Study of proximal femoral bone perfusion with 3D T1 dynamic contrast-enhanced MRI: a feasibility study

Objective

The objective of this study was to compare measurements of semi-quantitative and pharmacokinetic parameters in areas of red (RBM) and yellow bone marrow (YBM) of the hip, using an in-house high-resolution DCE T1 sequence, and to assess intra- and inter-observer reproducibility of these measurements.

Methods

The right hips of 21 adult patients under 50 years of age were studied. Spatial resolution was 1.8?×?1.8?×?1.8 mm³, and temporal resolution was 13.5 seconds. Two musculoskeletal radiologists independently processed DCE images and measured semi-quantitative and pharmacokinetic parameters in areas of YBM and RBM. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated. Intra- and inter-observer reproducibility was assessed.

Results

Area under the curve (AUC) and initial slope (IS) were significantly greater for RBM than for YBM (p?trans and k_ep were also significantly greater for RBM (p?p?Conclusions DCE study of the whole hip is feasible with high spatial resolution using a 3D T1 sequence. Measures were possible even in low vascularized areas of the femoral head. K^trans, k_ep, AUC, and IS values were significantly different between red and yellow marrow, whereas TTP values were not.

Key Points

? High-spatial-resolution dynamic contrast-enhanced MRI of hip structures is feasible. ? Intra- and inter-observer reproducibility is good. ? Red and yellow bone marrow have different perfusion patterns.     

Comparison of ASL and DCE MRI for the non-invasive measurement of renal blood flow: quantification and reproducibility

Objectives

To investigate the reproducibility of arterial spin labelling (ASL) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and quantitatively compare these techniques for the measurement of renal blood flow (RBF).

Methods

Sixteen healthy volunteers were examined on two different occasions. ASL was performed using a multi-TI FAIR labelling scheme with a segmented 3D-GRASE imaging module. DCE MRI was performed using a 3D-FLASH pulse sequence. A Bland-Altman analysis was used to assess repeatability of each technique, and determine the degree of correspondence between the two methods.

Results

The overall mean cortical renal blood flow (RBF) of the ASL group was 263?±?41 ml min^?1 [100 ml tissue]^?1, and using DCE MRI was 287?±?70 ml min^?1 [100 ml tissue]^?1. The group coefficient of variation (CV_g) was 18 % for ASL and 28 % for DCE-MRI. Repeatability studies showed that ASL was more reproducible than DCE with CV_gs of 16 % and 25 % for ASL and DCE respectively. Bland-Altman analysis comparing the two techniques showed a good agreement.

Conclusions

The repeated measures analysis shows that the ASL technique has better reproducibility than DCE-MRI. Difference analysis shows no significant difference between the RBF values of the two techniques.

Key Points

? Reliable non-invasive monitoring of renal blood flow is currently clinically unavailable. ? Renal arterial spin labelling MRI is robust and repeatable. ? Renal dynamic contrast-enhanced MRI is robust and repeatable. ? ASL blood flow values are similar to those obtained using DCE-MRI.     

Dynamic contrast-enhanced magnetic resonance imaging can assess vascularity within fracture non-unions and predicts good outcome

Objectives

To prospectively evaluate whether dynamic contrast-enhanced (DCE) MRI can assess vascularity within non-unions and predicts clinical outcome in combination with the clinical Non-Union Scoring System (NUSS).

Methods

Fifty-eight patients with non-unions of extremities on CT underwent 3-T DCE MRI. Signal intensity curves obtained from a region-of-interest analysis were subdivided into those with more intense contrast agent uptake within the non-union than in adjacent muscle (vascularised non-union) and those with similar or less contrast uptake. The pharmacokinetic parameters of the Tofts model K _trans, K _ep, iAUC and V _e were correlated with union at CT 1 year later (n?=?49).

Results

Despite inserted osteosynthetic material, DCE parameters could be evaluated in 57 fractures. The sensitivity/specificity of vascularised non-unions as an indicator of good outcome was 83.9 %/50.0 % compared to 96.8 %/33.3 % using NUSS (n?=?49). Logistic regression revealed a significant impact of NUSS on outcome (P?=?0.04, odds ratio?=?0.93). At first examination, median iAUC (initial area under the enhancement curve) for the ratio non-union/muscle was 10.28 in patients with good outcome compared with 3.77 in non-responders (P?=?0.023). K _trans, K _ep and V_e within the non-union were not significantly different initially (n?=?57) or 1 year later (n?=?19).

