The value of precontrast thoraco-abdominopelvic CT in polytrauma patients.

PURPOSE: To evaluate the utility and radiation dose of thoraco-abdominopelvic precontrast CT in polytrauma patients. MATERIALS AND METHODS: We examined retrospectively 125 patients who underwent a thoraco-abdominopelvic CT for trauma. Two radiologists, independently, evaluated precontrast CT acquisition and two other radiologists examined the contrast-enhanced scans. A further two radiologists assessed both the acquisitions. Mean value of sensitivity (SE), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) were calculated by each group of radiologists. For 104 patients, CTDIvol, DLP data and individual mean size were collected to calculate effective dose. RESULTS: Mean values of SE, SP, PPV and NPV of findings of radiologists who assessed contrast-enhanced acquisitions were respectively: SE=85%, SP=98%, PPV=86%, NPV=88% versus: SE=43%, SP=95%, PPV=69%, NPV=88% of radiologists who examined non-contrast-enhanced scans. Mean values of radiologists who analyzed both acquisitions were: SE=80%, SP=97%, PPV=80%, NPV=88%. Neither the precontrast scans nor the precontrast and postcontrast scans together provided additional useful information compared to the single contrast-enhanced acquisition. Patients received a mean dose of 12 mSv for the precontrast CT. CONCLUSIONS: Precontrast CT acquisition did not provide significant information in trauma patients, exposing them to an unjustified radiation dose.

Subcutaneous and visceral fat distribution according to sex, age, and overweight, evaluated by computed tomography.

Subcutaneous and visceral fat distribution as related to sex, age, and overweight was studied in 130 subjects and 10 women with Cushing's disease. Fat depots were evaluated by computed tomography at one thoracic and one abdominal level. Adipose tissue (density range - 50 to 250 Hansfield units) was highlighted and the fat areas were measured by a laser planimeter. The ratio between subcutaneous and visceral fat areas (S:V ratio) was assumed as an index. Ratios of both nonobese and obese groups were significantly higher in females than in males. Ratios decreased markedly over age 60. There was a significant inverse correlation between age and S:V ratios in females (r = 0.65; p less than 0.001) and in males (r = 0.61; p less than 0.001). Statistically significant correlations were found between S:V ratios at thoracic and abdominal levels. In Cushing's patients, the S:V ratio at the abdominal level was significantly lower than in controls matched for age, sex, and body mass index.

Multispectral magnetic resonance image analysis.

Multiecho magnetic resonance (MR) scanning produces tomographic images with approximately equal morphologic information but varying gray scales at the same anatomic level. Multispectral image classification techniques, originally developed for satellite imaging, have recently been applied to MR tissue characterization. Statistical assessment of multispectral tissue classification techniques has been used to select the most promising of several alternative methods. MR examinations of the head and body, obtained with a 0.35, 0.5, or 1.5T imager, comprised data sets with at least two pulse sequences yielding three images at each anatomical level: (1) TR = 0.3 sec, TE = 30 msec, (2) TR = 1.5, TE = 30, (3) TR = 1.5, TE = 120. Normal and pathological images have been analyzed using multispectral analysis and image classification. MR image data are first subjected to radiometric and geometric corrections to reduce error resulting from (1) instrumental variations in data acquisition, (2) image noise, and (3) misregistration. Training regions of interest (ROI) are outlined in areas of normal (gray and white matter, CSF) and pathological tissue. Statistics are extracted from these ROIs and classification maps generated using table lookup, minimum distance to means, maximum likelihood, and cluster analysis. These synthetic maps are then compared pixel by pixel with manually prepared classification maps of the same MR images. Using these methods, the authors have found that: (1) both supervised and unsupervised classification techniques yielded theme maps (class maps) which demonstrated tissue characteristic signatures and (2) tissue classification errors found in computer-generated theme maps were due to subtle gray scale changes present in the original MR data sets arising from radiometric inhomogeneity and spatial nonuniformity.

