Dynamic Contrast-enhanced MR Imaging Measurement of Vertebral Bone Marrow Perfusion May Be Indicator of Outcome of Acute Myeloid Leukemia Patients in Remission

Perfusion Imaging of the Musculoskeletal System

Perfusion imaging is the aspect of functional imaging, which is most applicable to the musculoskeletal system. In this review, the anatomy and physiology of bone perfusion is briefly outlined as are the methods of acquiring perfusion data on MR imaging. The current clinical indications of perfusion related to the assessment of soft tissue and bone tumors, synovitis, osteoarthritis, avascular necrosis, Keinbock's disease, diabetic foot, osteochondritis dissecans, and Paget's disease of bone are reviewed. Challenges and opportunities related to perfusion imaging of the musculoskeletal system are also briefly addressed.

Imaging Techniques and Clinical Application of the Marrow-Blood Barrier in Hematological Malignancies

The pathways through which mature blood cells in the bone marrow (BM) enter the blood stream and exit the BM, hematopoietic stem cells in the peripheral blood return to the BM, and other substances exit the BM are referred to as the marrow-blood barrier (MBB). This barrier plays an important role in the restrictive sequestration of blood cells, the release of mature blood cells, and the entry and exit of particulate matter. In some blood diseases and tumors, the presence of immature cells in the blood suggests that the MBB is damaged, mainly manifesting as increased permeability, especially in angiogenesis. Some imaging methods have been used to monitor the integrity and permeability of the MBB, such as DCE-MRI, IVIM, ASL, BOLD-MRI, and microfluidic devices, which contribute to understanding the process of related diseases and developing appropriate treatment options. In this review, we briefly introduce the theory of MBB imaging modalities along with their clinical applications.

Bone marrow MR perfusion imaging and potential for tumor evaluation

The physiology of bone perfusion is reviewed outlining how it can be measured with dynamic contrast-enhanced MRI as well as intravoxel incoherent imaging. Evaluation of bone perfusion provides a potential means of assessing tumor activity and treatment response beyond that possible with standard MR imaging.

Dynamic contrast-enhanced magnetic resonance perfusion volumetrics can differentiate tuberculosis of the spine and vertebral malignancy

BACKGROUND

There is considerable overlap in radiologic features of tubercular and malignant spinal lesions on conventional magnetic resonance imaging (MRI).

PURPOSE

To evaluate the role of dynamic contrast-enhanced (DCE) MRI perfusion parameters in differentiating vertebral malignancy from spinal tuberculosis.

MATERIAL AND METHODS

This was a prospective study and we enrolled consecutive patients presenting with a clinical/radiologic evidence of vertebral lesions. DCE-MRI of the spine was performed using 3D volume interpolated breath-hold examination (VIBE) sequence after intravenously injecting 0.1 mmol/kg body weight of gadopentetate dimeglumine. We used Tofts model to calculate DCE parameters that included K^trans (transfer constant), k_ep (rate constant), v_e (fractional volume of extracellular extravascular space), and iAUC (initial area under the curve). We compared the mean value of each perfusion parameter by type of lesion (tubercular/malignant) at 0.05 significance level and performed receiver operating characteristic curve analysis.

RESULTS

We could confirm histologic/cytologic diagnosis in 35 of the 45 patients recruited. Of these, 19 were tubercular and 16 were malignant lesions. The mean (± standard deviation) of k_ep (min^-1) was significantly higher (2.89 ± 3.3) in malignant compared to tubercular lesions (0.81 ± 0.19), whereas v_e was significantly lower in malignant (0.27 ± 0.13 mL/g) compared to benign lesions (0.47 ± 0.12 mL/g) at 0.05 significance level. k_ep cutoff of ≥1.17 min^-1 had a sensitivity of 93.8% and specificity of 100% with a diagnostic accuracy of 94.4% in detecting malignant disease.

CONCLUSION

High k_ep is the single best predictor of malignant vertebral lesions. We recommend k_ep cutoff value of ≥1.17 min^-1 that has high diagnostic accuracy in identifying malignant lesions.

Confounding factors in multi-parametric q-MRI protocol: A study of bone marrow biomarkers at 1.5 T

OBJECT

The MRI tissue characterization of vertebral bone marrow includes the measurement of proton density fat fraction (PDFF), T₁ and T₂* relaxation times of the water and fat components (T_1W, T_1F, T₂*_W, T₂*_F), IVIM diffusion D, perfusion fraction f and pseudo-diffusion coefficient D*. However, the measurement of these vertebral bone marrow biomarkers (VBMBs) is affected with several confounding factors. In the current study, we investigated these confounding factors including the regional variation taking the example of variation between the anterior and posterior area in lumbar vertebrae, B₁ inhomogeneity and the effect of fat suppression on f.

