High-attenuation Lesions Research Articles

A new projection correction based voting strategy for breast calcification artifact reduction

Objective. Digital Breast Tomosynthesis (DBT) is an imaging technique that combines traditional tomography with image processing and reconstruction techniques. In screening for breast cancer, high attenuation lesion will cause calcification hardening artifacts, which reduces the reconstructed image quality and limits diagnostic accuracy. We focus on the reconstruction artifacts that are caused by high-attenuation features in DBT, and aim to propose an efficient and accurate method to remove calcification artifacts and retain calcification information. Approach. The proposed method first introduces a new segmentation method, which can segment breast calcification accurately and effectively. Then an interpolation method is used to eliminate both the calcified area and artifact area in the projection images which are then used to reconstruct the image without artifacts and calcifications. Finally, the interpolated reconstructed image and the unprocessed reconstructed image are fused under the proposed voting strategy to obtain the DBT image with calcification artifacts removal. Main results. 18 groups of simulated projection data and 10 groups of real projection data collected by us are used to evaluate the proposed method. Experimental results show that our algorithm can effectively reduce the calcification artifact and preserve the effective information in the image as well. Significance. The proposed method utilizes a novel projection correction based voting fusion strategy for image fusion, and is advanced in reducing breast calcification artifacts compared with other state-of-the-art methods. Our work paves the way for more efficient and precise DBT breast cancer screening.

Comparison of true non-contrast and virtual non-contrast images in the characterization of renal lesions using detector-based spectral CT.

Renal lesions are sometimes incidentally detected during computed tomography (CT) examinations in which an unenhanced series is not included, preventing the lesions from being fully characterized. The aim of this study was to investigate the feasibility to use virtual non-contrast (VNC) images, acquired using a detector-based dual-energy CT, for the characterization of renal lesions. Twenty-seven patients (12 women) underwent a renal CT scan, including a non-contrast, an arterial, and a venous phase contrast-enhanced series, using a detector-based dual-energy CT scanner. VNC images were reconstructed from the venous contrast-enhanced series. The mean attenuation values of 65 renal lesions in both the VNC and true non-contrast (TNC) images were measured and compared quantitatively. Three radiologists blindly assessed all lesions using either VNC or TNC images in combination with contrast-enhanced images. Sixteen patients had cystic lesions, five had angiomyolipoma (AML), and six had suspected renal cell carcinomas (RCC). Attenuation values in VNC and TNC images were strongly correlated (ρ = 0.7, mean difference -6.0 ± 13 HU). The largest differences were found for unenhanced high-attenuation lesions. Radiologists classified 86% of the lesions correctly using VNC images. In 70% of the patients, incidentally detected renal lesions could be accurately characterized using VNC images, resulting in less patient burden and a reduction in radiation exposure. This study shows that renal lesions can be accurately characterized using VNC images acquired by detector-based dual-energy CT, which is in agreement with previous studies using dual-source and rapid X-ray tube potential switching technique.

Current state of management of struma ovarii and preoperative imaging features: A retrospective case series study of 18 patients at a single institution.

Even though 95% of struma ovarii are benign, it is often overtreated because of the difficulty to distinguish it from malignancy. In this study, our aim was to evaluate the current state of the preoperative diagnosis and the selection of the surgical procedure, and to improve preoperative diagnostic accuracy by retrospectively reviewing imaging findings. We retrospectively reviewed the clinical course and imaging characteristics of 18 patients who were diagnosed postoperatively with struma ovarii, pathologically, at our institution between 2015 and 2021. The preoperative diagnoses included benign ovarian tumor in eight cases, borderline in four cases, and malignant in six cases. None of the cases were diagnosed as struma ovarii preoperatively. Of the seven patients who had confirmed a desire for future childbearing, four patients were suspected for borderline or malignant tumor preoperatively, and underwent abdominal adnexectomy. In patients without a desire for childbearing, laparoscopic surgery was performed in only 45% of the patients whose preoperative diagnosis was benign. On magnetic resonance imaging (MRI), 54% of the cases showed enhanced solid components, which is characteristic of malignant tumors, but diffusion restriction was observed in only 11%. On computed tomography (CT), 78% of the cases showed a high attenuation lesion reflecting thyroid tissue. Struma ovarii is difficult to distinguish from malignancy preoperatively, making the choice of surgical approach complicated. A comprehensive evaluation of diffusion-weighted MRI and CT findings may improve the accuracy of preoperative diagnosis of struma ovarii.

