Giant high-flow type pulmonary arteriovenous malformation: coil embolization with flow control by balloon occlusion and an anchored detachable coil.

Pulmonary arteriovenous malformations (PAVMs) are often treated by pushable fibered or non-fibered microcoils, using an anchor or scaffold technique or with an Amplatzer plug through a guiding sheath. When performing percutaneous transcatheter microcoil embolization, there is a risk of coil migration, particularly with high-flow type PAVMs. The authors report on a unique treatment in a patient with a giant high-flow PAVM whose nidus had a maximum diameter of 6 cm. A detachable coil, not detached from a delivery wire (an anchored detachable coil), was first placed in the feeding artery under flow control by balloon occlusion, and then multiple microcoils were packed proximally to the anchored detachable coil. After confirming the stability of the microcoils during a gradual deflation of the balloon, we finally released the first detachable coil. The nidus was reduced in size to 15 mm at one year postoperatively.

Impact of [11C]methionine positron emission tomography for target definition of glioblastoma multiforme in radiation therapy planning.

PURPOSE: The purpose of this work was to define the optimal margins for gadolinium-enhanced T(1)-weighted magnetic resonance imaging (Gd-MRI) and T(2)-weighted MRI (T(2)-MRI) for delineating target volumes in planning radiation therapy for postoperative patients with newly diagnosed glioblastoma multiforme (GBM) by comparison to carbon-11-labeled methionine positron emission tomography ([(11)C]MET-PET) findings. METHODS AND MATERIALS: Computed tomography (CT), MRI, and [(11)C]MET-PET were separately performed for radiation therapy planning for 32 patients newly diagnosed with GBM within 2 weeks after undergoing surgery. The extent of Gd-MRI (Gd-enhanced clinical target volume [CTV-Gd]) uptake and that of T(2)-MRI of the CTV (CTV-T(2)) were compared with the extent of [(11)C]MET-PET (CTV--[(11)C]MET-PET) uptake by using CT--MRI or CT--[(11)C]MET-PET fusion imaging. We defined CTV-Gd (x mm) and CTV-T(2) (x mm) as the x-mm margins (where x = 0, 2, 5, 10, and 20 mm) outside the CTV-Gd and the CTV-T(2), respectively. We evaluated the relationship between CTV-Gd (x mm) and CTV-- [(11)C]MET-PET and the relationship between CTV-T(2) (x mm) and CTV-- [(11)C]MET-PET. RESULTS: The sensitivity of CTV-Gd (20 mm) (86.4%) was significantly higher than that of the other CTV-Gd. The sensitivity of CTV-T(2) (20 mm) (96.4%) was significantly higher than that of the other CTV-T(2) (x = 0, 2, 5, 10 mm). The highest sensitivity and lowest specificity was found with CTV-T(2) (x = 20 mm). CONCLUSIONS: It is necessary to use a margin of at least 2 cm for CTV-T(2) for the initial target planning of radiation therapy. However, there is a limit to this setting in defining the optimal margin for Gd-MRI and T(2)-MRI for the precise delineation of target volumes in radiation therapy planning for postoperative patients with GBM.

Neurofibromatosis Type 1: Transcatheter Arterial Embolization for Ruptured Occipital Arterial Aneurysms.

Two cases of ruptured aneurysms in the posterior cervical regions associated with type-1 neurofibromatosis treated by transcatheter embolization are reported. Patients presented with acute onset of swelling and pain in the affected areas. Emergently performed contrast-enhanced CT demonstrated aneurysms and large hematomas widespread in the posterior cervical regions. Angiography revealed aneurysms and extravasations of the occipital artery. Patients were successfully treated by percutaneous transcatheter arterial microcoil embolization. Transcatheter arterial embolization therapy was found to be an effective method for treating aneurysmal rupture in the posterior cervical regions occurring in association with type-1 neurofibromatosis. A literature review revealed that rupture of an occipital arterial aneurysm, in the setting of neurofibromatosis type 1, has not been reported previously.

Abdominal vascular and visceral parenchymal contrast enhancement in MDCT: effects of injection duration.