MATERIALS AND METHODS

A fat suppressed diffusion-weighted sequence and two 3D gradient multi-echo sequences were used for the measurements of the seven VBMBs. A turbo flash B₁ map sequence was used to estimate B₁ inhomogeneities and thus, to correct flip angle for T₁ quantification. We introduced a correction to perfusion fraction f measured with fat suppression, namely f_PDFF.

RESULTS

A significant difference in the values of PDFF, f and f_PDFF, T_1F, T₂*_W and D was observed between the anterior and posterior region. Although, little variations of flip angle were observed in this anterior-posterior direction in one vertebra but larger variations were observed in head-feet direction from L1 to L5 vertebrae.

DISCUSSION

The regional difference in PDFF, f_PDFF and T₂*_W can be ascribed to differences in the trabecular bone density and vascular network within vertebrae. The regional variation of VBMBs shows that care should be taken in reproducing the same region-of-interest location along a longitudinal study. The same attention should be taken while measuring f in fatty environment, and measuring T₁. Furthermore, the MRI-protocol presented here allows for measurements of seven VBMBs in less than 6 min and is of interest for longitudinal studies of bone marrow diseases.

Intravoxel Incoherent Motion Diffusion-weighted MRI of Infiltrated Marrow for Predicting Overall Survival in Newly Diagnosed Acute Myeloid Leukemia

Background Acute myeloid leukemia (AML) features relatively low overall survival (OS). Intravoxel incoherent motion (IVIM) diffusion-weighted MRI separates tissue microcapillary perfusion and diffusivity and may have potential for helping to assess prognosis in infiltrated marrow disease apart from solid tumor. Thus, a study of overall survival would contribute to clarifying the value of IVIM for assessing long-term prognosis in AML. Purpose To determine whether the IVIM-derived parameters of infiltrated bone marrow may be associated with OS in newly diagnosed AML. Materials and Methods This prospective study enrolled participants with newly diagnosed AML between July 2014 to March 2016 consecutively. Participants underwent MRI of the lumbar spine by using an IVIM sequence. Participant clinical characteristics and OS were collected. The median of follow-up period was 20 months (range, 1-56 months). The IVIM parameters (pseudoperfusion fraction, f; diffusion coefficient, D; and pseudodiffusion coefficient, D*) were obtained. A nonparametric log-rank test was used to identify the threshold of IVIM parameters for OS. Univariable Kaplan-Meier and multivariable Cox proportional hazards regression analyses were performed to investigate prognostic significance of possible indicators. Results Fifty-three participants (mean age, 42 years ± 17; 30 men) were evaluated. Nonparametric log-rank test results showed that the thresholds of f and D values for OS were 31.0% and 0.2 × 10^-3 mm²/sec, respectively. Univariable analyses indicated that high f value (>31.0%) and low D value (≤0.2 × 10^-3 mm²/sec) were associated with shorter OS (P = .003 and .01, respectively). An f value greater than 31.0% (hazard ratio, 2.4; 95% confidence interval: 1.0, 5.6; P = .046) was associated with OS, independent of clinical confounders (age, karyotype, and white blood cell counts) in a multivariable analysis. Conclusion Pseudoperfusion fraction and diffusion coefficient from intravoxel incoherent motion diffusion-weighted MRI may be viable prognosis predictors of newly diagnosed acute myeloid leukemia. © RSNA, 2020.

Evaluation of Early Response to Treatment of Hepatocellular Carcinoma with Yttrium-90 Radioembolization Using Quantitative Computed Tomography Analysis

Objective

To identify an imaging predictor for the assessment of early treatment response to yttrium-90 transarterial radioembolization (TARE) in patients with hepatocellular carcinoma (HCC), using a quantitative assessment of dynamic computed tomography (CT) images.

Materials and Methods

Dynamic contrast-enhanced CT was obtained pre- and 4 weeks post-TARE in 44 patients (34 men, 10 women; mean age, 60 years) with HCC. Computer software was developed for measuring the percentage increase in the combined delayed-enhancing area and necrotic area (pD + N) and the percentage increase in the necrotic area (pNI) in the tumor-containing segments pre- and post-TARE. Local progression-free survival (PFS) was compared between patient groups using Cox regression and Kaplan-Meier analyses.