The computer and stereotactic surgery in neurological surgery.

The technical aspects, current uses, and future clinical applications of stereotactic surgery and three-dimensional imaging in neurological surgery are reviewed.

Three-dimensional surface reconstruction of the carpal bones from CT scans: transaxial versus coronal technique.

Computer methods for reconstruction of three-dimensional (3-D) images from standard CT scans have been developed. The process does not require special computer knowledge and can be performed with a unmodified CT scanner. 3-D images are especially valuable for conveying information to nonradiologist physicians, who are unfamiliar with the numerous slice-format images produced in a standard CT examination. The utility of these methods for clarification of areas of complex skeletal anatomy has been previously demonstrated in the literature. We performed 3-D imaging on a normal isolated cadaver hand and on a patient with scaphoid fracture. In both cases the 3-D images obtained had excellent osseous anatomical detail. A method of acquisition of high quality wrist CT scans, suitable for 3-D processing, is suggested.

[Imaging of small renal tumors]. / L'imaging dei piccoli tumori renali.

The advent of ultrasound and computed tomography resulted in a great increase in detection and diagnosis of small renal parenchymal tumors. These are mainly slow growing tumors, without metastatic disease and with possible multicentricity at the diagnosis. Moreover there is not agreement about the best treatment for the small (< 3 cm) renal cell carcinoma. In this paper the role of ultrasound, computed tomography and magnetic resonance for detection and characterization of the small renal masses is discussed. On occasion it is possible to obtain the tissue characterization of a solid renal mass by diagnostic imaging (for example angiomyolipomas); however, most frequently, solid renal masses have an aspecific appearance. The majority of problematic renal masses have cystic components. The diagnosis of simple cyst is based on few simple but rigid criteria: homogeneous water density, very thin wall, well defined and sharp interface with renal parenchyma, lack of contrast enhancement. When there are intracystic septae, thickened wall or increased density, the cyst is "complicated". In these cases the classification suggested by Bosniack can be helpful. Bosniack class-1-lesions are simple cysts; they do not require any further work-up. Bosniack class-2-lesions are minimally complicated but reliably benign cysts (thin wall, thin calcifications, thin septae). Some of these lesions require follow-up; and the majority of them do not. Class-3-lesions have thick septae, thick calcifications and thick and irregular walls, but not contrast enhancement. In most cases these lesions require surgical exploration for diagnosis and therapy. Bosniack class-4 lesions are clearly malignant; they are indicated by contrast enhancing regions within cysts. They always require surgery.

Single-versus multidetector-row CT: comparison of sedation rates, conventional angiograms and motion artefacts in young children following liver transplantation.

PURPOSE: The aim of this study was to determine whether the use of multidetector computed tomography (MDCT) is associated with decreased sedation, frequency of motion artefacts and conventional angiograms compared with single-detector CT (SDCT). MATERIALS AND METHODS: CT examinations performed in young children between January 1993 and June 2005 were reviewed retrospectively. Prior to September 2000, SDCT was used; after that period, MDCT was used. The examinations obtained during these two periods were compared for the frequency of sedation, motion artefacts, and conventional angiograms. Statistical comparison between the two groups was determined by using the chi(2) test. RESULTS: A total of 126 infants and children younger than 6 years of age underwent 134 CT examinations. Eighty-eight were obtained with a SDCT (65%) (group 1) and 46 with a MDCT (35%) (group 2). Sedation was required in 31/88 (35%) CT examinations in group 1 and in 6/46 (13%) in group 2. Conventional angiography was performed in 20/88 (22%) cases in group 1 and in 6/46 (13%) in group 2. Motion artefacts were present in 8/88 (9%) CT examinations in group 1 and in 4/46 (8%) in group 2. There was significant statistical difference with regard to sedation and angiography rates between the two groups (p<0.001) whereas there was no significant difference with regard to motion artefacts (p>1). CONCLUSIONS: MDCT can reduce the need for sedation and conventional angiography in children after liver transplantation. There is no effect on patient motion artefacts.

