Dosimetry of computerized tomography in the evaluation of hip dysplasia

The usefulness of computerized tomography (CT) in the assessment of hip dysplasia has recently been given attention in the literature and concern regarding radiation dose has been raised. This study was undertaken to measure the radiation dose, both in and out of plaster, for plain films, arthrography, tomography, and CT. A method is suggested to reduce dosage by 80% without compromising diagnostic information. Our experience with 25 scans of patients aged 4 months to 39 years is presented.     

Bronchogenic carcinoma staging: comparison of magnetic resonance/computerized tomography]

The staging of bronchogenic carcinoma is an important factor to select the appropriate treatment. Indeed, the definition of locoregional spread and of hilar and mediastinal node involvement is essential for both correct preoperative assessment and prognostic evaluation of bronchogenic carcinoma. CT and MR imaging are the methods of choice in the evaluation of T and N, even though other techniques--e.g., US and nuclear medicine--can also provide valuable diagnostic information. The authors examined 50 patients with primary bronchogenic carcinoma by means of plain radiographs, CT and MR of the chest. MR and CT findings were compared with surgical results on the basis of TNM classification. In the evaluation of T, sensitivity and specificity were 66% and 88.6%, respectively, for CT and 76% and 92% for MR imaging. No statistically significant differences were found between the two imaging methods (p = 0.19). In the evaluation of N, sensitivity and specificity were 56% and 78%, respectively, for CT and 76% and 88% for MR imaging. A statistically significant difference was found between MR and CT accuracy rates (p = 0.934). CT and MR results were in disagreement especially in the evaluation of hilar lymph nodes. To date, MR imaging cannot be considered a substitute for or a routine adjunct to CT in the staging of bronchogenic carcinoma due to its poor spatial resolution, to the presence of artifacts (especially with high-intensity fields), its cost and limited availability. However, in the evaluation of specific anatomical regions--e.g., the pulmonary apex and the peridiaphragmatic region--MR can provide more diagnostic information than CT thanks to its multiplanarity and better contrast resolution.     

Aortic intramural hematoma: aspects with spiral computerized tomography

PURPOSE: To evaluate the signs of aortic intramural hematoma with helical CT and the diagnostic role of this technique in patients with this condition. MATERIAL AND METHODS: We reviewed the CT findings of 396 patients submitted to emergency examinations for suspected aortic dissection from 1995 to 1999. Only 18 patients (6 women and 12 men) had CT signs of aortic intramural hematoma. Helical CT studies were carried out with the following parameters: slice thickness 10 mm, reconstruction index 10, feed 1.5 mm, conventional algorithm with minimum values of 130 kV and 125 mA. All patients were examined with dynamic contrast-enhanced CT, before and after a power injection of 130 mL ionic contrast material. We studied: hematoma localization and longitudinal extension; thickness and density of aortic wall; presence and location of intimal calcifications; integrity of intimal wall; hemomediastinum and/or hemothorax. RESULTS: Aortic wall thickening appeared as a high density crescent-shaped area at baseline CT and had low density on enhanced images in all patients. Thickening was eccentric in 14/18 patients and concentric in 4/18 only; it always exceeded 4 mm. We found some intimal calcifications in 8 patients and hemothorax and/or hemomediastinum in 9 patients. A patient with type A hematoma died of cardiac tamponade a few hours after CT diagnosis. Six patients (5 type B and 1 type A) underwent anti-hypertensive treatment and radiological follow-up. Eleven patients (6 type A and 5 type B) underwent prosthesis replacement and 5 of them (3 type A and 2 type B) died of postoperative complications. In the 5 type B patients surgery was performed because of treatment-resistant pain and of the onset of ischemic complications to abdominal organs caused by involvement of the main collateral branches of the aorta. One patient with type A hematoma was submitted to drug treatment because it was judged unresectable. DISCUSSION AND CONCLUSIONS: Intramural hematoma of the aorta is a distinct pathological entity, which should not be confused with aortic dissection. The imaging techniques (TEE, CT, MRI) have an important role in the final diagnosis of aortic hematoma. Presently Helical CT and MR angiography are the main tools in the early diagnosis of this condition before the development of complications. In our experience helical CT, before and after the administration of contrast material, was accurate in identifying the hematoma localization and extension.     