Results

Post-TARE HCC with pD + N ≥ 35.5% showed significantly longer PFS than those with pD + N < 35.5% (p = 0.001). The local tumor progression hazard ratio was 17.3 (p = 0.009) for pD + N < 35.5% versus pD + N ≥ 35.5% groups. HCCs with a high pNI tended to have longer PFS, although this difference did not reach statistical significance.

Conclusion

HCCs with a larger pD + N are less likely to develop local progression after TARE.

Imaging biomarkers from multiparametric magnetic resonance imaging are associated with survival outcomes in patients with brain metastases from breast cancer

OBJECTIVES

The aim of this study is to investigate the correlation of survival outcomes with imaging biomarkers from multiparametric magnetic resonance imaging (MRI) in patients with brain metastases from breast cancer (BMBC).

METHODS

This study was approved by the institutional review board. Twenty-two patients with BMBC who underwent treatment involving bevacizumab on day 1, etoposide on days 2-4, and cisplatin on day 2 in 21-day cycles were prospectively enrolled for a phase II study. Three brain MRIs were performed: before the treatment, on day 1, and on day 21. Eight imaging biomarkers were derived from dynamic contrast-enhanced MRI (Peak, IAUC₆₀, K^trans, k_ep, v_e), diffusion-weighted imaging [apparent diffusion coefficient (ADC)], and MR spectroscopy (choline/N-acetylaspartate and choline/creatine ratios). The relative changes (Δ) in these biomarkers were correlated with the central nervous system (CNS)-specific progression-free survival (PFS) and overall survival (OS) using the Kaplan-Meier and Cox proportional hazard models.

RESULTS

There were no significant differences in the survival outcomes as per the changes in the biomarkers on day 1. On day 21, those with a low ΔK^trans (p = 0.024) or ΔADC (p = 0.053) reduction had shorter CNS-specific PFS; further, those with a low ΔPeak (p = 0.012) or ΔIAUC₆₀ (p = 0.04) reduction had shorter OS compared with those with high reductions. In multivariate analyses, ΔK^trans and ΔPeak were independent prognostic factors for CNS-specific PFS and OS, respectively, after controlling for age, size, hormone receptors, and performance status.

CONCLUSIONS

Multiparametric MRI may help predict the survival outcomes in patients with BMBC.

KEY POINTS

• Decreased angiogenesis after chemotherapy on day 21 indicated good survival outcome. • ΔK ^trans was an independent prognostic factors for CNS-specific PFS. • ΔPeak was an independent prognostic factors for OS. • Multiparametric MRI helps clinicians to assess patients with BMBC. • High-risk patients may benefit from more intensive follow-up or treatment strategies.

Early assessment of response to induction therapy in acute myeloid leukemia using 18F-FLT PET/CT

Background

We evaluated the suitability of ¹⁸F-fluorodeoxythymidine (¹⁸F-FLT) positron emission tomography (PET)/computed tomography (CT) for assessment of the early response to induction therapy and its value for predicting clinical outcome in patients with acute myeloid leukemia (AML). Adult patients who had histologically confirmed AML and received induction therapy were enrolled. All patients underwent ¹⁸F-FLT PET/CT after completion of induction. PET/CT images were visually and quantitatively assessed. Cases with intensely increased bone marrow uptake in more than one third of the long bones and throughout the central skeleton were interpreted as PET-positive for resistant disease (RD). PET results were compared to the clinical response and outcome.

Results

In visual PET analysis of 10 eligible patients (7 male, 3 female; median age 58 years), 5 patients were interpreted as being PET-positive and 5 as PET-negative. Standardized uptake values were significantly different between PET-positive and PET-negative groups. Eight of 10 patients achieved clinical complete remission (CR)/CR with incomplete blood count recovery (CRi). Five CR/CRi patients had PET-negative findings, but 3 CR patients had PET-positive findings. Both of the RD patients had PET-positive findings. During follow-up, 2 CR patients with PET-positive findings relapsed, or were strongly suspected of relapse, 4 months after consolidation.

Conclusion

¹⁸F-FLT PET/CT after induction therapy showed good sensitivity and negative-predictive value for evaluating RD in patients with AML. This preliminary study suggests that ¹⁸F-FLT PET/CT may be valuable as a noninvasive tool for early assessment of the response to treatment and may provide prognostic value for survival in patients with AML.