Non-traumatic adult acute abdomen with high-attenuation lesions or materials in the gastrointestinal tract on unenhanced computed tomography.

Computed tomography (CT) is an imaging modality that provides otherwise unobtainable information in the diagnostic workup for acute abdomen. The patient's clinical history, physical examination, and laboratory findings are essential for a correct diagnosis; however, some diagnoses are difficult to establish. Although contrast-enhanced CT is the preferred diagnostic tool and provides invaluable information, using only post-contrast images can lead to misdiagnoses. Unenhanced CT images are more useful than post-contrast images for detecting high-attenuation lesions or materials because surrounding tissues also show high attenuation on post-contrast images. Unenhanced CT often provides key imaging findings for a correct diagnosis; hence, the purpose of this article is to describe CT findings in acute abdomen with high-attenuation lesions in the gastrointestinal tract.

Laparoscopic Removal of Gossypiboma Following Cesarean Section

Gossypiboma refers to a tumorus mass that is caused by a foreign body reaction due to an accidentally retained gauze or sponge within the body following surgery. Here, we report the case of gossypiboma in a 29-year-old woman with lower abdominal discomfort over a period of 2 years. In her medical history, she had a Cesarean section 11 years ago. Transvaginal ultrasonography showed an 8.5 × 6.4 cm mixed echoic round mass and both adnexa were normal. Abdominal-pelvic computed tomography confirmed a high attenuation lesion with a suspected foreign body in the pelvic cavity. Thus, based on a diagnosis of gossypiboma, she received a laparoscopic operation. Upon laparoscopic view, the mass was discovered to be well encapsulated and solid, and located between the urinary bladder and uterus. The mass was completely removed without damage to other adjacent organs. The patient was discharged on the 5th postoperative day without complications.

Transient high density vertebral bone lesions

The contrast-enhanced CTexamination revealed sclerotic-like lesions associated with consecutive anterior and posterior elements from the fourth cervical vertebra to the fifth thoracic vertebra, without any lytic components, which could at first be considered as bony metastases (Fig. 1a–b). CT scan also highlighted significant collateral venous circulation secondary to a brachiocephalic left venous thrombosis. A PET-CT performed at the same time was negative. A non-contrast CT scan performed 10 days later did not reveal the initially noted bone lesions (Fig. 2a–b) and suggested diagnosis of intraosseous venous contrast media. The 1-year non-contrast CT follow-up did not show any progression of the disease. Given the lack of corresponding findings on the unenhanced CT, in the setting of central venous obstruction and collateral pathway formation, the high-attenuation lesions seen on the enhanced CTexamination can be explained by the presence of intraosseous venous collaterals. In fact, the left brachiocephalic vein obstruction was responsible for the development of an extensive collateral venous pathway (Fig. 2c–d) involving the mediastinum, anterior jugular veins, anterior, and basivertebral venous plexi. The venous pressure in the dilated capillaries allowed marrow enhancement through the anastomosis capillary sites: basivertebral veins bed (between the anterior external plexus and the posterior internal plexi) and pedicular sites (between the intervertebral veins and the vertebral plexi) (Fig. 3a–b). Our patient remained asymptomatic despite the huge collateral venous substitution. The rate of injection of contrast and the time of image acquisition following contrast injection might be factors influencing the appearance of these findings. Chest collateral veins usually occur in superior vena cava obstruction and then develop through four classic pathways: azygos and hemiazygos, internal thoracic and laterothoracic, superficial thoracoabdominal, and vertebral venous plexus (posterior way) [1, 2]. These patients usually present with a symptomatic superior vena cava syndrome [3]. Less frequently, chest collateral veins can develop secondary to unilateral thrombosis of the brachiocephalic venous trunk, as in our case where the posterior pathway was involved [4]. Several cases of visceral abnormalities related to superior vena cava syndrome, including pericardial and hepatic enhancement, have been described [5]. However, bone involvement is uncommon. Only, two cases of cervical vertebral bone high-density abnormalities have been described in the context of superior vena cava syndrome secondary to a mediastinal mass (epidermoid lung carcinoma and small-cell lung carcinoma) [6, 7]. To our knowledge, there are no reports of similar cases of vertebral marrow abnormalities in asymptomatic patients, without any mass syndrome or obstructed superior cava vein. In the case presented, the findings could be misinterpreted as lymphomatous bone marrow involvement because of the patient’s history even though bony features of osseous lymphoma are usually lytic and seldom sclerotic, with soft tissue involvement. In summary, the present case illustrates a benign lesion entity related to retrograde contrast filling in bone marrow. The case presentation can be found at doi: 10.1007/s00256-013-1619-2