PURPOSE: To evaluate and compare the effect of short and long injection durations on aortic, pancreatic and hepatic enhancement in abdominal MDCT. METHODS AND MATERIALS: Triphasic contrast-enhanced CT images (16-MDCT, 1.25-mm collimation, 5-mm thickness, 6.1-s acquisition time for each phase) were obtained with 2 mL/kg injection of 300 mgI/mL iodine contrast material in 116 patients. Patients were prospectively randomized into two groups: one receiving contrast medium for 25-s injection duration and the other for 35-s injection duration. In both groups, triphasic scans were initiated 5, 15, and 40s after the completion of contrast injection for the first, second and third phases, respectively. CT values (HU) in the abdominal aorta, liver, spleen, pancreas, splenic and superior mesenteric arteries, and veins (splenic, superior mesenteric, portal, and hepatic) were measured. Quantitative and qualitative analysis for the degree of contrast enhancement between the two groups in various organs was compared at each scan phase. RESULTS: The aortic and arterial enhancements in the first-phase scan were higher for the 25-s group than those of the 35-s group (P<.001). Hepatic enhancement was higher for the 35-s group in the first (P<.001) and second (P<.01) phases, but no difference in the third-phase. No difference was found between the groups for the pancreatic enhancement at any phases. Qualitative results were in good agreement with quantitative results. CONCLUSION: Contrast administration with shorter injection duration increased peak aortic and arterial enhancement and contributed to improvement in the quality of CT angiograms, but for the solid abdominal organs 35-s protocol is recommended.

Use of multidetector row CT to evaluate the need for bronchial arterial embolization in hemoptysis patients.

BACKGROUND: Bronchial artery (BA) embolization (BAE) is recommended as a minimally invasive therapy for hemoptysis, though some patients recover after only conservative treatment. OBJECTIVES: The purpose of our study was to assess the characteristics of BAs using multidetector row computed tomography (MDCT) and identify BAs requiring BAE without BA angiography (BAG). METHODS: We retrospectively studied 41 patients and classified the visualized BAs into groups based on their BAE and bleeding statuses. Patients presenting with massive hemoptysis requiring emergency BAE were excluded. Patients presenting with persistent hemoptysis that was resistant to conservative treatment received BAE. Radiologists measured BA diameters at the ostium, bronchial bifurcation and pulmonary hilum, and also evaluated the degree of vascularization. RESULTS: MDCT enabled visualization of 102 ostia and 96 traceable BAs. Among the participating patients, 13 had at least one ectopic origin. We obtained a good correlation between BAG and MDCT diameters (r = 0.709, p < 0.001). The diameters of BAs responsible for bleeding and receiving BAE were apparently larger in each measured segment than those that were not (p < 0.05). Moreover, the diameters of arteries receiving BAE remained largely unchanged from the origin to the hilum and through the mediastinum. BAs with low MDCT scores were significantly less likely to required BAE than those with high scores (p = 0.004), and in multiple logistic regression analysis, ostium diameter and bleeding status were independent predictive factors for BAE. CONCLUSIONS: Evaluation of BAs on MDCT could be useful for identifying the anatomical characteristics of bleeding-related BAs and determining whether BAE is indicated or whether conservative treatment is sufficient.

Detection and grading for esophageal varices in patients with chronic liver damage: comparison of gadolinium-enhanced and unenhanced steady-state coherent MR images.

The purpose of this study was to compare observer interpreted steady-state coherent coronal images and gadolinium-enhanced axial images in terms of the detection and grading of esophageal varices. Magnetic resonance imaging (MRI) and gastrointestinal endoscopy were performed within 2 weeks in 90 patients with chronic liver damage, including 55 with untreated esophageal varices, for periodic screening purposes. Two blinded readers retrospectively reviewed T1- and T2-weighted images with gadolinium-enhanced (gadolinium image set) and steady-state coherent (coherent image set) images. Sensitivity for the detection of esophageal varices was higher (P<.001) in the gadolinium image set (76%) than in the coherent image set (35%); on the other hand, specificity was higher (P<.001) in the coherent image set (91%) than in the gadolinium image set (66%). Furthermore, area under the ROC curve was higher for the gadolinium image set (Az=0.823) than the coherent image set (Az=0.761) (P=.48). Moderate and weak positive correlations with endoscopic grades were found for the gadolinium image (r=0.48, P<.01) and coherent image sets (r=0.34, P=.018). The addition of steady-state coherent imaging to the current routine liver imaging protocol did not improve the detection or grading of esophageal varices, whereas gadolinium-enhanced imaging was found to be potentially valuable. Nevertheless, endoscopy was confirmed to be mandatory in patients with esophageal varices suspected by MRI of the liver.

