Thick maximum intensity projections for the assessment of left ventricular function with 64-slice computed tomography

OBJECTIVE: The objective of this study was to assess the accuracy of thick maximum intensity projections (MIP) from computed tomography (CT) data sets mimicking projection images from biplane ventriculography for evaluation of left ventricular (LV) parameters. MATERIALS AND METHODS: Fifty-eight patients underwent 64-slice CT. Multiphase images were reconstructed in 10% steps of the RR interval. MIP images (70-mm thickness) of the contrast-enhanced LV in fixed 30 degrees right anterior oblique (RAO)/60 degrees left anterior oblique (LAO) and in adapted short-/long-axis planes were reconstructed. LV parameters were calculated using the area-length method formula. Three-dimensional assessment with semiautomated software served as reference standard. RESULTS: Use of thick MIP reconstructions had a high intermethod reliability (86-94%) compared with the 3-dimensional approach. Smaller measurement errors were found for thick MIP reconstructions in adapted short-/long-axis planes. A significant projection error (3.0%, P < 0.001) of thick MIP reconstructions was found using fixed 30 degrees RAO/60 degrees LAO compared with adapted short-/long-axis reconstructions. CONCLUSION: Thick MIP reconstructions with adapted short-/long-axis planes allow an accurate assessment of LV parameters compared with the established 3-dimensional method.     

Assessment of accuracy of renal artery stenosis grading in helical CT angiography using maximum intensity projections

The purpose of the study was to investigate whether visual inspection of maximum intensity projection (MIP) images is a reliable method for assessment of the severity of renal artery stenoses (RAS). Therefore, 20 RAS were investigated with helical CT. Native axial images and MIP images were analysed separately or in combination (two-step method). A phanton study was performed to investigate the influence of window setting on apparent stenosis severity. Accuracy for diagnosis of 50–69% and 70–99% RAS and the mean inter-observer agreement were 82.5%, 77.5% and 82.5% respectively, using study of MIP images alone, and 100%, 97.5% and 95% using the two-step method. The phantom study showed that the apparent severity of vascular stenoses on MIP images depends on the selected window centre values. It is concluded that combined evaluation of both MIP images and native axial images is more reliable than study of MIP images alone for assessing the severity of RAS. Correspondence to: L. Van Hoe     

Contrast-to-noise ratios in maximum intensity projection images.

We present a statistical analysis of the maximum intensity projection (MIP) algorithm, which is commonly used for MR angiography (MRA). The analysis explains why MIP projection images display as much as a twofold increase in signal- and contrast-to-noise ratios over those of the source image set. This behavior is demonstrated with simulations and in phantom and MRA image sets.     

Three-dimensional CT maximum intensity projections of the calvaria: a new approach for diagnosis of craniosynostosis and fractures

Three-dimensional CT maximum intensity projection (MIP) can depict suture patency, extent of synostosis (ie, complete versus incomplete bone bridging), fracture extent and conspicuity, and 3D calvarial deformity as a single set of projections in children with suspected craniosynostosis or skull fracture. Three-dimensional CT MIP may provide, in only eight views, all the required information to make the diagnosis of craniosynostosis and calvarial fracture extent currently requiring the combined information of 3D CT shaded surface displays and 2D axial CT images (a total of 58 views), and in some cases complementary skull radiographs. Three-dimensional MIP can be added to calvarial helical (spiral) CT imaging with only 5 minutes of additional postprocessing time.     

Dual-energy CT angiography in peripheral arterial occlusive disease-accuracy of maximum intensity projections in clinical routine and subgroup analysis

Objective  

To evaluate the accuracy of dual-energy CT angiography (DE-CTA) maximum intensity projections (MIPs) in symptomatic peripheral arterial occlusive disease (PAOD).     

A fast progressive method of maximum intensity projection.

