Contrast Index Research Articles

Intrarenal pH-Responsive Self-Assembly of Luminescent Gold Nanoparticles for Diagnosis of Early Kidney Injury.

Metabolic acidosis-induced kidney injury (MAKI) is asymptomatic and lack of clinical biomarkers in early stage, but rapidly progresses to severe renal fibrosis and ultimately results in end-stage kidney failure. Therefore, developing rapid and noninvasive strategies direct responsive to renal tubular acidic microenvironment rather than delayed biomarkers are essential for timely renoprotective interventions. Herein, we develop pH-responsive luminescent gold nanoparticles (p-AuNPs) in the second near-infrared emission co-coated with 2,3-dimethylaleic anhydride conjugated β-mercaptoethylamine and cationic 2-diethylaminoethanethiol hydrochloride, which showed sensitive pH-induced charge reversal and intrarenal self-assembly for highly sensitive and long-time (~24 h) imaging of different stages of MAKI. By integrating advantages of pH-induced intrarenal self-assembly and enhanced interactions between pH-triggered positively charged p-AuNPs and renal tubular cells, the early- and late-stage MAKI could be differentiated rapidly within 10 min post-injection (p.i.) with contrast index (CI) of 3.5 and 4.3, respectively. The corresponding maximum CI could reach 5.1 and 9.2 at 12 h p.i., respectively. Furthermore, p-AuNPs were demonstrated to effectively real-time monitor progressive recovery of kidney injury in MAKI mice after therapy, and also exhibit outstanding capabilities for drug screening. This pH-responsive strategy showed great promise for feedback on kidney dysfunction progression, opening new possibilities for early-stage diagnosis of pH-related diseases.

Intrarenal pH‐Responsive Self‐Assembly of Luminescent Gold Nanoparticles for Diagnosis of Early Kidney Injury

AbstractMetabolic acidosis‐induced kidney injury (MAKI) is asymptomatic and lack of clinical biomarkers in early stage, but rapidly progresses to severe renal fibrosis and ultimately results in end‐stage kidney failure. Therefore, developing rapid and noninvasive strategies direct responsive to renal tubular acidic microenvironment rather than delayed biomarkers are essential for timely renoprotective interventions. Herein, we develop pH‐responsive luminescent gold nanoparticles (p‐AuNPs) in the second near‐infrared emission co‐coated with 2,3‐dimethylaleic anhydride conjugated β‐mercaptoethylamine and cationic 2‐diethylaminoethanethiol hydrochloride, which showed sensitive pH‐induced charge reversal and intrarenal self‐assembly for highly sensitive and long‐time (~24 h) imaging of different stages of MAKI. By integrating advantages of pH‐induced intrarenal self‐assembly and enhanced interactions between pH‐triggered positively charged p‐AuNPs and renal tubular cells, the early‐ and late‐stage MAKI could be differentiated rapidly within 10 min post‐injection (p.i.) with contrast index (CI) of 3.5 and 4.3, respectively. The corresponding maximum CI could reach 5.1 and 9.2 at 12 h p.i., respectively. Furthermore, p‐AuNPs were demonstrated to effectively real‐time monitor progressive recovery of kidney injury in MAKI mice after therapy, and also exhibit outstanding capabilities for drug screening. This pH‐responsive strategy showed great promise for feedback on kidney dysfunction progression, opening new possibilities for early‐stage diagnosis of pH‐related diseases.

Early bruising detection of 'Korla' pears by low-cost visible-LED structured-illumination reflectance imaging and feature-based classification models.

Nondestructive detection of thin-skinned fruit bruising is one of the main challenges in the automated grading of post-harvest fruit. The structured-illumination reflectance imaging (SIRI) is an emerging optical technique with the potential for detection of bruises. This study presented the pioneering application of low-cost visible-LED SIRI for detecting early subcutaneous bruises in 'Korla' pears. Three types of bruising degrees (mild, moderate and severe) and ten sets of spatial frequencies (50, 100, 150, 200, 250, 300, 350, 400, 450 and 500 cycles m-1) were analyzed. By evaluation of contrast index (CI) values, 150 cycles m-1 was determined as the optimal spatial frequency. The sinusoidal pattern images were demodulated to get the DC, AC, and RT images without any stripe information. Based on AC and RT images, texture features were extracted and the LS-SVM, PLS-DA and KNN classification models combined the optimized features were developed for the detection of 'Korla' pears with varying degrees of bruising. It was found that RT images consistently outperformed AC images regardless of type of model, and LS-SVM model exhibited the highest detection accuracy and stability. Across mild, moderate, severe and mixed bruises, the LS-SVM model with RT images achieved classification accuracies of 98.6%, 98.9%, 98.5%, and 98.8%, respectively. This study showed that visible-LED SIRI technique could effectively detect early bruising of 'Korla' pears, providing a valuable reference for using low-cost visible LED SIRI to detect fruit damage.

