Peak Value Time Research Articles

Contrast-enhanced ultrasonography of the hepatic vein in normal dogs.

Contrast-enhanced ultrasonography (CEUS) of the hepatic vein can assess intrahepatic hemodynamic changes and has been studied as a noninvasive method to assess the severity of portal hypertension and hepatic fibrosis in humans. However, few reports have described its usefulness in veterinary medicine. The purpose of this study was to characterize CEUS findings of the hepatic vein in normal dogs and assess the repeatability of this method both in a conscious group (n=6) and a sedated group (n=6). Sonazoid® (0.01 ml/kg) was used as a contrast agent, and scanning of the hepatic vein was performed for 2 min. Time-intensity curves were generated from regions of interest in the hepatic vein. Four perfusion parameters were measured for quantitative analysis: hepatic vein arrival time (HVAT), time to peak (TTP), time to peak phase (TTPP) and wash-out ratio (WR). CEUS examinations were performed three times in each dog. The median (range) values of HVAT, TTP, TTPP and WR in the conscious group were 13.5 sec (9–22 sec), 12.5 sec (6–24 sec), 8 sec (6–13 sec) and 78.0% (60.7–91.7%), respectively. Median (range) values of HVAT, TTP, TTPP and WR in the sedated group were 12 sec (8–17 sec), 12.5 sec (9–17 sec), 9 sec (7–13 sec) and 84.1% (63.0–94.4%), respectively. The coefficients of variation of these parameters in the conscious and sedated groups were 7.6–29.7% and 11.8–14.8%, respectively.

Value of liver perfusion imaging of 256-slice CT in evaluation of the cirrhosis

To investigate the value of liver perfusion imaging of 256-slice CT in evaluating the compensated and decompensated cirrhosis. A total of 20 patients with liver cirrhosis, who were confirmed by liver biopsy, clinical symptoms and imaging, were selected from December 2012 to June 2014. According to the results of liver biopsy and the Child-Pugh classification, the patients were divided into a compensated cirrhosis group (n=8) and a decompensated cirrhosis group (n=12). Eleven cases without liver and spleen diseases were served as a control group. All subjects were under the 256-CT liver perfusion (256-CTP). The data of CTP [hepatic arterial perfusion (HAP), portal venous perfusion (PVP), total liver perfusion (TLP), hepatic perfusion index (HPI)] were obtained according to liver perfusion type, and the data of CTP [liver perfusion (LP), peak enhanced (PE), time to peak (TTP), blood volume (BV)] were obtained according to general perfusion type. Spearman rank correlation was used to analyze the correlation of liver cirrhosis with perfusion parameters. The receiver operating characteristic (ROC) curve was used to predict liver cirrhosis, and the maximized Youden index was served as the optimal cutoff value, then the area under curve, sensitivity and specificity were calculated. The PVP, TLP and PE values in the control group, the compensated cirrhosis group and the decompensated cirrhosis group were (76.63±37.26), (38.78±16.13) and (36.14± 15.31) mL/(100 mL·min); (98.48±43.58), (55.63±14.47) and (54.41±20.81) mL/(100 mL·min); (55.62±18.25), (44.11±5.79) and (41.08±7.74) HU, respectively, showing a gradual downward trend and a significant difference among the 3 groups (all P <0.05). HPI values were (19.50±6.08)%, (31.81±16.48)% and (34.47±16.04)%; TTP values were (37.32±8.59), (47.06±14.61), (59.86±20.87) s, respectively, showing a gradual upward trend and significant difference among the 3 groups ( all P<0.05). There was no significant difference in the HAP, LP and BV among the 3 groups (all P>0.05). PVP, TLP, PE and LP were negatively correlated with the process of liver cirrhosis (r=-0.592, -0.567, -0.409, -0.569, all P<0.05), but HPI and TTP were positively correlated with the process of liver cirrhosis (r=0.434 and 0.538, both P<0.05). 256-CTP could provide useful information for the assessment of liver cirrhosis by measuring a plurality of perfusion parameters. The hepatic microvascular changes in patients with liver cirrhosis could be quantitatively assessed by perfusion CT. TTP shows high efficiency in prediction of liver cirrhosis and decompensated liver cirrhosis.

The process of change in hemodynamics after revascularization in the ischemic brain.

