Quantitative analysis of technegas SPECT: evaluation of regional severity of emphysema.

UNLABELLED: The purpose of this study was to quantify the regional severity of emphysema by 3-dimensional fractal analysis of technegas (99mTc-carbon particle radioaerosol) SPECT images. METHODS: Technegas SPECT was performed on 22 patients with emphysema. The lungs were delineated using 4 cutoff levels (15%, 20%, 25%, and 30% of the maximal pixel radioactivity), and the total number of pixels was measured in the areas surrounded by the contours obtained with each cutoff level. We calculated fractal dimensions from the relationship between the total number of pixels and cutoff levels transformed into logarithms. Fractal dimension for total or regional lung was defined as the severity of emphysema. RESULTS: Total lung fractal dimension (T-FD), upper lung fractal dimension (U-FD), and lower lung fractal dimension (L-FD) for patients with emphysema were 1.84 +/- 0.46 (mean +/-SD), 2.22 +/- 0.61, and 1.77 +/- 0.49, respectively. U-FD was significantly greater than was L-FD. Patients with the ratio of U-FD to L-FD of <1.16 had a significantly greater percentage forced vital capacity (FVC) than did patients with the ratio of >1.16. Patients with an L-FD of <1.8 had a significantly greater forced expiratory volume in 1 s (FEV1)/FVC than did patients with that of >1.8. No significant difference was found between patient groups stratified by U-FD. CONCLUSION: The regional severity of emphysema was well shown by these fractal dimensions.

Hyperactivity of 99mTc-HMPAO within 6 hours in patients with acute ischemic stroke.

UNLABELLED: Intraarterial thrombolytic therapy has been used recently for treatment of acute ischemic stroke within 6 h after onset. Although hypoactivity of 99mTc-hexamethylpropyleneamine oxime (HMPAO) in stroke has been well documented, hyperactivity of HMPAO has not been evaluated in sufficient detail. The purpose of this study was to evaluate the incidence and clinical importance of hyperactivity of HMPAO in management of patients with acute ischemic stroke. METHODS: We retrospectively investigated HMPAO SPECT in 90 patients with acute ischemic stroke within 6 h after onset. The lesion-to-contralateral radioactivity ratios (L/Cs) were calculated on the SPECT images before treatment and were compared with the imaging results of CT or MRI (or both). RESULTS: Hyperactivity of HMPAO, accompanied by surrounding hypoactivity, was observed in 6 of 90 patients (7%) within 6 h after onset. The L/Cs ranged from 1.17 to 2.95. Two patients showed hyperactivity in the cortex and the other 4 patients showed hyperactivity in the basal ganglia. Angiography confirmed spontaneous recanalization of occluded vessels in accordance with the area of hyperactivity. In both patients with cortical hyperactivity, cerebral infarctions were revealed on follow-up CT; in 1 patient, hemorrhagic transformation developed after intraarterial thrombolytic therapy. In 3 of the 4 patients with hyperactivity in the basal ganglia, follow-up CT showed no infarction in the surrounding hypoperfused cortex (selective intraarterial thrombolytic therapy was performed on 2 patients), although various degrees of infarction were observed in the basal ganglia. Obvious infarctions developed in the basal ganglia and the cortex of the other patient. CONCLUSION: Hyperactivity of HMPAO could be seen in the basal ganglia and the cortex within 6 h after onset, reflecting spontaneous recanalization. The areas of hyperactivity may develop infarctions, whereas the accompanying areas of hypoactivity could be rescued by selective intraarterial thrombolytic therapy.

Fractal analysis of cerebral blood flow distribution in Alzheimer's disease.

