Biexponential Apparent Diffusion Coefficients Values in the Prostate: Comparison among Normal Tissue,Prostate Cancer,Benign Prostatic Hyperplasia and Prostatitis

Objective

To investigate the biexponential apparent diffusion parameters of diverse prostate tissues and compare them with monoexponential apparent diffusion coefficient (ADC) value in the efficacy to discriminate prostate cancer from benign lesions.

Materials and Methods

Eleven healthy volunteers and 61 patients underwent a conventional (b-factors 0, 1000 s/mm²) and a 10 b-factor (0 to 3000 s/mm²) diffusion-weighted imaging (DWI). The monoexponential ADC value and biexponential parameters of fast ADC (ADCf), fraction of ADCf (f), slow ADC (ADCs) value for 29 prostate cancer, 28 benign prostatic hyperplasia (BPH), 24 prostatitis lesions and normal tissue were calculated and compared. Receiver operating characteristic analysis was performed to determine the sensitivity, specificity and optimal cut-off points.

Results

Prostate cancer had lower ADC, ADCf, f, and ADCs than all other tissues (p < 0.01). Prostatitis exhibited a lower ADC, ADCf, ADCs and f than the peripheral zone tissue (p < 0.01), and BPH showed a lower ADC and ADCf than the central gland tissue (p < 0.01). The ADCf demonstrated a comparable accuracy with ADC in differentiating cancer from BPH [area under the curve (AUC) 0.93 vs. 0.92] and prostatitis AUC 0.98 vs. 0.99) (both p > 0.05), but the AUC of f and ADCs in differentiating cancer from BPH (0.73 and 0.81) and prostatitis (0.88 and 0.91) were significantly lower than ADC (all p < 0.05).

Conclusion

The biexponential DWI appears to provide additional parameters for tissue characterization in prostate, and ADCf helps to yield comparable accuracy with ADC in differentiating cancer from benign lesions.     

Osteosarcoma of the jaws: demographic and CT imaging features

Objective

The aim of this study was to evaluate the patient demographic and CT imaging findings of primary osteosarcoma of the jaws.

Methods

88 primary osteosarcomas of the jaws histopathologically diagnosed during 1997–2007 were reviewed. 21 cases of CT images were reviewed.

Results

Of 88 patients, 51 (58%) had tumours in the mandible and 37 (42%) in the maxilla. The mean age was 37.8 years (range 9–80 years). The male-to-female ratio was 1.32:1. The mean age of patients with mandibular lesions was 41.04 years and in those with maxillary lesions it was 33.3 years. CT imaging findings were available in 21 patients. In the maxilla (n = 9), all tumours (100%) arose from the alveolar ridge. In the mandible (n = 12), most tumours (9 cases, 75%), arose from the ramus and/or condyle. All except two lesions had the epicentrum within the medullary cavity of the involved bone. The presence of periosteal reaction was demonstrated in 13 cases (62%). Soft-tissue extension was present in 18 lesions (86%), with calcification identified in 13 (72%).

Conclusions

This study provides age, sex distribution, location and CT imaging features of primary osteosarcoma of the jaws.     

Dynamic CT Perfusion Imaging for the Detection of Crossed Cerebellar Diaschisis in Acute Ischemic Stroke

Objective

Although the detection of crossed cerebellar diaschisis (CCD) by means of different imaging modalities is well described, little is known about its diagnosis by computed tomography perfusion (CTP) imaging. We investigated the detection rate of CCD by CTP imaging and the factors related to CCD on CTP images in patients with acute ischemic stroke.

Materials and Methods

CT perfusion maps of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time-to-peak (TTP) obtained from 81 consecutive patients affected by an acute ischemic stroke were retrospectively reviewed. Whole-brain perfusion maps were obtained with a multichannel CT scanner using the toggling-table technique. The criteria for CCD was a unilateral supratentorial ischemic lesion and an accompanying decrease in perfusion of the contralateral cerebellar hemisphere on the basis of CTP maps by visual inspection without a set threshold. Maps were quantitatively analyzed in CCD positive cases.

Results

The criteria for CCD were fulfilled in 25 of the 81 cases (31%). Detection rates per CTP map were as follows: MTT (31%) > TTP (21%) > CBF (9%) > CBV (6%). Supratentorial ischemic volume, degree of perfusion reduction, and infratentorial asymmetry index correlated strongly (R, 0.555-0.870) and significantly (p < 0.05) with each other in CCD-positive cases.