In patients with a high-degree of internal carotid artery stenosis, cerebral hemodynamics and metabolism are compromised during ischemia. Revascularization improves cortical hemodynamics and oxygen metabolism during functional activity, but the process by which it occurs is still controversial. Therefore, using functional near-infrared spectroscopy (fNIRS), we investigated the process by which cerebral hemodynamics improve after revascularization surgery. Eight patients with severe carotid artery stenosis were examined using fNIRS during a motor task before and after surgery. We evaluated postoperative changes in total hemoglobin and deoxyhemoglobin (HbR), at 2 weeks after surgery, and again at 3 months after surgery. Parameters measured were the TTP (time to peak) value, defined as the time taken to reach 70% of the maximum total hemoglobin concentration, and the increase in HbR during the motor task. TTP was higher in four patients preoperatively, but this was no longer evident in two of the patients at 2 weeks after surgery. An increase in HbR during the task was observed in six patients before surgery, and was maintained at 2 weeks after surgery. However, in three of these patients, this increase was no longer evident 3 months later. These changes observed using fNIRS suggest that the increase in cerebral blood flow after revascularization surgery is followed by improvement in parenchymal vasodilation and neuronal oxygen metabolism.

SU‐E‐J‐07: A Functional MR Protocol for the Pancreatic Tumor Delineation

Purpose:Pancreatic cancer is one of the cancers with the poorest survival prognosis. At the time of diagnosis most of pancreatic cancers are unresectable and those patients can be treated by radiotherapy. Radiotherapy for pancreatic cancer is limited due to uncertainties in CT‐based delineations. MRI provides an excellent soft tissue contrast. Here, an MR protocol is developed to improve delineations for radiotherapy treatment of pancreatic cancer. In a later stage this protocol can also be used for on‐line visualization of the pancreas during MRI guided treatments.Methods:Nine pancreatic cancer patients were included. The MR protocol included T2 weighted(T2w), T1 weighted(T1w), diffusion weighted(DWI) and dynamic contrast enhanced(DCE) techniques. The tumor was delineated on T2w and T1w MRI by an experienced radiation oncologist. Healthy pancreas or pancreatitis (assigned by the oncologist based on T2w) areas were also delineated. Apparent diffusion coefficient(ADC), and area under the curve(AUC)/time to peak(TTP) maps were obtained from DWI and DCE scans, respectively.Results:A clear demarcation of tumor area was visible on b800 DWI images in 5 patients. ADC maps of those patients characterized tumor as an area with restricted water diffusion. Tumor delineations based on solely DCE were possible in 7 patients. In 6 of those patients AUC maps demonstrated tumor heterogeneity: a hypointense area with a hyperintense ring. TTP values clearly discriminated the tumor and the healthy pancreas but could not distinguish tumor and the pancreatitis accurately.Conclusion:MR imaging results in a more pronounced tumor contrast than contrast enhanced CT. The addition of quantitative, functional MRI provides valuable, additional information to the radiation oncologist on the spatial tumor extent by discriminating tumor from the healthy pancreas(TTP, DWI) and characterizing the tumor(ADC). Our findings indicate that tumor delineation in pancreatic cancer can greatly benefit from the addition of MRI and especially functional MR techniques.

Role of CT perfusion imaging in evaluating the effects of multiple burr hole surgery on adult ischemic Moyamoya disease

IntroductionTo evaluate the effects of the multiple burr hole (MBH) revascularization on ischemic type adult Moyamoya disease (MMD) by computed tomography perfusion (CTP).MethodsEighty-six ischemic MMD patients received CTP 1 week before and 3 weeks after MBH operation. Fifty-seven patients received it again at 6 month and underwent digital subtraction angiography (DSA) and mRS follow-up. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP), and relative values of ischemic symptomatic hemispheres were measured. Differences in pre- and post-surgery perfusion CT values were assessed.ResultsThere were significant differences of CBF, TTP, and relative time to peak (rTTP) in ischemic hemisphere between 1 week before and 3 weeks after surgery, and no significant difference in relative cerebral blood flow (rCBF), CBV, relative cerebral blood volume (rCBV), MTT, relative mean transit time (rMTT). According to whether there was symptom improvement or not on 3 weeks after MBH, the rTTP value was not statistically significant in the patients whose symptoms were not improved at all on 3 weeks after operation. Six-month follow-up showed that CBF, rCBF, and rCBV values were significantly higher than those before operation. Postoperative MTT, TTP, rMTT, and rTTP values were significantly lower than those before operation.ConclusionCTP is a sensitive method to obtain functional imaging of cerebral microcirculation, which can be a noninvasive assessment of the abnormalities of intracranial arteries and cerebral perfusion changes in MMD before and after surgery. CBF and TTP map, especially the relative values of TTP, seems to have the capability of being quite sensitive to the presence of altered brain perfusion at early time after indirect revascularization.Electronic supplementary materialThe online version of this article (doi:10.1007/s00234-013-1291-1) contains supplementary material, which is available to authorized users.