UNLABELLED: This study describes a method for quantifying cerebral blood flow (CBF) distribution in Alzheimer's disease (AD) from SPECT images obtained with (99m)Tc-hexamethylpropyleneamine oxime (HMPAO) by 3-dimensional fractal analysis (3D-FA). METHODS: HMPAO SPECT was performed on 68 patients with probable AD and 14 healthy control subjects. We delineated the CBF images using 4 cutoff levels (35%, 40%, 45%, and 50% of the maximal voxel radioactivity) and measured the total number of voxels in the areas surrounded by the contours obtained with each cutoff level. We calculated fractal dimensions from the relationship between the total number of voxels and the cutoff levels transformed into natural logarithms. RESULTS: The fractal dimensions (mean +/- SD) for patients with probable AD and healthy subjects were 0.74 +/- 0.33 and 0.52 +/- 0.09, respectively. A significant difference in the fractal dimension was found between groups (P = 0.001). Statistically significant correlations were obtained between the fractal dimension and the Mini-Mental State Examination score (r = -0.598; P < 0.0001) and between the fractal dimension and the AD Assessment Scale (r = 0.670; P < 0.0001). The fractal dimensions for subjects with clinical dementia rates (CDRs) of 0, 1, 2, and 3 were 0.52 +/- 0.09, 0.63 +/- 0.21, 0.77 +/- 0.23 (P < 0.05 vs. the group with a CDR of 1), and 1.43 +/- 0.49 (P < 0.0001 vs. the group with a CDR of 2), respectively. CONCLUSION: Quantification of CBF distribution on SPECT images in AD was possible using 3D-FA. The fractal dimension was well correlated with the cognitive impairment, as assessed in neuropsychologic tests. 3D-FA may be a useful method for objectively evaluating the progression of AD.

Preoperative histologic diagnosis of chest wall invasion by lung cancer using ultrasonically guided biopsy.

Before operation, we evaluated the usefulness of ultrasonically guided needle biopsy to detect histologically invasion of the chest wall by tumor in patients with lung cancer. Ultrasonically guided needle biopsy, computed tomography, and ultrasonography were done in 29 patients with lung cancer. In all of them, chest wall invasion was histologically confirmed by thoracotomy. As for the diagnosis of chest wall invasion, sensitivity, specificity, and accuracy of ultrasonically guided needle biopsy diagnosis were 61.5%, 100%, and 82.8%, respectively; for diagnosis by computed tomographic scan these figures were 69.2%, 75.0%, and 72.4%, respectively; and for diagnosis by ultrasonography they were 76.9%, 68.8%, and 72.4%, respectively. We had no false-positive cases in the ultrasonically guided needle biopsy assessment and no fatal complications or implantation metastases. Our results indicate that ultrasonically guided needle biopsy is safe and useful for preoperative histologic diagnosis of chest wall invasion in cases in which combined chest wall resection is being considered in patients with lung cancer.

Single-exposure dual-energy chest images with computed radiography. Evaluation with simulated pulmonary nodules.

RATIONALE AND OBJECTIVES: Dual-energy subtraction radiography using computed radiography (CR) can aid in the detection of pulmonary abnormalities such as nodules, but the subtracted image requires higher x-ray exposure than usual to reduce quantum mottle. To reduce quantum mottle without increasing x-ray exposure, a new dual-energy subtraction algorithm was investigated that included an edge-adaptive smoothing process and a subtraction process. The signal-to-noise ratio and the image quality of this new subtracted image was significantly superior to that of conventional subtracted images. METHODS: Observer performance of the subtracted digital radiography in detecting simulated pulmonary nodules was compared with original CR images and conventional subtracted digital radiography of 50 patients. RESULTS: A combination of an original CR image and a new subtracted CR image was significantly superior to a single original CR image or a combination of an original CR image and a conventional subtracted CR image (P < .01). DISCUSSION: The single-exposure dual-energy subtraction method is superior to the conventional subtraction method in the detection of pulmonary nodules.

An image analyzing system for interstitial lung abnormalities in chest radiography. Detection and classification by Laplacian-Gaussian filtering and linear opacity judgment.

