9.1 % in solid type and 9.7 % in cystic type) that were not noted by PET/CT.

Conclusions

In diagnosing pancreatic lesions, FDG-PET/MRI fusion image was useful in differentiating pancreatic cancer from benign lesions. Furthermore, it was helpful in evaluating relationship between lesions and surrounding tissues as well as in detecting extra benign cysts.     

Detection and quantification of focal uptake in head and neck tumours: 18F-FDG PET/MR versus PET/CT

Purpose

Our objectives were to assess the quality of PET images and coregistered anatomic images obtained with PET/MR, to evaluate the detection of focal uptake and SUV, and to compare these findings with those of PET/CT in patients with head and neck tumours.

Methods

The study group comprised 32 consecutive patients with malignant head and neck tumours who underwent whole-body ¹⁸F-FDG PET/MR and PET/CT. PET images were reconstructed using the attenuation correction sequence for PET/MR and CT for PET/CT. Two experienced observers evaluated the anonymized data. They evaluated image and fusion quality, lesion conspicuity, anatomic location, number and size of categorized (benign versus assumed malignant) lesions with focal uptake. Region of interest (ROI) analysis was performed to determine SUVs of lesions and organs for both modalities. Statistical analysis considered data clustering due to multiple lesions per patient.

Results

PET/MR coregistration and image fusion was feasible in all patients. The analysis included 66 malignant lesions (tumours, metastatic lymph nodes and distant metastases), 136 benign lesions and 470 organ ROIs. There was no statistically significant difference between PET/MR and PET/CT regarding rating scores for image quality, fusion quality, lesion conspicuity or anatomic location, number of detected lesions and number of patients with and without malignant lesions. A high correlation was observed for SUV_mean and SUV_max measured on PET/MR and PET/CT for malignant lesions, benign lesions and organs (ρ?=?0.787 to 0.877, p?<?0.001). SUV_mean and SUV_max measured on PET/MR were significantly lower than on PET/CT for malignant tumours, metastatic neck nodes, benign lesions, bone marrow, and liver (p?<?0.05). The main factor affecting the difference between SUVs in malignant lesions was tumour size (p?<?0.01).

Conclusion

In patients with head and neck tumours, PET/MR showed equivalent performance to PET/CT in terms of qualitative results. Comparison of SUVs revealed an excellent correlation for measurements on both modalities, but underestimation of SUVs measured on PET/MR as compared to PET/CT.     

The diagnostic value of 18F-FDG PET and MRI in paediatric histiocytosis

Purpose

To analyse the diagnostic value of ¹⁸F-FDG PET and MRI for the evaluation of active lesions in paediatric Langerhans cell histiocytosis.

Methods

We compared 21 ¹⁸F-FDG PET scans with 21 MRI scans (mean time interval 17 days) in 15 patients (11 male, 4 female, age range 4 months to 19 years) with biopsy-proven histiocytosis. Primary criteria for the lesion-based analysis were signs of vital histiocyte infiltrates (bone marrow oedema and contrast enhancement for MRI; SUV greater than the mean SUV of the right liver lobe for PET). PET and MR images were analysed separately and side-by-side. The results were validated by biopsy or follow-up scans after more than 6 months.

Results

Of 53 lesions evaluated, 13 were confirmed by histology and 40 on follow-up investigations. The sensitivity and specificity of PET were 67 % and 76 % and of MRI were 81 % and 47 %, respectively. MRI showed seven false-positive bone lesions after successful chemotherapy. PET showed five false-negative small bone lesions, one false-negative lesion of the skull and three false-negative findings for intracerebral involvement. PET showed one false-positive lesion in the lymphoid tissue of the head and neck region and two false-positive bone lesions after treatment. Combined PET/MR analysis decreased the number of false-negative findings on primary staging, whereas no advantage over PET alone was seen in terms of false-positive or false-negative results on follow-up.

Conclusion

Our retrospective analysis suggests a pivotal role of ¹⁸F-FDG PET in lesion follow-up due to a lower number of false-positive findings after chemotherapy. MRI showed a higher sensitivity and is indispensable for primary staging, evaluation of brain involvement and biopsy planning. Combined MRI/PET analysis improved sensitivity by decreasing the false-negative rate during primary staging indicating a future role of simultaneous whole-body PET/MRI for primary investigation of paediatric histiocytosis.     

The role of diffusion-weighted MR imaging for differentiating benign from malignant bile duct strictures

Objectives

To assess the added value of diffusion-weighted imaging (DWI) to conventional magnetic resonance imaging (MRI) for differentiating benign from malignant bile duct strictures.