Real-time processing and visualization of the 3D image data are the most important requirements for medical imaging. Among various 3D visualization methods, maximum intensity projection (MIP) is a useful tool to visualize 3D medical images. However, a large computation amount is a drawback of using the MIP image in clinical diagnosis. The processing time of the MIP depends on the number of voxels of the 3D data. In order to overcome the large amount of computation for the MIP, we have developed a progressive MIP method that can perform the MIP with low-resolution for fast processing, and use the low-resolution MIP image to generate a full-resolution MIP image with a reduced computation time. In this paper, the progressive MIP method is implemented and its computation complexity is analyzed.     

Diagnostic value of maximum intensity projections versus source images for assessment of contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography

RATIONALE AND OBJECTIVES: We compared maximum intensity projections (MIP) versus original source images (SI) in respect to detection of coronary artery stenoses by means of magnetic resonance (MR) coronary angiography. METHODS: MR coronary angiography was performed on 61 patients. MIP and SI were independently evaluated as to presence of significant stenoses in the proximal and midcoronary segments and compared with x-ray angiography. RESULTS: A total of 315 of 427 (74%) coronary artery segments could be evaluated in MIP and 328 of 427 (77%) in SI. In segments able to be evaluated, MIP images demonstrated 84% (54/64) sensitivity and 87% (219/251) specificity, whereas SI images showed 85% (58/68) sensitivity and 90% (235/260) specificity. Overall accuracy was 87% (273/310) for MIP and 89% (293/328) for SI. There was no statistically significant difference between both modalities. CONCLUSIONS: The MIP reconstructions showed comparable accuracy to unprocessed SI. However, MIP postprocessing is compromised by a higher number of images that were unable to be evaluated due to overlap of coronary arteries with adjacent cardiac structures.     

CT angiography with spiral CT and maximum intensity projection.

The authors describe a technique for obtaining angiographic images by means of spiral computed tomography (CT), preprocessing of reconstructed three-dimensional sections to suppress bone, and maximum intensity projection. The technique has some limitations, but preliminary results in 48 patients have shown excellent anatomic correlation with conventional angiography in studies of the abdomen, the circle of Willis in the brain, and the extracranial carotid arteries. With continued development and evaluation, CT angiography may prove useful as a screening tool or replacement for conventional angiography in some patients.     

Assessment of ureteric obstruction with 16-MDCT: Curved planar reformats versus three-dimensional volume-rendered images and their corresponding maximum intensity projections

Aim

To compare the sensitivity and diagnostic accuracy of curved planar reformation (CPR) image on the one hand versus combined volume-rendered (VR) image and its corresponding maximum intensity projection (MIP) image on the other hand for determination of the cause and level of ureteral obstruction.

Materials and methods

The study included 60 patients with clinical and sonographic manifestations of ureteral obstruction who underwent two-phase multidetector CT urography (MDCTU) using a 16-slice machine. A total of 82 ureters were examined. CPR images were performed to display the entire course of ureters in the same image. 3D VR reformats and their corresponding MIP were used to enhance visualization of opacified ureters. The sensitivity and accuracy of CPR, and combined 3D VR and MIP for diagnosis of ureteral obstruction were calculated and compared in reference to the gold standard.

Results

The cause of ureteral obstruction was calculous in 28/82 ureters (34.14%), and noncalculous in 50/82 (61%). The lower third ureter was the most affected level in 48/82 ureters (58.5%). The total sensitivity and accuracy of CPR for the cause of the ureteric obstruction (97.5% and 95.3%, respectively) were higher than those of 3D VR and its corresponding MIP (75% and 73.2%, respectively). CPR also was more sensitive and accurate (total sensitivity of 100% and accuracy of 100%) compared with those of combined 3D VR and its corresponding MIP (79.5% and 75.9%, respectively) for the level of ureteral obstruction.

Conclusions

CPR had superior diagnostic accuracy than 3D VR and MIP in detecting the cause and level of ureteral obstruction.     

