Radiation dose in multidetector row computed tomography cardiac imaging

Multidetector row computed tomography (MDCT) with its markedly improved temporal and spatial resolution has opened up a new opportunity in cardiac CT imaging. MDCT scanners are increasingly available and have become the preferred CT scanners for the entire spectrum of clinical CT examinations. As a consequence, the number of cardiac CT studies is continuously growing. Because cardiac CT studies involve considerable radiation doses, it is compelling for us to understand the radiation dose estimates associated with cardiac CT imaging. In this article, we review the concepts of radiation dose measurement in CT, discuss MDCT scan parameters affecting radiation exposure, and provide a reference summary of radiation dose estimates associated with MDCT cardiac imaging.     

Portal biliopathy: imaging manifestations on multidetector computed tomography and magnetic resonance imaging

Portal biliopathy refers to biliary abnormalities secondary to extrahepatic portal vein obstruction and cavernous transformation and is caused by vascular compression from peribiliary collateral vessels, producing segmental stenoses of the common bile duct and abnormal liver function test (LFT) results. A review of imaging studies yielded 18 patients with abnormal LFT results, biliary tract dilatation, and extrahepatic portal vein obstruction with cavernous transformation. Multidetector computed tomography and magnetic resonance imaging showed biliary stenotic segments in 11 patients secondary to extrinsic compression from enlarged peribiliary collaterals. Clinical and imaging follow-up demonstrated improvement in LFT results with minimal decrease in bile duct dilatation, eliminating percutaneous or endoscopic biliary intervention.     

Assessment of cardiac function using multidetector row computed tomography

In patients with suspected or documented heart disease, a precise quantitative and qualitative assessment of cardiac function is critical for clinical diagnosis, risk stratification, management and prognosis. Cardiac CT is increasingly being used in diagnosis of coronary artery disease. Initially multi-detector row computed tomography (MDCT) was used chiefly for detecting coronary artery stenosis and assessment of cardiac morphology. Electron beam computed tomography has been shown to provide a highly accurate ejection fraction (+/-1%), with 50 ms image acquisition per image. Retrospective electrocardiographic gating allows for image reconstruction in any phase of the cardiac cycle. Thus, end systolic and end diastolic images can be produced to assess ventricular volumes and function. Despite lower temporal resolution than electron beam computed tomography, the ability of MDCT to assess ejection fraction is preserved. In the assessment of cardiac function, MDCT has been shown to be in good agreement with echocardiography, cineventriculography, single photon emission computed tomography and magnetic resonance imaging. The fast technical development of scanner hardware along with multisegmental image reconstruction has led to rapid improvement of spatial and temporal resolution and significantly faster cardiac scans. The same data that is acquired for MDCT angiography can also be used for evaluation of cardiac function. Considering contrast media application, radiation exposure, and limited temporal resolution, MDCT solely for analysis of cardiac function parameters seems not reasonable at the present time. However, because the data is already obtained during coronary evaluation, the combination of noninvasive coronary artery imaging and assessment of cardiac function with MDCT is a suitable approach to a conclusive cardiac workup in patients with suspected coronary artery disease. MDCT seems suitable for assessment of cardiac function by MDCT when results are held in comparison to magnetic resonance imaging as the reference standard. Given the radiation dose and contrast requirement, referring a patient to MDCT only for evaluation of function is not warranted, but rather adds important clinical information to the already acquired data during retrospective triggering for MDCT angiography.     

Ferucarbotran-enhanced 3.0-T magnetic resonance imaging using parallel imaging technique compared with triple-phase multidetector row computed tomography for the preoperative detection of hepatocellular carcinoma

