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.     

Functional imaging of head and neck squamous cell carcinoma with diffusion-weighted MRI and FDG PET/CT: quantitative analysis of ADC and SUV

Purpose

Head and neck squamous cell carcinoma (HNSCC) may cause a decreased apparent diffusion coefficient (ADC) on diffusion-weighted magnetic resonance imaging (DW MRI) and an increased standardized uptake value (SUV) on fluorodeoxyglucose (FDG) positron emission tomography (PET/CT). We analysed the reproducibility of ADC and SUV measurements in HNSCC and evaluated whether these biomarkers are correlated or independent.

Methods

This retrospective analysis of DW MRI and FDG PET/CT data series included 34 HNSCC in 33 consecutive patients. Two experienced readers measured tumour ADC and SUV values independently. Statistical comparison and correlation with histopathology was done. Intra- and inter-observer agreement for ADC and SUV measurements was assessed.

Results

Intraclass correlation coefficient (ICC) analysis showed almost perfect reproducibility (>0.90) for ADC_mean, ADC_min, SUV_max and SUV_mean values for intra-observer and inter-observer agreement. Mean ADC_mean and ADC_min in HNSCC were 1.05?±?0.34 × 10^?3?mm²/s and 0.65?±?0.29 × 10^?3?mm²/s, respectively. Mean SUV_mean and mean SUV_max were 7.61?±?3.87 and 12.8?±?5.0, respectively. Although statistically not significant, a trend towards higher SUV and lower ADC was observed with increasing tumour dedifferentiation. Pearson’s correlation analysis showed no significant correlation between ADC and SUV measurements (r ?0.103, ?0.051; p 0.552, 0.777).

Conclusion

Our data suggest that ADC and SUV values are reproducible and independent biomarkers in HNSCC.     

Quantitative evaluation of bone metastases from prostate cancer with simultaneous [18F] choline PET/MRI: combined SUV and ADC analysis

Objective

To quantitatively analyze bone metastases from prostate cancer and correlate the apparent diffusion coefficients (ADCs) and standardized uptake values (SUVs).

Methods

Fifty-five patients with biopsy-proven prostate cancer or suspected recurrent prostate cancer were examined with simultaneous [¹⁸F] choline Positron emission tomography (PET)/MRI at 3 T. In 11 patients, thirty-two PET-positive bone lesions could be identified that were located in the field-of-view of the Diffusion weighted imaging-sequence. Region-of-interest and volume-of-interest analyses were performed to measure the mean and minimal ADCs and to assess maximum and mean SUVs of every bone lesion. Correlations between maximum and mean SUVs and mean and minimal ADCs were calculated.

Results

The SUV_max of all lesions was 5.5 ± 3.1 (mean ± SD). The SUV_mean was 1.8 ± 0.9. The mean ADC (ADC_mean) of all lesions was 0.67 ± 0.13 × 10^?3 mm²/s. The minimal ADC (ADC_min) of all lesions was 0.56 ± 0.14 × 10^?3 mm²/s. There was a moderate but significant inverse correlation of SUV_max vs. ADC_mean with a correlation coefficient of ?0.4 (p = 0.02). There was also a significant inverse correlation of SUV_max vs. ADC_min with r = ?0.41 (p = 0.02).

Conclusion

Our initial results demonstrate a moderate but significant inverse correlation between increased choline metabolism and ADC values of bone metastases from prostate cancer. Further research on a multimodality approach using simultaneous PET/MRI in bone metastasis of prostate cancer seems to be justified.     

Diagnostic accuracy of diffusion weighted imaging for differentiation of supratentorial pilocytic astrocytoma and pleomorphic xanthoastrocytoma

Purpose

Supratentorial pilocytic astrocytoma (PA) may mimic pleomorphic xanthoastrocytoma (PXA) on conventional MR imaging, and a differentiation is clinically important because of distinct recurrence rate and anaplastic transformation rate. The purpose of this study was to investigate the diagnostic potential of diffusion-weighted imaging (DWI) in differentiating supratentorial PA from PXA.