Conclusion

It is possible to detect CCD on all four of the CTP-based maps. Of these maps, MTT is most sensitive in detecting CCD. Our data indicate that CTP imaging is a valid tool for the diagnosis of CCD in patients affected by an acute hemispheric stroke.     

Intra-Individual,Inter-Vendor Comparison of Diffusion-Weighted MR Imaging of Upper Abdominal Organs at 3.0 Tesla with an Emphasis on the Value of Normalization with the Spleen

Objective

To compare the apparent diffusion coefficient (ADC) values of upper abdominal organs with 2 different 3.0 tesla MR systems and to investigate the usefulness of normalization using the spleen.

Materials and Methods

Forty-one patients were enrolled in this prospective study, of which, 35 patients (M:F, 27:8; mean age ± standard deviation, 62.3 ± 12.3 years) were finally analyzed. In addition to the routine liver MR protocol, single-shot spin-echo echo-planar diffusion-weighted imaging using b values of 0, 50, 400, and 800 s/mm² in 2 different MR systems was performed. ADC values of the liver, spleen, pancreas, kidney and liver lesion (if present) were measured and analyzed. ADC values of the spleen were used for normalization. The Pearson correlation, Spearman correlation, paired sample t test, Wilcoxon signed rank test and Bland-Altman method were used for statistical analysis.

Results

For all anatomical regions and liver lesions, both non-normalized and normalized ADC values from 2 different MR systems showed significant correlations (r = 0.5196–0.8488). Non-normalized ADC values of both MR systems differed significantly in all anatomical regions and liver lesions (p < 0.001). However, the normalized ADC of all anatomical regions and liver lesions did not differ significantly (p = 0.065–0.661), with significantly lower coefficient of variance than that of non-normalized ADC (p < 0.009).

Conclusion

Normalization of the abdominal ADC values using the spleen as a reference organ reduces differences between different MR systems, and could facilitate consistent use of ADC as an imaging biomarker for multi-center or longitudinal studies.     

Diffusion-Weighted Imaging of a Prostate Cancer Xenograft Model Seen on a 7 Tesla Animal MR Scanner: Comparison of ADC Values and Pathologic Findings

Objective

To assess the relationship between apparent diffusion coefficient (ADC) values on diffusion-weighted magnetic resonance (MR) imaging and pathologic measures of a tumor using a prostate cancer xenograft model.

Materials and Methods

Eighteen athymic nude mice with 36 PC-3-induced tumors were sacrificed to obtain specimens immediately after MR imaging in order to compare the findings on MR images with those seen on pathological specimens. Using a high-field small-animal MR scanner, T1- and T2-weighted imaging and DW MR imaging was performed. Tumors were then processed for Hematoxylin and Eosin staining to evaluate tumor cellularity, intratumoral necrosis and immunostaining using antibodies directed against CD31 and vascular endothelial growth factor (VEGF) to determine the levels of microvessel density (MVD). Mean ADC values that were measured on the solid portion within each tumor were compared with tumor volume, cellularity, degree of necrosis, VEGF expression, and MVD in the corresponding section of the pathological specimen.

Results

Mean ADC values of the solid portion within the PC-3-induced high-grade tumors were significantly correlated with the degree of intratumoral necrosis (r = 0.63, p < 0.0001) and MVD (r = -0.44, p = 0.008) on pathologic slides. The ADC values were not significantly correlated with tumor cellularity, VEGF expression, or tumor volume in high-grade prostate cancer tissues.

Conclusion

In the xenografted prostate cancer model, the ADC values of the solid portion of the tumors are significantly correlated with tumor necrosis and MVD of the pathologic specimens. The ADC values may be utilized as surrogate markers for the noninvasive assessment of tumor necrosis and MVD in high-grade prostate cancer.     

Diffusion-Weighted MR Imaging of Intracerebral Hemorrhage

Objective

To document the signal characteristics of intracerebral hemorrhage (ICH) at evolving stages on diffusion-weighted images (DWI) by comparison with conventional MR images.