Methods

Twenty-seven patients with a benign stricture and 42 patients with a malignant stricture who had undergone gadoxetic acid-enhanced MRI with DWI were enrolled. Qualitative (signal intensity, dynamic enhancement pattern) and quantitative (wall thickness and length) analyses were performed. Two observers independently reviewed a set of conventional MRI and a combined set of conventional MRI and DWI, and receiver operating characteristic (ROC) curve analysis was assessed.

Results

Benign strictures showed isointensity (18.5–70.4 %) and a similar enhancement pattern (22.2 %) to that of normal bile duct more frequently than malignant strictures (0–40.5 % and 0 %) on conventional MRI (P?<?0.05). Malignant strictures (90.5–92.9 %) showed hypervascularity on arterial and portal venous phase images more frequently than benign strictures (37.0–70.4 %) (P?<?0.01) On DWI, all malignant strictures showed hyperintensity compared with benign cases (70.4 %) (P?<?0.001). Malignant strictures were significantly thicker and longer than benign strictures (P?<?0.001). The diagnostic performance of both observers improved significantly after additional review of DWI.

Conclusions

Adding DWI to conventional MRI is more helpful for differentiating benign from malignant bile duct strictures than conventional MRI alone.

Key points

? Accurate diagnosis and exclusion of benign strictures of bile duct are important. ? Diffusion-weighted MRI helps to distinguish benign from malignant bile duct strictures. ? DWI plus conventional MRI provides superior diagnostic accuracy to conventional MRI alone.     

Initial clinical results of simultaneous 18F-FDG PET/MRI in comparison to 18F-FDG PET/CT in patients with head and neck cancer

Purpose

The aim of this study was to evaluate the diagnostic capability of simultaneous ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/MRI compared to ¹⁸F-FDG PET/CT as well as their single components in head and neck cancer patients.

Methods

In a prospective study 17 patients underwent ¹⁸F-FDG PET/CT for staging or follow-up and an additional ¹⁸F-FDG PET/MRI scan with whole-body imaging and dedicated examination of the neck. MRI, CT and PET images as well as PET/MRI and PET/CT examinations were evaluated independently and in a blinded fashion by two reader groups. Results were compared with the reference standard (final diagnosis determined in consensus using all available data including histology and follow-up). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated.

Results

A total of 23 malignant tumours were found with the reference standard. PET/CT showed a sensitivity of 82.7 %, a specificity of 87.3 %, a PPV of 73.2 % and a NPV of 92.4 %. Corresponding values for PET/MRI were 80.5, 88.2, 75.6 and 92.5 %. No statistically significant difference in diagnostic capability could be found between PET/CT and PET/MRI. Evaluation of the PET part from PET/CT revealed highest sensitivity of 95.7 %, and MRI showed best specificity of 96.4 %. There was a high inter-rater agreement in all modalities (Cohen’s kappa 0.61–0.82).

Conclusion

PET/MRI of patients with head and neck cancer yielded good diagnostic capability, similar to PET/CT. Further studies on larger cohorts to prove these first results seem justified.     

Limitation of 2-deoxy-2-[F-18]fluoro-d-glucose positron emission tomography (FDG-PET) to detect early synchronous primary cancers in patients with untreated head and neck squamous cell cancer

Objective

Patients with head and neck squamous cell carcinoma (HNSCC) often develop synchronous multiple primary cancers. It is important to detect second primary cancer in HNSCC patients, because it influences treatment selection of primary cancer. The aim of this study was to evaluate the utility of 2-deoxy-2-[F-18]fluoro-d-glucose (FDG)-positron emission tomography (PET) for detecting synchronous primary cancers at the initial staging of patients with HNSCC.

Methods

Three hundred and forty-seven patients with untreated HNSCC underwent FDG-PET with or without computed tomography fusion and other routine workups, including upper gastrointestinal Lugol chromoendoscopy, for the initial staging. We examined the prevalence of second primary cancer in these patients and the utility of PET.

Results

We identified 57 synchronous primary cancers in 53 patients, of which only 33 % were detected with PET. The most common site for the second primary cancer was the esophagus (49 %), followed by stomach (14 %) and head and neck (11 %). Most early-stage esophageal cancers and stomach cancers were detected using Lugol chromoendoscopy but not PET.