[Role of echography and phlebography in the assessment of patients with clinically suspected deep venous thrombosis of the legs]. / Ruolo dell'ecografia e della flebografia nella valutazione dei pazienti con sospetto clinico di trombosi venosa profonda degli arti inferiori.

The roles of US and venography in the evaluation of the patients with clinical suspicion of deep venous thrombosis are discussed relative to personal and literature data. The patients were divided into three groups: outpatients with previous history of venous thrombosis (group I), inpatients without previous history of venous thrombosis (group II) and patients with suspected recurrent venous thrombosis (group III). In group I, compression US yielded very good results: so much so that it can replace venography. In this group of patients, pulsed Doppler added no significant information, while color-Doppler appeared to be a valuable technique. As for the other two groups, venography was confirmed as the most useful technique, even though MR imaging is likely to play, in the future, an important role, since it allows better demonstration of the central thrombus, especially in diffuse occlusive thromboses.

Soft-tissue sarcomas: use of textural patterns in skeletal muscle as a diagnostic feature in postoperative MR imaging.

The authors assessed the value of tissue textural patterns as a diagnostic feature for differentiating nonspecific posttreatment tissue changes from musculoskeletal sarcoma recurrence on magnetic resonance (MR) images. The MR imaging studies of 40 patients who had previously undergone surgery and radiation therapy for soft-tissue sarcomas of the lower extremities were evaluated in a blind fashion. In 31 of the MR imaging studies, T2-weighted images demonstrated diffuse areas of high signal intensity in soft tissues at the operative region. Close examination of the corresponding regions on high-resolution transverse T1-weighted images demonstrated textural features typical of skeletal muscle in 23 patients and the absence of such features in eight. None of the 23 patients with the "texture sign" proved to have macroscopic tumor recurrence at clinical or surgical follow-up. Among the eight patients without recognizable textural features of muscle in the regions suspicious for tumor recurrence, two proved to have recurrent tumor at surgery. Recognition of a texture sign on high-resolution T1-weighted spin-echo images of regions suggestive of tumor recurrence helps improve the diagnostic specificity of follow-up MR examinations in patients who have undergone treatment for soft-tissue sarcomas.

Computed tomography of deep fat masses in multiple symmetrical lipomatosis.

Deep fat masses were evaluated by computed tomography (CT) in 15 patients with multiple symmetrical lipomatosis. In 4 patients, peritracheal accumulations of fat were observed. In 3 of them, tracheal compression by lipomatous tissue was demonstrated: 2 were asymptomatic and the third had severe respiratory insufficiency secondary to blockage of the airway by the vocal cords as the result of recurrent nerve palsy. In 6 patients, lipomatous tissue occupied the potential space between the spinal scapulae and the trapezius, supraspinatus, and infraspinatus muscles. In 2, calcification of lipomatous masses was observed. There was no relationship between extension of subcutaneous fat and accumulation at deep sites. CT facilitates early detection of peritracheal lipomatous tissue and is helpful in follow-up when deep fat accumulation is responsible for space-occupying lesions requiring surgery.

[White and black in nuclear magnetic resonance (NMR). Impulse sequences and their significance in the NMR image]. / Bianco e nero in risonanza nucleare magnetica (RNM). Sequenze di impulsi e loro significato nell'immagine RNM.

In order to understand how pulse sequences affect what is black and what is white in Nuclear Magnetic Resonance (NMR) images, the tissue parameters (proton density; relaxation times T1 and T2) are related to the operator selectable controls (type of pulse sequence; repetition time TR; interpulse delay TI; echo delay TE). The pulse sequences "Saturation Recovery"; "Inversion Recovery"; "Spin Echo" are discussed. The authors also analyze the effect of flowing blood on NMR images.