Materials and Methods

In our retrospective study, 38 patients with ICH underwent a set of imaging sequences that included DWI, T1-and T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR). In 33 and 10 patients, respectively, conventional and echo-planar T2* gradient-echo images were also obtained. According to the time interval between symptom onset and initial MRI, five stages were categorized: hyperacute (n=6); acute (n=7); early subacute (n=7); late subacute (n=10); and chronic (n=8). We investigated the signal intensity and apparent diffusion coefficient (ADC) of ICH and compared the signal intensities of hematomas at DWI and on conventional MR images.

Results

DWI showed that hematomas were hyperintense at the hyperacute and late subacute stages, and hypointense at the acute, early subacute and chronic stages. Invariably, focal hypointensity was observed within a hyperacute hematoma. At the hyperacute, acute and early subacute stages, hyperintense rims that corresponded with edema surrounding the hematoma were present. The mean ADC ratio was 0.73 at the hyperacute stage, 0.72 at the acute stage, 0.70 at the early subacute stage, 0.72 at the late subacute stage, and 2.56 at the chronic stage.

Conclusion

DWI showed that the signal intensity of an ICH may be related to both its ADC value and the magnetic susceptibility effect. In patients with acute stroke, an understanding of the characteristic features of ICH seen at DWI can be helpful in both the characterization of intracranial hemorrhagic lesions and the differentiation of hemorrhage from ischemia.     

Serial diffusion-weighted imaging in MELAS

Clinical features of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) resemble those of cerebral infarcts, but the pathogenesis of infarct-like lesions is not fully understood. To characterise these infarct-like lesions, we studied two patients with MELAS using diffusion-weighted (DWI) MRI before and after stroke-like episodes and measured the apparent diffusion coefficient (ADC) in the new infarct-like lesions. These gave high signal on DWI and had much higher ADC than normal-appearing regions. The ADC remained high even 30 days after a stroke-like episode then decreased in lesions, with or without abnormality as shown by conventional MRI. We speculate that early elevation of ADC in the acute or subacute phase reflects vasogenic rather than cytotoxic edema. The ADC of the lesions, which disappeared almost completely with clinical improvement, returned to normal levels, which may reflect tissue recovery without severe damage. To our knowledge, this is the first study of DWI in MELAS. Received: 13 September 1999/Accepted: 7 January 2000     

Effects of MR Parameter Changes on the Quantification of Diffusion Anisotropy and Apparent Diffusion Coefficient in Diffusion Tensor Imaging: Evaluation Using a Diffusional Anisotropic Phantom

Objective

To validate the usefulness of a diffusional anisotropic capillary array phantom and to investigate the effects of diffusion tensor imaging (DTI) parameter changes on diffusion fractional anisotropy (FA) and apparent diffusion coefficient (ADC) using the phantom.

Materials and Methods

Diffusion tensor imaging of a capillary array phantom was performed with imaging parameter changes, including voxel size, number of sensitivity encoding (SENSE) factor, echo time (TE), number of signal acquisitions, b-value, and number of diffusion gradient directions (NDGD), one-at-a-time in a stepwise-incremental fashion. We repeated the entire series of DTI scans thrice. The coefficients of variation (CoV) were evaluated for FA and ADC, and the correlation between each MR imaging parameter and the corresponding FA and ADC was evaluated using Spearman''s correlation analysis.

Results

The capillary array phantom CoVs of FA and ADC were 7.1% and 2.4%, respectively. There were significant correlations between FA and SENSE factor, TE, b-value, and NDGD, as well as significant correlations between ADC and SENSE factor, TE, and b-value.

Conclusion

A capillary array phantom enables repeated measurements of FA and ADC. Both FA and ADC can vary when certain parameters are changed during diffusion experiments. We suggest that the capillary array phantom can be used for quality control in longitudinal or multicenter clinical studies.     

Assessment of Tissue Viability Using Diffusion- and Perfusion-Weighted MRI in Hyperacute Stroke

Objective

The aim of this study was to investigate the relationship between the diffusion and perfusion parameters in hyperacute infarction, and we wanted to determine the viability threshold for the ischemic penumbra using diffusion- and perfusion-weighted imaging (DWI and PWI, respectively).