Radiological evaluation of interstitial lung disease

Chest radiograph, computed tomography and high-resolution computed tomography (HRCT) are an integral part in the diagnosis and evaluation of diffuse interstitial lung disease (DILD) and are reviewed briefly. This review then delves into the burgeoning interest associated with enhanced imaging and computational capabilities of multidetector HRCT in the automated evaluation of computer-aided recognition of different patterns associated with DILD, automated regional and global distribution and quantitation of DILD, and automated longitudinal comparison of HRCT scans to estimate progression of DILD. Problems associated with automatic segmentation of lung in DILD because of high-attenuation lesions in subpleural locations have been overcome to a large extent. Use of two-dimensional HRCT has made it possible to automate identification and quantification of patterns associated with DILD with an overall accuracy of 89%. Significant progress has been made with automated image registration and noise reduction, which are essential for sequential comparison of HRCT in DILD. Early experience with automated determination of progression or regression of DILD on two-dimensional HRCT, using the dissimilarity-based feature strategy, compared favorably with radiologist assessment and approached a concordance rate of 80%. The combination of multidetector HRCT, the support vector machine classifier and various computational algorithms have made it possible to fully automate isolation of lungs in DILD, recognize radiographic patterns associated with DILD and sequentially estimate progression of DILD. It is hoped there will be further improvement when these are extended to three-dimensional HRCT.

Diagnosis of Struma ovarii with medical imaging

To analyze the imaging features of Struma ovarii (SO), and to correlate the imaging results with the pathological findings so as to enhance the knowledge of the imaging diagnostics of this disease. The clinical records, CT and MRI features of twelve patients with pathologically proved SO were retrospectively analyzed. Imaging features were compared with pathological results. Most tumors (n = 11, 91.7%) were unilateral. In CT and MRI images, the lesions presented as defined irregularly shaped masses, showing mainly cystic (n = 6, 50%) or cystic (n = 6, 50%). The cystic portions presented as well defined, multiple, various size, and a whole cyst wall with smooth inner wall. Eight cases of tumors (66.7%) showed a high attenuation lesion in the cyst portion of the mass on CT precontrast scans, in which two cases showed high signal on T1WI and low signal on T2WI. The solid portions, which distributed in the cyst showed irregular tissue density. After contrast administration, the cystic portions showed no enhancement, the solid portions marked enhancement, and the cyst wall demonstrated no, moderate, or marked enhancement. Eight cases of tumors (66.7%) showed stippled calcification in the cyst wall. Four cases of tumors (33.3%) accompany a great of abdominal dropsy and pleural fluid. In general, SO appeared as a smooth marginated multicystic mass with a high attenuation lesion on precontrast scans on CT scans, and signal intensities on T1-weighted images were partly intermediate to high, or high, and those on T2-weighted images were low. The CT and MRI characteristic findings of SO might be of great value for the diagnosis.