RATIONALE AND OBJECTIVES: The effectiveness of a computerized analysis system to detect and characterize interstitial lung abnormalities seen on chest radiographs was evaluated. This method included a process of four-directional Laplacian-Gaussian filtering and a process of linear opacity judgement. For quantitative analysis of interstitial opacities, the radiographic index, which is the percentage of opacity areas in a region of interest, was obtained and evaluated in the images. These opacities represented interstitial lung abnormalities. METHODS: Two regions of interest were selected in each right lung of 50 patients with normal lung parenchyma and 50 patients with diffuse interstitial lung abnormalities, confirmed with high-resolution computed tomography. These regions of interest were processed by our computerized analysis system. RESULTS: Abnormal lungs were well differentiated from normal lungs by the radiographic indices obtained from the images filtered by four-directional Laplacian-Gaussian filters and from those processed by linear opacity judgement. However, honeycomb lesions and other interstitial abnormalities (interstitial changes other than honeycombing) were differentiated from each other only by the radiographic indices obtained from the image processed by linear opacity judgment (P < .05). DISCUSSION: These results indicate that this system is useful for the detection and characterization of interstitial lung abnormalities.

Gravity-dependent atelectasis. Radiologic, physiologic and pathologic correlation in rabbits on high-frequency oscillation ventilation.

The authors identify the radiologic features of progressive atelectasis induced under conditions of reduced lung volume. Control (n = 5) and experimental (n = 7) animals were placed on high-frequency oscillation (HFO) ventilation (mean airway pressure: 3 cm H2O) for 6 hours. In the experimental animals, lung volume was artificially reduced by pneumoperitoneum during HFO ventilation. Computed tomography scans and chest radiographs were obtained every hour, and arterial blood gases analyzed. No changes were detected in the control animals. In the experimental animals, in which hypoxemia developed, homogeneous opacity in the dependent lung was found on CT images, and chest radiographs showed a diffuse homogenous shadow with loss of lung volume. Study of pathologic sections from the lung showed that the roentgenographic findings represented atelectasis. The lung was divided into three zones, from dependent to nondependent regions: severe atelectasis, mild atelectasis, and normal lung. Hyperinflations eliminated atelectasis seen on the CT images and alleviated hypoxemia; however an undesirable effect that causes barotrauma also was observed.

Mechanism of gravity-dependent atelectasis. Analysis by nonradioactive xenon-enhanced dynamic computed tomography.

RATIONALE AND OBJECTIVES: The physiologic mechanism of gravity-dependent atelectasis (GDA), a common finding identified during anesthesia, is not well understood. The purpose of this study was to determine whether an inherent reduction in alveolar volume or a reduction in alveolar ventilation is the more important causative factor for the development of GDA in an experimental animal model. METHODS: After uniform reduction of lung volume in ten rabbits by artificially induced pneumoperitoneum, dynamic inhalation computed tomography (CT) was performed using 50% nonradioactive xenon in oxygen. Time-CT attenuation value curves were fitted to an exponential function, CT value = a - b x e(-kt), and K value, which is proportional to the alveolar ventilation/alveolar volume ratio, was calculated by regression analysis. RESULTS: Gravity-dependent atelectasis occurred only in 5 of 10 rabbits. In this group, K values in the dorsal regions increased before the appearance of GDA. No significant change in K values in the ventral regions was observed. CONCLUSION: One mechanism of GDA may be a preferential reduction in alveolar volume without small airway collapse rather than alveolar volume loss secondary to decreased ventilation.

CT of parotid tumors.

Computed tomographic (CT) appearances of 18 surgically proven parotid tumors were studied. Digital radiography (GE, ScoutView) was performed to select the desired gantry angulations and then plain CT and CT combined with sialography were performed. Plain CT clearly showed parotid tumors in nine of the patients. CT combined with sialography was more helpful than plain CT for delineating the tumors in the other patients who had either tumors in high-density parotid glands for tumors low density. CT allows more accurate evaluation of tumor location and extent in the parotid gland than any other method and helps distinguish malignant from benign lesions. The normal CT appearances of the parotid region are necessary for precise interpretation of CT images in this region.

Evaluation of cerebral perfusion from bypass arteries using selective intraarterial microsphere tracer after vascular reconstructive surgery.