Materials and Methods

Both DWI and PWI were performed within six hours from the onset of symptoms for 12 patients who had suffered from acute stroke. Three regions of interest (ROIs) were identified: ROI 1 was the initial lesion on DWI; ROI 2 was the DWI/PWI mismatch area (the penumbra) that progressed onward to the infarct; and ROI 3 was the mismatch area that recovered to normal on the follow-up scans. The ratios of apparent diffusion coefficient (ADC), the relative cerebral blood volume (rCBV), and the time to peak (TTP) were calculated as the lesions'' ROIs divided by the contralateral mirror ROIs, and these values were then correlated with each other. The viability threshold was determined by using the receiver operating characteristic (ROC) curves.

Results

For all three ROIs, the ADC ratios had significant linear correlation with the TTP ratios (p < 0.001), but not with the rCBV ratios (p = 0.280). There was no significant difference for the ADC and rCBV ratios within the ROIs. The mean TTP ratio/TTP delay between the penumbras'' two ROIs showed a significant statistical difference (p < 0.001). The cutoff value between ROI 2 and ROI 3, as the viability threshold, was a TTP ratio of 1.29 (with a sensitivity and specificity of 86% and 73%, respectively) and a TTP delay of 7.8 sec (with a sensitivity and specificity of 84% and 72%, respectively).

Conclusion

Determining the viability thresholds for the TTP ratio/delay on the PWI may be helpful for selecting those patients who would benefit from the various therapeutic interventions that can be used during the acute phase of ischemic stroke.     

Transient Ischemic Attack and Stroke Can Be Differentiated by Analyzing the Diffusion Tensor Imaging

Objective

We wanted to differentiate between transient ischemic attack (TIA) and minor stroke using fractional anisotropy and three-dimensional (3D) fiber tractography.

Materials and Methods

The clinical data, conventional magnetic resonance imaging (MRI), diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) were obtained for 45 TIA patients and 33 minor stroke patients. The fractional anisotrophy ratio (rFA) between the lesion and the mirrored corresponding contralateral normal tissue was calculated and analyzed. The spatial relationship between the lesion and the corticospinal tract (CST) was analyzed and the lesion sizes in the minor stroke patients and TIA patients were compared.

Results

Twenty-two of the 45 TIA patients (49%) revealed focal abnormalities following DWI. The rFA was significantly lower (p < 0.05) in the stroke patients (0.71 ± 0.29) compared to that of the TIA patients (1.05 ± 0.37). The CST was involved in almost all stroke lesions, but it was not involved in 68% of the TIA lesions. The TIA patients had significantly lower CST injury scores (3.25 ± 1.75) than did the stroke patients (8.80 ± 2.39) (p = 0.004).

Conclusion

Our data indicate that TIA and minor stroke can be identified by analyzing the rFA and the degree of CST involvement, and this may also allow more accurate prediction of a patient''s long-term recovery or disability.     

Imaging Features of Gray-Scale and Contrast-Enhanced Color Doppler US for the Differentiation of Transient Renal Arterial Ischemia and Arterial Infarction

Objective

To characterize the imaging features on gray-scale and contrast-enhanced color Doppler US images which differentiate renal ischemia from renal infarction.

Materials and Methods

The segmental renal arteries of eight healthy rabbits were surgically ligated. In four of these rabbits, the ligated renal artery was released 60 minutes after arterial occlusion to cause transient ischemia. In the remaining four rabbits, the arterial ligation was retained to cause a permanent infarction. The gray-scale and contrast-enhanced color Doppler US imaging features of the involved renal parenchyma of both ischemia and infarction groups were compared with respect to the presence or absence of parenchymal swelling, echogenicity changes, tissue loss and perfusion defects.

Results

Parenchyma swelling, echogenic changes, tissue loss and perfusion defects were found to be more extensive in the infarction than the ischemia group. The hyperechoic areas reperfused with blood flow recovered normal echogenicity and perfusion, whereas the hyperechoic areas without reperfusion became renal infarcts.

Conclusion

Gray-scale and contrast-enhanced color Doppler US showed that the hyperechoic areas with reperfusion may reverse to normal parenchyma and allow the differentiation of renal ischemia from renal infarction.     

MRI findings in the lumbar spines of asymptomatic, adolescent, elite tennis players

Objective

To describe magnetic resonance imaging (MRI) findings in the lumbar spine in asymptomatic elite adolescent tennis players, to serve as the baseline for a future prospective longitudinal cohort study.

Design

Observational study.