An imaging‑based diagnostic approach to vascular anomalies of the oral and maxillofacial region.

The accurate diagnosis of vascular anomalies (VAs) is considered a challenging endeavor. Misdiagnosis of VAs can lead clinicians in the wrong direction, such as the performance of an unnecessary biopsy or inappropriate surgical procedures, which can potentially lead to unforeseen consequences and increase the risk of patient injury. The purpose of the present study was to develop an approach for the diagnosis of VAs of the oral and maxillofacial region based on computed tomography (CT), magnetic resonance imaging (MRI) and dynamic contrast-enhanced MRI (DCE-MRI). In the present study, the CT and MR images of 87 VAs were examined, and the following imaging features were evaluated: Detectability of the lesion, the periphery of the lesion, the inner nature of the lesion, the density of the lesion on CT, the signal intensity of the lesion on MRI, the detectability of phleboliths and the shape of the lesion. A total of 29 lesions were further evaluated using the contrast index (CI) curves created from the DCE-MRI images. A diagnostic diagram, which is based on the imaging features of VAs and CI curve patterns, was subsequently extrapolated. The results obtained demonstrated that the VAs were detected more readily by MRI compared with CT, whereas the detectability of phleboliths was superior when using CT compared with MRI. VAs showed a propensity for homogeneous isodensity on CT, whereas, by contrast, they exhibited a propensity for heterogeneous hyperdensity on CE-CT. VAs also showed a propensity for homogeneous intermediate signal intensity when performing T1-weighted imaging (T1WI), heterogeneous high signal intensity when performing short tau inversion recovery MRI, and heterogeneous high signal intensity when performing fat-saturated CE-T1WI. The CI curves of VAs were found to exhibit a specific pattern: Of the 29 CI curves, 23 (79.3%) showed early weak enhancement, followed by a plateau leading up to 400-600 sec. An imaging-based diagnostic diagram was ultimately formulated. This diagram can act as an aid for radiologists when they are expecting to find a VA, and hopefully serve the purpose of simplifying the diagnostic process. Taken together, the findings of the present study indicated that DCE-MRI may be considered a useful tool for the diagnosis of VAs.

Dynamic contrast‑enhanced MRI as a predictor of programmed death ligand‑1 expression in patients with oral squamous cell carcinoma

Immune checkpoint inhibitors (ICIs) targeting programmed death ligand-1 (PD-L1) are highly promising therapies for oral squamous cell carcinoma (OSCC). The assessment of PD-L1 expression may help predicting the therapeutic effect of ICIs and, thus, benefit patient selection. Contrast index (CI) parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) have been proven as efficient to assess microvessel density (MVD) in OSCC. The present study aimed to determine the correlation between DCE-MRI parameters and MVD and between DCE-MRI parameters and PD-L1 expression to determine whether DCE-MRI could be used non-invasively to evaluate PD-L1 expression in patients with OSCC. A total of 21 patients with primary OSCC who had undergone a 3T MRI scan, including DCE-MRI, were included in the present study, and CI curve-derived parameters were examined. The MVD and PD-L1 expression in the surgically resected specimens were analyzed using immunohistochemistry (IHC) staining for CD31 and IHC staining for PD-L1, respectively. The results demonstrated that the expression levels of these markers were correlated with DCE-MRI parameters. PD-L1 expression levels were found to be significantly correlated with the maximum CI (CI-max; P=0.007), peak CI (CI-peak; P=0.007), maximum CI gain (CI-gain; P=0.006) and MVD (P=0.001) values. The mean CI-max, CI-peak, CI-gain and MVD values were significantly higher in tumors with high PD-L1 expression (P<0.05). MVD levels were also significantly correlated with the time of CI-max (T-max; P=0.003) and CI-gain (P=0.037). The mean CI-gain was significantly increased, and the mean T-max was significantly shorter in high MVD tumors (P<0.05 and P<0.01, respectively). In summary, the findings from the present study confirmed the correlation between CI parameters, derived from DCE-MRI, and MVD, and suggested that these parameters may be correlated with PD-L1 expression in OSCC tumor cells.