MRI protocol optimization for quantitative DCE-MRI of the spine

PURPOSE

In this study we systematically investigated different Dynamic Contrast Enhancement (DCE)-MRI protocols in the spine, with the goal of finding an optimal protocol that provides data suitable for quantitative pharmacokinetic modelling (PKM).

MATERIALS AND METHODS

In 13 patients referred for MRI of the spine, DCE-MRI of the spine was performed with 2D and 3D MRI protocols on a 3T Philips Ingenuity MR system. A standard bolus of contrast agent (Dotarem - 0.2ml/kg body weight) was injected intravenously at a speed of 3ml/s. Different techniques for acceleration and motion compensation were tested: parallel imaging, partial-Fourier imaging and flow compensation. The quality of the DCE MRI images was scored on the basis of SNR, motion artefacts due to flow and respiration, signal enhancement, quality of the T₁ map and of the arterial input function, and quality of pharmacokinetic model fitting to the extended Tofts model.

RESULTS

Sagittal 3D sequences are to be preferred for PKM of the spine. Acceleration techniques were unsuccessful due to increased flow or motion artefacts. Motion compensating gradients failed to improve the DCE scans due to the longer echo time and the T₂* decay which becomes more dominant and leads to signal loss, especially in the aorta. The quality scoring revealed that the best method was a conventional 3D gradient-echo acquisition without any acceleration or motion compensation technique. The priority in the choice of sequence parameters should be given to reducing echo time and keeping the dynamic temporal resolution below 5s. Increasing the number of acquisition, when possible, helps towards reducing flow artefacts. In our setting we achieved this with a sagittal 3D slab with 5 slices with a thickness of 4.5mm and two acquisitions.

CONCLUSION

The proposed DCE protocol, encompassing the spine and the descending aorta, produces a realistic arterial input function and dynamic data suitable for PKM.

Diagnosis of Spinal Lesions Using Heuristic and Pharmacokinetic Parameters Measured by Dynamic Contrast-Enhanced MRI

RATIONALE AND OBJECTIVES

This study aimed to evaluate the diagnostic performance of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in differentiation of four spinal lesions by using heuristic and pharmacokinetic parameters analyzed from DCE signal intensity time course.

MATERIALS AND METHODS

DCE-MRI of 62 subjects with confirmed myeloma (n = 9), metastatic cancer (n = 22), lymphoma (n = 7), and inflammatory tuberculosis (TB) (n = 24) in the spine were analyzed retrospectively. The region of interest was placed on strongly enhanced tissues. The DCE time course was categorized as the "wash-out," "plateau," or "persistent enhancement" pattern. The maximum enhancement, steepest wash-in enhancement, and wash-out slope using the signal intensity at 67 seconds after contrast injection as reference were measured. The Tofts 2-compartmental pharmacokinetic model was applied to obtain K^trans and k_ep. Pearson correlation between heuristic and pharmacokinetic parameters was evaluated, and receiver operating characteristic curve analysis was performed for pairwise group differentiation.

RESULTS

The mean wash-out slope was -22% ± 10% for myeloma, 1% ± 0.4% for metastatic cancer, 3% ± 3% for lymphoma, and 7% ± 10% for TB, and it could significantly distinguish myeloma from metastasis (area under the curve [AUC] = 0.884), lymphoma (AUC = 1.0), and TB (AUC = 1.0) with P = .001, and distinguish metastasis from TB (AUC = 0.741) with P = .005. The k_ep and wash-out slope were highly correlated (r = 0.92), and they showed a similar diagnostic performance. The K^trans was significantly correlated with the maximum enhancement (r = 0.71) and the steepest wash-in enhancement (r = 0.85), but they had inferior diagnostic performance compared to the wash-out slope.

CONCLUSIONS

DCE-MRI may provide additional diagnostic information, and a simple wash-out slope had the best diagnostic performance. The heuristic and pharmacokinetic parameters were highly correlated.

Dynamic contrast-enhanced MR imaging in osteoid osteoma: relationships with clinical and CT characteristics

OBJECTIVE

To correlate dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) features to clinical and computed tomography (CT) morphological features of osteoid osteoma (OO).

MATERIALS AND METHODS

Our institutional review board approved this retrospective study, waiving the need for informed consent. We included the 102 patients treated with interstitial laser ablation for histologically documented OO at our institution in 2008-2013. DCE-MRI variables were the time-enhancement pattern and rising slope (Slope_rise) and CT variables were the bone and segment involved (OO_bone and OO_segment, respectively), OO location relative to the native cortex (OO_cortex), nidus surface area, vessel sign, and largest neighboring-vessel diameter (Dmax_vessel). Descriptive statistics and correlations linking DCE-MRI findings to clinical and CT characteristics were computed.