BACKGROUND AND PURPOSE: To detect areas of cerebral perfusion from bypass arteries after vascular reconstruction, we administered selective intraarterial microsphere tracer into the external carotid arteries and determined (via single-photon emission computed tomography [IA-SPECT]) whether the distribution of radiotracer matched the arteriographic distribution of contrast material as shown on external carotid angiograms. METHODS: We compared the extent of regional distribution of tracer after external carotid artery injection of 20 to 40 MBq of 99mTc-HMPAO or 99mTc-ECD with that of contrast medium on the external carotid angiograms in 582 cortical regions in 12 patients with atherosclerotic occlusive disease and in 18 patients with moyamoya disease. RESULTS: Marked accumulation of tracer was found only in the expected, specific, newly developed areas of cerebral perfusion from bypass arteries. The regional distribution of tracer corresponded to that of contrast medium in 523 regions (90%) and did not correspond in 59 regions (10%). Significant overestimation of the distribution of contrast material relative to that of tracer was observed in the patients with moyamoya disease. CONCLUSION: SPECT showed slightly different distribution of tracer from that predicted by conventional angiography. IA-SPECT should enhance the analysis of newly developed areas of cerebral perfusion from the bypass arteries.

Curved planar reformatted CT angiography: usefulness for the evaluation of aneurysms at the carotid siphon.

BACKGROUND AND PURPOSE: Three-dimensional CT angiography uses the data obtained on a contrast-enhanced CT brain scan to generate 3D images of the intracranial vasculature. We describe the methodology of curved planar reformatting (CPR) for CT angiography and characterize its usefulness in the evaluation of aneurysms at the carotid siphon, comparing it with the shaded surface display technique (SSD). METHODS: Eighty-seven patients with suspected intracranial aneurysms at CT angiography were examined by conventional cerebral angiography, and the patients with aneurysm(s) at the carotid siphon were selected for study. For these patients, the visibility of the neck and fundus of the aneurysms on CT angiograms was compared for those obtained with SSD and those with CPR, and observer reproducibility was evaluated with the kappa statistic. RESULTS: Eighteen patients were confirmed to have an aneurysm at the carotid siphon on conventional angiograms. Seventeen aneurysms were depicted at CT angiography with SSD; 18 aneurysms with CPR. The number of visible aneurysmal necks and fundi was nine and 12, respectively, with SSD; 18 and 18, respectively, with CPR. CONCLUSION: CPR allows better demonstration of the body and neck of an aneurysm at the carotid siphon, which has a tortuous course and is surrounded by complex bony structures. CPR may be a useful adjunct for the evaluation of aneurysms in this region.

Measurement of cerebral hemodynamics with perfusion-weighted MR imaging: comparison with pre- and post-acetazolamide 133Xe-SPECT in occlusive carotid disease.

BACKGROUND AND PURPOSE: We generated regional cerebral blood volume (rCBV) and regional cerebral blood flow (rCBF) studies from dynamic susceptibility contrast-enhanced MR images after an intravenous bolus injection of contrast agent (perfusion-weighted imaging [PWI]) by applying indicator dilution theory. We used a multishot echo-planar imaging (EPI) sequence to obtain adequate arterial input function (AIF). Our purpose was to compare the cerebral hemodynamics measured by PWI with the rCBF values and cerebral perfusion reserve obtained by xenon-133 single-photon emission CT (133Xe-SPECT). METHODS: Eight patients with chronic internal carotid artery occlusion or stenosis were examined. PWI data were acquired using a multishot EPI sequence, and the AIF was determined automatically. Our procedure was based on indicator dilution theory and deconvolution analysis. To eliminate the effect of superficial vessels, the automatic threshold selection method was used. RESULTS: AIF was adequate to generate rCBF and rCBV images. The rCBF and rCBV images by PWI were superior to 133Xe-SPECT scans in spatial resolution, and the rCBF values obtained by PWI correlated well with those obtained by 133Xe-SPECT. The regions with severely decreased perfusion reserve, which were determined by pre- and post-acetazolamide 133Xe-SPECT, showed significantly lower rCBF and higher rCBV by PWI than did regions with normal and moderately decreased perfusion reserve. CONCLUSION: The rCBF and rCBV images generated by our procedure using PWI data appear to provide important clinical information for evaluating the degree of cerebral perfusion reserve impairment in patients with chronic ischemia.

CT evaluation of anaplastic thyroid carcinoma.