CT findings of high-attenuation pulmonary abnormalities

ObjectivesTo review the computed tomography (CT) findings of common and uncommon high-attenuation pulmonary lesions and to present a classification scheme of the various entities that can result in high-attenuation pulmonary abnormalities based on the pattern and distribution of findings on CT.BackgroundHigh-attenuation pulmonary abnormalities can result from the deposition of calcium or, less commonly, other high-attenuation material such as talc, amiodarone, iron, tin, mercury and barium sulphate. CT is highly sensitive in the detection of areas of abnormally high attenuation in the lung parenchyma, airways, mediastinum and pleura. The cause of the calcifications and other high-attenuation conditions may be determined based on the location and pattern of the abnormalities within the lung parenchyma and knowledge of the associated clinical features.ResultsWe have presented a diagnostic approach based on the presence and distribution of five main patterns of high-attenuation conditions on CT: (1) small hyperdense nodules, (2) large calcified nodules or masses, (3) high-attenuation linear or reticular pattern, (4) high-attenuation consolidation and (5) high attenuation extraparenchymal lesions.ConclusionsSome high-attenuation pulmonary abnormalities have characteristic CT findings suggesting the correct diagnosis. In other diseases, a combination of clinical features and radiological findings can significantly improve diagnostic accuracy.

Focal Cystic High-Attenuation Lesions: Characterization in Renal Phantom by Using Photon-counting Spectral CT—Improved Differentiation of Lesion Composition

To evaluate the capability of spectral computed tomography (CT) to improve the characterization of cystic high-attenuation lesions in a renal phantom and to test the hypothesis that spectral CT will improve the differentiation of cystic renal lesions with high protein content and those that have undergone hemorrhage or malignant contrast-enhancing transformation. A renal phantom that contained cystic lesions grouped in nonenhancing cyst and hemorrhage series and an iodine-enhancing series was developed. Spectral CT is based on new detector designs that may possess energy-sensitive photon-counting abilities, thereby facilitating the assessment of quantitative information about the elemental and molecular composition of tissue or contrast materials. Imaging of the renal phantom was performed with a prototype scanner at 20 mAs and 70 keV, allowing characterization of x-ray photons at 25-34, 34-39, 39-44, 44-49, 49-55, and more than 55 keV. Region of interest analysis was used to determine lesion attenuation values at various x-ray energies. Statistical analysis was performed to assess attenuation patterns and identify distinct levels of attenuation on the basis of curve regression analysis with analysis of variance tables. Spectral CT depicted linear clusters for the cyst (P < .001, R(2) > 0.940) and hemorrhage (P < .001, R(2) > 0.962) series without spectral overlap. A distinct linear attenuation profile without spectral overlap was also detected for the iodine-enhancing series (P < .001, R(2) > 0.964), with attenuation values attained in the 34-39-keV energy bin statistically identified as outliers (mean slope variation, >37%), corresponding with iodine k-edge effects at 33.2 keV. Spectral CT has the potential to enable distinct characterization of hyperattenuating fluids in a renal phantom by helping identify proteinaceous and hemorrhagic lesions through assessment of their distinct levels of attenuation as well as by revealing iodine-containing lesions through analysis of their specific k-edge discontinuities.

Ureteral Pseudodiverticulosis

Presented is a case of ureteral pseudodiverticulosis diagnosed by multidetector computed tomography (CT). Axial and coronal reformatted CT images revealed multiple small (2-4 mm) outpouchings of both ureters, characteristic of ureteral pseudodiverticulosis. The unenhanced CT also revealed a 6-mm stone at the left ureterovesical junction and a high attenuation lesion at the right ureterovesical junction suspect for an associated uroepithelial neoplasm.