Conclusion

Although PET is useful for detecting synchronous primary cancers, it is not a sensitive technique for detecting early esophageal cancers and gastric cancers. Therefore, Lugol chromoendoscopy is indispensable for detecting synchronous upper gastrointestinal cancers in HNSCC patients.     

Additional value of integrated PET/CT over PET alone in the initial staging and follow up of head and neck malignancy

Objective

Clinical application of FDG-PET in head and neck cancer includes identification of metastases, unknown primary head and neck malignancy, or second primary carcinoma, and also recurrent tumor after treatment. In this study, the additional value of PET/CT fusion images over PET images alone was evaluated in patients with initial staging and follow up of head and neck malignancy.

Methods

Forty patients with suspected primary head and neck malignancy and 129 patients with suspected relapse after treatment of head and neck malignancy were included. FDG-PET/CT study was performed after the intravenous administration of FDG (5 MBq/kg). Target of evaluation was set at primary tumor, cervical lymph node, and whole body. PET images and PET with CT fusion images were compared. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Results of PET and PET/CT were compared with postoperative histopathological examination, and case by case comparison of PET and PET/CT results for each region was performed. The additional value of CT images over PET only images was assessed. Statistical differences in sensitivity and specificity were evaluated.

Results

In the comparative evaluation of 507 targets by PET alone and PET/CT, 401 targets showed agreement of the results. Of the 106 discordant targets, 103 showed a positive result on PET alone and negative result on PET/CT. These results showed a significant difference (p < 0.01). Sensitivity of PET/CT was slightly higher than that of PET without statistical significance, while specificity of PET/CT was significantly higher than that of PET alone (Initial staging: 90.5% vs. 62.2%, p < 0.01; Follow up: 97.2% vs. 74.4%, p < 0.01). In Fisher’s direct probability test, a significant difference was noted in the sensitivity (Initial staging: 91.3% vs. 87.0%, p < 0.01; Follow up: 93.9% vs. 91.4%, p < 0.01).

Conclusions

Combined PET/CT showed improved diagnostic performance than PET alone by decreasing the number of false positive findings in patients with initial staging and follow up of head and neck malignancy.     

MRI-only lesions: application of diffusion-weighted imaging obviates unnecessary MR-guided breast biopsies

Objective

To assess if the application of diffusion-weighted imaging (DWI) obviates unnecessary MR-guided biopsies in suspicious breast lesions visible only on contrast-enhanced MRI (CE-MRI).

Methods

This institutional review board (IRB)-approved, retrospective, single-centre study included 101 patients (mean age, 49.5; SD 13.9 years) who underwent additional DWI at 1.5 T prior to MRI-guided biopsy of 104 lesions classified as suspicious for malignancy and visible on CE-MRI only. An experienced radiologist, blinded to histopathologic and follow-up results, measured apparent diffusion coefficient (ADC) values obtained from DWI. Diagnostic accuracy was investigated using receiver operating characteristics (ROC) analysis.

Results

Histopathology revealed 20 malignant and 84 benign lesions. Lesions were masses in 61 (15 malignant, 24.6 %) and non-masses in 43 cases (five malignant, 11.6 %). Mean ADC values were 1.53?±?0.38?×?10^?3 mm²/s in benign lesions and 1.06?±?0.27?×?10^?3 mm²/s in malignant lesions. ROC analysis revealed exclusively benign lesions if ADC values were greater than 1.58?×?10^?3 mm²/s. As a consequence, 29 false-positive biopsies (34.5 %) could have been avoided without any false-negative findings. Both in mass and in non-mass lesions, rule-in and rule-out criteria were identified using flexible ADC thresholds based on ROC analysis.

Conclusion

Additional application of DWI in breast lesions visible only on MRI can avoid false-positive, MR-guided biopsies. Thus, DWI should be an integral part of breast MRI protocols.

Key Points

? DWI measurements are a fast and helpful technique for improved breast lesion diagnosis ? DWI application in breast lesions visible only on MRI obviates false-positive, MR-guided biopsies ? Flexible ADC thresholds provide rule-in and rule-out criteria for breast lesion malignancy     

A proposal for combined MRI and PET/CT interpretation criteria for preoperative nodal staging in non-small-cell lung cancer

Objectives

To determine the positive reading criteria for malignant nodes when interpreting combined MRI and PET/CT images for preoperative nodal staging in non-small-cell lung cancer (NSCLC).