CT findings in 19 patients with anaplastic thyroid carcinoma were compared retrospectively with pathologic findings and the results of palpation. The carcinoma appeared as a large mass of low attenuation accompanied by dense calcification in 58% of the patients; there was necrosis in 74%. Often, adjacent structures were infiltrated. CT correctly showed tumor invasion of the carotid artery (7/7), internal jugular vein (9/10), larynx (5/6), trachea (8/10), esophagus (4/5), mediastinum (5/5), and regional lymph nodes (14/16). Seven patients (50%) had necrotic nodes. CT was superior to palpation in the detection of a primary tumor in one patient and of metastatic nodes in seven patients. It suggested a suitable place for biopsy in two patients, leading to a correct diagnosis. CT altered surgical planning in five patients with intrathoracic extension of the thyroid tumor, and in three patients with laryngeal or esophageal invasion of the tumor. CT can increase diagnostic accuracy in patients with anaplastic thyroid carcinoma by suggesting a likely diagnosis and by indicating an appropriate site for biopsy. It is indispensable in the planning of surgery for patients with this disorder.

Tongue cancer: correlation of MR imaging and sonography with pathology.

Ten patients with tongue cancer underwent both MR imaging and sonography. In seven of these patients, pathologic findings from glossectomies were correlated with MR and sonographic results. MR images of resected specimens also were obtained in two patients, and relaxation time was calculated in one of these patients. MR images (5- to 7-mm thick slices) were obtained by using a 0.1-T resistive magnet with a 128 x 256 acquisition matrix. MR and sonography had almost the same sensitivity for detecting primary-site tongue cancer. However, in the three patients with extraorgan spread of tumor, MR was superior, showing three of three cases, compared with sonography, which showed extraorgan spread in only one of the three cases. Although MR failed in one patient to differentiate postradiation scar tissue from tumor, because of similar relaxation time of both, this imaging technique proved to be an important adjunct to the physical examination in the staging of tongue cancer.

Successful combination chemotherapy (cisplatinum, vinblastine, and bleomycin) against peritoneal dissemination of intracranial germ cell tumor.

We found combination chemotherapy with cisplatinum, vinblastine, and bleomycin (PVB therapy) effective in the treatment of a patient with a pineal germ cell tumor with peritoneal dissemination. The metastatic complication may have been attributable to the ventriculoperitoneal shunt tube. After the first course of PVB therapy, the disseminated tumors were decreased in size; no residual tumors were detected after the third course by laparoscopic examination, computed tomographic scanning, or echogram. Our results suggest that combined PVB therapy is effective in the treatment of extraneural metastasis from intracranial germ cell tumors.

An anisotropic diffusion method for denoising dynamic susceptibility contrast-enhanced magnetic resonance images.

The purpose of this study was to present an application of a novel denoising technique for improving the accuracy of cerebral blood flow (CBF) images generated from dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI). The method presented in this study was based on anisotropic diffusion (AD). The usefulness of this method was firstly investigated using computer simulations. We applied this method to patient data acquired using a 1.5 T MR system. After a bolus injection of Gd-DTPA, we obtained 40-50 dynamic images with a 1.32-2.08 s time resolution in 4-6 slices. The dynamic images were processed using the AD method, and then the CBF images were generated using pixel-by-pixel deconvolution analysis. For comparison, the CBF images were also generated with or without processing the dynamic images using a median or Gaussian filter. In simulation studies, the standard deviation of the CBF values obtained after processing by the AD method was smaller than that of the CBF values obtained without any processing, while the mean value agreed well with the true CBF value. Although the median and Gaussian filters also reduced image noise, the mean CBF values were considerably underestimated compared with the true values. Clinical studies also suggested that the AD method was capable of reducing the image noise while preserving the quantitative accuracy of CBF images. In conclusion, the AD method appears useful for denoising DSC-MRI, which will make the CBF images generated from DSC-MRI more reliable.

Subluxation of the patella: evaluation of patellar articular cartilage with MR imaging.