Setting

Institutional, national tennis centre.

Participants

33 asymptomatic elite adolescent tennis players, mean (SD) age, 17.3 (1.7) years (18 male, 15 female).

Methods

Sagittal T1, T2, STIR, and axial T2 weighted MRI images were reviewed for the presence of abnormalities by two radiologists in consensus. Abnormalities included disc degeneration, disc herniation, pars lesions (fracture or stress reaction), and facet joint arthropathy.

Results

Five players (15.2%) had a normal MRI examination and 28 (84.8%) had an abnormal examination. Nine players showed pars lesions (10 lesions; one at two levels) predominately at the L5 level (9/10, L5; 1/10, L4). Three of the 10 lesions were complete fractures; two showed grade 1 and one grade 2 spondylolisthesis, both of which resulted in moderate narrowing of the L5 exit foramen. There were two acute and five chronic stress reactions of the pars. Twenty three patients showed signs of early facet arthropathy occurring at L5/S1 (15/29 joints) and L4/5 (12/29 joints). These were classified as mild degeneration (20/29) and moderate degeneration (9/29), with 20/29 showing sclerosis and 24/29 showing hypertrophy of the facet joint. Synovial cysts were identified in 14 of the 29 joints. Thirteen players showed disc desiccation and disc bulging (mild in 13; moderate in two) most often at L4/5 and L5/S1 levels (12 of 15 discs).

Conclusions

Abnormalities were frequent, predominately in the lower lumbar spine, almost exclusively at L4/5 and L5/S1 levels. Pars injuries and facet joint arthroses were relatively common.     

Brain MRI Findings of Carbon Disulfide Poisoning

Objective

To evaluate the findings of brain MRI in patients with carbon disulfide poisoning.

Materials and Methods

Ninety-one patients who had suffered carbon disulfide poisoning [male:female=87:4; age, 32-74 (mean 53.3) years] were included in this study. To determine the extent of white matter hyperintensity (Grade 0-V) and lacunar infarction, T2-weighted MR imaging of the brain was performed.

Results

T2-weighted images depicted white matter hyperintensity in 70 patients (76.9%) and lacunar infarcts in 27 (29.7%).

Conclusion

In these patients, the prevalent findings at T2-weighted MR imaging of the brain were white matter hyperintensity and lacunar infarcts. Disturbance of the cardiovascular system by carbon disulfide might account for these results.     

Myocardial Blood Flow and Flow Reserve in Proximal and Mid-to-Distal Lesions of Left Anterior Descending Artery Measured By N-13 Ammonia PET/CT

Purpose

The purpose of this study is to compare the myocardial blood flow (MBF) and flow reserve (MFR) between proximal and mid-to-distal lesions of the left anterior descending artery (pLAD and mdLAD, respectively) using N-13 ammonia positron emission tomography/computed tomography (PET/CT).

Methods

Subjects were 11 patients (six men and five women, mean age 64.5 years) with known coronary artery disease (CAD) involving LAD studied by N-13 ammonia PET/CT. They were divided into two groups by the location of stenotic lesions, i.e. pLAD versus mdLAD. Global and regional MBF and MFR were measured and compared. Characteristics of perfusion defects including the number of involved segments, basal area involvement, location, size, and shape were also compared between the two groups.

Results

The regional MFR in mid-anterior segment was significantly lower in pLAD group (1.80 ± 0.35 vs 2.76 ± 1.13 for pLAD and mdLAD groups, respectively, p = 0.034), while global MFR was not different (2.10 ± 1.10 vs 2.34 ± 0.84). Both stress and rest MBF in LAD territories were not different in both groups. The size of the perfusion defects were significantly larger in pLAD group (44.0 ± 11.5 % vs 21.1 ± 15.8 %, p = 0.041). Other characteristics such as location, basal area involvement, and shape were not significantly different between two groups.

Conclusions

The proximal lesion makes lower MFR in the mid-anterior segment and larger perfusion defect in the LAD territory but comparable MBF compared with mdLAD lesion.

Electronic supplementary material

The online version of this article (doi:10.1007/s13139-013-0208-6) contains supplementary material, which is available to authorized users.     

Effect of Arterial Deprivation on Growing Femoral Epiphysis: Quantitative Magnetic Resonance Imaging Using a Piglet Model

Objective

To investigate the usefulness of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion MRI for the evaluation of femoral head ischemia.