Adult Moyamoya disease: 320-Multidetector row CT for evaluation of revascularization in STA–MCA bypasses surgery

PurposeTo evaluate the utility of 320-multidetector row whole-brain computed tomography perfusion (WBCTP) and whole-head subtracted dynamic angiography (WHSDCTA) for assessing the revascularization of blood flow after superficial temporal artery (STA) to middle cerebral artery (MCA) bypass surgery in adults with Moyamoya disease (MD) in the short and long term. Patients and methods320-multidetector row WBCTP and WHSDCTA were applied in 20 patients with MD before and after surgery (for an average of 3 days and 3 months). The bypass arteries were investigated using WHSDCTA and compared with DSA. The regions of interests (ROIs) in the surgical and mirror sides of the cerebral cortex were drawn on a Vitrea Workstation. Cerebral blood volume (CBV), time to peak (TTP), cerebral blood flow (CBF), mean transit time (MTT), and delay time were recorded. Preoperative and postoperative perfusion parameters in the MCA distribution were compared using the paired t-test. ResultsWHSDCTA could clearly demonstrate 24 bypass arteries in 26 arteries for 20 patients, results which were in accordance with the results of digital subtraction angiography (DSA). When comparing preoperative values to those within 3 days after surgery, only TTP and delay time were significantly different (P<0.05). Values of CBV, TTP, CBF, delay time, and MTT 3 months after surgery were significantly different (P<0.05) from those of preoperative perfusion. ConclusionThese data suggest that 320-multidetector row WBCTP and WHSDCTA can be used to evaluate the revascularization of blood flow after STA–MCA bypass surgery in patients with MD in the short and long term.

Identification of the Iodine Concentration That Yields the Highest Intravascular Enhancement in MDCT Angiography

The objective of our study was to identify the iodine concentration that yields the highest intravascular contrast enhancement in MDCT angiography by intraindividual comparison in an animal model. Six pigs underwent repeated chest MDCT examinations under standardized conditions using the same contrast medium (iopromide) with different iodine concentrations (150, 240, 300, and 370 mg I/mL). The contrast injection protocol was adapted to ensure an identical iodine delivery rate of 1.5 g I/s and the same total iodine dose of 300 mg/kg of body weight for all studies. Dynamic CT scans were acquired at the levels of the pulmonary artery and the ascending and descending aorta. Pulmonary and aortic peak enhancement values as well as time to peak (TTP) were calculated from time-enhancement curves. Pulmonary and aortic peak contrast enhancement values were significantly higher with the 240 and 300 mg I/mL contrast media than the 150 and 370 mg I/mL contrast media (e.g., ascending aorta: 240 vs 150, p = 0.0070; 300 vs 150, p = 0.0096; 240 vs 370, p = 0.0262; 300 vs 370, p = 0.0079). TTP values tended to be lower for the 150 mg I/mL contrast medium than for the contrast media with higher iodine concentrations. Comparison of contrast media with iodine concentrations ranging from 150 to 370 mg I/mL showed that contrast enhancement was significantly improved with the use of 240 and 300 mg I/mL contrast media given a fixed identical iodine delivery and normalized total iodine load in a porcine model. Contrast media with a moderate iodine concentration are most suitable for obtaining the highest intravascular contrast enhancement in CT angiography.