Conclusions

DCE MRI can assess vascularity in fracture non-unions. A vascularised non-union correlates with good outcome.

Key points

? Dynamic contrast-enhanced magnetic resonance imaging can assess vascularity within bony non-unions. ? Vascularised ununited fractures appear better at 1-year CT than poorly vascularised fractures. ? Non-union healing after osteosynthesis or osteoinductive drugs fundamentally requires vascularity. ? DCE MRI predicts treatment outcome better than the clinical Non-Union Scoring System. ? DCE MRI is clinically feasible to predict treatment outcome in bony non-unions.     

Is dynamic contrast-enhanced MRI useful for assessing proximal fragment vascularity in scaphoid fracture delayed and non-union?

Objective

To assess dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) as a measure of vascularity in scaphoid delayed-union or non-union.

Materials and methods

Thirty-five patients (34 male, one female; mean age, 27.4?±?9.4 years; range, 16–51 years) with scaphoid delayed-union and non-union who underwent DCE MRI of the scaphoid between September 2002 and October 2012 were retrospectively reviewed. Proximal fragment vascularity was classified as good, fair, or poor on unenhanced MRI, contrast-enhanced MRI, and DCE MRI. For DCE MRI, enhancement slope, E_slope comparison of proximal and distal fragments was used to classify the proximal fragment as good, fair, or poor vascularity. Proximal fragment vascularity was similarly graded at surgery in all patients. Paired t test and McNemar test were used for data comparison. Kappa value was used to assess level of agreement between MRI findings and surgical findings.

Results

Twenty-five (71 %) of 35 patients had good vascularity, four (11 %) had fair vascularity, and six (17 %) had poor vascularity of the proximal scaphoid fragment at surgery. DCE MRI parameters had the highest correlation with surgical findings (kappa?=?0.57). Proximal scaphoid fragments with surgical poor vascularity had a significantly lower E_max and E_slope than those with good vascularity (p?=?0.0043 and 0.027). The sensitivity, specificity, positive and negative predictive value and accuracy of DCE MRI in predicting impaired vascularity was 67, 86, 67, 86, and 80 %, respectively, which was better than that seen with unenhanced and post-contrast MRI. Flattened time intensity curves in both proximal and distal fragments were a feature of protracted non-union with a mean time interval of 101.6 ± 95.5 months between injury and MRI.

Conclusions

DCE MRI has a higher diagnostic accuracy than either non-enhanced MRI or contrast enhanced MRI for assessing proximal fragment vascularity in scaphoid delayed-union and non-union. For proper interpretation of contrast-enhanced studies in scaphoid vascularity, one needs to incorporate the time frame between injury and MRI.     

Intravoxel incoherent motion MR imaging for breast lesions: comparison and correlation with pharmacokinetic evaluation from dynamic contrast-enhanced MR imaging

Objectives

To compare diagnostic performance for breast lesions by quantitative parameters derived from intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and to explore whether correlations exist between these parameters.

Methods

IVIM and DCE MRI were performed on a 1.5-T MRI scanner in patients with suspicious breast lesions. Thirty-six breast cancers and 23 benign lesions were included in the study. Quantitative parameters from IVIM (D, f and D*) and DCE MRI (K^trans, K_ep, V_e and V_p) were calculated and compared between malignant and benign lesions. Spearman correlation test was used to evaluate correlations between them.

Results

D, f, D* from IVIM and K^trans, K_ep, V_p from DCE MRI were statistically different between breast cancers and benign lesions (p?<?0.05, respectively) and D demonstrated the largest area under the receiver-operating characteristic curve (AUC?=?0.917) and had the highest specificity (83 %). The f value was moderately statistically correlated with V_p (r?=?0.692) and had a poor correlation with K^trans (r?=?0.456).

Conclusions

IVIM MRI is useful in the differentiation of breast lesions. Significant correlations were found between perfusion-related parameters from IVIM and DCE MRI. IVIM may be a useful adjunctive tool to standard MRI in diagnosing breast cancer.

Key Points

? IVIM provided diffusion as well as perfusion information ? IVIM could help differential diagnosis of breast lesions ? Correlations were found between perfusion-related parameters from IVIM and DCE MRI

     

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.     

Prognostic Aspects of DCE-MRI in Recurrent Rectal Cancer

Objective

To explore whether pre-reoperative dynamic contrast-enhanced (DCE)-MRI findings correlate with clinical outcome in patients who undergo surgical treatment for recurrent rectal carcinoma.