OBJECTIVE: To compare diagnostic performance of ferucarbotran-enhanced 3.0-T magnetic resonance (MR) imaging using parallel imaging technique with that of triple-phase multidetector row computed tomography (MDCT) for the preoperative detection of hepatocellular carcinoma (HCC). METHODS: Eighty-six consecutive patients with a total of 128 surgically proven HCCs were enrolled in this study. All patients underwent ferucarbotran-enhanced 3.0-T MR imaging using parallel imaging technique and triple-phase MDCT before hepatic resection. Three experienced radiologists independently analyzed each images on a segment-by-segment basis. The accuracy of these techniques for the detection of HCC was assessed by performing a receiver operating characteristic (ROC) analysis of 104 resected hepatic segments with at least 1 HCC and 113 resected hepatic segments without HCC. RESULTS: The mean value of the area under the ROC curve (Az) of the ferucarbotran-enhanced 3.0-T MR imaging (0.990) was significantly higher than that of the triple-phase MDCT (0.964) (P = 0.00). The mean sensitivity of the ferucarbotran-enhanced 3.0-T MR imaging (98.1%) was significantly higher than that of the triple-phase MDCT (92.9%) (P = 0.00). The higher sensitivity was largely attributable to a greater ability of the 3.0-T MR imaging to detect small HCC (< or =1 cm) (92.6% in 3.0-T MR imaging and 37.0% in MDCT; P = 0.00). No significant difference was found for their mean specificities (98.2% in 3.0-T MR imaging and 97.6% in MDCT; P = 0.86). CONCLUSIONS: Ferucarbotran-enhanced 3.0-T MR imaging using parallel imaging technique is a more accurate diagnostic tool than triple-phase MDCT for the preoperative detection of HCC. Ferucarbotran-enhanced 3.0-T MR imaging has a higher sensitivity than triple-phase MDCT, especially for small HCCs (< or =1 cm).     

Evaluation of the acute effects of distal coronary microembolization using multidetector computed tomography and magnetic resonance imaging

The purpose of this study was to test the potential of clinical imaging modalities, 64-slice multidetector computed tomography (MDCT) and 1.5T magnetic resonance imaging (MRI) for qualitative and quantitative evaluation of acute microinfarcts and to determine the effects of <120 μm microemboli on left ventricular function, perfusion, cardiac injury biomarkers, arrhythmia, and cellular and vascular structures. Under X-ray fluoroscopy, 40-120 μm (16 mm(3) ) microemboli were delivered to embolize the left anterior descending (LAD) coronary artery of nine pigs. MDCT/MRI were performed at 72 h in a single session. Microinfarcts were visible in six of nine animals on delayed contrast-enhanced MDCT/MR images but measurable in all animals using semiautomated threshold methods. Other MDCT and MRI sequences demonstrated decline in left ventricular ejection fraction, regional strain and perfusion in visible and invisible microinfarcted regions. Microemboli caused significant elevation in cardiac injury enzymes and arrhythmias. Various sizes of microinfarcts appeared microscopically as distinct aggregates of macrophages replacing myocardium. Semiautomated threshold methods are necessary to measure and confirm/deny the presence of myocardial microinfarcts. This study offers support for alternative applications of MDCT/MRI in assessing clinical cases in which microemboli <120 μm escape protective devices during percutaneous coronary interventions. Although microembolization resulted in no mortality, it caused left ventricular dysfunction, perfusion deficit, cellular damage increase in cardiac injury enzymes, and arrhythmias.     

Efficacy of multidetector row computed tomography of the spine in patients with multiple myeloma: comparison with magnetic resonance imaging and fluorodeoxyglucose-positron emission tomography

PURPOSE: The aim of our study was to compare the efficacy of multidetector row computed tomography (MDCT) with magnetic resonance imaging (MRI) and fluorodeoxyglucose-positron emission tomography (FDG-PET) for detection of spinal bone marrow involvement in patients with multiple myeloma. MATERIALS AND METHODS: Ten patients with multiple myeloma stage III underwent MDCT and MRI of the spine and FDG-PET. The number and location of lesions detected by 3 modalities were recorded, and a lesion-by-lesion analysis was completed, using McNemar test. For MDCT, image analysis was performed according to the type of lesion (established by Laroche et al), and the efficacy of lesion detection was compared with that of the MRI and FDG-PET. P values less than 0.05 were considered statistically significant. RESULTS: The MDCT, MRI, and FDG-PET detected the following numbers of lesions: 102 of 140 vertebrae, 95 of 140 vertebrae, and 84 of 140 vertebrae, respectively. The difference between the abilities of MDCT and MRI to detect lesions was not statistically significant (P = 0.289). However, the difference in effectiveness between MDCT and FDG-PET was statistically significant (P < 0.001). For small osteolytic lesions, less than 5 mm, the difference in effectiveness between MDCT and MRI was also statistically significant (P = 0.031). CONCLUSIONS: The MDCT is very sensitive in detecting small osteolytic lesions in the spine, as compared with MRI and FDG-PET.     