Role of computerized tomography in dental implantology

The authors report their experience using CT examination in implantology, outlining the advantages of this method in the study of the perimplantar bone, both in cases undergoing a favourable evolution and in those with an unsatisfactory outcome.     

Combined use of real-time digital subtraction radioscopy and computerized tomography: potential advantages in diagnostic and interventional radiology]

The idea of combining fluoroscopy and CT arose from the daily practice in diagnostic and interventional radiology. A Diasonics OEC high-performance image intensifier complete with a digital subtraction system was connected to a Siemens Somatom-DRH CT scanner to work in tandem. CT is used for a localization in-depth and fluoroscopy for the subsequent maneuvers within an organ or body compartment. With this combination, complex procedures such as transarterial portography, percutaneous embolizations, pain treatment and manipulation for catheterization of the bile ducts and urinary tract could be performed in one place and in one session. CTF is especially useful when patients should not be moved about from room to room or undergo an examination in several sessions, as it happens with children or critically ill or contagious patients.     

Dosimetry in diagnostic radiology

Dosimetry is an area of increasing importance in diagnostic radiology. There is a realisation amongst health professionals that the radiation dose received by patients from modern X-ray examinations and procedures can be at a level of significance for the induction of cancer across a population, and in some unfortunate instances, in the acute damage to particular body organs such as skin and eyes.The formulation and measurement procedures for diagnostic radiology dosimetry have recently been standardised through an international code of practice which describes the methodologies necessary to address the diverging imaging modalities used in diagnostic radiology. Common to all dosimetry methodologies is the measurement of the air kerma from the X-ray device under defined conditions. To ensure the accuracy of the dosimetric determination, such measurements need to be made with appropriate instrumentation that has a calibration that is traceable to a standards laboratory.Dosimetric methods are used in radiology departments for a variety of purposes including the determination of patient dose levels to allow examinations to be optimized and to assist in decisions on the justification of examination choices. Patient dosimetry is important for special cases such as for X-ray examinations of children and pregnant patients. It is also a key component of the quality control of X-ray equipment and procedures.     

Single-slice and multi-slice computerized tomography: dosimetric comparison with diagnostic reference dose levels]

PURPOSE: The absorbed dose during clinical examinations of the head, thorax, abdomen and pelvis performed with a single-slice CT scanner and a new multi-slice CT system was measured and compared. Technical parameters, defined at installation and memorized on the two CT machines relate to a standard-sized patient and were considered the reference standard. Our experimental data were also been compared with the Diagnostic Reference Levels (D.L. 26/5/2000 n.187, Annex V). MATERIAL AND METHODS: We compared the performance of a multi-slice GE LightSpeed QX/i ADVANTAGE to that of a single-slice GE ProSpeed SX. The radiation beam profiles were measured at isocenter using a phosphor plate. Dose measurements were performed, according to the EUR 16262 EN Guidelines, with a 10-cm long CT pencil ionisation chamber and two PMMA phantoms (CEI EN 61223-2-6) for head and body respectively. RESULTS: The obtained (normalised and weighted) computed tomographic dose index (nCTDIW) values were systematically higher for the multi-slice system (up to 36%) and the dose-length product (DLP) values on the multi-slice scanner exceeded the equivalent single-slice DLP values. The values were, however, always lower than DRLs, except in the case of the head multi-slice protocol, the technical parameters of which need to be improved. Our results allowed moreover to calibrate the automatic dose evaluation system of the multi-slice system, which systematically underestimated DLP values. DISCUSSION AND CONCLUSIONS: The comparison showed that the multi-slice scanner delivers a higher dose compared to the single-slice scanner. This is due to the radiation beam profile which is wider than the total active detector width, to the shorter focal spot-to-isocenter distance and to the effective scan length, which is longer than the nominal irradiated volume because the reconstruction algorithm of a multi-slice helical CT image requires the projection data from all detector rows. Nevertheless, the technology of new CT systems equipped with a multiple row detectors array can improve the protection of the patient thanks to very short irradiation time (less than 1 s) and reduced current values. In order to optimize the dose to the patient some acquisition parameters have been adjusted for head examinations.     

Comparative study of traditional radiology, echography and computerized tomography in chest pathology

The authors have examined 57 cases of thoracic pathology by conventional radiology, ultrasounds and computed tomography (CT). The conventional radiology remains the test of first choice; the ultrasounds proved sometimes useful to distinguish between solid and cystic lesions while CT is the method in the evaluation of the extension.     