Methods

A retrospective study of DCE-MRI in patients with recurrent rectal cancer was performed after obtaining an IRB waiver. We queried our PACS from 1998 to 2012 for examinations performed for recurrent disease. Two radiologists in consensus outlined tumour regions of interest on perfusion images. We explored the correlation between K^trans, K_ep, V_e, AUC90 and AUC180 with time to re-recurrence of tumour, overall survival and resection margin status. Univariate Cox PH models were used for survival, while univariate logistic regression was used for margin status.

Results

Among 58 patients with pre-treatment DCE-MRI who underwent resection, 36 went directly to surgery and 18 had positive margins. K^trans (0.55, P?=?0.012) and K_ep (0.93, P?=?0.04) were inversely correlated with positive margins. No significant correlations were noted between K^trans, K_ep, V_e, AUC90 and AUC180 and overall survival or time to re-recurrence of tumour.

Conclusion

K^trans and K_ep were significantly associated with clear resection margins; however overall survival and time to re-recurrence were not predicted. Such information might be helpful for treatment individualisation and deserves further investigation.

Key Points

? Morphological MRI features are not sufficiently predictive of complete rectal tumour resection. ? Survival and time to re-recurrence of tumour were not predicted by DCE-MRI. ? But perfusion data from dynamic enhanced MRI may provide more helpful information. ? Ktrans/Kep were shown to be significantly associated with clear resection margins. ? Functional information from DCE-MRI might be helpful for treatment individualisation.     

Stereotactic radiosurgery for newly diagnosed brain metastases

Background and purpose

Three doses were compared for local control of irradiated metastases, freedom from new brain metastases, and survival in patients receiving stereotactic radiosurgery (SRS) alone for one to three newly diagnosed brain metastases.

Patients and methods

In all, 134 patients were assigned to three groups according to the SRS dose given to the margins of the lesions: 13–16 Gy (n?=?33), 18 Gy (n?=?18), and 20 Gy (n?=?83). Additional potential prognostic factors were evaluated: age (≤?60 vs. >?60 years), gender, Karnofsky Performance Scale score (70–80 vs. 90–100), tumor type (non-small-cell lung cancer vs. melanoma vs. others), number of brain metastases (1 vs. 2–3), lesion size (?24 months).

Results

For 13–16 Gy, 18 Gy, and 20 Gy, the 1-year local control rates were 31, 65, and 79?%, respectively (p?p?p?p?=?0.12); 18 Gy showed a strong trend toward better local control when compared with 13–16 Gy (p?=?0.059). Freedom from new brain metastases (p?=?0.57) and survival (p?=?0.15) were not associated with SRS dose in the univariate analysis.

Conclusion

SRS doses of 18 Gy and 20 Gy resulted in better local control than 13–16 Gy. However, 20 Gy and 18 Gy must be compared again in a larger cohort of patients. Freedom from new brain metastases and survival were not associated with SRS dose.     

MRI assessment of experimental gliomas using 17.6 T

Introduction

Using ultra-high-field contrast-enhanced magnetic resonance imaging (MRI), an increase of field strength is associated with a decrease of T ₁ relaxivity. Yet, the impact of this effect on signal characteristics and contrast-enhanced pathology remains unclear. Hence, we evaluated the potential of a 17.6-T MRI to assess contrast-enhancing parts of experimentally induced rat gliomas compared to 3 T.

Methods

A total of eight tumor-bearing rats were used for MRI assessments either at 17.6 T (four rats) or at 3 T (four rats) at 11 days after stereotactic implantation of F98 glioma cells into the right frontal lobe. T ₁-weighted sequences were used to investigate signal-to-noise-ratios, contrast-to-noise-ratios, and relative contrast enhancement up to 16 min after double-dose contrast application. In addition, tumor volumes were calculated and compared to histology.

Results

The 17.6-T-derived contrast-enhancing volumes were 31.5?±?15.4 mm³ at 4 min, 38.8?±?12.7 mm³ at 8 min, 51.1?±?12.6 mm³ at 12 min, and 61.5?±?10.8 mm³ at 16 min after gadobutrol injection. Corresponding histology-derived volumes were clearly higher (138.8?±?8.4 mm³; P?<?0.01). At 3 T, contrast-enhancing volumes were 85.2?±?11.7 mm³ at 4 min, 107.3?±?11.0 mm³ at 8 min, 117.0?±?10.5 mm³ at 12 min, and 129.1?±?10.0 mm³ at 16 min after contrast agent application. Averaged histology-derived volumes (139.1?±?13.4 mm³) in this group were comparable to the 16-min volume (P _{?16 min}?=?0.38). Compared to ultra-high-field MRI, all 3-T-derived volumes were significantly higher (P?<?0.02).