In patients with subluxation of the patella, injury of the patellar articular cartilage is frequently observed, and correct evaluation of this cartilage injury is extremely important for the management of these patients. Magnetic Resonance (MR) studies were performed on 102 patellofemoral (PF) joints of 51 patients with subluxation of the patella and 20 PF joints of 10 healthy volunteers. In 77 of the 102 PF joints with subluxation, arthroscopy and/or operation were performed. MR images were obtained with spin-echo and FLASH sequences, and para-axial images were obtained. We retrospectively analysed the MR findings of the 77 joints with special attention to the surface and thickness of the cartilage, and classified them into four grades. These MR grades were compared with the grades on arthroscopy, and the following results were obtained: MR grade 0, normal cartilage (n = 27, sensitivity 90.9%, specificity 74.2%); MR grade 1, thickening of the cartilage (n = 24, sensitivity 50%, specificity 89.1%); MR grade 2, surface irregularity of the cartilage (n = 20, sensitivity 85%, specificity 94.7%); MR grade 3, loss of the cartilage (n = 6, sensitivity 100%, specificity 100%). Although the early changes observed by arthroscopy were underestimated from the MR images, MR imaging proved to be extremely useful for evaluating moderately or advanced patellar cartilage injury.

Inclined coronal scans in thoracic MR imaging.

To determine the value of inclined coronal MR in diagnosing thoracic abnormalities, the multiscan coronal and inclined coronal spin echo MR images of 4 normal subjects and 10 patients with thoracic abnormalities were reviewed. The major airway such as trachea, main bronchi and lobar bronchi, left atrium and its junctions with pulmonary veins required less slices for visualization on inclined coronal images than on standard coronal images, and these normal structures and the lesions located in this region were easy to evaluate in several cases. The left pulmonary artery, especially the upper and lower lobe branches were better visualized on inclined coronal images. The pericardium and the other great vessels were equally visualized on inclined and on standard coronal images. There was no case in which normal structures or lesions were more difficult to demonstrate on inclined coronal images compared with standard coronal images. We conclude that an inclined coronal MR scan of the thorax is valuable to evaluate the mediastinal structures and lesions, especially in diagnosing the abnormalities of the airway, left atrium and its junctions with pulmonary veins.

High-resolution CT and pulmonary function tests in collagen vascular disease: comparison with idiopathic pulmonary fibrosis.

To estimate whether the lung abnormalities seen in collagen vascular diseases (CVD) were similar or distinct to those seen in idiopathic pulmonary fibrosis (IPF), and to ascertain whether the extent of the abnormalities on high-resolution CT (HRCT) correlated with pulmonary function, we reviewed HRCT findings and pulmonary function test results of 64 patients with either CVD (n = 55) or IPF (n = 9). Response to corticosteroid treatment was also evaluated in 20 of the 64. High incidence of honeycomb lesion was observed in IPF (9/9, 100%) and in progressive systemic sclerosis (PSS) (11/14, 79%). CVD, except for PSS, had a low incidence of honeycomb lesion (27%). On the other hand, incidence of ground-glass shadow in CVD (47/55, 85%) was the same as that in IPF (8/9, 89%). Diffusing capacity significantly correlated with the extent of all parenchymal abnormalities in all CVD and IPF, with honeycomb lesion in PSS, and with ground-glass shadow or air-space consolidation in CVD except for PSS (r < -0.7, P < 0.001). In all 15 cases in which corticosteroid therapy was effective, no honeycomb lesions were seen. Collagen vascular disease, except for PSS, had a different pattern of disease than IPF. The morphologic changes seen on HRCT correlated well with pulmonary function in CVD.

CT of intrathoracic neurogenic tumours.

Fifteen patients with primary intrathoracic neurogenic tumours were evaluated using computed tomography (CT) scans. Schwannomas were demonstrated as homogeneous or slightly inhomogeneous densities on plain CT images; 4 of 5 schwannomas showed rim enhancement with some enhancement in the central portion of the tumour on post-enhancement CT images. Neurofibromas and ganglioneuromas were visualized as homogeneous densities on plain CT images. Three of 5 ganglioneuromas revealed homogeneous contrast enhancement of post-contrast CT images. A ganglioneuroblastoma and 2 neuroblastomas manifested slightly inhomogeneous tumour density on plain CT images. The inhomogeneity of the tumours was accentuated on contrast enhancement CT images.