Methods

We retrospectively reviewed DWI and conventional MR imaging of 16 patients with supratentorial PA and 8 patients with PXA. Variables of mean ADC values (ADC_mean) and minimum ADC values (ADC_min) were calculated from the ROIs containing the contrast-enhancing lesion on DWI. ADC_mean values and ADC_min values were compared among all supratentorial PA and PXA as well as between the subgroup of lobar PA and PXA by using an unpaired Student’s t test. The optimum threshold, sensitivity, specificity, accuracy, and the area under the receiver operating characteristic curve (AUC) were determined.

Results

Both ADC_mean values (1542?±?186 vs 1084?±?201?×?10^?6 mm²/s; P?<?0.001) and ADC_min values (1355?±?183 vs 988?±?180?×?10^?6 mm²/s; P?<?0.001) were significantly higher in supratentorial PA compared with PXA. The ADC_mean values and ADC_min values were also significantly higher in lobar PA than those in PXA. The ADC_mean values were useful for differentiating supratentorial PA from PXA, with a threshold value of >?1189.8?×?10^?6 mm²/s (sensitivity, 93.8%; specificity, 100%). The optimal threshold values of >?1189.8?×?10^?6 mm²/s for ADC_mean values provide sensitivity and specificity of 85.7 and 100%, respectively, for discriminating lobar PA from PXA. The optimum threshold value for ADC_min was >?1063.5?×?10^?6 mm²/s.

Conclusion

DWI is helpful in characterization and differentiation of supratentorial PA from PXA.

     

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.     

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

Purpose

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

Methods

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

Results

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

Conclusion

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

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     

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.     

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.     

Diffusion-weighted imaging of focal renal lesions: a meta-analysis

Objectives

Contrast-enhanced MRI can only distinguish to a limited extent between malignant and benign focal renal lesions. The aim of this meta-analysis is to review renal diffusion-weighted imaging (DWI) to compare apparent diffusion coefficient (ADC) values for different renal lesions that can be applied in clinical practice.

Methods

A PubMed search was performed to identify relevant articles published 2004–2011 on renal DWI of focal renal lesions. ADC values were extracted by lesion type to determine whether benign or malignant. The data table was finalised in a consensus read. ADC values were evaluated statistically using meta-regression based on a linear mixed model. Two-sided P value <5 % indicated statistical significance.

Results

The meta-analysis is based on 17 studies with 764 patients. Renal cell carcinomas have significant lower ADC values than benign tissue (1.61?±?0.08?×?10^-3 mm²/s vs 2.10?±?0.09?×?10^-3 mm²/s; P?<?0.0001). Uroepithelial malignancies can be differentiated by lowest ADC values (1.30?±?0.11?×?10^-3 mm²/s). There is a significant difference between ADC values of renal cell carcinomas and oncocytomas (1.61?±?0.08?×?10^-3 mm²/s vs 2.00?±?0.08?×?10^-3 mm²/s; P?<?0.0001).

Conclusions

Evaluation of ADC values can help to determine between benign and malignant lesions in general but also seems able to differentiate oncocytomas from malignant tumours, hence potentially reducing the number of unnecessarily performed nephrectomies.

Key Points

? This meta-analysis assesses the role of diffusion-weighted MRI in renal lesions. ? ADC values obtained by DW MRI have been compared for different renal lesions. ? ADC values can help distinguish between benign and malignant tumours. ? Differentiating oncocytomas from malignant tumours can potentially reduce inappropriate nephrectomies.     

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.     

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.     

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.     

Multiple antiplatelet therapy contributes to the reversible high signal spots on diffusion-weighted imaging in elective coiling of unruptured cerebral aneurysm

Introduction

Our aim was to systematically investigate radiographic characteristics and outcome of diffusion-weighted imaging (DWI) changes in the elective coiling of unruptured cerebral aneurysm with analyzing the correlation of antiplatelet therapy (APT).

Methods

In a total of 34 consecutive patients with unruptured cerebral aneurysms initially treated by coiling without stent assist, 26 (76.5 %) had DWI changes with 91 high signal spots within 24–48 h after the procedure. We recorded DWI parameters (location, volume, mean, and minimum values of the apparent diffusion coefficient: expressed as ADC_AVE and ADC_MIN) for each lesion, and evaluated its radiographic outcome on conventional MRI at follow-up (interval, 58.4?±?37.2 days) in the modes of APT.