[Diagnosis of deep venous thrombosis of the legs: accuracy of ultrasonography using vein compression]. / Diagnosi di trombosi venosa profonda degli arti inferiori: accuratezza dell'ecotomografia con compressione venosa.

We prospectively compared real-time US findings with venographic results in the legs of 171 consecutive outpatients with clinically suspected deep venous thrombosis (DVT). In each leg the common femoral and the popliteal veins were evaluated with venography and US. The two examinations were independently performed and reviewed. Vein compressibility (VC), intraluminal echogenicity and response to Valsalva maneuver were evaluated with US. Venography detected DVT in 54/171 legs. 10/54 legs had isolated distal DVT. With VC, US was 100% specific, 87% sensitive and 96% accurate. 6/7 false negative US studies were due to isolated distal DVT; therefore US sensitivity for proximal DVT was 98%. The other two US diagnostic criteria were much less accurate than VC. VC-US is an accurate, cheap and reproducible test for the detection of DVT in symptomatic outpatients.

CT demonstration of bilateral Castleman tumors in the mediastinum.

A case of bilateral Castleman tumors in the posterior mediastinum is described. Computed tomography proved to be an accurate, noninvasive method of investigation since it identified not only a large mass but also a smaller mass, which was not visible on standard chest X-ray film. Complete surgical excision was possible. The high attenuation values of both masses demonstrated the hypervascularity of the lesion.

Computed tomography of the liver in von Gierke's disease.

The computed tomography findings in the liver of a patient with von Gierke's disease are presented. Precontrast scans demonstrated diffuse decreased density throughout the liver. In the postcontrast scans, a focal right sided hyperdense area was visualized.

[High-resolution echography of the neck. Preoperative evaluation of lymph node metastases in patients with thyroid carcinoma]. / Ecografia ad alta risoluzione del collo. Valutazione preoperatoria delle metastasi linfonodali nei pazienti con carcinoma tiroideo.

Twenty-six patients with papillary and 4 with medullary thyroid carcinoma were examined by HRUS before surgery in order to evaluate its accuracy in detecting lymph node metastasis (N) of the neck from thyroid carcinoma. All patients underwent total thyroidectomy and nodal dissection. HRUS was accurate in 73% of cases in N staging, while clinical staging was accurate in 60% of cases only. In 50% of patients HRUS provided with interesting additional information, such as disclosing lymphadenopathy in 8 patients with no clinical evidence, proving nodal involvement in 5 cases, and showing extranodal extension in 5 cases. HRUS allowed the observation of anechoic necrotic areas and microcalcified nodes. On the other hand, according to our results, HRUS cannot either discriminate metastatic from benign nodal involvement, or identify mediastinal adenopathy. False negatives are possible due to micrometastatic areas in normal size nodes. Nevertheless, HRUS proved to be a valuable aid to complete clinical examination of the neck, and a good guide for the surgeon during nodal neck dissection.

Evaluation of post-pneumonectomy space by computed tomography.

Twenty-two patients who had undergone pneumonectomy for various reasons were evaluated by computed tomography (CT) in order to study the post-pneumonectomy space (PPS). In 13 of 22 cases, the residual PPS contained fluid, even years following surgery. In 9 of 22 cases, the PPS was obliterated. Obliteration of the PPS, one of the events that may follow pneumonectomy, is significantly correlated with the expansion of the nonoperated lung (coefficient, 0.84). Obliteration of the PPS does not present a significant coefficient of correlation with the following parameters, also considered in this study: time interval between surgery and CT, presurgical tests of respiratory function, hemidiaphragm elevation, and retraction of operated hemithorax. The fluid contained in the PPS does not organize but persists or is reabsorbed. Mediastinal shift depends on the expansion of the residual lung. The mediastinum rotates following right pneumonectomy and shifts following left pneumonectomy. The usefulness of CT in the follow-up of the pneumonectomized patient is stressed.