Dual-Energy Computed Tomography Imaging of Head: Virtual High-Energy Monochromatic (190 keV) Images Are More Reliable Than Standard 120 kV Images for Detecting Traumatic Intracranial Hemorrhages

High-energy monochromatic (190 keV) images may be more reliable than standard 120 kV Images for detecting intracranial hemorrhages. We aimed to retrospectively compare virtual high monochromatic (190 keV) and standard 120 kV images from dual-energy computed tomography (CT; DECT) for the diagnosis of intracranial hemorrhages in traumatic brain injury (TBI). We analyzed admission CT studies in 100 trauma patients. Three radiologists independently reviewed four image sets: 120 kV and 190 keV (thin [1 mm] and thick [5 mm] section) images for the presence of various types of intracranial hemorrhages. The proportions of positive variables were compared and differences calculated by McNemar test and sensitivities determined by contingency tables. Randomly selected hemorrhagic lesions were analyzed for contrast index (CI). Thin-section 190 keV images were superior in the detection of subdural hematomas (SDH) (p < 0.0001), supratentorial contusions (p < 0.0001), and epidural hematomas (EDH) (p = 0.014), when compared with standard 120 kV images. However, 190 keV images were inferior to standard 120 kV images in diagnosis of subarachnoid hemorrhage (SAH) (thin-sections, p = 0.059; thick-sections, 0.0075). The 190 keV images yielded moderate increase in CI of contusions (Cohen's d > 0.53) and a large increase in CI of extra-axial hematomas (Cohen's d > 0.86). Our results indicate that virtual high monochromatic (190 keV, thin-section) images combined with standard 120 kV images may provide optimal diagnostic performance for evaluation of patients suspected of TBI.

THE TECHNIQUE OF MAGNETIC RESONANCE IMAGING WITH DYNAMIC CONTRAST ENHANCEMENT WITH FOCAL BENIGN LUNG FORMATION

MRT with dynamic contrast enhancement has not found wide application in lung pathology, there are no clear recommendations for its implementation, no criteria for the goodness of the changes have been developed. The aim: of the study was to clarify the procedure for analyzing the data of DKU-MRI, the search for predictors of the quality of focal changes in the lungs. DKE-MRT performed 28 patients with verified benign changes in the lungs at a magnetic resonance tomograph of 1,5 T. As the analysis shows, the use of relative rather than absolute values with the calculation of the contrast index (CI), reflecting the degree of accumulation of a paramagnetic substance in the object of investigation relative to the main anatomical landmark-aorta, is a reliable sign of angiogenesis. In this case, it is necessary to focus on the zones of maximum intensity of the MR signal of the structure under study, the value of ROI can vary considerably. The CI in the hamartomas was 0,23–0,35. In the scar tissue, the CI values did not practically change throughout the study, being 0,21–0,25 relative to the peak density in the aorta. CI soft tissues and benign focal lesions of the lungs, the form of the curve of the paramagnetic circulation was comparable, being 0,25–0,3 relative to the peak density to the aorta. When analyzing the DKE-MRT curves, the concentration/time should be oriented to the zones of maximum intensity of the MR signal from vascular structures, focal lesions of the lungs, soft tissues of the back, while the ROI area is of no fundamental importance. As a criterion of good-quality focal formation of the lung should be guided by CI in soft tissues.

Indocyanine green fluorescence-navigated thoracoscopic anatomical segmentectomy.