Materials and Methods

Unilateral femoral head ischemia was induced by selective embolization of the medial circumflex femoral artery in 10 piglets. All MRIs were performed immediately (1 hour) and after embolization (1, 2, and 4 weeks). Apparent diffusion coefficients (ADCs) were calculated for the femoral head. The estimated pharmacokinetic parameters (Kep and Ve from two-compartment model) and semi-quantitative parameters including peak enhancement, time-to-peak (TTP), and contrast washout were evaluated.

Results

The epiphyseal ADC values of the ischemic hip decreased immediately (1 hour) after embolization. However, they increased rapidly at 1 week after embolization and remained elevated until 4 weeks after embolization. Perfusion MRI of ischemic hips showed decreased epiphyseal perfusion with decreased Kep immediately after embolization. Signal intensity-time curves showed delayed TTP with limited contrast washout immediately post-embolization. At 1-2 weeks after embolization, spontaneous reperfusion was observed in ischemic epiphyses. The change of ADC (p = 0.043) and Kep (p = 0.043) were significantly different between immediate (1 hour) after embolization and 1 week post-embolization.

Conclusion

Diffusion MRI and pharmacokinetic model obtained from the DCE-MRI are useful in depicting early changes of perfusion and tissue damage using the model of femoral head ischemia in skeletally immature piglets.     

Diagnosing Small Hepatic Cysts on Multidetector CT: an Additional Merit of Thinner Coronal Reformations

Objective

We wanted to validate the additional merit of the thinner coronal reformation images from multidetector CT (MDCT) for making the diagnosis of hepatic cysts.

Materials and Methods

For the 90 benign hepatic cysts confirmed on MRI, the transverse (5-mm thickness) and additional coronal (2-mm thickness) reformation images from MDCT were compared with each other in terms of the Hounsfield units (HUs) and the size of each hepatic cyst.

Results

The attenuations (mean: 17.2 HUs, standard deviation: ± 14.4) on the thinner coronal images were significantly lower than those (mean: 40.7 HUs; standard deviation: ± 20.6) on the thicker transverse images for the small hepatic cysts (≤ 10 mm on the transverse image, p < 0.01). Twenty-three (79%) of the 29 cysts between 5 mm and 10 mm and 21 (51%) of 41 lesions up to 5 mm showed a mean HU value of 20 or less on the coronal reformation images.

Conclusion

By reducing the partial volume effect, routine coronal reformation of MDCT with a thinner section thickness can provide another merit for making a confidential diagnosis of many small sub-centimeter hepatic cysts, and these small cysts are not easily characterized on the conventional transverse images.     

The value of diffusion-weighted MRI in the diagnosis of malignant and benign urinary bladder lesions

Objectives

To investigate the role of diffusion-weighted MRI (DWI) in the diagnosis of urinary bladder (UB) tumours by means of measuring apparent diffusion coefficient (ADC) values.

Methods

A total of 83 people aged between 18 and 86 years were included in the study: 63 patients with UB pathology (46 malignant, 17 benign) constituted the case group; 20 individuals without any UB pathology constituted the control group. DWI was applied to all individuals. The ADC values were measured based on the tissue of the UB mass entities and normal UB wall in the control group.

Results

The mean ADC value in the UB carcinoma group was significantly lower than that in the control group: 1.0684 ± 0.26 × 10⁻³ mm² s^–1 and 2.010 ± 0.11 × 10⁻³ mm² s^–1, respectively (p<0.01). There was a significant difference among the mean ADC values of different grades of malignant tumours, corresponding to 0.9185 ± 0.20 mm² s^–1 and 1.281 ± 0.18 mm² s^–1 in high-grade and low-grade malignant UB carcinomas, respectively (p<0.01). The ADC value in the carcinoma group was significantly lower than that in the benign lesion group: 1.0684 ± 0.26 × 10⁻³ mm² s^–1 and 1.803 ± 0.19 × 10⁻³ mm² s^–1, respectively (p<0.01). All 46 malignant lesions displayed a restriction in diffusion; 4 of the 17 benign lesions displayed a mild restriction in diffusion. The sensitivity, specificity and accuracy of DWI in the diagnosis of malignant UB lesions was 100%, 76.5% and 93.65%, respectively.