Conclusion

Compared to 3-T-derived images and histology, tumor volumes were underestimated by approximately 50 % at 17.6 T. Hence, contrast-enhanced 17.6-T MRI provided no further benefits in tumor measurement compared to 3 T.     

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.     

Diffusion-weighted imaging with acquisition of three b-values for response evaluation of neuroendocrine liver metastases undergoing selective internal radiotherapy

Objectives

To evaluate diffusion-weighted MRI with acquisition of three b-values and calculation of fractioned ADCs for response evaluation of neuroendocrine liver metastases undergoing selective internal radiotherapy (SIRT).

Methods

Ten consecutive patients with neuroendocrine liver metastases underwent MRI before and following SIRT. Diffusion-weighted imaging included acquisition of the b-values 0, 50 and 800 s/mm² and calculation of ADC_(50,800), ADC_(0,50) and ADC_(0,800) maps. According to therapy response, lesions were categorised into group A [≥20 % reduction of the longest diameter (LD) in comparison to baseline MRI] and group B (<20 % reduction of the LD).

Results

Twelve out of 31 metastases were categorised as group A and 19 out of 31 metastases were categorised as group B. Pretherapeutic values of ADC_(0,800) and ADC_(50,800) did not differ significantly between the two groups; however, ADC_(0,50) was 32 % lower in group A (P?=?0.049). ADC_(0,800) and ADC_(50,800) increased significantly after therapy in both groups, however, group differences were not statistically significant. Conversely, the increase in ADC_(0,50) was about a factor of 7 larger in group A than in group B (P?=?0.023).

Conclusions

Our study showed that the ADC_(0,50) is a promising biomarker for response assessment of neuroendocrine liver metastases following SIRT.

Key Points

? Diffusion-weighted MRI offers new information about neuroendocrine hepatic metastases. ? Evaluation of perfusion and diffusion components requires fractioned apparent diffusion coefficients (ADCs). ? Perfusion effects represented by ADC (0.50) can be observed in neuroendocrine metastases. ? Pretherapeutic ADC (0.50) was significantly lower in metastases with a response ≥20 %. ? Such biomarkers may help evaluate liver metastases in patients undergoing therapy.     

Does 11C-choline PET-CT contribute to multiparametric MRI for prostate cancer localisation?

Background and purpose

The aim of this work was to determine whether ¹¹C-choline positron emission tomography (PET)–computed tomography (CT) makes a positive contribution to multiparametric magnetic resonance imaging (MRI) for localisation of intraprostatic tumour nodules.

Patients and methods

A total of 73 patients with biopsy-proven intermediate- and high-risk prostate cancer were enrolled in a prospective imaging study consisting of T2-weighted (T2w), dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) MRI and ¹¹C-choline PET-CT before radical prostatectomy. Cancerous regions were delineated on the whole-mount prostatectomy sections and on the different MRI modalities and analysed in 24 segments per patient (3 sections, 8 segments each). To analyse PET-CT images, standardized uptake values (SUV) were calculated per segment.

Results

In total, 1,752 segments were analyzed of which 708 (40.4?%) were found to be malignant. A high specificity (94.7, 93.6 and 92.2?%) but relatively low sensitivity (31.2, 24.9 and 44.1?%) for tumour localisation was obtained with T2w, DCE and DW MRI, respectively. Sensitivity values significantly increased when combining all MRI modalities (57.2?%). For PET-CT, mean SUV_max of malignant octants was significantly higher than mean SUV_max of benign octants (3.68?±?1.30 vs. 3.12?±?1.02, p?<?0.0001). In terms of accuracy, the benefit of adding PET-CT to (multiparametric) MRI was less than 1?%.

Conclusion

The additional value of ¹¹C-choline PET-CT to MRI in localising intraprostatic tumour nodules is limited, especially when multiparametric MRI is used.     

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.     

Dynamic contrast-enhanced MRI for monitoring bisphosphonate therapy in Paget’s disease of bone

Purpose

The purpose of this study was to evaluate changes in regional bone perfusion in Paget’s disease (PD) following bisphosphonate therapy. We used dynamic contrast-enhanced MRI (DCE-MRI) for assessment of bone perfusion and compared MRI findings with alkaline phosphatase (AP) as a serum marker of bone turnover.