Preoperative T staging of urinary bladder cancer: does diffusion-weighted MRI have supplementary value?

OBJECTIVE: The objective of our study was to evaluate whether diffusion-weighted MRI has supplementary value in the preoperative T staging of urinary bladder cancer. MATERIALS AND METHODS: Nineteen consecutive patients (18 men and one woman; age range, 55-83 years; mean, 71 years) known to have or suspected of having urinary bladder cancer underwent MRI at our institution. Urinary bladder cancer was pathologically proven in 18 patients. The pathologic stages were T1 in 14 patients, T2 in two, T3 in one, and T4 in one. Three separate MR image sets were retrospectively reviewed by two independent radiologists: unenhanced T1-weighted images (TR/TE, 607/10) and T2-weighted images (TR(eff)/TE(eff), 4,415/100); unenhanced T1-weighted, T2-weighted, and gadolinium-enhanced images (TR/TE, 10/4.2); and unenhanced T1-weighted, T2-weighted, and diffusion-weighted images (TR(eff)/TE(eff), 2,191/69; b factor, 1,000 s/mm(2)). The radiologists, who were blinded to the pathology findings, assigned T stages and confidence levels for tumors of stage T2 or greater. We used pathologic stages documented in the official pathologic reports as the standard of reference. Observer performance was tested using Spearman's rank correlation, the McNemar test, and receiver operating characteristic (ROC) curve analysis. RESULTS: The correlation between the radiologic and pathologic stages was greater with the diffusion sequence (rho = 0.66) than with the unenhanced (0.62) or gadolinium-enhanced (0.62) sequence (p = 0.34). The sensitivity, specificity, accuracy, and area under the ROC curve for tumors of stage T2 or greater were 80%, 79%, 79%, and 0.71 for the unenhanced sequence; 80%, 79%, 79%, and 0.77 for the gadolinium sequence; and 40%, 93%, 79%, and 0.56 for the diffusion-weighted sequence, respectively (p > 0.05). CONCLUSION: Our results suggest that diffusion-weighted MRI might have high specificity for the detection of invasive urinary bladder tumors. Patients with suspected urinary bladder carcinomas may well be evaluated by MRI including diffusion-weighted imaging for better preoperative T staging.

Optimal scan delays for multiphasic renal multidetector row computed tomography performed with fixed injection duration of contrast medium.

OBJECTIVE: The purpose of our study was to prospectively determine optimal scan delays for multiphasic imaging of the kidney performed with multidetector row computed tomography (CT) and fixed injection duration of intravenous contrast medium. MATERIALS AND METHODS: One hundred ninety-eight patients underwent 3-phase CT of the kidney with 8-slice CT after receiving 2 mL/kg of an intravenous contrast medium of 300 mg I/mL for a fixed duration of 30 seconds. The patients were prospectively randomized into 4 groups according to different scan delays from the start of injection: group 1 (25, 45, 65 seconds), group 2 (30, 50, 70 seconds), group 3 (35, 55, 75 seconds), and group 4 (40, 60, 80 sec). Mean CT values (Hounsfield units [HU]) of the abdominal aorta, renal arteries, veins, cortexes, and medulla were measured. Increases in CT values from precontrast to postcontrast CT (deltaHU) and renal artery-to-vein and renal cortex-to-medulla differential contrasts (deltaHU) were assessed. Qualitative analysis was also performed. RESULTS: Abdominal aorta and renal artery enhancements peaked at 35 seconds (305 DeltaHU; 253 DeltaHU) after injection start, and renal veins peaked at 45 seconds (196 DeltaHU). Renal cortexes peaked at 40 seconds (197 DeltaHU), and renal medullae peaked at 75 seconds (152 DeltaHU). Renal artery-to-vein differential contrasts were high (95-137 deltaHU) at 25 to 30 seconds, and cortex-to-medulla contrasts were high (79-130 deltaHU) at 30 to 55 seconds and then decreased to less than 10 deltaHU at 75 seconds. Qualitative results were in good agreement with quantitative results. CONCLUSIONS: With a fixed 30-second injection, estimated optimal scan delays for multiphasic imaging the kidney were, from the start of injection, 25 to 30 seconds for renal arterial CT angiography, 35 to 45 seconds for the corticomedullary, and 75 seconds for the nephrographic phase.