Whole-Brain CT Perfusion and CT Angiography Assessment of Moyamoya Disease before and after Surgical Revascularization: Preliminary Study with 256-Slice CT

Background/AimsThe 256-slice CT enables the entire brain to be scanned in a single examination. We evaluated the application of 256-slice whole-brain CT perfusion (CTP) in determining graft patency as well as investigating cerebral hemodynamic changes in Moyamoya disease before and after surgical revascularization.MethodsThirty-nine cases of Moyamoya disease were evaluated before and after surgical revascularization with 256-slice CT. Whole-brain perfusion images and dynamic 3D CT angiographic images generated from perfusion source data were obtained in all patients. Cerebral blood flow (CBF), cerebral blood volume (CBV), time to peak (TTP) and mean transit time (MTT) of one hemisphere in the region of middle cerebral artery (MCA) distribution and contralateral mirroring areas were measured. Relative CTP values (rCBF, rCBV, rTTP, rMTT) were also obtained. Differences in pre- and post- operation perfusion CT values were assessed with paired t test or matched-pairs signed-ranks test.ResultsPreoperative CBF, MTT and TTP of potential surgical side were significantly different from those of contralateral side (P<0.01 for all). All graft patencies were displayed using the 3D-CTA images. Postoperative CBF, rCBF and rCBV values of surgical side in the region of MCA were significantly higher than those before operation (P<0.01 for all). Postoperative MTT, TTP, rMTT and rTTP values of the surgical side in the region of MCA were significantly lower than those before operation (P<0.05 for all).ConclusionThe 256-slice whole-brain CTP can be used to evaluate cerebral hemodynamic changes in Moyamoya disease before and after surgery and the 3D-CTA is useful for assessing the abnormalities of intracranial arteries and graft patencies.

The influence of pacing site to left ventricular myocardial contraction patterns and function

Objective To evaluate left ventricular(LV)myocardial contraction patterns and function when pacing in different right ventricular(RV)sites and discuss echocardiogarphic method to evaluate physiologcal pacing mode.Methods This study included 26 patients with paroxysmal supraventricular tachycardia without organic heart disease.Four pacing modes including right atrium pacing(AAI),RV apex pacing(VVI-RVA),RV septal pacing(VVI-IVS)and RV outflow tract pacing(VVI-RVOT)were performed on the patients in a random order after succussful radiofrequency ablation.The parameters measured in each pacing mode included(1)LV systolic function parameters:LV twist angle(Twist),aortic systolic velocity-time integral(VTIAo)and LV global strain(Ge)；(2)LV contracting pattern:segmental peak systolic strain(Se),the time to peak value(TPe),and the distribution of segmental Se,TPe in each layer or wall.The relationship between Se,TPe of each wall was analyzed.[Results]Pacing from RV sites showed lower Twist,VTIAO and Ge than AAI mode.Ge demonstrated significant difference in three RV sites pacing mode(VVI-RVOT＞VVI-IVS＞VVI-RVA,P＜0.05).Compared with the AAI mode,the distribution of segmental Se,TPe in the each layer or wall alerted significantly in three RV sites pacing mode,especially in VV1-RVA.The distribution pattern was similar in VVI-RVOT and VVI-IVS.Furthermore,the wall Se collated negtively with wall TPe(r =-0.51,P＜0.001).[Conclusions]Compared with AAI mode,RV pacing,especially the VVI-RVA induced the alternation of LV contraction patterns and reduction of systolic function.Longitudinal strain parameters can be used to assess the myocardial contraction patterns and function in different pacing mode. Key words: Echocardiography; Cardiac pacing,artificial; Ventricular function,left; Speckle tracking imaging

Fifty percent reduced-dose cerebral CT perfusion imaging of Alzheimer's disease: regional blood flow abnormalities.