Materials and methods

We examined 20 patients (8 women, 12 men, 66?±?11 years) with symptomatic PD of the axial skeleton. Patients were selected for infusion therapy with the bisphosphonate pamidronate. The most affected bone of lumbar spine or pelvis was examined by DCE-MRI prior to therapy and after a 6-month follow-up. The contrast uptake was evaluated using a two-compartment model with the parameters amplitude A and exchange rate constant K_ep. Color-coded parametric images were generated to visualize bone vascularization.

Results

After a 6-month follow-up there was a significant decrease in alkaline phosphatase and in DCE-MRI parameters A and K_ep (p?<?0.0001). Patients without previous bisphosphonate treatment showed a significantly greater decrease in alkaline phosphatase and K_ep (p?<?0.001).

Conclusion

DCE-MRI shows a significant reduction in regional bone perfusion in PD following parenteral bisphosphonate treatment. Reduction in bone perfusion is greater in bisphosphonate-naïve patients than in those who had been previously treated.     

A dedicated automated injection system for dynamic contrast‐enhanced MRI experiments in mice

Purpose:

To develop a reproducible small‐animal dynamic contrast‐enhanced (DCE) MRI set‐up for mice through which volumes <100 μL can be accurately and safely injected and to test this set‐up by means of DCE measurements in resting muscle and tumor tissue.

Materials and Methods:

The contrast agent (CA) injection system comprised 2 MR‐compatible syringe pumps placed 50 cm from the 7T magnet bore where the fringe field is approximately 40 mT. Microbore tubing and T‐connector, close to the injection site, minimized dead volume (<10 μL). For DCE‐MRI measurements in 8 CB‐17 SCID mice with 1500–2500 mm³ large orthotopic neuroblastoma, a bolus of 10‐fold‐diluted Gd‐DTPA CA solution (0.1 mmol/kg) was delivered (5 μL/s), followed by a 50‐μL saline flush. Retro‐orbital injections were given instead of tail vein injections, because the peripheral vasculature was reduced because of large tumor burden.

Results:

The CA injection was successful in 19 of 24 experiments. Optical assessment showed minimal dispersion of ink‐colored CA bolus. Mean (±SD) pharmacokinetic parameters retrieved from DCE‐MRI examinations in resting muscle (K^trans = 0.038 ± 0.025 min^?1, k_ep = 0.66 ± 0.48 min^?1, v_e = 0.060 ± 0.014, v_p = 0.033 ± 0.021) and tumor (K^trans = 0.082 ± 0.071 min^?1, k_ep = 0.82 ± 0.80 min^?1, v_e = 0.121 ± 0.075, v_p = 0.093 ± 0.051) agreed with those reported previously.

Conclusion:

We successfully designed and implemented a DCE‐MRI set‐up system with short injection lines and low dead volume. The system can be used at any field strength with the syringe pumps placed at a sufficiently low fringe field (<40 mT). J. Magn. Reson. Imaging 2013;37:746–751. © 2012 Wiley Periodicals, Inc.

     

Dixon-based MRI for assessment of muscle-fat content in phantoms,healthy volunteers and patients with achillodynia: comparison to visual assessment of calf muscle quality

Objectives

To quantify the muscle fat-content (MFC) in phantoms, volunteers and patients with achillodynia using two-point Dixon-based magnetic resonance imaging (2pt-MRI_DIXON) in comparison to MR spectroscopy (MRS) and visual assessment of MFC.

Methods

Two-point Dixon-based MRI was used to measure the MFC of 15 phantoms containing 0-100 % fat-content and calf muscles in 30 patients (13 women; 57?±?15 years) with achillodynia and in 20 volunteers (10 women; 30?±?14 years) at 1.5 T. The accuracy of 2pt-MRI_DIXON in quantification of MFC was assessed in vitro using phantoms and in vivo using MRS as the standard of reference. Fat-fractions derived from 2pt-MRI_DIXON (FF_DIXON) and MRS (FF_MRS) were related to visual assessment of MFC (Goutallier grades 0–4) and Achilles-tendon quality (grade 0-4).

Results

Excellent linear correlation was demonstrated for FF_DIXON with phantoms and with FF_MRS in patients (p _c?=?0.997/0.995; p?<?0.001). FF_DIXON of the gastrocnemius muscle was significantly higher (p?=?0.002) in patients (7.0 %?±?4.7 %) compared with volunteers (3.6 %?±?0.7 %), whereas visual-grading showed no difference between both groups (p?>?0.05). FF_MRS and FF_DIXON were significantly higher in subjects with (>grade 1) structural damage of the Achilles-tendon (p?=?0.01).