Struma ovarii: CT findings

The purpose of this study was to evaluate computed tomographic findings of struma ovarii. Computed tomography (CT) scans of 13 pathologically proven struma ovarii were retrospectively reviewed by two radiologists in consensus. Scans were evaluated for the laterality, size, mass configuration, margins, internal architecture, presence of intracystic high attenuation lesions on precontrast scans, and cyst wall enhancement. The mean size of the tumors was 11.4 cm (range 4.7-21.0 cm). Mainly cystic (n = 8, 61.5%) or cystic (n = 5, 38.5%) appearance was common to all the tumors. All tumors were unilateral and had smooth margins. The most common internal architecture in the tumors was multicystic architecture (n = 11, 84.6%). Eleven tumors (84.6%) showed a high attenuation lesion in the cyst portion of the mass on precontrast scans and the attenuation ranged from 92.2 to 120.5 Hounsfield units (HU) (mean, 106.8 +/- 8.8 HU). The cyst wall showed no (n = 7, 53.8%), moderate (n = 5, 38.5%), or marked (n = 1, 7.7%) enhancement after administration of contrast medium. On CT scans, struma ovarii appeared most often as a smooth marginated multicystic mass with a high attenuation lesion on precontrast scans and no or moderate cyst wall enhancement.

Rapid tumor doubling in the CNS

We quantify a three day tumor doubling time for small cell lung cancer metastatic to the brain in a case of a 61 yearold woman with a 30 pack-year smoking history. She was diagnosed with extensive stage small cell lung carcinoma with bone metastases and was treated with four cycles of carboplatin and etoposide. After four cycles of chemotherapy, a restaging body CT scan demonstrated a partial response with near-total resolution of right hilar nodules, but retained residual diffuse patchy bony metastases. The patient also underwent an MRI of the brain, which demonstrated no evidence of disease (Figure, image c, d, and g includes Axial T1 MRI images using a 1.5 Tesla magnet with Gadolinium contrast and TI flair image). Thirty-nine days after the MRI of the brain, the patient presented with complaints of headache, nausea and vomiting, blurred and double vision, and severe dizziness. Neurological examination was unremarkable. An MRI study demonstrated multiple areas of high attenuation lesions throughout the meninges, cortex, and grey-white matter junction (image a, b, and f, axial T1 with contrast and T1 flair). She was treated with whole brain irradiation, at a total dose of 30 Gy in 3 Gy fractions and oral dexamethasone 4 mg three times a day, and her neurologic symptoms improved. A repeat MRI study two weeks following the completion of radiation therapy (image e and h, axial T1 with contrast and T1 flair from a 3.0 GE Tesla magnet), demonstrated a complete response, but the response was not enduring. The patient elected to enroll in a palliative care program six weeks following her last radiation treatment and soon passed away. The development of demonstrable new disease within thirty-nine days allowed us to calculate a tumor growth doubling time based on volume. Although the first MRI study did not demonstrate disease, we estimated the initial tumor size (diameter) to be the limit of spatial resolution of our GE 1.5 Tesla scanner, which is 0.7 mm. Approximate tumor doubling times were then calculated based on the diameter from the second MRI study using the formula: VDT = (t 9 log2) / (log (Vt/Vo)), where t = the interval between two CT scans, Vt = the tumor volume at the second MRI scan and Vo = the tumor volume at the initial MRI scan [1]. The calculations only provide lower ranges of the tumor doubling time, as the actual and upper range are unknown. Using this equation, the tumor doubling times were calculated to be three days for the two largest parenchymal brain metastases and four days for the next three largest lesions. Interest in tumor doubling times has been rekindled with improved imaging studies used in screening for lung and liver cancers, and with the use of volumetric doubling to determine treatment plans and to assess the malignant potential of various small lesions [1–5]. Factors affecting tumor volume doubling include the type of cancer, local environment, the rate of cell death, and the cell-cycling time [6]. For small cell lung cancer the mean volume doubling times reported range from 30 to 97 days, however, as median survival without treatment is only 3 to 1.5 months depending on limited or extensive stage, respectively, the disease is clinically aggressive [1, 7–9]. J. A. Christensen L. Bressler K. Bath S. Chichili J. L. Villano (&) Section of Hematology/Oncology, Neurology, and Department of Pharmacy Practice, University of Illinois at Chicago, 909 S. Wolcott Av. M/C 734, Chicago, IL 60612, USA e-mail: jvillano@uic.edu