RESULTS

DCE-MRI showed early arterial peak enhancement in 95 (93%) cases, with a mean Slope_rise of 9.30 ± 8.10. CT visualized a vessel sign in 84 (82%) cases with a mean Dmax_vessel of 1.10 ± 0.60 mm. By univariate analysis, Slope_rise correlated significantly with pain duration and Dmax_vessel (r = 0.30, P = 0.003; and r = 0.22, P = 0.03; respectively). Analysis of variance showed that Slope_rise correlated significantly with OO_bone (P < 0.001), with a steeper slope for OOs located in short or flat bones.

CONCLUSION

This study suggests more abundant vascularization of OOs with long-lasting pain and location on short or flat bones.

A pilot study to determine the timing and effect of bevacizumab on vascular normalization of metastatic brain tumors in breast cancer

Background

To determine the appropriate time of concomitant chemotherapy administration after antiangiogenic treatment, we investigated the timing and effect of bevacizumab administration on vascular normalization of metastatic brain tumors in breast cancer patients.

Methods

Eight patients who participated in a phase II trial for breast cancer-induced refractory brain metastases were enrolled and subjected to 4 dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) examinations that evaluated Peak, Slope, iAUC₆₀, and Ktrans before and after treatment. The treatment comprised bevacizumab on Day 1, etoposide on Days 2–4, and cisplatin on Day 2 in a 21-day cycle for a maximum of 6 cycles. DCE-MRI was performed before treatment and at 1 h, 24 h, and 21 days after bevacizumab administration.

Results

Values of the 4 DCE-MRI parameters reduced after bevacizumab administration. Compared with baseline values, the mean reductions at 1 and 24 h were −12.8 and −24.7 % for Peak, −46.6 and −65.8 % for Slope, −27.9 and −55.5 % for iAUC₆₀, and −46.6 and −63.9 % for Ktrans, respectively (all P < .05). The differences in the 1 and 24 h mean reductions were significant (all P < .05) for all the parameters. The generalized estimating equation linear regression analyses of the 4 DCE-MRI parameters revealed that vascular normalization peaked 24 h after bevacizumab administration.

Conclusion

Bevacizumab induced vascular normalization of brain metastases in humans at 1 and 24 h after administration, and the effect was significantly higher at 24 h than at 1 h.

Trial registration

ClinicalTrials.gov, identifier NCT01281696, registered prospectively on December 24, 2010

Imaging of Spinal Manifestations of Hematological Disorders

Imaging manifestations of hematological diseases and their potential complications are broad, and there may be significant overlap in features of various disease processes. Knowledge of appropriate choice of imaging test, pertinent imaging patterns, and pathophysiology of disease can help the reader increase specificity in the diagnosis and treatment of the patient. Most importantly, we encourage readers of this review to engage their radiologists during the diagnostic, treatment, and management phases of care delivery.

Dynamic Contrast-enhanced MR Imaging of Advanced Hepatocellular Carcinoma: Comparison with the Liver Parenchyma and Correlation with the Survival of Patients Receiving Systemic Therapy

Purpose To retrospectively compare the perfusion parameters of advanced hepatocellular carcinoma (HCC) measured with dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging with surrounding liver parenchyma to determine the relationship between these parameters and uncensored overall survival (OS). Materials and Methods This retrospective study had institutional review board approval, and informed consent was waived. DCE MR imaging was performed in 92 patients with advanced HCC before systemic treatment was administered (19 patients received a placebo). Three semiquantitative (peak, slope, and area under the gadolinium concentration-time curve [AUC]) and six quantitative (arterial fraction, arterial flow, portal flow, total blood flow, distribution volume, and mean transit time) parameters were calculated by placing regions of interest in the largest area of the tumor and background liver parenchyma. The DCE MR imaging parameters between the tumor and normal liver were compared with paired Wilcoxon test. By using the Cox proportional hazards model for univariate and multivariate analyses, the association of DCE MR imaging parameters and OS was investigated. Results HCC demonstrated significantly higher peak, slope, AUC, arterial fraction, and arterial flow but lower portal flow, distribution volume, and mean transit time than did the background liver (all P < .05). Patients with high peak in the tumor had longer OS (P = .005) than did those with low peak. Cox multivariate analysis identified peak as an independent predictor of OS (P = .032) after adjusting for age, sex, treatment, tumor size, and portal vein thrombosis. Conclusion DCE MR imaging parameters can be used to differentiate advanced HCC from the background liver, and peak, a semiquantitative parameter, is associated with outcome in patients with advanced HCC before systemic therapy. ^© RSNA, 2016 An earlier incorrect version of this article appeared online. This article was corrected on July 22, 2016.