Results

All patients with DWI high spots had no clinical symptoms. There was a strong correlation between ADC_AVE and ADC_MIN (r?=?0.82, p?<?0.0001). The mean ADC_AVE and rADC_AVE were 0.74?±?0.14?×?10^?3?mm²/s and 87?±?10 %. DWI high spots were small with a mean volume of 0.13?±?0.12 cm³, ranging from 0.04 to 0.86 cm³. A negative correlation was observed between the volume and values of ADC_AVE (r?=??0.48, p?<?0.0001). The DWI volume was significantly larger in single APT than in multiple (0.15?±?0.14 versus 0.10?±?0.07 cm³, p?=?0.0091). The permanent signal change was more observed in single APT than in multiple (24.5 % versus 5.2 %, p?=?0.02).

Conclusion

DWI high spots after elective coiling were small without significant decrease of ADC, and do not correspond to brain infarction. Periprocedural use of multiple antiplatelet agents is expected to reduce the volume of thromboembolism and permanent tissue damages.     

Suppression of myocardial 18F-FDG uptake with a preparatory “Atkins-style” low-carbohydrate diet

Objectives

Physiological myocardial uptake of 18F-FDG during positron emission tomography can mask adjacent abnormal uptake in mediastinal malignancy and inflammatory cardiac diseases. Myocardial uptake is unpredictable and variable. This study evaluates the impact of a low-carbohydrate diet in reducing myocardial FDG uptake.

Method

Patients attending for clinically indicated oncological FDG PET were asked to have an “Atkins-style” low-carbohydrate diet (less than 3 g) the day before examination and an overnight fast. A total of 120 patients following low-carbohydrate diet plus overnight fast were compared with 120 patients prepared by overnight fast alone. Patients having an Atkins-style diet also completed a diet compliance questionnaire. SUV_max and SUV_mean for myocardium, blood pool and liver were measured in both groups.

Results

Myocardial SUV_max fell from 3.53?±?2.91 in controls to 1.77?±?0.91 in the diet-compliant group. 98 % of diet-compliant patients had a myocardial SUV_max less than 3.6 compared with 67 % of controls. Liver and blood pool SUV_max rose from 2.68?±?0.49 and 1.82?±?0.30 in the control group to 3.14?±?0.57 and 2.06?±?0.30.

Conclusion

An Atkins-style diet the day before PET, together with an overnight fast, effectively suppresses myocardial FDG uptake.

Key Points

? Low-carbohydrate diet (LCD) the day before PET suppresses myocardial FDG uptake. ? LCD before PET increases liver and blood pool SUV _max and SUV _mean . ? Suppression of myocardial uptake may improve PET imaging of thoracic disease. ? Suppression of myocardial uptake may help imaging cardiac inflammatory disease with PET.     

Pilot prospective evaluation of <Superscript>18</Superscript>F-FPPRGD<Subscript>2</Subscript> PET/CT in patients with cervical and ovarian cancer

Purpose

We report the effect of antiangiogenic therapy on the biodistribution of ¹⁸F-FPPRGD₂ (a surrogate biomarker of integrin α_vβ₃ expression), and the potential of ¹⁸F-FPPRGD₂ to predict the prognosis in patients with cervical cancer and ovarian cancer in this clinical scenario.

Methods

Data from six women, age range 30 – 59 years (mean?±?SD 44.0?±?12.5 years), who had undergone a ¹⁸F-FPPRGD₂ PET/CT scan and bevacizumab-containing therapy were prospectively collected and analyzed. We compared baseline ¹⁸F-FPPRGD₂ and ¹⁸F-FDG uptake in the lesions and tumor-to-background (T/B) ratios. The maximum and mean ¹⁸F-FPPRGD₂ standardized uptake values (SUV_max and SUV_mean) were recorded for 13 normal organs, as well as in all the identified malignant lesions on the pretreatment scan and the 1-week post-treatment scan. We also measured changes in ¹⁸F-FPPRGD₂ uptake from before to 1 week after treatment_, and compared them to the changes in ¹⁸F-FDG uptake from before to 6 weeks after treatment. Treatment outcomes were correlated with these changes.