To evaluate the value of 50% reduced-dose cerebral computed tomography (CT)perfusion imaging (CTPI) to show the perfusion abnormalities in Alzheimer's disease (AD), as an attempt to develop a new imaging protocol with lower radiation dose to track the correlation of AD with regional blood flow abnormalities. A total of 52 patients with AD were assigned to the AD group and 28 healthy volunteers served as the control group. All participants were given a 50% reduced-dose cerebral CTPI (current was reduced from 160 to 80 mA) test by a multislice spiral CT scanner. Perfusion parameters of the bilateral frontal cortex, temporal cortex, hippocampus, and basal ganglia were measured, including the cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time to peak (TTP). Both the CBV and CBF values of the measured regions were significantly higher in the healthy control group than in the AD group (P < .05), while the MTT and TTP values of these cerebral areas were significantly lower in the healthy control group than in the AD group (P < .05). Four perfusion parameters, namely the MTT of the left frontal cortex, right temporal cortex, right basal ganglia, and right hippocampus, had the greatest sensitivity and a striking correlation with the incidence of AD. The blood flow per unit of time in the regions of interest was significantly lower in the AD group, which provides new evidence for the existence of microcirculation disturbance and ischemia in AD. The 50% reduced-dose cerebral CTPI scan is valuable to show the regional perfusion abnormalities in the patients with AD.

Time‐intensity curve parameters in colorectal tumours measured using double contrast‐enhanced ultrasound: correlations with tumour angiogenesis

The aim of the study was to assess the correlation between time-intensity curve (TIC) parameters and colorectal tumour angiogenesis using double contrast-enhanced ultrasound (DCEUS), in which an intraluminal contrast agent was used in combination with an intravascular contrast agent. Thirty nine patients with colorectal tumours were examined preoperatively. During hydrocolonal examination with the intraluminal contrast agent, an intravascular contrast agent, SonoVue, was used to perform the DCEUS. The parameter arrival time (AT), time to peak (TTP), peak intensity (PI) and area under the curve (AUC) were measured. Postoperative specimens were assessed for microvessel density (MVD) and vascular endothelial growth factor (VEGF). The correlation between TIC parameters and the expression of VEGF or MVD was studied. The mean values of AT, TTP, PI and AUC of the colorectal tumours were 14.32 ± 11.36 s, 30.61 ± 18.65 s, 20.38 ± 17.45 dB and 221.10 ± 156.09 dB.s, respectively. Both AUC and MVD were significantly higher in colorectal adenocarcinomas than in adenomas (all P < 0.05). A positive linear correlation was found between the AUC and MVD in colorectal tumours (r = 0.686, P = 0.0019). No correlation was found between VEGF and any TIC parameter. DCEUS is a valuable method for evaluating angiogenesis in colorectal tumours in vivo. The AUC has a positive linear correlation with MVD and could form a new index for assessing angiogenesis and the biological behaviour of colorectal tumours.

Assessment of Cortical Visual Impairment in Infants with Periventricular Leukomalacia: a Pilot Event-Related fMRI Study

ObjectiveWe wanted to investigate the usefulness of event-related (ER) functional MRI (fMRI) for the assessment of cortical visual impairment in infants with periventricular leukomalacia (PVL).Materials and MethodsFMRI data were collected from 24 infants who suffered from PVL and from 12 age-matched normal controls. Slow ER fMRI was performed using a 3.0T MR scanner while visual stimuli were being presented. Data analysis was performed using Statistical Parametric Mapping software (SPM2), the SPM toolbox MarsBar was used to analyze the region of interest data, and the time to peak (TTP) of hemodynamic response functions (HRFs) was estimated for the surviving voxels. The number of activated voxels and the TTP values of HRFs were compared. Pearson correlation analysis was performed to compare visual impairment evaluated by using Teller Acuity Cards (TAC) with the number of activated voxels in the occipital lobes in all patients.ResultsIn all 12 control infants, the blood oxygenation level-dependent (BOLD) signal was negative and the maximum response was located in the anterior and superior part of the calcarine fissure, and this might correspond to the anterior region of the primary visual cortex (PVC). In contrast, for the 24 cases of PVL, there were no activated pixels in the PVC in four subjects, small and weak activations in six subjects, deviated activations in seven subjects and both small and deviated activations in three subjects. The number of active voxels in the occipital lobe was significantly correlated with the TAC-evaluated visual impairment (p < 0.001). The mean TTP of the HRFs was significantly delayed in the cases of PVL as compared with that of the normal controls.ConclusionDetermining the characteristics of both the BOLD response and the ER fMRI activation may play an important role in the cortical visual assessment of infants with PVL.