To evaluate the feasibility and efficacy of thoracoscopic anatomical segmentectomy (TS-S) using three-dimensional computed tomography (3D-CT) reconstruction and indocyanine green-fluorescence (ICGF) navigation. Twenty TS-S procedures were performed for 15 primary lung cancers and 5 metastatic lung tumors. Preoperatively we evaluated the target segmental pulmonary artery and created a virtual intersegmental plane using 3D-CT reconstruction. Intraoperatively, the target segmental artery and bronchus were divided, and after intravenous systemic injection of indocyanine green (ICG, 0.25 mg/kg), ICGF of the non-target segments (NTS) was observed using infrared thoracoscopy (KARL STORZ Endoskope Japan K.K., Tokyo, Japan). We marked the border between target and NTS with electrocautery and divided the lung parenchyma along this border using electrocautery or staples. Strength of contrast between target and NTS was quantified as contrast index (CI) and compared over time. ICGF provided demarcation of sufficient clarity and duration to mark the lung surface in 19 patients (95%). TS-S was successfully performed in all patients. Mean operative duration was 186 min (90-310 min) and mean blood loss was 30 mL (0-107 mL). Demarcation appeared 20 s (10-100 s) after injection of ICG, and ICGF lasted 180 s (90-300 s). CI peaked 30 s after the appearance of ICGF and decreased over time. Effective contrast continued for 70 s (30-116 s), which was sufficient to mark the line of demarcation. There were no complications attributable to this method. ICGF navigation is a safe and effective technique for TS-S.

Orbital malignant lesions in adults: multiparametric MR imaging

To assess the benefit of combining diffusion-weighted imaging and dynamic contrast-enhanced (DCE) MR imaging in the preoperative evaluation of orbital lymphoma and other malignancies in adults. This retrospective study was institutional review board-approved and informed consent was waived. Pretreatment MR imaging was performed in 52 patients with malignant orbital lesions. Apparent diffusion coefficient (ADC) and DCE MR parameters were evaluated in 30 patients with orbital lymphoma and 22 patients with other orbital malignancies. Independent-samples t-test or Wilcoxon rank-sum test was used to compare parameters. The diagnostic capability was evaluated by using receiver operating characteristic curve (ROC) analysis. Lymphoma demonstrated significantly lower mean ADC (P<0.001), T max (P=0.001), enhancement ratio (ER) (P<0.001), contrast index (CI) (P<0.001) and significantly higher washout ratio (WR) (P=0.002) than other malignancies in the orbit. ROC analysis indicated that T max alone or a combination with ADC and ER showed the optimal sensitivity (96.67%), a combination of ADC and WR showed optimal specificity (95.45%), while a combination of ADC and ER showed optimal accuracy (90.38%) in differentiating lymphoma from other malignancies. Multiparametric MRI can help to differentiate orbital lymphoma and other malignancies.

A quantitative metrology for performance characterization of five breast tomosynthesis systems based on an anthropomorphic phantom.

In medical imaging systems, proper rendition of anatomy is essential in discerning normal tissue from disease. Currently, digital breast tomosynthesis (DBT) systems are evaluated using subjective evaluation of lesion visibility in uniform phantoms. This study involved the development of a new methodology to objectively measure the rendition of a 3D breast model by an anthropomorphic breast phantom, and its implementation on five clinical DBT systems of different makes and models. A 3D, patient-based breast phantom was fabricated based on XCAT breast models. This phantom was imaged on representative breast tomosynthesis systems. The ability of tomosynthesis systems to accurately reproduce the 3D structure of the breast was assessed by computational analysis of the resultant images in terms of three groups of indices: contrast index (CI), reflective of local difference between adipose and glandular material; adipose variability index (AVI), reflective of contributions of noise and artifacts within uniform adipose regions; and contrast detectability, which describes contrast against local background variability and is described by contrast variability index (CVI), coefficient of variation (COV), contrast to adipose variability index (CAVI), and contrast to noise ratio index (CNRI). The indices were obtained by comparing the image data to the gold standard 3D distribution of breast tissue in the model. Corresponding indices were measured within variable region of interest (ROI) sizes ranging from 10 to 37 mm. The characterization was performed on five tomosynthesis systems: Fuji Aspire Crystal, GE Essential, Hologic Dimension, IMS Giotto, and Siemens Inspiration, all evaluated at a fixed dose of 1.5 mGy average glandular dose, anonymized in random order from A to E. Results are provided as a function of ROI size. The systems ranked orders in terms of CI with values of 7.4%, 7.0%, 6.9%, 6.4%, and 5.2% for systems A-E, respectively. This system ranking was identical for CNRI. Both CI and CNRI were constant over ROI size. The ranking was similar for CVI. The COV also changed little with ROI size and was similar across systems. For 10 mm ROIs, the average system COV was 0.7, which reduced to 0.5 with 37 mm ROIs. Two systems (A and B) exhibited highest AVI values when measured in 10 mm ROIs. This, however, was ROI-size-dependent with the three other systems (C-E) yielding higher AVI values when measured with 37 mm ROIs. Two systems (B and E) showed inferior CAVI compared to others. The quality of rendition tracked with differences in image appearance across systems. The findings illustrate that the anthropomorphic phantom can be used as a basis to extract quantitative values of image attributes in DBT.