Neurosarcoidosis: evaluation using computed tomography and magnetic resonance imaging

Two patients with unusual central nervous system sarcoid were investigated using computed tomography and magnetic resonance imaging, as well as other x-ray studies. A patient with intramedullary involvement of the spinal cord as well as nerve root involvement was examined. Follow-up examination after treatment with steroids showed a return to normal. The second patient had optic nerve involvement as well as two intracranial parenchymal lesions and granulomatous arachnoiditis. In this patient magnetic resonance imaging offered no advantages over computed tomography in the orbit but was significantly more accurate intracranially.     

Automated vs. manual assessment of left ventricular function in cardiac multidetector row computed tomography: comparison with magnetic resonance imaging

We compared semiautomatic contour detection and manual contour tracing in cardiac multidetector row computed tomography (MDCT) with magnetic resonance imaging (MRI) for calculation of left-ventricular (LV) volumes. The study included 30 patients who underwent contrast-enhanced cardiac MDCT and cardiac cine-MRI. Were calculated 8 mm short-axis slices from MDCT data using three-dimensional multiphase image reconstruction. LV volumes including peak ejection rate and peak filling rate were calculated from manually and semiautomatically determined contours. Results were compared to those from cine-MRI with manually drawn contours as the standard of reference. We found good agreement for the LV volumes, with an ejection fraction of 47.1±9.4% for manually drawn contours, 47.9±9.9% for semiautomatically detected contours on MDCT, and 48.0±10.2% for MRI. Except for peak-filling rate analysis of variance revealed no difference between any of these techniques. Bland-Altman plots and Lin’s concordance correlation coefficient showed best agreement between MRI and manual contour tracing in MDCT. Calculation of LV volumes using either semiautomatic or manual contour tracing in cardiac MDCT is therefore feasible when compared to MRI. Automated contour detection needs to be improved to equal manual contour tracing.     

Preoperative assessment of focal liver lesions: multidetector computed tomography challenges magnetic resonance imaging

PURPOSE: To investigate prospectively multidetector computed tomography (CT) (MDCT) and magnetic resonance (MR) imaging (MRI) in the preoperative assessment of focal liver lesions. MATERIAL AND METHODS: Multiphasic MDCT and conventional gadolinium-enhanced MRI were performed on 31 consecutive patients prior to hepatic surgery. All images were blindly analyzed as consensus reading. Lesion counts and their relation to vascular structures and possible extrahepatic disease were determined. The data from the MDCT and MRI were compared with the results obtained by intraoperative ultrasound (IOUS) and palpation. Histopathologic verification was available. RESULTS: At surgery, IOUS and palpation revealed 45 solid liver lesions. From these, preoperative MDCT detected 43 (96%) and MRI 35 (78%) deposits. MDCT performed statistically better than MRI in lesion detection (P=0.008). Assessment of lesion vascular proximity was correctly determined by MDCT in 98% of patients and by MRI in 87%. Statistical difference was found (P=0.002). IOUS and palpation changed the preoperative surgical plan as a result of extrahepatic disease in 8/31 (26%) cases. In MDCT as well in MRI extrahepatic involvement was suspected in two cases. CONCLUSION: MDCT was superior to MRI and nearly equal to IOUS in liver lesion detection and in the determination of lesion vascular proximity. However, both techniques fail to reliably detect extrahepatic disease.     

Bladder trauma: multidetector computed tomography cystography

Multidetector computed tomography (MDCT) cystography is rapidly becoming the most recommended study for evaluation of the bladder for suspected trauma. This article reviews the bladder trauma with emphasis on the application of MDCT cystography to traumatic bladder injuries using a pictorial essay based on images collected in our level I trauma center.     