MR perfusion imaging of the liver: early findings after transcatheter arterial chemoembolization of hepatocellular carcinoma

Objective To investigate the value of MR perfusion imaging in early detection of findings following arterial chemoembolization of hepatocellular carcinoma Methods Twenty eight consecutive patients with pathologically-confirmed HCC were evaluated. All patients underwent MR perfusion imaging at pre-TACE and 3 to 10 days after TACE. The negative enhancement integral (NEI) ,the time to peak(TTP) ,the maximum slope of decrease (MSD) , the signal enhance ratio (SER) were acquired from MRI software FuncTool 2. 5.36a Version. Statistical analysis using SPSS 14, least significant difference test (t test) were utilized. Results The time intensive curve of tumor was observed to descend rapidly to reach the peak at pre-TACE studies, whereas it descended slowly to reach the peak on post TACE studies. The Value of TTP and SER prior to TACE were(51.2 ± 10. 3) s, 60. 6 ± 36. 3 respectively, and post TACE (43.7 ± 12. 0)s, 41.2 ±27. 5 respectively. The values of TTP and SER post TACE were lower than those prior to TACE (P ＜ 0. 05). The value of NEI prior to TACE was 108.7 ± 58.9, and after TACE 149. 6 ±80. 1 and there was statistically significant difference (P ＜0. 05). The Value of MSD post TACE were lower than those prior to TACE, but there was no statistical significance (P ＞ 0. 05). Conclusion PWI is a very sensitive imaging technique that can be used to monitor early dynamic changes of HCC following TACE. Key words: Liver neoplasms; Magnetic resonance imaging; Radiology,interventional

Dynamic Contrast Enhanced Magnetic Resonance Imaging of Diffuse Spinal Bone Marrow Infiltration in Patients with Hematological Malignancies

ObjectiveTo investigate the significance of the dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) parameters of diffuse spinal bone marrow infiltration in patients with hematological malignancies.Materials and MethodsDynamic gadolinium-enhanced MR imaging of the lumbar spine was performed in 26 patients with histologically proven diffuse bone marrow infiltration, including multiple myeloma (n = 6), acute lymphoblastic leukemia (n = 6), acute myeloid leukemia (n = 5), chronic myeloid leukemia (n = 7), and non-Hodgkin lymphoma (n = 2). Twenty subjects whose spinal MRI was normal, made up the control group. Peak enhancement percentage (Emax), enhancement slope (ES), and time to peak (TTP) were determined from a time-intensity curve (TIC) of lumbar vertebral bone marrow. A comparison between baseline and follow-up MR images and its histological correlation were evaluated in 10 patients. The infiltration grade of hematopoietic marrow with plasma cells was evaluated by a histological assessment of bone marrow.ResultsDifferences in Emax, ES, and TTP values between the control group and the patients with diffuse bone marrow infiltration were significant (t = -11.51, -9.81 and 3.91, respectively, p < 0.01). Emax, ES, and TTP values were significantly different between bone marrow infiltration groups Grade 1 and Grade 2 (Z = -2.72, -2.24 and -2.89 respectively, p < 0.05). Emax, ES and TTP values were not significantly different between bone marrow infiltration groups Grade 2 and Grade 3 (Z = -1.57, -1.82 and -1.58 respectively, p > 0.05). A positive correlation was found between Emax, ES values and the histological grade of bone marrow infiltration (r = 0.86 and 0.84 respectively, p < 0.01). A negative correlation was found between the TTP values and bone marrow infiltration histological grade (r = -0.54, p < 0.01). A decrease in the Emax and ES values was observed with increased TTP values after treatment in all of the 10 patients who responded to treatment (t = -7.92, -4.55, and 5.12, respectively, p < 0.01).ConclusionDCE-MRI of spine can be a useful tool in detecting diffuse marrow infiltration of hematological malignancies, while its parameters including Emax, ES, and TTP can reflect the malignancies' histological grade.