Conclusion

DWI can be beneficial in the differentiation of benign and malignant UB lesions, as well as of high-grade and low-grade UB carcinomas, using quantitative ADC measurements.In recent years, a number of different MRI methods together with conventional ones have been used as part of a routine radiodiagnostic application. Diffusion-weighted MRI (DWI) is considered to be such an imaging method, evaluated within the context of functional MRI and based on the measurement of the accelerated or decelerated microscopic diffusion movements in the protons of the tissues'' water molecules. Images can be obtained in short-period snapshots and do not require any contrast [1-4].The use of DWI had previously been limited to brain examinations because it is sensitive to cardiac, respiratory and peristaltic movements; however, it has been adopted for a much broader use, i.e. for other parts of the body, with the development of fast MRI sequences such as echoplanar imaging (EPI). In early studies, the diffusion-weighted images and the apparent diffusion coefficient (ADC) of tissues and lesions were measured, and the different values obtained were shown to be useful in the differential diagnosis. In later studies, it was reported that ADC vales were related to the cellular intensity of a tumour, and a significant reduction in ADC indicated a malignant tumour [1-4].In DWI studies conducted on patients with head and neck lesions, the mean ADC level was significantly lower in malignant lymphomas, moderately low in patients with carcinomas, moderately high in those with a benign solid masses and markedly higher in those with benign cystic lesions [5].In recent years, DWI has been adopted for widespread use in abdominal examinations. In DWI studies conducted on liver masses, patients with metastatic lesions and hepatocellular carcinoma showed significantly lower ADC levels, those with cavernous haemangiomas showed moderately higher ADC levels, and those with cysts showed markedly higher ADC levels [6].There are also studies reporting that benign renal tumours have much higher ADC values than malignant tumours, and that cystic renal lesions have much higher ADC values than benign solid renal tumours [7].Various researchers in different studies have pointed out that DWI can be an important diagnostic tool in the detection and characterisation of tumours in different regions such as breast, prostate, bladder, cervix, colon, ovary, pancreas and liver. In these studies, it was also indicated that malignant tumours showed much more diffusion restriction and much lower ADC levels than benign tumours owing to their cellularity [8,9].Although DWI studies conducted on bladder masses have not been reported on a broader scale, there has been an increasing tendency to conduct such studies recently. In these studies, the mean ADC levels in bladder tumours have been compared with the surrounding soft tissues and statistically significant results have been obtained. ADC levels in bladder carcinomas were found to be significantly lower than those of the surrounding soft tissues. DWI was also found to have a high sensitivity and specificity in the detection of bladder tumours [10,11].In this study, the mean ADC values obtained from malignant and benign urinary bladder wall pathologies in patients referred to our clinic with a prediagnosis of bladder tumour were compared with the mean ADC values of normal bladder wall in the control group. Also, the ADC levels of the histopathological subgroups of patients with urinary bladder carcinomas were compared among each other. Our aim was to investigate whether DWI could be used in the differentiation of malignant and benign urinary bladder lesions, and whether ADC values found in malignancies could provide any information about the nature of the malignant masses, and thus to research the diagnostic contribution of DWI in standard treatment protocols.     

Time Efficiency and Diagnostic Accuracy of New Automated Myocardial Perfusion Analysis Software in 320-Row CT Cardiac Imaging

Objective

We aimed to evaluate the time efficiency and diagnostic accuracy of automated myocardial computed tomography perfusion (CTP) image analysis software.

Materials and Methods

320-row CTP was performed in 30 patients, and analyses were conducted independently by three different blinded readers by the use of two recent software releases (version 4.6 and novel version 4.71GR001, Toshiba, Tokyo, Japan). Analysis times were compared, and automated epi- and endocardial contour detection was subjectively rated in five categories (excellent, good, fair, poor and very poor). As semi-quantitative perfusion parameters, myocardial attenuation and transmural perfusion ratio (TPR) were calculated for each myocardial segment and agreement was tested by using the intraclass correlation coefficient (ICC). Conventional coronary angiography served as reference standard.