Routine interim disease assessment in patients undergoing induction chemotherapy for acute myeloid leukemia: Can we do better?

The presence of >5% blasts at "day 14" (D14), in patients undergoing induction chemotherapy for acute myeloid leukemia (AML) is problematic. It is unclear if a second course of chemotherapy for early persistent disease will alter outcome in these patients. We conducted a retrospective study of AML patients undergoing induction chemotherapy where diagnostic, interim (around day 14), and recovery (days 21-42) bone marrow (BM) evaluations were available for review. Of the 113 patients included in the final analysis, 99 (87.6%) achieved CR at hematologic recovery. At D14, 90 patients (79.6%) had <5% blasts and of these, 87 (96.7%) ultimately achieved CR. At D14, Twenty-three (20.4%) patients had residual leukemia (>5% blasts). Of these, 11 (47.8%) received a second course of chemotherapy (double induction [DI]) and 12 (52.2%) were observed until count recovery (single induction [SI]). No significant difference in CR rates was observed between these two groups (58.3% DI group vs. 45.5% SI group, P value = 0.684). In our analysis, D14 BM evaluation did not uniformly identify patients with primary induction failure. To unequivocally determine the value of a D14 marrow assessment in AML, prospective studies in the context of large cooperative group trials are required. Considering our findings and similar reports from others, we propose that D14 marrow assessment should be individualized, and that other factors, such as cytogenetics and early peripheral blood blast clearance should be considered, to identify patients most likely to benefit from interim disease assessment during AML induction therapy.

Functional imaging of the musculoskeletal system

Functional imaging, which provides information of how tissues function rather than structural information, is well established in neuro- and cardiac imaging. Many musculoskeletal structures, such as ligaments, fascia and mineralized bone, have by definition a mainly structural role and clearly don't have the same functional capacity as the brain, heart, liver or kidney. The main functionally responsive musculoskeletal tissues are the bone marrow, muscle and nerve and, as such, magnetic resonance (MR) functional imaging has primarily addressed these areas. Proton or phosphorus spectroscopy, other fat quantification techniques, perfusion imaging, BOLD imaging, diffusion and diffusion tensor imaging (DTI) are the main functional techniques applied. The application of these techniques in the musculoskeletal system has mainly been research orientated where they have already greatly enhanced our understanding of marrow physiology, muscle physiology and neural function. Going forwards, they will have a greater clinical impact helping to bridge the disconnect often seen between structural appearances and clinical symptoms, allowing a greater understanding of disease processes and earlier recognition of disease, improving prognostic prediction and optimizing the monitoring of treatment effect.

Hepatic necro-inflammation and elevated liver enzymes: evaluation with MRI perfusion imaging with gadoxetic acid in chronic hepatitis patients

AIM

To evaluate liver necro-inflammation and function by using gadoxetic acid-enhanced dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), with histological analysis as the reference standard.

MATERIALS AND METHODS

Seventy-nine subjects (21 healthy subjects; 58 chronic hepatitis patients) who received gadoxetic acid-enhanced DCE-MRI were divided into three subgroups: no (A0, n = 31), mild (A1, n = 27), and moderate-severe (A2-A3, n = 21) activities. Two DCE-MRI models were measured: (1) a dual-input single-compartment model to obtain absolute arterial, portal venous, and total blood flow, arterial fraction (ART), distribution volume, and mean transit time; (2) a curve analysis method to obtain peak, slope, and AUC (area under curve). The serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels also obtained. Statistical testing included Kruskal-Wallis tests for continuous data, Pearson's correlation tests, and multiple linear regression analyses.

RESULTS

Hepatic necro-inflammatory activity grades were significantly correlated with fibrotic stages, serum ALT level, ART and AUC. ART was helpful to predict the mild activity (≤ A1 versus >A1; Az = 0.728), whereas AUC could differentiate no activity from any activity (A0 versus >A0; Az = 0.703). Peak, slope and AUC were all associated with AST and ALT (p < 0.05).