Relative value of sliding-thin-slab multiplanar reformations and sliding-thin-slab maximum intensity projections as reformatting techniques in multisection CT angiography of the cervicocranial vessels

BACKGROUND AND PURPOSE: To investigate image quality and vascular delineation of multisection CT (MSCT) angiography of the cervicocranial vessels with sliding-thin-slab (STS) maximum intensity projections (MIP) and multiplanar reformations (MPR). MATERIALS AND METHODS: Ten patients examined with a standardized protocol on a 16-section MSCT were included in the study. The data were reformatted as MIP and MPR in 3 planes for each subject; both reformatting techniques were applied in an STS technique with an increment of 3 mm. Images were evaluated independently by 3 blinded readers grading image quality parameters and vascular delineation of supra-aortic arteries and veins. An extension of the Mantel-Haenzel row mean score test was used to compare the distribution of scores for vascular delineation and image quality between STS MIP and STS MPR. RESULTS: STS MIP reformations were significantly superior to STS MPR in the delineation of all extra- and intracranial arteries and arterial segments and in the delineation of the cavernous sinus and the internal cerebral veins (P < .05). No significant differences were found for the large venous vessels, the visual assessment of vascular contrast, or the impact of imaging artifacts. CONCLUSION: Because STS MIP reformations were preferred to or equal to STS MPR in all aspects, we recommend STS MIP as the primary reformatting technique in MSCT angiography of the cervicocranial vessels in addition to viewing the source images.     

Curved-slab maximum intensity projection: method and evaluation

The authors developed and evaluated a method to produce curved-slab maximum intensity projections (MIPs) through blood vessels that semiautomatically excludes soft tissue and bone. Results obtained with the algorithm were compared with those obtained with rectangular-slab MIPs by using computed tomographic (CT) data from four patients with abdominal aortic aneurysms. Curved-slab MIPs exhibited increased mean vessel-to-perivascular tissue contrast of 55.1 HU (36%), allowed a 10% increase in contrast-to-noise ratio, and decreased apparent vessel narrowing by 0.12-1.09 mm, without increasing processing time. Curved-slab MIPs may also include multiple vessels in a single image, thereby improving interpretation efficiency by reducing the number of MIPs required in these patients from eight to three.     

Pulmonary nodule detection on MDCT images: evaluation of diagnostic performance using thin axial images,maximum intensity projections,and computer-assisted detection

This study aimed at evaluating the diagnostic benefits of maximum intensity projections (MIP) and a commercially available computed-assisted detection system (CAD) for the detection of pulmonary nodules on MDCT as compared with standard 1-mm images on lung cancer screening material. Thirty subjects were randomly selected from our database. Three radiologists independently reviewed three types of images: axial 1-mm images, axial MIP slabs, and CAD system detections. Two independent experienced chest radiologists decided which were true-positive nodules. Two hundred eighty-five nodules ≥1 mm were identified as true-positive by consensus of two independent chest radiologists. The detection rates of the three independent observers with 1-mm axial images were 22 ± 4.8%, 30 ± 5.3%, and 47 ± 2.8%; with MIP: 33 ± 5.4%, 39 ± 5.7%, and 45 ± 5.8%; and with CAD: 35 ± 5.6%, 36 ± 5.6%, and 36 ± 5.6%. There was a reading technique effect on the observers’ sensitivity for nodule detection: sensitivities with MIP were higher than with 1-mm images or CAD for all nodules (F-values = 0.046). For nodules ≥3 mm, readers’ sensitivities were higher with 1-mm images or MIP than with CAD (p < 0.0001). CAD was the most and MIP the less time-consuming technique (p < 0.0001). MIP and CAD reduced the number of overlooked small nodules. As MIP is more sensitive and less time consuming than the CAD we used, we recommend viewing MIP and 1-mm images for the detection of pulmonary nodules. This study was presented at the ECR 2006.     

Fast maximum intensity projection algorithm using shear warp factorization and reduced resampling.

Maximal intensity projection (MIP) is routinely used to view MRA and other volumetric angiographic data. The straightforward implementation of MIP is ray casting that traces a volumetric data set in a computationally expensive manner. This article reports a fast MIP algorithm using shear warp factorization and reduced resampling that drastically reduced the redundancy in the computations for projection, thereby speeding up MIP by more than 10 times.     