Results

The uptake in lesions and T/B ratio of ¹⁸F-FPPRGD₂ were lower than those of ¹⁸F-FDG (SUV_max 3.7?±?1.3 vs. 6.0?±?1.8, P?<?0.001; SUV_mean 2.6?±?0.7 vs. 4.2?±?1.3, P?<?0.001; T/B ratio based on SUV_max 2.4?±?1.0 vs. 2.6?±?1.0, P?<?0.04; T/B ratio based on SUV_mean 1.9?±?0.6 vs. 2.4?±?1.0, P?<?0.003). One patient did not return for the follow-up scan and in another patient no lesions were identified on the pretreatment scan. ¹⁸F-FPPRGD₂ uptake in lesions in the remaining four patients had significantly changed 1 week after treatment (SUV_mean 3.3?±?1.0 vs. 2.7?±?1.0, P?<?0.001), while uptake in all normal tissues analyzed was not affected by treatment. One patient with clinical disease progression had a decrease in lesional ¹⁸F-FPPRGD₂ SUV_mean of 1.6 % and in ¹⁸F-FDG SUV_mean of 9.4 %. Two patients with a clinical complete response to treatment had decreases in lesional ¹⁸F-FPPRGD₂ SUV_mean of 25.2 % and 25.0 % and in ¹⁸F-FDG SUV_mean of 6.1 % and 71.8 %. One patient with a clinical partial response had a decrease in lesional ¹⁸F-FPPRGD₂ SUV_mean of 7.9 % and in ¹⁸F-FDG SUV_mean of 76.4 %.

Conclusion

This pilot study showed that ¹⁸F-FPPRGD₂ and ¹⁸F-FDG provide independent information about the biology of ovarian and cervical cancers. Bevacizumab-containing therapy does not affect ¹⁸F-FPPRGD₂ uptake in normal organs, but does result in statistically significant changes in lesions. In addition, ¹⁸F-FPPRGD₂ may have potential for early prediction of response to such treatments. These preliminary findings have to be confirmed in larger studies.

     

Diffusion-weighted MR imaging in liver metastases of colorectal cancer: reproducibility and biological validation

Objectives

Before diffusion-weighted imaging (DWI) can be implemented in standard clinical practice for response monitoring, data on reproducibility are needed to assess which differences outside the range of normal variation can be detected in an individual patient. In this study we assessed the reproducibility of the apparent diffusion coefficient (ADC) values in colorectal liver metastases. To provide a biological basis for these values, their relation with histopathology was assessed.

Methods

DWI was performed twice in 1 week in patients scheduled for metastasectomy of colorectal liver metastases. Correlation between ADC values and apoptosis marker p53, anti-apoptotic protein BCL-2, proliferation marker Ki67 and serum vascular endothelial growth factor (VEGF) concentration were assessed.

Results

A good reproducibility coefficient of the mean ADC (coefficient of reproducibility 0.20 × 10^?3?mm²/s) was observed in colorectal liver metastases (n?=?21). The ADC value was related to the proliferation index and BCL-2 expression of the metastases. Furthermore, in metastases recently treated with systemic therapy, the ADC was significantly higher (1.27 × 10^?3?mm²/s vs 1.05 × 10^?3?mm²/s, P?=?0.02).

Conclusions

The good reproducibility, correlation with histopathology and implied sensitivity for systemic treatment-induced anti-tumour effects suggest that DWI might be an excellent tool to monitor response in metastatic colorectal cancer.

Key Points

? ADC values are becoming important oncological biomarkers ? DWI provides reproducibile ADC values in colorectal liver metastases ? The coefficient of reproducibility of the mean ADC is 0.20 × 10 ^?3 ? mm ² /s ? ADC values correlate with proliferation index and are related to BCL-2 expression     

Morphological, functional and metabolic imaging biomarkers: assessment of vascular-disrupting effect on rodent liver tumours

Objectives

To evaluate effects of a vascular-disrupting agent on rodent tumour models.

Methods

Twenty rats with liver rhabdomyosarcomas received ZD6126 intravenously at 20 mg/kg, and 10 vehicle-treated rats were used as controls. Multiple sequences, including diffusion-weighted imaging (DWI) and dynamic contrast-enhanced MRI (DCE-MRI) with the microvascular permeability constant (K), were acquired at baseline, 1 h, 24 h and 48 h post-treatment by using 1.5-T MRI. [¹⁸F]fluorodeoxyglucose micro-positron emission tomography (¹⁸F-FDG µPET) was acquired pre- and post-treatment. The imaging biomarkers including tumour volume, enhancement ratio, necrosis ratio, apparent diffusion coefficient (ADC) and K from MRI, and maximal standardised uptake value (SUV_max) from FDG µPET were quantified and correlated with postmortem microangiography and histopathology.