Hepatic hemangioma: correlation of enhancement types with diffusion-weighted MR findings and apparent diffusion coefficients.

PURPOSE: To correlate hepatic hemangioma enhancement types in gadolinium-enhanced magnetic resonance (MR) images with diffusion-weighted MR findings and apparent diffusion coefficients (ADCs). MATERIALS AND METHODS: Respiratory-triggered diffusion-weighted MR images (TR/TE, 2422/46 ms; parallel imaging factor, 2; b factor, 500 s/mm(2); number of averaging, 6) obtained in 35 patients with 44 hepatic hemangiomas diagnosed by gadolinium-enhanced MR and by follow-up imaging were retrospectively evaluated. Hemangiomas were classified into three enhancement types based on gadolinium-enhanced MR imaging findings: type I, early-enhancement type; type II, peripheral nodular enhancement type; type III, delayed enhancement type. Two blinded readers qualitatively assessed lesion sizes and signal intensities on T2-weighted turbo spin-echo and diffusion-weighted images. The ADCs of hemangiomas were also measured. RESULTS: No significant difference was observed between the three enhancement types in terms of signal intensities on T2-weighted images. Signal intensities on diffusion-weighted images were lower in the order type I to III (P<.01), and mean ADCs were 2.18 x 10(-3), 1.86 x 10(-3), and 1.71 x 10(-3) mm(2)/s for types I, II, and III, respectively (P<.01). No correlation was found between lesion sizes and ADCs. CONCLUSION: Hepatic hemangiomas were found to have enhancement type dependent signal intensities and ADCs on diffusion-weighted MR images. Further studies will have to substantiate that these diffusion patterns might reflect intratumoral blood flow or perfusion.

Magnetic resonance imaging of hepatocellular carcinoma.

In hepatocellular carcinomas (HCCs), T(1) shortening occurs due to internal protein, fat, copper, iron, hypercellularity, or a combination thereof. T(1)-weighted magnetic resonance imaging (MRI) is obtained with a non-fat-suppressed phase shift [in- (4 ms) and opposed- (2 ms) phase] gradient-echo sequence. Internal fat deposition is often (36%) seen in well-differentiated HCCs between 1.1 and 1.5 cm in size. T(2)-weighted MRI is crucial in differentiating HCCs from premalignant or borderline lesions in cirrhosis and serves as a tie breaker for small early-enhancing lesions. Gadolinium-enhanced MRI has advantages over contrast-enhanced CT: greater contrast enhancement, smaller volume of contrast, and less frequent adverse reactions. Double hepatic arterial-phase imaging has been performed in many centers, allowing less frequent off-timing arterial-phase imaging and improved temporary resolution. Hypervascular HCCs often show 'corona' enhancement in the late hepatic arterial phase, which makes it possible to distinguish small HCCs from enhancing pseudolesions. Liposoluble gadolinium chelate (e.g., Gd-EOB-DTPA) behaving both as an extracellular and hepatobiliary agent is very useful in the diagnosis. Diffusion-weighted imaging has become a routine imaging tool thanks to the parallel imaging technique. However, diffusion-weighted imaging may not significantly improve detection, characterization, or estimation of tumor grade for HCCs, and it should still be supplementary. In summary, we believe MRI outperforms CT in the diagnosis of HCCs.

Abdomen: angiography with 16-detector CT--comparison of image quality and radiation dose between studies with 0.625-mm and those with 1.25-mm collimation.