Validation of spiral computed tomography for dental implants

OBJECTIVES: To investigate the accuracy of 2DCT orthoradial reformatted images from spiral computed tomography (CT) for pre-surgical planning of dental implants in proximity to the mental foramen. METHODS: Eight cadaver heads were imaged by spiral CT (S/Xpress, Toshiba-America, Tustin, CA) with 1 mm thick axial slices by 1 mm/sec of table feed. The image data set was transferred to a networked computer workstation. Using computer graphics the data was analysed with 2D orthoradial reformatting using the ToothPix (Cemax, Fremont, CA, USA) protocol. Linear measurements were made by two oral radiologists independently from the superior border of the mental foramen to the crest of the alveolar process and from the inferior border of the mental foramen to the mandibular inferior border. The soft tissues were removed and physical measurements made using a 3 Space (Polhemus, Colchester, VT) electromagnetic digitizer with a personal computer running Windows 95. RESULTS: The differences between the measurements on orthoradial 2DCT images and the physical measurements were not statistically significant (P > 0.05). CONCLUSIONS: Two-dimensional spiral CT imaging allows highly accurate measurements for dental implant placement in proximity to the mental foramen. Computer graphics software, using reformatted reconstruction, is suitable for implant planning.     

Multiple-phase spiral computerized tomography of small hepatocellular carcinoma: technique optimization and diagnostic yield

PURPOSE: Spiral imaging has dramatically increased the diagnostic capabilities of Computed Tomography (CT) in the evaluation of small hepatocellular carcinomas (HCCs, O < 3 cm). We report our experience with multiple-phase CT of small HCC relative to both examination technique and lesion patterns. We compared the yield of biphasic (arterial-dominant + portal-dominant phases) and triphasic (arterial-dominant + portal-dominant + delayed phases) and also reviewed the literature for a meta-analysis of the techniques used. MATERIAL AND METHODS: December 1996 to July 1998, forty-eight patients with small nodular HCCs were examined--98 nodules in all (range 1-9, mean 2 per patient). After baseline CT, a nonionic contrast agent (350 mgI/mL, 130-140 mL, 4 mL/s) was administered through a power injector and a 16-gauge needle. Biphasic volume images were acquired in 19 subjects (early-phase delay 24 s, venous-phase delay 75 s) and triphasic images in 29 (early-phase delay 24 s, venous-phase delay 60 s, delayed-phase delay 100 s). Retrospectively we assessed the number of nodules detected with each protocol in every phase, nodule conspicuity (graded I-IV) relative to surrounding parenchyma, and nodule patterns in the various phases. Nodule patterns were distinguished into homogeneous, peripheral, central and mixed hyperdensity, and homogeneous hypodensity. RESULTS: Thirty-seven lesions were found in the patients examined with the biphasic technique: baseline images showed 35% of the nodules, arterial images 92%, portal images 76% and combined arterial and portal acquisitions 95%. Sixty-one lesions were found in the patients examined with the triphasic technique: baseline images showed 43% of the nodules, arterial images 93%, portal images 70%, and delayed images 77%; combined arterial and portal acquisitions detected 93% of the nodules, combined arterial and delayed images 95%, combined arterial and delayed images 80%. Finally, 95% of lesions were demonstrated when the three phases were combined. Overall conspicuity grades were I in 44% of cases, II in 28%, III in 18% and IV in 10% of cases at baseline scanning; I in 9%, II in 24%, III in 34% and IV in 33% in the arterial phase; I in 28%, II in 41%, III in 18% and IV in 13% in the portal phase; I in 23%, II in 30%, III in 26% and IV in 21% of cases in the delayed phase. At baseline, 10% of lesions were hyperdense (homogeneously and peripherally in 5% each); mixed density was seen in 8%, and hypodensity in 82%. In the arterial phase, 93% of lesions were hyperdense (homogeneously in 80%, peripherally in 10% and centrally in 3%); mixed density was seen in 5%, and hypodensity in 1%. In the portal phase, 4% of lesions were hyperdense (homogeneously in 1% and centrally in 3%); mixed density was seen in 11%, and hypodensity in 85%. In the delayed phase, the lesions appeared mixed in 11% of cases and hypodense in 89%. CONCLUSIONS: Spiral CT scanning of small HCCs requires dedicated and meticulous technique. Multipassage assessment is mandatory, with 2 or 3 dynamic acquisitions of the whole liver. No major difference in nodule detection was demonstrated between these two options and thus the choice rests with the radiologist's preference. Early CT images proved best for lesion detection, followed by delayed, venous, and baseline studies; lesion recognition depends largely on nodular diameter. The same applies to conspicuity, which however depends on tumor volume less. Lesion patterns are quite typical and constant in all phases and are independent of lesion diameter.     