Methods

Forty-nine patients with biopsy-proven NSCLC underwent both PET/CT and thoracic MRI [diffusion weighted imaging (DWI)]. Each nodal station was evaluated for the presence of metastasis by applying either inclusive (positive if either one read positive) or exclusive (positive if both read positive) criteria in the combined interpretation of PET/CT and MRI. Nodal stage was confirmed pathologically. The combined diagnostic accuracy of PET/CT and MRI was determined on per-nodal station and per-patient bases and compared with that of PET/CT alone.

Results

In 49 patients, 39 (19%) of 206 nodal stations harboured malignant cells. Out of 206 nodal stations, 186 (90%) had concordant readings, while the rest (10%) had discordant readings. Inclusive criteria of combined PET/CT and MRI helped increase sensitivity for detecting nodal metastasis (69%) compared with PET/CT alone (46%; P?=?0.003), while specificity was not significantly decreased.

Conclusion

Inclusive criteria in combined MRI and PET/CT readings help improve significantly the sensitivity for detecting nodal metastasis compared with PET/CT alone and may decrease unnecessary open thoracotomy. Key Points ? Combined interpretation of MRI and PET/CT enhances the detection of nodal metastasis. ? Inclusive criteria of combined MRI/PET/CT improved the sensitivity for detecting nodal metastasis. ? Combined interpretation of MRI and PET/CT may reduce unnecessary open thoracotomies.     

Diffusion-weighted MR imaging in primary rectal cancer staging demonstrates but does not characterise lymph nodes

Objectives

To evaluate the performance of diffusion-weighted MRI (DWI) for the detection of lymph nodes and for differentiating between benign and metastatic nodes during primary rectal cancer staging.

Methods

Twenty-one patients underwent 1.5-T MRI followed by surgery (± preoperative 5?×?5 Gy). Imaging consisted of T2-weighted MRI, DWI (b0, 500, 1000), and 3DT1-weighted MRI with 1-mm isotropic voxels. The latter was used for accurate detection and per lesion histological validation of nodes. Two independent readers analysed the signal intensity on DWI and measured the mean apparent diffusion coefficient (ADC) for each node (ADC_node) and the ADC of each node relative to the mean tumour ADC (ADC_rel).

Results

DWI detected 6 % more nodes than T2W-MRI. The signal on DWI was not accurate for the differentiation of metastatic nodes (AUC 0.45–0.50). Interobserver reproducibility for the nodal ADC measurements was excellent (ICC 0.93). Mean ADC_node was higher for benign than for malignant nodes (1.15?±?0.24 vs. 1.04?±?0.22 *10^-3 mm²/s), though not statistically significant (P?=?0.10). Area under the ROC curve/sensitivity/specificity for the assessment of metastatic nodes were 0.64/67 %/60 % for ADC_node and 0.67/75 %/61 % for ADC_rel.

Conclusions

DWI can facilitate lymph node detection, but alone it is not reliable for differentiating between benign and malignant lymph nodes.

Key Points

? Diffusion-weighted (DW) magnetic resonance imaging (MRI) offers new information in rectal cancer. ? DW MRI demonstrates more lymph nodes than standard T2-weighted MRI. ? Visual DWI assessment does not discriminate between benign and metastatic nodes. ? Apparent diffusion coefficients do not discriminate between benign and metastatic nodes.     

Diffusion-weighted MR imaging for the differentiation of malignant from benign strictures in the periampullary region

Objectives

To investigate the value of DWI for differentiating malignant from benign strictures in the periampullary region.

Methods

We retrospectively analysed data from 78 patients who had undergone magnetic resonance cholangiopanreatography (MRCP) and diffusion-weighted imaging (DWI), in whom biliary strictures in the periampullary region were suspected. Twenty-two malignant and 56 benign lesions were included. One radiologist compared the signal intensity of malignant and benign periampullary lesions on DWI using b?=?500 and 800 s/mm². The signal intensity of bile was also compared, and an optimal b value was determined for periampullary lesions. Two other radiologists reviewed MRCP alone and combined DWI and MRCP for the possibility of malignant periampullary lesions. Diagnostic accuracy was calculated for each reviewer by receiver operating characteristic (ROC) curve analysis.

Results

Malignant periampullary lesions more frequently appeared hyperintense than benign lesions on DWI using the two b values (P?<?0.001). Bile more frequently appeared hyperintense on DWI using b?=?500 s/mm² (87.2 %) than b?=?800 s/mm² (24.4 %). Therefore, b?=?800 s/mm² was determined as the preferred sequence. Diagnostic accuracy for malignant periampullary lesions improved for both reviewers after adding DWI; from 0.714 to 0.924 (P?=?0.006, for reviewer 1) and from 0.714 to 0.919 (P?=?0.007, reviewer 2).