CONCLUSION

Gadoxetic acid-enhanced DCE-MRI parameters may be used to evaluate the severity of hepatic necro-inflammation and function.

Time dependency of bone density estimation from computed tomography with intravenous contrast agent administration

Our study has demonstrated that in contrast-enhanced multi-detector computed tomography (MDCT)-based bone density measurements, the scan delay time after contrast agent administration is a statistically significant variable for the derivation of quantitative computed tomography (QCT)-equivalent bone mineral density (BMD) values.

INTRODUCTION

Earlier investigators have proposed to derive QCT-equivalent BMD values from contrast-enhanced MDCT scans by using a merely density-based conversion equation. The purpose of this study was to investigate whether the scan delay after intravenous (IV) contrast agent administration might affect BMD values derived in this way.

METHODS

A retrospective data analysis was performed on 198 subjects who underwent standardized biphasic MDCT. Average densities values (in Hounsfield units) of lumbar vertebral bodies 1 to 3 (L1-L3) were compared between phases I and II of the biphasic MDCT scan. Furthermore, QCT-equivalent BMD (BMDQCT) values were calculated using a previously published conversion equation.

RESULTS

Paired t-test analysis revealed that IV contrast agent administration leads to a statistically significant increase (8.6 %; p < 0.0001) in overall density of L1-L3 from phases I to II. Moreover, comparison of BMDQCT values between phases I and II reveals a change from osteoporotic to osteopenic in 4.5 % of the study population and from osteopenic to normal for 11.1 % of the subjects. Furthermore, it was revealed that the density increase from phases I to II shows a weak, yet statistically significant (p < 0.001) age dependency.

CONCLUSIONS

Our study demonstrates that the use of a mere density-based conversion equation for deriving BMDQCT from MDCT scans ignores time dependency as an important variable. Furthermore, our results indicate that the actual age-dependent BMD itself might be another relevant variable that needs to be included in a MDCT-to-QCT conversion equation.

Triple-phase dynamic MRI: a new clue to predict malignant transformation of giant cell tumor of bone

OBJECTIVE

Our purpose was, through the comparison of the characteristics of time-intensity curve on triple-phase dynamic contrast-enhanced MRI among groups of giant cell tumor of bone (GCTB), recurrent benign giant cell tumor of bone (RBGCTB), and secondary malignant giant cell tumor of bone (SMGCTB), to find clues to predict the malignant transformation of GCTB.

SUBJECTS AND METHODS

21 patients diagnosed as GCTB were included in this study. All cases took recurrence after intralesional curettage. 9 cases were confirmed as SMGCTB and 12 cases were confirmed as RBGCTB. Cases were divided into four groups: group A, GCTB (n=9); group B, SMGCTB (n=9); group C, GCTB (n=12); group D, RBGCTB (n=12). Enhancement index(EI) of lesions on DCEMRI was calculated using formula: EI(t)=[S(t)-S(0)]/S(0), where S(0) was signal intensity of lesion on non-contrast-enhanced T1-weighted images and S(t) was signal intensity of lesion on DCEMRI (t=30, 60, 180s). Enhancement index of each group in each phase was compared using One-Way ANOVA analysis. Slope values of time-intensity curve were compared by the same way.

RESULTS

Time-intensity curve of SMGCTB was characterized by a steep upward slope followed by an early and rapid washout phase. Time-intensity curve of GCTB and RBGCTB was characterized by a steep slope followed by a relatively slow washout phase. No significant difference in enhancement index was found in the first phase (p>0.05). There was significant difference in the second and the third phase (p<0.05). Enhancement index of group B (SMGCTB) was smaller. There was no difference in rising slope value (p>0.05).

CONCLUSIONS

Dynamic contrast-enhanced MRI appears a helpful method to find new clues to predict malignant transformation of GCTB.

Quantitative dynamic contrast-enhanced MRI of pelvic and lumbar bone marrow: effect of age and marrow fat content on pharmacokinetic parameter values

OBJECTIVE

The purpose of this study was to determine the effects of age and fat content on quantitative dynamic contrast-enhanced MRI (DCE-MRI) parameters in the bone marrow of the lumbar spine and pelvis. The interreader reproducibility of this technique will also be assessed.

MATERIALS AND METHODS

Forty-three DCE-MRI studies of the female pelvis defined the study group. Quantitative pharmacokinetic perfusion parameters of lumbar and pelvic marrow were analyzed by three readers on a DCE-MRI postprocessing platform. Linear regression analysis was performed to determine the effect of age and marrow fat fraction on the parameters of transfer constant (K(trans)), efflux rate constant (K(ep)), extravascular extracellular space (V(e)), and initial area under the gadolinium curve at 60 seconds (iAUGC(60)). Interreader agreement was assessed by means of intraclass correlation coefficient calculation.