Dynamic cine mode imaging of the normal aortic valve using 16-channel multidetector row computed tomography

BACKGROUND: We investigated the feasibility and image quality of dynamic cine-mode imaging of the normal aortic valve using multidetector row computed tomography (MDCT). MATERIALS AND METHODS: We acquired contrast-enhanced retrospectively echocardiography (ECG)-gated cardiac MDCT datasets of 35 patients (mean age, 62 years; range, 53-77) who received a transoesophageal echocardiography (TOE) precedent to cardiac bypass graft surgery. Twenty data sets in 5% steps of the R-R interval were reconstructed, and data analysis was performed using a 4D software. Read-out of the MDCT data was performed in parallel and perpendicular planes, similar to TOE standard planes, by 2 independent, blinded readers using a 4-point Likert scale (best score: 4) for the following parameters: image quality of the aortic valve components, contrast media enhancement, contrast media inflow related artifacts, and ECG gating-related artifacts. The aortic valve area (AVA) was measured planimetrically and was compared between TOE and MDCT. RESULTS: The best phase for assessing the open valve using MDCT was at 5% and the closed valve at 65% of the cardiac cycle. The mean image quality scores for cine-mode MDCT ranged between 3.26 and 3.75, with inter-reader agreements ranging between good (kappa = 0.723) and excellent (kappa = 1.00). They did not differ significantly from TOE scores for assessment of the closed and open valve. In transitional phases (close-to-open and open-to-close) TOE performed significantly better when compared with static MDCT images, whereas no significant difference was present between cine-mode presentation of MDCT and TOE. Planimetric AVA measurements correlated significantly between TOE and MDCT (Pearson correlation coefficient, r = 0.96; P < 0.0001). Contrast media inflow-related and ECG gating related artifacts were rated as slightly compromising (scores 3.24 and 3.21). CONCLUSION: Retrospectively ECG-gated MDCT offers a noninvasive, accurate, and dynamic imaging method for quantitative and qualitative evaluation of the normal aortic valve allowing determination of morphology and function throughout the cardiac cycle. Further studies regarding assessment of diseased valves are necessary.     

Pancreatitis: computed tomography and magnetic resonance imaging

The value of CT in management of severe acute pancreatitis is well established. Some, but not all, experimental studies suggest a detrimental effect of intravenous iodinated contrast agents in acute pancreatitis, but although initial clinical data tends to support this, the positive advantages of enhanced CT outweigh the possible risks. Magnetic resonance imaging has been shown to be as effective as CT in demonstrating the presence and extent of pancreatic necrosis and fluid collections, and probably superior in indicating the suitability of such collections for percutaneous drainage. Image-guided intervention remains a key approach in the management of severely ill patients, and the indications, techniques and results of radiological intervention are reviewed herein. Both CT and MRI can be used to diagnose advanced chronic pancreatitis, with the recent addition of MRCP as a viable alternative to diagnostic endoscopic retrograde cholangiopancreatography (ERCP). Both MRCP and CT/MR imaging of the pancreatic parenchyma still have limitations in the recognition of the earliest changes of chronic pancreatitis – for which ERCP and tests of pancreatic function remain more sensitive – but the clinical significance of these minor changes remains contentious. Received: 12 February 1998; Revision received: 17 June 1998; Accepted: 22 June 1998     

Assessing the extent of breast cancer using multidetector row helical computed tomography

OBJECTIVE: The aim of the study was to evaluate the usefulness of multidetector row helical computed tomography (MD-CT) in assessing the local extent of breast cancer. METHODS: Seventy-five breast cancer patients were examined using MD-CT with scanning performed in the supine position at 1-mm collimation. The extent of the breast tumors determined using CT was compared with that based on histopathologic mapping with continuous 5-mm slices. RESULTS: The CT evaluation of the maximum diameter of the extent of breast cancer was much better correlated with the histopathologic diagnosis (correlation coefficient=0.90) than the pre-CT diagnosis (correlation coefficient=0.46). Computed tomography correctly detected mammographically and clinically occult cancer other than the index lesion in 14 of 15 patients. The sensitivity, specificity, and accuracy in the diagnosis of the additional lesions were 93.3%, 98.3%, and 97.3%, respectively. Because the images were obtained in the supine position, they were useful for surgical planning. CONCLUSION: The extent of breast cancer can be determined accurately using MD-CT.     