Conclusions

Combined DWI with MRCP can improve the diagnostic accuracy for differentiating malignant from benign strictures in the periampullary region.

Key Points

? Diffusion-weighted magnetic resonance imaging provides yet more information about hepatobiliary structures. ? Diffusion-weighted imaging (DWI) has now been applied to the biliary tree. ? Most periampullary carcinomas appear hyperintense on high b value DWI. ? DWI can help differentiate between malignant and benign periampullary lesions.     

Diffusion-weighted imaging in breast lesion evaluation

Purpose

The purpose of this study was to investigate the ability of diffusion-weighted imaging (DWI) and the apparent diffusion coefficient (ADC) in the detection and characterisation of breast lesions.

Materials and methods

From September 2005 to September 2007, 86 patients with breast lesions who underwent magnetic resonance imaging (MRI) in our department were included in our study. MRI was performed with a 1.5-T unit using a standard protocol including DWI sequence. For each breast lesion, the ADC value was calculated and compared with that of normal breast tissue and to the definitive pathological diagnosis. Mann-Whitney U and Kruskal-Wallis tests were used for statistical analysis.

Results

A total of 126 breast lesions were detected. Pathology results revealed 100 malignant and 26 benign lesions. Mean diameter of lesions was 26.02 mm (range 4–90 mm), including 52 lesions ≤15 mm in size. Mean ADC value of normal glandular tissue was 1.55×10^?3 mm²/s. Mean ADC value of malignant lesions was 0.97×10^?3 mm²/s. Mean ADC value for benign lesions was 1.66×10^?3 mm²/s. Benign lesions showed ADC values significantly higher than malignant lesions (p<0.0001).

Conclusions

DWI provides reliable information to support MRI diagnosis of breast masses. ADC value appears a promising adjunctive parameter in distinguishing malignant from benign breast lesions.     

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.     

Usefulness of diffusion-weighted MR imaging in the evaluation of pulmonary lesions

Purpose

The role of diffusion-weighted MR imaging (DWI) in the differential diagnosis of pulmonary malignant tumours and solid benign lesions was investigated.

Methods

Sixty-two patients with 66 lesions underwent conventional MRI and DWI (diffusion factor of 0 and 500 s/mm²) examinations with 1.5-T MRI. The signal intensity of DWI images was observed and the apparent diffusion coefficient (ADC) values of the lesions were measured. Statistical analyses were performed with the independent samples t test, Pearson’s chi-square test and receiver operating characteristic (ROC) analysis.

Results

The signal intensities of pulmonary malignant tumours and solid benign lesions were not significantly different, but the ADC value of benign lesions was statistically higher than that of malignant tumours (p?=?0.001). By ROC analysis, the optimal threshold of ADC was 1.400?×?10^–3 mm²/s and the sensitivity and specificity were 83.3% and 74.1%, respectively. There were statistical differences between small cell carcinoma (SCLC) and non-small cell carcinoma (NSCLC) as well; the former was lower than the latter (p?=?0.007).

Conclusion

Our data indicate that quantitative analysis of ADC values may help diagnose or distinguish pulmonary lesions, and it also provides a promising method for characterising the pulmonary masses.     

Differentiation of malignant from benign soft tissue tumours: use of additive qualitative and quantitative diffusion-weighted MR imaging to standard MR imaging at 3.0 T

Objectives

To determine the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) to differentiate malignant from benign soft tissue tumours at 3.0 T.

Methods

3.0 T MR images including DWI in 63 patients who underwent surgery for soft tissue tumours were retrospectively analyzed. Two readers independently interpreted MRI for the presence of malignancy in two steps: standard MRI alone, standard MRI and DWI with qualitative and quantitative analysis combined.

Results

There were 34 malignant and 29 non-malignant soft tissue tumours. In qualitative analysis, hyperintensity relative to skeletal muscle was more frequent in malignant than benign tumours on DWI (P=0.003). In quantitative analysis, ADCs of malignant tumours were significantly lower than those of non-malignant tumours (P≤0.002): 759±385 vs. 1188±423 μm²/sec minimum ADC value, 941±440 vs. 1310±440 μm²/sec average ADC value. The mean sensitivity, specificity and accuracy of both readers were 96 %, 72 %, and 85 % on standard MRI alone and 97 %, 90 %, and 94 % on standard MRI with DWI.

Conclusions

The addition of DWI to standard MRI improves the diagnostic accuracy for differentiation of malignant from benign soft tissue tumours at 3.0 T.