胰腺供血动脉的16层CT血管成像对比研究

目的 探讨16层CT血管成像3种重组技术：最大密度投影（MIP）、薄层最大密度投影（TSMIP）和容积重组（VR）对胰腺供血动脉的显示率，比较显示胰腺供血动脉的优势。方法 40例非胰腺病变的患者行腹部16层CT增强扫描和动脉期血管成像。统计TSMIP、MIP及VR对胰腺直接、间接供血动脉的显示率及显示状况。用配对X^2。检验观察显示率的差异；用配对秩和检验观察显示状况的差异。结果 （1）3种重组技术对胰腺间接供血动脉的显示率均为100％（40／40）。TSMIP、MIP、VR对胰十二指肠上后动脉（PSPDA）的显示率分别为92．5％（37／40）、77．5％（31／40）、67．5％（27／40）；对胰十二指肠上前动脉（ASPDA）的显示率分别为95．0％（38／40）、82．5％（33／40）、75．0％（30／40）；对胰十二指肠下动脉（IPDA）的显示率分别为92．5％（37／40）、75．0％（30／40）、57．5％（23／40）。（2）TSMIP与VR对ASPDA、PSPDA、IPDA的显示率的差异有统计学意义（X^2值分别为6．27、7．81、13．07、P值均〈0．01）；TSMIP与MIP对IPDA的显示率差异有统计学意义（X^2值为4．50，P〈0．05）。（3）TSMIP与MIP对胃十二指肠动脉（Z=-3．317，P=0．001）、胃左动脉（Z=-3．557，P=0．000）、肝固有动脉（Z=-2．810，P：0．005）、ASPDA（Z=-4．796，P=0．000）、PSPDA（Z=-4．400，P=0．000）和IPDA（z=-4．811，P=0．000）的显示状况的差异有统计学意义：TSMIP与VR对胃十二指肠动脉（Z=-3．162，P=0．003）、胃左动脉（Z=-3．051，P=0．002）、肝固有动脉（Z=-2．460，P=0．014）、ASPDA（Z=-5．166，P=0．000）、PSPDA（Z=-5．056．P=0．000）和IPDA（Z=-5．564，P=0．000）的显示状况的差异有统计学意义；MIP与VR对ASPDA（Z=-3．000，P=0．002）、PSPDA（Z=-2．352，P=0．019）和IPDA（Z=-3．500，P=0．000）显示状况的差异有统计学意义。结论 TSMIP显示胃左动脉、肝固有动脉、胃十二指肠动脉和胰腺直接供血动脉优于MIP及VR。MIP显示胰腺直接供血动脉优于VR。     

Comparison of conventional time-intensity curves vs. maximum intensity over time for post-processing of dynamic contrast-enhanced ultrasound

Our aim was to prospectively compare two post-processing techniques for dynamic contrast-enhanced ultrasound and to evaluate their impact for monitoring antiangiogenic therapy.Thus, mice with epidermoid carcinoma xenografts were examined during administration of polybutylcyanoacrylate-microbubbles using a small animal ultrasound system (40 MHz). Cine loops were acquired and analyzed using time-intensity (TI) and maximum intensity over time (MIOT) curves. Influences of fast (50 μl/2 s) vs. slow (50 μl/10 s) injection of microbubbles on both types of curves were investigated. Sensitivities of both methods for assessing effects of antiangiogenic treatment (SU11248) were examined. Correlative histological analysis was performed for vessel-density. Mann-Whitney test was used for statistical analysis.Microbubble injection rates significantly influenced upslope, time-to-peak and peak enhancement of conventional TI curves (p < 0.05) but had almost no impact on maximum enhancement of MIOT curves (representing relative blood volume). Additionally, maximum enhancement of MIOT curves captured antiangiogenic therapy effects more reliably and earlier (already after 1 day of therapy; p < 0.05) than peak enhancement of TI curves. Immunohistochemistry validated the significantly (p < 0.01) lower vessel densities in treated tumors and high correlation (R² = 0.95) between vessel-density and maximum enhancement of MIOT curves was observed.In conclusion, MIOT is less susceptible to variations of the injection's speed. It enables to assess changes of the relative blood volume earlier and with lower standard deviations than conventional TI curves. It can easily be translated into clinical practice and thus may provide a promising tool for cancer therapy monitoring.