PURPOSE: To prospectively compare image quality and volume computed tomographic (CT) dose index (CTDI(vol)) of 16-detector CT angiograms of the abdomen acquired with 0.625-mm collimation with those of images acquired with 1.25-mm collimation. MATERIALS AND METHODS: This study had institutional review board approval, and informed consent was obtained from all patients. Dual-phase contrast material-enhanced CT was performed in 78 patients (48 men and 30 women; age, 34-91 years; mean age, 64.8 years) by using a 16-detector CT scanner. Patients were prospectively randomized into two equal-sized groups: those who underwent CT with 0.625-mm collimation and nonoverlapped reconstruction and those who underwent CT with 1.25-mm collimation and 50% overlapped reconstruction. Scan acquisition time was 7.5 seconds in both groups. CTDI(vol) was recorded. Arterial phase volume-rendered, arterial phase multiplanar reformatted, and portal venous phase multiplanar reformatted CT angiograms were generated. Qualitative assessment was performed for image quality and for depiction of splanchnic, intercostal, and lumbar arteries and veins. The unpaired t test was used for statistical comparison. RESULTS: On the arterial phase CT angiograms, there was no difference between the two collimation groups for the depiction of proximal splanchnic arteries, while the dorsal pancreatic, intercostal, and lumbar arteries and some peripheral splanchnic arterial branches were better delineated on CT scans obtained with 0.625-mm collimation than on scans obtained with 1.25-mm collimation (P < .05). Regarding the portal venous phase CT angiograms, no difference between the two groups was found in most veins, except the right adrenal vein (P = .003). Image quality was superior for 1.25-mm collimation (P < .001). CTDI(vol) values were positively correlated with patient body weight (r = 0.34, P < .001) but had no correlation with collimation size (P = .24). CONCLUSION: Scanning with 1.25-mm collimation seems adequate for a routine CT angiography examination of most arteries and veins at 16-detector CT, while scanning with 0.625-mm collimation facilitates improved delineation of fine vessels. CTDI(vol) values correlate positively with body weight but have no correlation with collimation size.

Diffusion-weighted imaging of the liver: optimizing b value for the detection and characterization of benign and malignant hepatic lesions.

PURPOSE: To determine the optimal b values required for diffusion-weighted (DW) imaging of the liver in the detection and characterization of benign and malignant hepatic lesions. MATERIALS AND METHODS: MR images obtained in 76 patients including 28 malignant hepatic lesions (21 hepatocellular carcinomas and 7 metastases) and 27 benign lesions (12 hemangiomas and 15 cysts) were reviewed. DW-echo planner images (EPIs; b values with 100, 200, 400, and 800 s/mm2) were reviewed solely first, and then with T2-weighted EPIs (b=0 s/mm2). RESULTS: Sensitivity for malignant lesions (74%) was highest on DW-EPIs with b value of 100 s/mm2 and T2-weighted EPIs combined (P<0.05), and sensitivity for benign lesions (87%) was highest on DW-EPIs with b value of 800 s/mm2 and T2-weighted EPIs (P<0.05). Specificities were comparably high for all sequences. The Az values for malignant lesions were 0.94, 0.90, 0.87, and 0.89, and those for benign lesions were 0.91, 0.89, 0.87, and 0.94 on DW-EPIs with b values of 100, 200, 400, and 800 and T2-weighted EPIs combined, respectively. Hepatic cysts were clearly distinguished with the cutoff ADC value of 2.5x10(-3) mm2/s using a b value of 400 s/mm2 or greater. CONCLUSION: DW-EPIs with middle b values were not required in the detection and characterization of benign and malignant hepatic lesions.

Carcinosarcoma of the uterus: radiologic-pathologic correlations with magnetic resonance imaging including diffusion-weighted imaging.

The authors describe the MRI findings, including diffusion-weighted imaging findings, of histopathologically proven uterine carcinosarcoma in four postmenopausal women. In three of four patients, diffusion-weighted images clearly revealed hypointense areas corresponding to hypocellular regions caused by intratumoral necrosis, and apparent diffusion coefficient (ADC) mapping images indicated that necrotic areas had high ADC values. In the remaining patient, diffusion-weighted and ADC mapping images clearly distinguished components of adenocarcinoma from sarcoma. In all patients, diffusion-weighted and ADC mapping images precisely reflected histopathological findings. Diffusion-weighted images were found to demonstrate complicated tissue components in carcinosarcomas of the uterus, and thus, which may be useful for the diagnosis of this disease.