Pseudocalcification on chest CT scan

Liquid ventilation with perfluorocarbons is used in severe respiratory failure that cannot be managed by conventional methods. Very little is known about the use of liquid ventilation in paediatric patients with respiratory failure and there are no reports describing the distribution and excretion of perfluorocarbons in paediatric patients with severe respiratory failure. The aim of this report is to highlight the prolonged retention of perfluorocarbons in a paediatric patient, mimicking pulmonary calcification and misleading the interpretation of the chest CT scan. A 10-year-old girl was admitted to our intensive care unit with severe respiratory failure due to miliary tuberculosis. Extracorporeal membrane oxygenation (ECMO) was used to support gas exchange and partial liquid ventilation (PLV) with perfluorodecalin was used to aid in oxygenation, lavage the lungs and clear thick secretions. The patient developed a pneumothorax (fluorothorax) on the next day and PLV was discontinued. Multiple bronchoalveolar lavages were performed to clear thick secretions. With no improvement in lung function over the next month a CT scan of the chest was performed. This revealed extensive pulmonary fibrosis and multiple high attenuation lesions suggestive of pulmonary calcification. To exclude perfluorodecalin as the cause for high attenuation lesions, a sample of perfluorodecalin was scanned to estimate the Hounsfield unit density, which was similar to the density of high attenuation lesions on chest CT scan. High-density opacification should be interpreted with caution, especially following liquid ventilation.

An update of the Bosniak renal cyst classification system

w m s [ i s m t n he Bosniak renal cyst classification was first introduced in 19861 and has been accepted by rologists and radiologists as a way of diagnosing, iscussing, and determining the management aproach to cystic renal masses.2–4 Using the lesion’s orphology and enhancement characteristics, ach lesion can be categorized into one of five roups (categories I, II, IIF, III, and IV; Table I), ith associated recommendations for patient treatent. With additional experience during the past wo decades, the Bosniak renal cyst classification as been updated and refined.5,6 However, pubished reports have incorrectly described and aplied the classification system,7–10 leading to conusion in its use that could be detrimental to atient care. Therefore, the purpose of this comentary is to present an up-to-date version of the osniak renal cyst classification, point out potenial errors in its use, and present our approach to he evaluation of cystic lesions of the kidney. We elieve that this is particularly relevant in this age f laparoscopic surgery and ablative techniques. ecause these procedures are less invasive, there ay be a tendency to treat patients using these techiques on the basis of imaging studies that are not echnically adequate or have been interpreted incorectly. High-quality imaging studies are needed for ccurate characterization of renal masses to avoid unecessary surgery, even if it is minimally invasive. One of the major changes in the original classifiation was the introduction of category IIF (F for ollow-up), which was added to include cystic leions that are slightly more complex than category I, but not complex enough to fulfill the criteria for ategory III.6,11–13 This category was introduced on he basis of experience gained after the removal of enign category III cysts. Category IIF lesions are

Effect of CT digital image compression on detection of coronary artery calcification.