Key Points

? DWI has added value for differentiating malignant from benign soft tissue tumours. ? Addition of DWI to standard MRI at 3.0 T improves the diagnostic accuracy. ? Measurements of both ADC _min within solid portion and ADC _av are helpful.

     

Comparison between MRI with spin-echo echo-planar diffusion-weighted sequence (DWI) and histology in the diagnosis of soft-tissue tumours

Purpose

Our aim was to assess the usefulness of magnetic resonance imaging (MRI) with spin-echo echo-planar diffusion-weighted sequences (SE-EPI-DWI) in the study of primary and secondary soft-tissue tumours by correlating the results of imaging and histology.

Material and methods

We retrospectively studied 23 patients (14 men, 9 women; age range 25?C87 years) affected by soft-tissue lesions. The MRI study was performed with baseline and contrast-enhanced SE-T1, proton density/T2-weighted (PD/T2), fat-saturated (FATSAT) DP/T2 and single-shot SE-EPI-DWI (b value 50-400- 800s/mm2) sequences.

Results

We identified 7/23 benign lesions (three myxoid, four nonmyxoid) and 16/23 malignant tumours (four myxoid, 12 nonmyxoid) with a mean diameter between 21 mm and 20 cm. Qualitative analysis of DWI showed persistence of high signal intensity for increasing b-values in all malignant tumours. Quantitative DWI analysis of the apparent diffusion coefficient (ADC) maps showed a statistical difference between benign and malignant lesions.

Conclusions

In our experience, DWI with qualitative and quantitative analysis correlated well with histology.     

Usefulness of Integrated PET/MRI in Head and Neck Cancer: A Preliminary Study

Purpose

The new modality of an integrated positron emission tomography/magnetic resonance imaging (PET/MRI) has recently been introduced but not validated. Our objective was to evaluate clinical performance of ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG) PET/MRI in patients with head and neck cancer.

Methods

This retrospective study was conducted between January 2013 and February 2013. Ten patients (eight men, two women; mean age, 61.4 ± 13.4 years) with histologically proven head and neck tumors were enrolled. Whole-body PET/MRI and regional positron emission tomography (PET) with dedicated MRI were sequentially obtained. Maximum standardized uptake value (SUVmax), SUVmean, metabolic tumor volume, total lesion glycolysis and contrast enhancement were analyzed. A total of ten whole-body positron emission tomography (PET), ten regional positron emission tomography (PET), ten dedicated MRI and ten regional PET/gadolinium-enhanced T1-weighted (Gd)-MRI images were analyzed for initial staging. Two nuclear medicine physicians analyzed positron emission tomography (PET) and PET/MRI with a consensus. One radiologist analyzed dedicated MRI. The primary lesions and number of metastatic lymph nodes analyzed from each image were compared.

Results

Eight patients were diagnosed with head and neck cancer (one tongue cancer, four tonsillar cancers, one nasopharyngeal cancer and two hypopharyngeal cancers) by histological diagnosis. Two benign tumors (pleomorphic adenoma and Warthin tumor) were diagnosed with surgical operation. Whole-body positron emission tomography (PET) and regional positron emission tomography (PET) attenuated by MRI showed good image quality for the lesion detection. Whole-body positron emission tomography (PET) and regional positron emission tomography (PET) detected ten primary sites and compensated for a missed lesion on dedicated MRI. A discordant number of suspicious lymph node metastases was noted according to the different images; 22, 16, 39 and 40 in the whole-body positron emission tomography (PET) only, dedicated MR, regional positron emission tomography (PET) only and regional PET/Gd-MRI, respectively. There was no distant metastasis based on analysis of whole-body positron emission tomography (PET) and whole-body PET/Dixon-volume interpolated breathhold examination (VIBE) MRI. Regional PET/Gd-MRI combined with whole-body PET/MRI modified staging in three patients. Lesions of primary tumor and suspicious metastasis were well detected on both value of SUVmax and visual analysis. The regional PET/Gd-MRI combined with whole-body PET/MRI showed convenient clinical staging performance compared with positron emission tomography (PET) and MRI alone.

Conclusion

In this preliminary study, PET attenuated by MRI showed good image quality to detect lesions. And whole-body PET/MRI as a single modality was feasible for staging in a clinical setting. Whole-body positron emission tomography (PET), regional positron emission tomography (PET), dedicated MRI and regional PET/Gd-MRI showed discordant results in lesion detection. These discordant results might be synergistic effect for accurate staging.