Automatic Mapping Extraction from Multiecho T2-Star Weighted Magnetic Resonance Images for Improving Morphological Evaluations in Human Brain

Mapping extraction is useful in medical image analysis. Similarity coefficient mapping (SCM) replaced signal response to time course in tissue similarity mapping with signal response to TE changes in multiecho T2-star weighted magnetic resonance imaging without contrast agent. Since different tissues are with different sensitivities to reference signals, a new algorithm is proposed by adding a sensitivity index to SCM. It generates two mappings. One measures relative signal strength (SSM) and the other depicts fluctuation magnitude (FMM). Meanwhile, the new method is adaptive to generate a proper reference signal by maximizing the sum of contrast index (CI) from SSM and FMM without manual delineation. Based on four groups of images from multiecho T2-star weighted magnetic resonance imaging, the capacity of SSM and FMM in enhancing image contrast and morphological evaluation is validated. Average contrast improvement index (CII) of SSM is 1.57, 1.38, 1.34, and 1.41. Average CII of FMM is 2.42, 2.30, 2.24, and 2.35. Visual analysis of regions of interest demonstrates that SSM and FMM show better morphological structures than original images, T2-star mapping and SCM. These extracted mappings can be further applied in information fusion, signal investigation, and tissue segmentation.

Magnetic resonance imaging (MRI) and dynamic MRI evaluation of extranodal non-Hodgkin lymphoma in oral and maxillofacial regions

The purpose of this study was to evaluate the diagnostic value of magnetic resonance imaging (MRI), especially dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), in extranodal non-Hodgkin lymphoma (NHL) of oral and maxillofacial regions. Thirteen cases with extranodal NHL were examined using MRI. T1-weighted images (T1WI) and T2-weighted images (T2WI) or short TI inversion recovery (STIR) images were obtained in all cases. Contrast-enhanced images and DCE-MRI were acquired in 10 and 7 cases, respectively. On DCE-MRIs, we analyzed the parameters as follows: contrast index at maximal contrast enhancement (CImax), maximum contrast index (CI) gain/CImax ratio, and washout ratios (WR(300), WR(600), and WR(900)) at 300, 600, and 900 seconds after contrast medium injection. The signal intensity of all lesions was hypointense to isointense on T1WIs and showed variable contrast enhancement patterns. On T2WIs and STIR images, the signal intensity was isointense to hyperintense in almost all cases. Analysis of DCE-MRI parameters in extranodal NHLs resulted in the identification of 4 types of CI curves according to CImax and WR: (1) CImax greater than 2.0 and WR(900) greater than 40%, (2) CImax greater than 2.0 and WR(900) less than 40%, (3) CImax less than 1.5 and WR(900) greater than 40%, and (4) CImax less than 1.5 and WR(900) greater than 40%. The signal intensities on MRI were not specific to extranodal NHL and resembled those of other tumor types. When CImax was less than 1.5 or WR900 was less than 40%, these parameters contributed to diagnosis in extranodal NHLs.

Minor salivary gland tumors in the oral cavity: Diagnostic value of dynamic contrast-enhanced MRI

ObjectiveTo evaluate the diagnostic value of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for minor salivary gland tumors in the oral cavity. Materials and methodsThirty-two patients with minor salivary gland tumors were examined preoperatively using DCE-MRI. Their maximum contrast index (CImax), time of CImax (Tmax), Tpeak; i.e., the time that corresponded to the CImax×0.90, and washout ratios (WR300 and WR600) were determined from contrast index (CI) curves. We compared these parameters between benign and malignant tumors and among the different histopathological types of minor salivary gland tumors. Then, we categorized the patients’ CI curves into four patterns (gradual increase, rapid increase with high washout ratio, rapid increase with low washout, and flat). ResultsStatistically significant differences in Tmax (P=0.004) and Tpeak (P=0.002) were observed between the benign and malignant tumors. Regarding each histopathological tumor type, significant differences in Tmax (P<0.001), Tpeak (P<0.001), and WR600 (P=0.026) were observed between the pleomorphic adenomas and mucoepidermoid carcinomas. It was difficult to distinguish between benign and malignant tumors using our CI curve classification because that two-thirds of the cases were classified into the same type (gradual increase). ConclusionThe DCE-MRI parameters of minor salivary gland tumors contributed little to their differential diagnosis compared with those for major salivary gland tumors. During the diagnosis of minor salivary gland tumors, Tmax is useful for distinguishing between benign and malignant tumors.