To test the effect of digital compression of CT images on the detection of small linear or spotted high attenuation lesions such as coronary artery calcification (CAC). Fifty cases with and 50 without CAC were randomly selected from a population that had undergone spiral CT of the thorax for screening lung cancer. CT image data were compressed using JPEG (Joint Photographic Experts Group) or wavelet algorithms at ratios of 10:1, 20:1 or 40:1. Five radiologists reviewed the uncompressed and compressed images on a cathode-ray-tube. Observer performance was evaluated with receiver operating characteristic analysis. CT images compressed at a ratio as high as 20:1 were acceptable for primary diagnosis of CAC. There was no significant difference in the detection accuracy for CAC between JPEG and wavelet algorithms at the compression ratios up to 20:1. CT images were more vulnerable to image blurring on the wavelet compression at relatively lower ratios, and "blocking" artifacts occurred on the JPEG compression at relatively higher ratios. JPEG and wavelet algorithms allow compression of CT images without compromising their diagnostic value at ratios up to 20:1 in detecting small linear or spotted high attenuation lesions such as CAC, and there was no difference between the two algorithms in diagnostic accuracy.

EFFECT OF CT DIGITAL IMAGE COMPRESSION ON DETECTION OF CORONARY ARTERY CALCIFICATION

To test the effect of digital compression of CT images on the detection of small linear or spotted high attenuation lesions such as coronary artery calcification (CAC). Fifty cases with and 50 without CAC were randomly selected from a population that had undergone spiral CT of the thorax for screening lung cancer. CT image data were compressed using JPEG (Joint Photographic Experts Group) or wavelet algorithms at ratios of 10:1, 20:1 or 40:1. Five radiologists reviewed the uncompressed and compressed images on a cathode-ray-tube. Observer performance was evaluated with receiver operating characteristic analysis. CT images compressed at a ratio as high as 20:1 were acceptable for primary diagnosis of CAC. There was no significant difference in the detection accuracy for CAC between JPEG and wavelet algorithms at the compression ratios up to 20:1. CT images were more vulnerable to image blurring on the wavelet compression at relatively lower ratios, and "blocking" artifacts occurred on the JPEG compression at relatively higher ratios. JPEG and wavelet algorithms allow compression of CT images without compromising their diagnostic value at ratios up to 20:1 in detecting small linear or spotted high attenuation lesions such as CAC, and there was no difference between the two algorithms in diagnostic accuracy.

Percutaneous needle evaluation of intradural extramedullary lesions of the lumbar spine.

A total of eight patients in whom five intradural extramedullary lesions and three epidural lesions were present were evaluated by percutaneous needle biopsy. In four patients the level of aspiration biopsy was determined using the initial myelogram and in those patients fluoroscopic guided percutaneous needle biopsies were performed. Three of these patients had large intradural extramedullary masses (above 1 cm); one patient had an epidural lesion. Diagnostic material was obtained in all cases (medulloblastoma, astrocytoma, small cell carcinoma, adenocarcinoma). Immediate post procedure CT and clinical followup showed no complications. In three patients with small lesions (below 1 cm), post myelographic CT was used to determine the level of aspiration. Post myelographic CT showed an intradural extramedullary mass in one patient and epidural lesions in two cases. Plain CT showed a high attenuation lesion in one patient. CT guided percutaneous needle biopsies in these four patients yielded diagnostic specimens (neurofibroma, uroepithelial carcinoma, hematoma, Thorotrast deposit). Clinical follow up showed no complications. Our experience indicates that percutaneous needle biopsy of intradural extramedullary and epidural lesions of the lumbar spine is safe and efficacious. Depending upon the size of the lesions, myelography or CT can be utilized to determine the level of aspiration.

Angiographically occult arteriovenous malformations of the brain

Six patients with cerebral arteriovenous malformations which did not show any pathological circulation at angiography are described. Computed tomogram appearances of such lesions may be difficult to distinguish from tumours. The need for surgical exploration in localised high attenuation lesions of uncertain nature is stressed, and the literature is reviewed.