Angiography with spiral computerized tomography in the study of aneurysms of the visceral arteries. Techniques and results]

INTRODUCTION: The aneurysms of visceral vessels are characterized by few or no symptoms and the diagnosis is often occasional. We investigated the usefulness of CT angiography in the diagnosis and preoperative assessment of this condition. MATERIALS AND METHODS: From January 1993 to March 1998, twenty-five patients (aged 32-69 years) with 28 aneurysms underwent CT angiography before and after contrast agent injection to study lesion number, site, size, neck, intraluminal thrombosis and wall calcifications. Data from axial images were postprocessed on an external work-station to obtain CT angiograms. CT angiography findings were analyzed with a double blinded method by 2 radiologists comparing CT angiography with digital subtraction angiography images and evaluating the information obtained from Multiplanar (MPR), Maximum Intensity Projection (MIP) and Shaded Surface Display (SSD) reconstructions. Surgical findings were available for 10 patients. RESULTS: There was complete agreement between CT angiography and digital subtraction angiography in the identification of all lesions; the correlation rate was 94.42% for lesion location, 89.28% for lesion size, 85.71% for detection of endoluminal thrombosis and 82.14% for identification of wall calcifications. Axial and MPR images were useful in the assessment of ali parameters, while MIP images accurately demonstrated wall calcifications and the lesion relationships with adjacent structures. No additional information was obtained from SSD reconstructions. CONCLUSIONS: In our experience CT angiography can replace digital subtraction angiography in the diagnosis and preoperative work-up of visceral vessels aneurysms. CT angiography was superior to digital angiography in the evaluation of the lesion exact dimensions in cases with large thrombotic component and diffuse wall calcifications.     

Pre- and postoperative study of the bile ducts with spiral computerized tomography

PURPOSE: To investigate the capabilities of Helical CT in imaging the biliary tract after administration of an oral cholecystographic contrast agent. MATERIAL AND METHODS: Forty-five adult patients and one 8-year-old child were examined with Helical CT 12 hours after the oral administration of hyopanoic acid (3 g). All the examinations were performed with the following parameters: thickness 5 mm, pitch factor 1.5, standard reconstruction algorithm, acquisition time 20-30 s, image index 2.5 mm, 130 kV, 125 mA. In 37 cases CT was performed in patients candidate to laparoscopic cholecystectomy, in 8 cases to assess the positioning of surgical clips in patients with postcholecystectomy syndrome and in 1 case (the 8-year-old child) to confirm the US diagnosis of choledochal cystic dilatation. Helical CT images were reconstructed with a Volume Rendering (VR) software. RESULTS: The extrahepatic biliary tract was visualized in all the cases with CT and VR. II grade biliary ducts were visualized in 87% (CT) and 91% (VR), III grade ducts in 76% (CT) and 78% (VR), IV grade ducts in 28% and 35%, respectively. No statistically significant difference was found between CT and VR in the visualization of the biliary structures (p > 0.05), while three-dimensional VR reconstructions improved the evaluation of the anatomical relations in the biliary tract in comparison with CT both in normal cases and in patients with congenital abnormalities of the biliary tract. Also, three-dimensional VR reconstructions were superior in assessing the correct positioning of surgical clips in patients with postcholecystectomy syndrome (p < 0.05). DISCUSSION AND CONCLUSIONS: Cholecysto-cholangio-CT with VR reconstructions is a reliable imaging technique for the biliary tract in patients candidate to laparoscopic cholecystectomy, to diagnose choledochal cystic dilatation and to assess the positioning of surgical clips.     