13N-NH3: a selective contrast-enhancing tracer for brain tumor

The purpose of this study is to determine whether there is a qualitative and quantitative relationship between the breakdown of the blood-brain barrier, defined radiologically by the contrast enhancement of MRI, and the uptake of N-NH3 in brain tumors. The results of N-NH3 PET in 42 patients suspected of having brain tumors were compared with the findings of contrast-enhanced MRI. A histopathological diagnosis was carried out in 33 patients, and a clinical diagnosis was performed in the remaining patients. PET and MRI images were visually inspected, and the contrast index (CI) of MRI and the uptake index (UI) of N-NH3 were measured. Contrast enhancement of MRIs was seen in 20 of 29 brain tumors (69%). Increased uptake of N-NH3 was seen in 24 of 29 brain tumors (83%). Nineteen of 20 contrast-enhancing brain tumors exhibited the increased uptake of N-NH3 (95%). Areas of the increased N-NH3 uptake corresponded to areas enhanced on MR images in the majority of cases. Five out of nine nonenhancing tumors exhibited increased uptake of N-NH3 (56%). The contrast enhancement of MRIs was seen in nine of 13 nonneoplastic lesions (69%). None of the nonneoplastic lesions showed increased uptake of N-NH3, yielding a specificity of 100% for brain tumors (0 of 13). CI for tumor tissue was 1.46+/-0.64. UI of N-NH3 for tumor tissue was 1.64+/-0.71. CI and UI for tumor tissue were significantly correlated (r=0.86, P<0.01). A statistically significant difference in uptake levels of N-NH3 between contrast-enhancing tumors and nonenhancing tumors (1.88+/-0.66, n=20 vs. 1.11+/-0.52, n=9, P<0.01) was observed. UI was higher in brain tumors compared with the nonneoplastic lesions (1.64+/-0.71 vs. 0.71+/-0.19, P<0.01). N-NH3 is a potential selective contrast-enhanced tracer for brain tumor, and may prove especially useful for evaluating the contrast-enhancing lesions on MRI to distinguish brain tumors from nonneoplastic lesions.

Diagnostic value of dynamic contrast-enhanced MRI in the salivary gland tumors

To evaluate the diagnostic value of dynamic contrast-enhanced MRI (DCE-MRI) in salivary gland tumors, thirty-five patients (47 lesions) who underwent MR examinations and were histopathologically diagnosed with salivary gland tumors in Okayama University Hospital, between April 1998 and March 2005, were entered in the present study. The parameters included CI(max300) or CI(max600), which was the contrast index (CI) at maximal contrast enhancement upon 300 s or 600 s, and Tmax, which was the time that corresponded to the CI(max300). Washout ratio (WR(300) or WR(600)) was defined as follows: CI(max300)-CI(300s)/CI(max300) or CI(max600)-CI(600s)/CI(max600)x100 (%), where CI(300) or CI(600) was the CI at 300s or 600s after contrast medium administration. We obtained the following results from the analysis of DCE-MRI parameters; (a) The salivary gland tumors were categorized into three CI curve types according to Tmax and WR300; Pleomorphic adenoma; Tmax > 210 s and WR300 < 10%, Warthin tumor; Tmax < 60 s and WR300 > 40%, and malignant tumor; 60s < Tmax < 210 s and 10% < WR300 < 30%; (b) On the basis of the relationship between Tmax and CImax or WR, all pleomorphic adenomas were successfully differentiated from Warthin tumor lesions. Of the 20 pleomorphic adenomas, 18 (90.0%) were successfully differentiated from malignant tumors. All Warthin tumor lesions were successfully differentiated from pleomorphic adenomas and malignant tumors. Of 12 the malignant tumors, 11 (91.7%) were successfully differentiated from pleomorphic adenomas. All malignant tumors were successfully differentiated from Warthin tumors. Thus, DCE-MRI parameters are useful in diagnosing salivary gland tumors on the basis of the combined assessment of Tmax and CImax or WR.