Parametric Perfusion Imaging Based on Low-Cost Ultrasound Platform

In this study, we attempted to implement parametric perfusion imaging to quantify blood perfusion based on modified low-cost ultrasound platform. A novel ultrasound contrast-specific imaging method called pulse-inversion harmonic sum-squared-differences (PIHSSD) was proposed for improving the sensitivity for detecting contrast agents and the accuracy of parametric perfusion imaging, which combined pulse-inversion harmonic (PIH) with pulse-inversion sum-squared-differences (PISSD) threshold-based decision. PIHSSD method just involved simple operations including addition and multiplication and was easy to realize. The sequences of contrast images without logarithmic compression were used to acquire time intensity curves (TICs) from numerous equal-sized regions-of-interest (ROI) covering the entire image plane. Parametric perfusion images were obtained based on the parameters extracted from the TICs, including peak value (PV), area under curve (AUC), mean transit time (MTT), peak value time (PVT), peak width (PW) and climbing rate (CR). Flow phantom was used for validation and the results suggested that PIHSSD method provided 9.6 to 20.3 dB higher contrast-to-tissue ratio (CTR) than PIH method. The results of the experiments of rabbit kidney also showed that the CTR of PIHSSD images was higher than that of PIH images, and the parametric perfusion images based on PIHSSD method provided more accurate quantification of blood perfusion compared with those based on PIH and PISSD methods. It demonstrated that the parametric perfusion imaging achieved good performance though implemented on low-cost ultrasound platform. (E-mail: mxwan@mail.xjtu.edu.cn)

Increasing Sampling Interval in Cerebral Perfusion CT: Limitation for the Maximum Slope Model

The aim of this study was to evaluate increased sampling intervals on cerebral dynamic perfusion computed tomographic (PCT) imaging calculated using software relying on the maximum slope model. PCT data sets from 32 patients with suspected acute stroke were acquired with a sampling interval of 1 image/s. The PCT data sets were modified to simulate sampling intervals of 2, 3, and 4 seconds. Maps of cerebral blood flow (CBF), cerebral blood volume, and time to peak (TTP) were calculated using software relying on the maximum slope model. Parenchymal and vascular peak enhancement; absolute values of CBF, cerebral blood volume, and TTP in the nonischemic hemisphere; and ischemic area in the different perfusion maps were measured. Parenchymal peak enhancement of the nonischemic hemisphere was statistically significantly decreased in all simulated data sets with >1-second sampling intervals (P < .001). Absolute CBF and TTP values in the nonischemic hemisphere were increased in all simulated data sets with >1-second sampling intervals (P = .044-.001 and P = .008-.001, respectively). The ischemic area was significantly underestimated for CBF and TTP in all simulated data sets with >1-second sampling intervals (P = .022-.005 and P = .019-.005, respectively). Sampling intervals of >1 second on PCT imaging calculated using software relying on the maximum slope model significantly alter absolute CBF and TTP values and the size of ischemia in CBF and TTP. Thus, increasing the sampling interval on dynamic PCT imaging cannot be recommended in combination with this algorithm.

Diagnostic Value of Dynamic Perfusion MR Imaging in Benign and Malignant Musculoskeletal Lesions

Purpose: To assess the diagnostic value of dynamic perfusion MR imaging for differentiation between benign and malignant musculoskeletal lesions. Materials and Methods: Dynamic perfusion MR imaging was performed using a 3.0 T system in 32 female and 30 male patients (aged 10-90 years, mean age, 43 years). Following the assessment of the precontrast imaging, a dynamic study was performed. This dynamic technique allowed for 638 images to be obtained at 11 levels throughout the lesion. Twenty-eight lesions originated within bone (8 benign, 20 malignant), whereas 34 lesions were of soft tissue origin (22 benign, 12 malignant). The final diagnosis was histopathologically confirmed in all patients. To differentiate between benign and malignant lesions, we analyzed the four parameters: (maximal relative enhancement (MRE), time to peak (TTP), wash in rate (WI), steepest slope (SS) and the distribution of time intensity curve (TIC) patterns. Results: The TTP, WI, and SS values of malignant lesions were statistically significant from those of benign lesions (p

Dynamic MR Perfusion Measurements Before and After TIPS in Cirrhotic Patients With Refractory Ascites

We sought to assess changes in liver perfusion parameters induced by transjugular intrahepatic portosystemic shunt (TIPS) creation in cirrhotic patients with refractory ascites using dynamic MR perfusion measurements. MR perfusion measurements were performed before and after TIPS creation in 15 cirrhotic patients all with refractory ascites. Measurements were performed over a time period of 120 seconds providing 60 images for each examination and calculations were done in both liver and splenic parenchyma. Different perfusion parameters were assessed: time to peak (TTP), time to inflow deceleration (TID), maximal or peak perfusion (C-peak) and the wash-in rate. TIPS procedures were successful in all 15 patients but were complicated by hepatic encephalopathy in 3 patients (20%), and in another 4 patients (26%), persistent refractory ascites was still noted during follow-up. Overall, liver TID values decreased significantly (P = .001) after TIPS creation; liver wash-in values increased significantly (P = .04) after TIPS. TTP values did not decrease significantly (P = .16) and liver C-peak values did not change equally (P = .99). In cirrhotic patients with refractory ascites, TIPS induced a faster, but not an increased, contrast enhancement in the liver.