Closed loop intestinal obstruction: role of computerized tomography]

PURPOSE: The obstruction of a bowel segment at both ends results in a closed loop obstruction. Progression to strangulation frequently occurs if surgical intervention is delayed. The role of plain radiography in the diagnosis of closed loop obstruction and strangulation has been shown to be limited, while the recent literature has demonstrated the growing role of computed tomography (CT). This paper reports our experience in the study of closed loop obstruction by CT. MATERIAL AND METHODS: The CT studies of 12 patients with surgically confirmed closed loop obstruction were retrospectively reviewed. The following CT signs were used for the diagnosis: a) fluid-filled distended loops, b) C-shaped incarcerated loop, c) radial distribution of several dilated bowel loops and mesenteric vessels converging toward the point of obstruction, d) triangular or fusiform tapering of the closed loop and/or whirl sign in the site of obstruction. RESULTS: On the basis of these signs, the diagnosis was made in 11 of 12 patients. Only 1 patient, who had a negative CT study, was positive at a subsequent enteroclysis. CT findings of strangulation were associated in 3 cases: slight wall thickening with vascular congestion and mesenteric ascites, confirmed at surgery. DISCUSSION AND CONCLUSIONS: Small bowel obstruction can be distinguished into simple and closed loop obstructions. The latter is a more severe condition which is often complicated by strangulation with vascular impairment, edema and intramural and mesenteric hemorrhage. Consequent arterial insufficiency rapidly leads to ischemia, infarction and necrosis. The radiologist plays a role in the early recognition of the closed loop obstruction and of any sign of strangulation. The role of CT in the diagnosis and workup of patients with suspected intestinal occlusion has been analyzed in the literature with reported 63% sensitivity, 78% specificity and 66% accuracy. CT is also capable of revealing the causes of occlusion in 73-95% of cases. The above CT signs, as confirmed in our experience, allow to identify closed loop obstruction and also small bowel strangulation, thus supplying a valuable contribution to diagnosis and accurate preoperative evaluation. We conclude that CT can accurately demonstrate the presence of closed loop obstruction and can be the technique of choice in patients in whom obstruction is associated with clinical signs suggestive of strangulation.     

3D spiral computerized tomography in the reconstructive treatment of malignant maxillofacial tumors

PURPOSE: To investigate the role of Helical CT and the usefulness of three-dimensional (3D) imaging for preoperative planning and follow-up of reconstructive maxillofacial surgery with alloplastic material in neoplastic disease involving this region. MATERIAL AND METHODS: From 1996 to 1999 eleven patients were examined with Helical CT and 3D images for planning of maxillofacial plastic and reconstructive surgery for advanced cancer of this anatomically complex region. A 3D-modulated titanium mesh (100%) or micronets was used to rebuild the anterior surface of maxillary bone and the orbital floor. The mesh was cut to the appropriate size and shape and curved where necessary. Within the residual sinusal cavity a siliconed filling was used surmounting an acrylic prosthesis with dental arch to rebuild the palate. A rehydrated bovine pericardium was affixed and moduled on the borders in two cases only. Three-dimensionally reconstructed CT images were obtained preoperatively and at least 6 months postoperatively in all patients. The images were generated on a computer workstation using the shaded surface display (SSD) software with threshold values ranging 425 to 630 HU, and a more closed window for the imaging of titanium mesh/bone interface in the postsurgical follow-up. RESULTS: We always obtained an excellent complete spatial depiction of maxillofacial region both before and after surgery, with no artefacts so important as to affect the 3D reconstruction process and the image quality. Together with the head-neck surgical team we could work for preoperative planning through CT scans by different 3D points of view. The 3D reconstructed follow-up scans showed good filling of the defect in the area where the titanium mesh had been used. Then efficacious bone modelling and good biocompatibility of the alloplastic material were seen in all patients, with no inflammatory reactions. CONCLUSIONS: Titanium is a well-known material, which is widely used for cranioplasty. It is a radiolucent, nonferrous metal of low atomic number that allows very clear CT and MR images to be obtained. Further Ti features are strength, biocompatibility and easy handling. 3D Helical CT scan has proved to be the most complete and accurate imaging technique for reconstructive plastic surgery with alloplastic material in advanced maxillofacial cancer, also considering the anatomic and functional complexity of this area. The prospect is provided to identify virtual 3D presurgical ablation planes. These may allow the surgeon to improve plastic reconstruction and shorten intervention time.