Contrast‐enhanced magnetic resonance angiography of the lower extremities: Standard‐dose vs. high‐dose gadodiamide injection

To compare the efficacy and safety of two different doses (0.1 and 0.3 mmol/kg of body weight [BW]) of gadodiamide for contrast-enhanced magnetic resonance angiography (ce-MRA) of the lower extremities with intraarterial digital subtraction angiography (IA-DSA). A total of 30 patients with peripheral arterial occlusive disease underwent IA-DSA and ce-MRA from the aortic bifurcation down to the ankle. Patients were randomized to receive a total dose of 0.1 or 0.3 mmol/kg of BW gadodiamide (Omniscan, Amersham Buchler), administered intravenously as a series of three automatic bolus injections. Ce-MRA was performed with a 1.5-T system using a body phased-array coil, centered stepwise over the calf, thigh, and pelvic region. A fast T1-weighted, three-dimensional gradient-echo sequence was obtained before and after injection of the allocated dose. IA-DSA was performed using the Seldinger technique and a femoral approach. The vessels under investigation were divided into 31 segments, and ce-MRA and IA-DSA image sets were evaluated in a double-blind fashion for the presence of stenosis, presence of collateral vessels, vessel delineation, and overall image quality. Both dose groups were compared with regard to contrast index (CI) and signal- and contrast-to-noise ratios (SNR, CNR). The occurrence of adverse events or side effects was also documented. Sensitivity, specificity, and accuracy were calculated in relation to the results of stenosis grading. A total of 26 patients were entered in the efficacy evaluation, while all 30 patients were included in the safety assessment. The sensitivity, specificity, and accuracy for the 0.1 and 0.3 mmol/kg dose groups were 78.8%/93.0%/88.9% vs. 60.2.%/91.5%/83.2%, respectively. The detection of collaterals was similar to IA-DSA for the 0.3 mmol/kg dose group (30.2% vs. 27.4%), but was lower in the 0.1 mmol/kg dose group (27.3% vs. 12.3%). The high-dose gadodiamide injection proved to be superior to the 0.1 mmol/kg dose group with regard to vessel delineation and overall image quality (P = 0.007 and P = 0.002, respectively). The difference between the two dose groups regarding CI, SNR, and CNR was significant (P = 0.0001), in favor of the 0.3 mmol/kg dose group. No adverse events were observed in any of the patients. Ce-MRA with gadodiamide is safe and efficacious. Comparison of two different doses with IA-DSA as the standard of reference showed that the 0.3 mmol/kg dose is superior to the standard 0.1 mmol/kg dose with respect to contrast enhancement, vessel delineation, image quality, and detection of collaterals. However, the 0.1 mmol/kg dose was superior to the high dose in the grading of stenosis.

Application of dynamic contrast-enhanced MRI to differentiate malignant lymphoma from squamous cell carcinoma in the head and neck

Because malignant lymphoma, the second most common malignant tumor of the head and neck, and squamous cell carcinoma (SCC), the most common malignant tumor of the head and neck, require different treatments, it is important to be able to differentiate them. In the present study, we attempted to differentiate malignant lymphomas from SCCs using dynamic contrast-enhanced MRI (DCE-MRI). Seventeen lesions (in 8 cases) of malignant lymphoma and 30 cases of SCC were compared by DCE-MRI. Thirteen of 17 malignant lymphomas (76.5%) showed the maximum contrast index (CI) at 90–180 s, while 26 of 30 SCCs (86.7%) showed the maximum CI at a much faster 60–105 s. There was a statistically significant difference between SCC and malignant lymphoma in the time needed reach the maximum CI ( p=0.0177). There was also significant difference between SCC and malignant lymphoma in their maximum CIs ( p<0.001), with the maximum CIs of 29/30 SCCs (96.7%) above 2.0, while 12/17 malignant lymphomas (70.6%) showed CIs of less than 2.0. We consider these findings to be useful for distinguishing lymphomas from SCCs.