Dynamic susceptibility contrast perfusion magnetic resonance imaging in patients with symptomatic unilateral middle cerebral artery stenosis or occlusion

To evaluate cerebral hemodynamic disturbance in patients with symptomatic unilateral middle cerebral artery (MCA) high-grade stenosis or occlusion using dynamic susceptibility contrast perfusion magnetic resonance imaging (DSC-pMRI). DSC-pMRI was performed in 28 patients with symptomatic unilateral MCA high-grade stenosis or occlusion. Hemodynamic parameters including relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), relative mean transit time (rMTT), and time to peak (TTP) were calculated and compared between the stenosed or occluded side and contralateral side. Seven of the 28 patients underwent surgery or interventional therapy, and hemodynamic changes between pre- and post-therapy were investigated. Prolonged rMTT and TTP were found in the stenosed or occluded MCA territories in all 28 patients. Significant differences were found in rCBV (P<0.05), rMTT (P<0.001), and TTP (P<0.001) between the stenosed or occluded side and the contralateral side. However, no significant difference was observed in rCBF (P>0.05). In the seven patients with surgical or interventional therapy, the values of rMTT and TTP significantly decreased after surgery or interventional therapy (P<0.001). DSC-pMRI may be a useful tool for evaluating and monitoring cerebral hemodynamic disturbance in patients with symptomatic unilateral MCA high-grade stenosis or occlusion.

Calf Muscles Imaged at BOLD MR: Correlation with TcPo2and Flowmetry Measurements during Ischemia and Reactive Hyperemia—Initial Experience

To prospectively compare the blood oxygen level-dependent (BOLD) magnetic resonance (MR) signal intensity of calf muscle during ischemia and reactive hyperemia with laser Doppler flowmetry (LDF) and transcutaneous oxygen pressure (TcPo2) measurements, two parameters routinely used to evaluate peripheral arterial occlusive disease. The study was institutional review board approved; all volunteers gave informed consent. Fifteen healthy volunteers (eight male, seven female; mean age, 33.0 years +/- 6.1 [standard deviation]) underwent LDF, TcPo2 measurement, and BOLD MR imaging of the calf during ischemia and reactive hyperemia. The BOLD signal intensity of the gastrocnemius muscle was measured at 1.5-T single-shot multiecho gradient-echo echo-planar imaging. Time to half ischemia minimum (THIM), time to half hyperemia peak (THHP), and time to peak (TTP) after cuff deflation were measured with each method. Correlation coefficients (CCs) for associations of BOLD response with LDF and TcPo2 time courses were calculated. Student t testing of key BOLD MR, LDF, and TcPo2 measurement parameters was performed. During ischemia, normalized LDF and TcPo2 measurements decreased similarly to BOLD MR signal intensity (CCs: 0.86 and 0.96 for associations with LDF and TcPo2 measurements, respectively). Mean THIM values were 136.0, 82.5, and 121.3 seconds for BOLD MR, LDF (P < .01), and TcPo2 (P > .05) measurements, respectively. During early reactive hyperemia, LDF and TcPo2 measurements increased rapidly to peak values, similarly to BOLD MR signal intensity (CCs: 0.81 and 0.78, respectively). Mean THHP values were 26.0, 12.5, and 44.0 seconds for BOLD MR, LDF (P < .01), and TcPo2 (P < .01) measurements, respectively. Mean TTP values were 48.7, 47.5, and 98.0 seconds for BOLD MR, LDF (P > .05), and TcPo2 (P < .01) measurements, respectively. BOLD MR imaging of calf muscles-depending on underlying key parameters-has moderate to good correlation with LDF and TcPo2 measurements during ischemia and reactive hyperemia.