Results

The analysis time was significantly reduced with the novel automated software version as compared with the former release (Reader 1: 43:08 ± 11:39 min vs. 09:47 ± 04:51 min, Reader 2: 42:07 ± 06:44 min vs. 09:42 ± 02:50 min and Reader 3: 21:38 ± 3:44 min vs. 07:34 ± 02:12 min; p < 0.001 for all). Epi- and endocardial contour detection for the novel software was rated to be significantly better (p < 0.001) than with the former software. ICCs demonstrated strong agreement (≥ 0.75) for myocardial attenuation in 93% and for TPR in 82%. Diagnostic accuracy for the two software versions was not significantly different (p = 0.169) as compared with conventional coronary angiography.

Conclusion

The novel automated CTP analysis software offers enhanced time efficiency with an improvement by a factor of about four, while maintaining diagnostic accuracy.     

Multiphasic Perfusion CT in Acute Middle Cerebral Artery Ischemic Stroke: Prediction of Final Infarct Volume and Correlation with Clinical Outcome

Objective

To assess the utility of multiphasic perfusion CT in the prediction of final infarct volume, and the relationship between lesion volume revealed by CT imaging and clinical outcome in acute ischemic stroke patients who have not undergone thrombolytic therapy.

Materials and Methods

Thirty-five patients underwent multiphasic perfusion CT within six hours of stroke onset. After baseline unenhanced helical CT scanning, contrast-enhanced CT scans were obtained 20, 34, 48, and 62 secs after the injection of 90 mL contrast medium at a rate of 3 mL/sec. CT peak and total perfusion maps were obtained from serial CT images, and the initial lesion volumes revealed by CT were compared with final infarct volumes and clinical scores.

Results

Overall, the lesion volumes seen on CT peak perfusion maps correlated most strongly with final infarct volumes (R²=0.819, p<0.001, slope of regression line=1.016), but individual data showed that they were less than final infarct volume in 31.4% of patients. In those who showed early clinical improvement (n=6), final infarct volume tended to be overestimated by CT peak perfusion mapping and only on total perfusion maps was there significant correlation between lesion volume and final infarct volume (R²=0.854, p=0.008). The lesion volumes depicted by CT maps showed moderate correlation with baseline clinical scores and clinical outcomes (R=0.445-0.706, p≤0.007).

Conclusion

CT peak perfusion maps demonstrate strong correlation between lesion volume and final infarct volume, and accurately predict final infarct volume in about two-thirds of the 35 patients. The lesion volume seen on CT maps shows moderate correlation with clinical outcome.     

The Significance of Perfusion Defect at Myocardial Perfusion MR Imaging in a Cat Model of Acute Reperfused Myocardial Infarction

Objective

To determine whether the size of a perfusion defect seen at myocardial perfusion MR imaging represents the extent of irreversibly damaged myocardium in acute reperfused myocardial infarction.

Materials and Methods

In nine cats, reperfused myocardial infarction was induced by occlusion of the left anterior descending coronary artery for 90 minutes and subsequent reperfusion for 90 minutes. At single-slice myocardial perfusion MR imaging at the midventricular level using a turbo-FLASH sequence, 60 short-axis images were sequentially obtained with every heart beat after bolus injection of gadomer-17. The size of the perfusion defect was measured and compared with both the corresponding unstained area seen at triphenyl tetrazolium chloride (TTC) staining and the hyperenhanced area seen at gadophrin-2-enhanced MR imaging performed in the same cat six hours after myocardial perfusion MR imaging.

Results

The sizes of perfusion defects seen at gadomer-17-enhanced perfusion MR imaging, unstained areas at TTC staining, and hyperenhanced areas at gadophrin-2-enhanced MR imaging were 20.4 ± 4.3%, 29.0 ± 9.7%, and 30.7 ± 10.6% of the left ventricular myocardium, respectively. The perfusion defects seen at myocardial perfusion MR imaging were significantly smaller than the unstained areas at TTC staining and hyperenhanced areas at gadophrin-2-enhanced MR imaging (p < .01). The sizes of both the perfusion defect at myocardial perfusion MR imaging and the hyperenhanced area at gadophrin-2-enhanced MR imaging correlated well with the sizes of unstained areas at TTC staining (r = .64, p = .062 and r = .70, p = .035, respectively).

Conclusion

In this cat model, the perfusion defect revealed by myocardial perfusion MR imaging underestimated the true size of acute reperfused myocardial infarction. The defect may represent a more severely damaged area of infarction and probably has prognostic significance.