Assessment of pleomorphic adenomas using MRI and dynamic contrast enhanced MRI

We evaluated magnetic resonance images (MRI) and the value of dynamic contrast enhanced MRI (DCE-MRI) of pleomorphic adenomas retrospectively. MRI was performed for 18 pleomorphic adenomas, including 11 cases with DCE-MRI. We obtained the following results on the MRI and DCE-MRI. (a) Pleomorphic adenomas showed a predilection for homogeneous intermediate signal intensity on T1-weighted images (T1WI), heterogeneous high signal intensity on T2-weighted images, and heterogeneous enhancement on Gd-T1WI. (b) Of 11 contrast index (CI) curves of pleomorphic adenomas, nine CI curves (81.8%) increased gradually to 600 s or increased gradually, reached a plateau, and sustained the plateau to 600 s. The remaining two (18.2%) increased gradually and decreased gradually thereafter. (c) CI curves reached the maximum CI index at 135–300 s.

The value of dynamic contrast-enhanced MRI in diagnosis of malignant lymphoma of the head and neck

In this study, we attempted to diagnose malignant lymphoma on the basis of magnetic resonance imagings (MRIs) and dynamic contrast-enhanced MRI (DCE-MRI). Eighteen lesions (in eight patients), all of which had been proven histopathologically, were detected on MRI. The eight patients included five patients with diffuse large B-cell lymphoma, one with B-cell low-grade MALT lymphoma, one with follicular lymphoma, and one with Hodgkin's lymphoma. Nine lesions were located in the submandibular region, three in the buccal region, two in the orbit region, two in the submental region, and one each in the palatal and tonsil regions. The diameter of the lesions ranged between 9 and 42.2 mm (average: 22.4 mm). The signal intensities (SIs) of the 18 lesions were examined on T1-weighted (T1WI), T2WI, and gadopentetate (Gd)-T1WI. One lesion in case 8 was excluded from DCE-MRI findings, i.e., the regions of interest could not be adequately set on DCE-MRIs. The contrast index (CI) curves of the remaining 17 lesions were prepared. All 18 lesions showed almost the same images on T1WI, T2WI, and Gd-T1WI, although they represented four types of lymphoma. The images showed homogeneous SI that was intermediate to slightly high SI on T1WI, slightly high SI on T2WI, and moderately enhanced on Gd-T1WI. Thus, the cases of malignant lymphoma in this study showed relatively characteristic features based on MRI; however, these features might be non-specific. The CI curves in this study showed a relatively rapid increase, reaching a maximum CI at 45–120 s, and a relatively rapid decrease in most lesions (14/17; 82.4%); on the other hand, the curves of 3 of the 15 lesions (17.6%) showed relatively rapid increase, sustenance of a plateau, and a gradual decrease thereafter. These patterns of CI curves may indicate characteristic features useful for distinguishing malignant lymphomas from other lesions.

Analysis of optical density and contrast in mammograms.

The objective of this project is the development of tools for the UK NHSBSP to assess image quality quantitatively in clinical films, for the purposes of optimizing imaging procedures and audit. As an initial step, 120 mammograms of 46 women on a single day of screening were digitized and analysed to produce indices of optical density (OD) and contrast. Analysis was performed on three regions of interest (ROI): pectoral muscle, main breast and skin edge. Two radiologists independently graded the quality of information in the different parts of each mammogram, and categorized breast type as either "dense", "mixed density" or "fatty". Measurements of contrast and OD generally correlated well with the opinions of the radiologists. For the oblique mammograms, the mean OD in the main breast ranged between films from 1.25 to 2.24 with a mean of 1.69 +/- 0.02. In the craniocaudal mammograms, the mean OD in the main breast ROI ranged from 1.14 to 1.94 with a mean of 1.61 +/- 0.05. The OD for a quality control film of a 40 mm block of PMMA exposed on the same day with this system was 1.53. A contrast index (CI) was calculated for each mammogram as the difference between the points of maximum and minimum OD in the main breast. Mean CI was 1.02 +/- 0.09 for fatty breasts, 1.50 +/- 0.10 for mixed density breasts and 2.05 +/- 0.23 for dense breasts. A review of the radiologist assessments indicated that the main breast was satisfactorily displayed when glandular and fatty tissues were displayed within the OD range 0.8-2.9. An analysis of the dynamic range requirements showed that 17% of films had a dynamic range that lay above that calculated using the suggested OD limits.