Evaluating local hepatocellular carcinoma recurrence post-transcatheter arterial chemoembolization: is diffusion-weighted MRI reliable as an indicator?

PURPOSE: To evaluate the detectability of local hepatocellular carcinoma (HCC) recurrence after transcatheter arterial chemoembolization (TACE) by diffusion-weighted MR imaging in correlation with those of gadolinium-enhanced MR imaging. MATERIALS AND METHODS: Respiratory-triggered diffusion-weighted MR images (b factor, 500 s/mm(2); number of averaging, six were obtained in 25 patients with 39 HCCs. Two independent radiologists evaluated diffusion-weighted MR images, gadolinium-enhanced MR images after TACE, and assigned confidence levels for postoperative HCC recurrence. Apparent diffusion coefficients (ADCs) in HCCs were also measured. Sensitivities and specificities were compared using an extension of the McNemar test. Observer performance was also determined by ROC curve analysis. RESULTS: Local recurrences in 14 HCCs and complete tumor necrosis in 25 HCCs after TACE were determined. Sensitivity for the detection of local HCC recurrence was higher on gadolinium-enhanced MR imaging (82%) than on diffusion-weighted MR imaging (60.7%) for the two readers in combination and separately (P < 0.05). Specificities were comparably high for both sequences. Az values were higher for gadolinium-enhanced MR images (0.92) than for diffusion-weighted MR images (0.74) for readers in combination and separately (P < 0.05). Mean ADC values showed an increase after TACE (P < 0.001). CONCLUSION: Diffusion-weighted MR imaging was not found to be a reliable predictor of local HCC recurrence after TACE as compared with gadolinium-enhanced MR imaging.

Borna disease virus RNA detected in Japanese macaques (Macaca fuscata).

We have examined the seroprevalence of BDV in wild Japanese macaques (Macaca fuscata) in the peninsula (Chiba prefecture), Japan. Serum samples from macaques were examined by the ELISA, Western blot and immunofluorescence assays to detect the presence of serum antibodies that react specifically to BDV antigens. Among 49 investigated individuals, 6 (12.2%) showed positive reaction to BDV antigens. RT-PCR studies detected BDV sequences in brain tissue of one case among four seropositive cases examined. Sequence analysis revealed a high degree of genetic conservation between BDV sequences derived from Japanese macaques and those documented for other animal species. Nevertheless, phylogenetic analysis revealed unique differences between macaque and other species derived BDV sequences.

Gadolinium-enhanced multiphasic 3D MRI of the liver with prospective adaptive navigator correction: phantom study and preliminary clinical evaluation.

OBJECTIVE: The purpose of this study was to determine whether prospective adaptive navigator correction improves slice position invariability while maintaining image quality and enables efficient cine display observation on gadolinium-enhanced multiphasic thin-slice 3D MRI of the liver. MATERIALS AND METHODS: The study consisted of two parts: a phantom study and a clinical study. To explore the effect of navigator correction, a phantom was imaged in the resting state and in continuous movement. In the clinical study, gadolinium-enhanced four-phase 3D spoiled turbo field-echo images (3-mm thickness with no intersectional gap, 60 slices for whole liver) were retrospectively assessed. The subjects were 83 patients with 130 focal hepatic lesions randomized into two groups: with (n = 45) and without (n = 38) navigator correction. Images were qualitatively assessed by two blinded radiologists using a three-point slice position invariability scale for liver and focal hepatic lesions. Image degradation due to motion or artifacts was qualitatively assessed. RESULTS: Phantom images were obtained with excellent slice position invariability while image quality was maintained with navigator correction. Navigator correction substantially degraded the quality of the images of two patients (one with a large amount of ascites and the other with a large hepatic cyst). In the other 81 patients, the degree of slice position invariability for the liver was greater (p < 0.001) with (score, 2.84 +/- 0.43 [SD]) than without (score, 2.37 +/- 0.75) navigator correction. For focal hepatic lesions, slice position invariability also was greater (p < 0.0001) with (score, 2.95 +/- 0.21) than without (score, 2.18 +/- 0.88) navigator correction. No difference in degree of image degradation was found with or without navigator correction. CONCLUSION: Prospective navigator correction improves slice position invariability for cine display observation while preserving image quality for gadolinium-enhanced multiphasic thin-slice 3D MRI of the liver.