RESULTS

A weak but statistically significant correlation was established between both age and fat fraction and the parameters K(trans) (R(2) = 0.14) and K(ep) (R(2) = 0.09). There was also a weak but statistically significant correlation between fat fraction and V(e) (R(2) = 0.116) and iAUGC(60) (R(2) = 0.108), but no correlation between age and these parameters. Intraclass correlation coefficients of parameter measurements by different readers were all greater than 0.7 at the p < 0.05 level.

CONCLUSION

Age and fat fraction have small measurable effects on quantitative DCE-MRI parameters in bone marrow. However, given the wide interindividual variation of these parameters, these effects are unlikely to confound changes related to malignancy or treatment. Also of note, there was strong interreader reproducibility of parameter measurements among a range of experience levels, suggesting that the reader-reader experience level may not represent a significant source of variability in bone marrow DCE-MRI.

Evaluation of rectus extraocular muscles using dynamic contrast-enhanced MR imaging in patients with Graves' ophthalmopathy for assessment of disease activity

BACKGROUND

It is important to assess the activity of Graves' ophthalmopathy (GO) for planning optimal treatment strategy. Dynamic contrast-enhanced MR imaging (DCE-MRI) is a technique for assessment of microcirculation status. The correlation between disease activity and the microcirculation characteristics of extraocular muscles (EOMs) has been demonstrated in GO.

PURPOSE

To investigate the changes of rectus EOMs in patients with active vs. inactive GO using DCE-MRI, and to evaluate the value of DCE-MRI in assessing the activity of GO.

MATERIAL AND METHODS

Rectus EOMs of 20 healthy controls, 18 patients with active GO, and 16 patients with inactive GO were studied. The signal intensity (SI) of rectus EOMs on T(2)W images was evaluated. Regions of interest were placed on each rectus on DCE-MRI images. The DCE-MRI parameters including time to peak enhancement (Tpeak), enhancement ratio (ER), and wash-out ratio (WR) were calculated.

RESULTS

There were significant differences in SI and T(peak), ER and WR values among the three groups (P = 0.000). However, there was no significant difference in SI between the active and inactive groups (P = 0.07). T(peak) values of each rectus were significantly increased in inactive group compared with the active group (P < 0.05). ER and WR values of the inferior rectus and WR values of the superior rectus in inactive group were significantly lower than those in active group (P < 0.05). There was significant correlation between clinical activity score (CAS) and minimum T(peak) (minT(peak)), maximum ER (maxER) and maximum WR (maxWR) (P < 0.001). The cut-off values of minT(peak), maxER and maxWR were 156.98s, 1.31 and 13.50% respectively, giving positive predictive values of 68.00%, 88.90%, and 94.44% for the assessment of disease activity.

CONCLUSION

DCE-MRI could demonstrate the microcirculatory changes of rectus EOMs in both active and inactive GO, and this MRI method is a useful tool in differentiating active from inactive GO.

Hematopoietic tumors and metastases involving bone

This review explores in depth the most common malignant process involving the bone, namely metastatic disease, as well as some of the more common proliferative forms of hematopoietic disease of bone marrow. These are commonly encountered pathologic processes that often have vague nonspecific symptoms. Imaging findings are frequently subtle on initial radiographs; however, advanced imaging techniques, including CT, MR, and positron emission tomography, allow for accurate diagnosis, staging, and follow-up in most cases.

Angiogenesis in acute myeloid leukemia and opportunities for novel therapies

Acute myeloid leukemia (AML) arises from neoplastic transformation of hematopoietic stem and progenitor cells, and relapsed disease remains one of the greater challenges in treating this hematologic malignancy. This paper focuses on angiogenic aspects of AML including the significance and prognostic value of bone marrow microvessel density and circulating cytokine levels. We show three general mechanisms whereby AML exploits angiogenic pathways, including direct induction of angiogenesis, paracrine regulation, and autocrine stimulation. We also present early evidence that leukemia cells contribute directly to vascular endothelia. Novel treatment strategies are proposed, and a review of relevant antiangiogenic clinical trials is presented. By understanding how blood vessels can serve as a reservoir for refractory and relapsed AML, new diagnostics and promising treatment strategies can be developed.