Syringomyelia: myelography, computed tomography, and magnetic resonance imaging

Seventeen patients with cervical spinal cord cavities were studied with myelography, postmyelographic computed tomography scanning, and magnetic resonance imaging. The three diagnostic techniques were compared for accuracy, patient comfort, and ease of procedure. Magnetic resonance imaging was the best diagnostic and most comfortable procedure. There is no need for myelography or postmyelographic computed tomography scanning for the evaluation of cervical syringomyelia.     

Advanced gastric cancer and perfusion imaging using a multidetector row computed tomography: correlation with prognostic determinants.

OBJECTIVE: To investigate the relationship between the perfusion CT features and the clinicopathologically determined prognostic factors in advanced gastric cancer cases. MATERIALS AND METHODS: A perfusion CT was performed on 31 patients with gastric cancer one week before surgery using a 16-channel multi-detector CT (MDCT) instrument. The data were analyzed with commercially available software to calculate tumor blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability surface (PS). The microvessel density (MVD), was evaluated by immunohistochemical staining of the surgical specimens with anti-CD34. All of the findings were analyzed prospectively and correlated with the clinicopathological findings, which included histological grading, presence of lymph node metastasis, serosal involvement, distant metastasis, tumor, node, metastasis (TNM) staging, and MVD. The statistical analyses used included the Student's t-test and the Spearman rank correlation were performed in SPSS 11.5. RESULTS: The mean perfusion values and MVD for tumors were as follows: BF (48.14+/-16.46 ml/100 g/min), BV (6.70+/-2.95 ml/100 g), MTT (11.75+/-4.02 s), PS (14.17+/-5.23 ml/100 g/min) and MVD (41.7+/-11.53). Moreover, a significant difference in the PS values was found between patients with or without lymphatic involvement (p = 0.038), as well as with different histological grades (p = 0.04) and TNM stagings (p = 0.026). However, BF, BV, MTT, and MVD of gastric cancer revealed no significant relationship with the clinicopathological findings described above (p > 0.05). CONCLUSION: The perfusion CT values of the permeable surface could serve as a useful prognostic indicator in patients with advanced gastric cancer.     

Adrenal gland volume determination by computed tomography and magnetic resonance imaging in normal subjects

To compare the usefulness of computed tomography (CT) and magnetic resonance imaging (MRI) for the quantitative determination of adrenal gland size in human subjects, adrenal gland volumes were determined by both techniques in five female and five male, normal, nonstressed adult volunteers. Mean left and right adrenal volumes were slightly larger by CT, and the left adrenal volume was slightly larger than the right by both imaging techniques. Volume determinations by CT and MRI correlated +0.85 and +0.82 for the left and right glands, respectively. Body surface area was highly correlated, and sex moderately correlated, with left and right adrenal volumes by both techniques. Both CT and MRI somewhat overestimated the known volumes of a set of phantoms, CT by an average of 42% and MRI by an average of 20%. The results of this initial study suggest that MRI holds promise as a technique for in vivo adrenal gland measurements, and that the influence of both body surface area and sex should be considered in comparative studies of adrenal size.     

Comparison of magnetic resonance imaging and multidetector computed tomography for evaluating intraductal tumor extension of breast cancer

Magnetic resonance imaging (MRI) and computed tomography (CT) can be used for pretreatment evaluation of intraductal tumor extension of breast cancer. Images of intraductal tumor extension obtained by MRI and multidetector CT (MDCT) are shown to illustrate the similarities and differences in the imaging features of these two techniques. MRI is an excellent tool and MDCT is a fair one for evaluating intraductal tumor extension of breast cancer.