Multi-detector row CT of the kidney: optimizing scan delays for bolus tracking techniques of arterial, corticomedullary, and nephrographic phases.

PURPOSE: To determine optimal scan delays for renal arterial-, corticomedullary-, and nephrographic-phase imaging with multi-detector row computed tomography (MDCT) of the kidney using a bolus-tracking technique. METHODS AND MATERIALS: One hundred and twenty-eight patients underwent three-phase CT scan of the kidney with eight-row MDCT after receiving 2 mL/kg of 300 mgI/mL contrast medium at 4 mL/s. Patients were prospectively randomized into three groups with different scan delays for the three scan phases (arterial, corticomedullary, and nephrographic) after bolus-tracking triggered at 50 HU of aortic contrast enhancement: group 1 (5, 20, 45 s); group 2 (10, 25, 50s); and group 3 (15, 30, 55 s). Mean CT values (HU) of the abdominal aorta, renal artery, renal vein, renal cortex, and renal medulla were measured; increases in CT values pre- to post-contrast were assessed as contrast enhancement. Renal artery-to-vein and renal cortex-to-medulla contrast differences were also assessed. Qualitative analysis was also performed. RESULTS: Mean renal artery enhancement was 240-288 HU at 5-15s after the trigger and peaked at 10s (P<.001). Mean renal cortical enhancement was 195-217 HU at 10-30s and peaked at 25s (P<.01). Contrast enhancement in the renal medulla increased gradually and reached mean 145 HU at 55 s. Cortex-to-medulla contrast difference was high (110-140 HU) at 5-30s and decreased below 30 HU at 45 s after the trigger. Renal artery-to-vein contrast difference was high (121-125 HU) at 5-10s. Qualitative results correlated well with quantitative results. CONCLUSION: For the injection protocol used in this study, optimal scan delays after the bolus-tracking trigger were 5-10 s for renal arterial, 15-25 s for corticomedullary, and 50-55 s for nephrographic phases.

Pancreas: optimal scan delay for contrast-enhanced multi-detector row CT.

PURPOSE: To prospectively determine optimal scan delays for multiphasic contrast medium-enhanced imaging of the pancreas with multi-detector row computed tomography (CT). MATERIALS AND METHODS: This study was approved by an institutional review committee, and patients gave written informed consent. One hundred ninety-one patients underwent three-phase CT of the pancreas after receiving intravenous contrast medium with a fixed duration injection of 30 seconds. Patients were prospectively assigned among four groups with scan delays of 25, 45, and 65 seconds (group 1); 30, 50, and 70 seconds (group 2); 35, 55, and 75 seconds (group 3); and 40, 60, and 80 seconds (group 4). Mean CT numbers of abdominal aorta, spleen, pancreatic parenchyma, superior mesenteric artery and vein, splenic vein, and hepatic parenchyma were measured, and increases in contrast enhancement on enhanced images were assessed. Qualitative analysis was performed with a four-point scale. RESULTS: Abdominal aorta and superior mesenteric artery enhanced at a mean of 35 seconds from the start of injection (both P < .001). Pancreatic parenchyma enhanced most intensely at 35-45 seconds (P < .001) with a peak enhancement at the mean of 40 seconds. Liver parenchyma enhanced most intensely at 55-65 seconds with a peak at 60 seconds (P < .001). The mean time to peak enhancement was 45 seconds for the splenic vein and 55 seconds for the superior mesenteric vein. Qualitative results were in good agreement with quantitative results (both P < .001). CONCLUSION: With the injection protocol used in this study, optimal scan delays for imaging the pancreas were 30-35 seconds for the abdominal aorta and the superior mesenteric artery, 35-45 seconds for the pancreas, 45 seconds for the splenic vein, and 55 seconds or later for the liver.