Conclusions

Two-point Dixon-based MRI allows for accurate quantification of MFC, outperforming visual assessment of calf muscle fat. Structural damage of the Achilles tendon is associated with a significantly higher MFC.

Key points

? Two-point Dixon-based MRI allows accurate quantification of muscular fat content (MFC). ? Quantitative analysis outperforms visual analysis in the detection of elevated MFC. ? Achillodynia results in an increased MFC of the gastrocnemius muscles. ? Structural damage of the Achilles tendon further increases the MFC.     

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.     

Prognostic aspects of dynamic contrast-enhanced magnetic resonance imaging in synchronous distant metastatic rectal cancer

Objectives

To explore the correlations between DCE-MRI quantitative parameters and synchronous distant metastasis and the clinicopathological factors in rectal cancers.

Methods

Sixty-three patients with rectal cancer (synchronous distant metastasis, n?=?31; non-metastasis, n?=?32) were enrolled in this study. Student’s t test and ANOVA were used to compare DCE-MRI parameters (K ^trans , K _ep and V _e ). The receiver operating characteristic (ROC) analysis was used to find the reasonable threshold of DCE-MRI parameters to differentiate lesions with synchronous distant metastasis from those without metastasis.

Results

The K ^trans , K _ep , and V _e value were significantly higher in the lesions with distant metastasis than in the lesions without distant metastasis (0.536?±?0.242 vs. 0.299?±?0.118 min^-1, p?<?0.001; 1.598?±?0.477 vs. 1.341?±?0.390 min^-1, p?=?0.022; and 0.324?±?0.173 vs. 0.249?±?0.091, p?=?0.034; respectively). The K ^trans showed the highest AUCs of 0.788 (p?<?0.001), with sensitivity of 61.29 % and specificity of 87.5 %, respectively.

Conclusions

DCE-MRI parameters may represent a prognostic indicator for synchronous distant metastases in patients with rectal cancer.

Key Points

? The K ^trans , K _ep and V _e values correlated with synchronous distant metastasis. ? Higher K ^trans , K _ep and V _e values were noted among patients with metastasis. ? DCE-MRI parameters might represent a prognostic indicator for synchronous distant metastases.

     

Association of trochlear dysplasia with degenerative abnormalities in the knee: data from the Osteoarthritis Initiative

Objective

To evaluate trochlear morphology as a potential risk factor for patellofemoral osteoarthritis, determined by morphological and quantitative measurements of cartilage degeneration using 3-T magnetic resonance imaging (MRI) of the knee.

Materials and methods

MRI of the right knees of 304 randomly selected subjects, aged 45–60 years, from the Osteoarthritis Initiative (OAI) progression cohort were screened for trochlear dysplasia, defined by an abnormal trochlear depth. Out of 304 subjects, n?=?85 demonstrated a shallow trochlea (depth ≤3 mm; 28 %). In these, and also in a random sample of controls with normal trochlear depth (n?=?50), the facet ratio and the sulcus angle were calculated and knee structural abnormalities were assessed by using a modified Whole Organ MR Imaging Score (WORMS). Cartilage segmentation was performed and T₂ relaxation times and patellar cartilage volume were determined. ANOVA and multivariate regression models were used for statistical analysis of the association of MRI structural measures and trochlear morphology.

Results

Knees with a shallow trochlea showed higher patellofemoral degeneration (WORMS mean ± standard deviation, 11.2?±?0.5 versus 5.7?±?0.6; multivariate regression, P?<?0.001) and lower patellar cartilage volume than controls (900?±?664 mm³ versus 1,671?±?671 mm³; P?<?0.001). Knees with an abnormal medial-to-lateral facet ratio (<0.4) showed increased patellofemoral WORMS scores (12.3?±?0.9 versus 8.3?±?0.5; P?<?0.001). Knees with an abnormal sulcus angle (>170°) also showed increased WORMS scores (12.2?±?1.1 versus 8.6?±?0.6; P?=?0.003). T₂ values at the patella were significantly lower in the dysplasia group with a shallow trochlea. However, significance was lost after adjustment for cartilage volume (P?=?0.673).

Conclusion

Trochlear dysplasia, defined by a shallow trochlea, was associated with higher WORMS scores and lower cartilage volume, indicating more advanced osteoarthritis at the patellofemoral joint.     

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