Results

In the ZD6126-treated group, tumours grew slower with higher necrosis ratio at 48 h (P?<?0.05), corresponding well to histopathology; tumour K decreased from 1 h until 24 h, and partially recovered at 48 h (P?<?0.05), parallel to the evolving enhancement ratios (P?<?0.05); ADCs varied with tumour viability and perfusion; and SUV_max dropped at 24 h (P?<?0.01). Relative K of tumour versus liver at 48 h correlated with relative vascular density on microangiography (r?=?0.93, P?<?0.05).

Conclusions

The imaging biomarkers allowed morphological, functional and metabolic quantifications of vascular shutdown, necrosis formation and tumour relapse shortly after treatment. A single dose of ZD6126 significantly diminished tumour blood supply and growth until 48 h post-treatment.     

Value of diffusion-weighted imaging to detect small malignant pelvic lymph nodes at 3 T

Objective

To investigate the usefulness of diffusion-weighted imaging (DWI) to discriminate between metastatic and non-metastatic small lymph nodes in pelvic carcinoma.

Materials and Methods

A total of 259 patients (180 normal, 79 metastatic) prospectively underwent DWI at 3 T. We measured the short-axis diameter and the mean apparent diffusion coefficient (ADC) value. Lymph nodes with a short-axis diameter larger than 8 mm were recorded as being suspected metastatic lymph nodes. Imaging data were correlated station by station with histopathological results.

Results

A total of 140 metastatic nodes were accurately matched with histology. On T2w, the short-axis diameter for non-metastatic and metastatic lymph nodes was 6.4 mm?±?2.5 mm and 8.3 mm?±?4.5 mm, respectively. Almost all metastatic or non-metastatic nodes had similar high signal intensity on DWI (except in 5 cases) with a homogeneous pattern. The mean ADC values (10^?3 mm³/s ± standard deviation) of involved lymph nodes, control iliac nodes and control inguinal nodes were 924?±?217, 968?±?182 and 1,036?±?181, respectively. There were no statistically significant differences in the ADC of metastatic and non-metastatic nodes.

Conclusion

Isolated measurement of mean ADC values in a suspected station does not contribute to the diagnosis of metastatic nodes, in patients with small ambiguous nodes.     

Prognostic value of FDG-PET and DWI in breast cancer

Objective

To investigate the prognostic value of preoperative FDG-PET/CT and diffusion weighted imaging (DWI) in patients with breast cancer.

Methods

A total of 73 patients with newly diagnosed invasive breast cancer who had undergone preoperative whole-body FDG-PET/CT and 3-Tesla breast MRI including DWI followed by surgery were identified. Effects of primary tumor PET parameters [maximum standardized uptake value (SUV_max), mean SUV (SUV_mean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG)] and DWI parameters [mean apparent diffusion coefficient (ADC_mean) and minimum ADC (ADC_min)] including clinicopathologic factors on disease-free survival (DFS) were retrospectively evaluated using the log-rank and Cox methods.

Results

After a median overall follow-up of 32.3 months in all patients, 6 (8.2%) of the 73 patients had recurrence. Receiver operating characteristic curve analysis and log-rank tests showed that patients with a high primary tumor SUV_max (≥?3.60), MTV (≥?3.15), and TLG (≥?16.0) had a significantly lower DFS rate than those with a low SUV_max (<?3.60), MTV (<?3.15), and TLG (<?16.0), respectively (p?=?0.0054, p?=?0.0054, and p?<?0.0001, respectively). SUV_mean, ADC_mean, and ADC_min were not significantly associated with recurrence. Univariate analysis showed that SUV_max (p?=?0.0054), MTV (p?=?0.0054), TLG (p?<?0.0001), tumor size (p?=?0.0083), estrogen receptor negativity (p?=?0.046), progesterone receptor negativity (p?=?0.0023), human epidermal growth factor receptor 2 positivity (p?=?0.043), and the presence of axillary lymph node metastasis (p?=?0.0037) were also significantly associated with recurrence. However, in multivariate analysis, none of them were an independent factor.

Conclusions

The preoperative SUV_max, MTV, and TLG of primary breast cancer are prognostic factors for recurrence, whereas ADC values are not.