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.

[Imaging of small renal tumors]

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.

[Role of echography and phlebography in the assessment of patients with clinically suspected deep venous thrombosis of the legs]

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.

[Diagnosis of deep venous thrombosis of the legs: accuracy of ultrasonography using vein compression]

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.

[The side effects of phlebography of the lower extremities using iohexol. A prospective study]

In this prospective study 463 consecutive outpatients, who had undergone phlebography because of clinically suspected deep venous thrombosis (DVT) were examined with clinical follow-up and impedance plethysmography to evaluate the rate of contrast media complications. Seventy-nine patients had immediate and mild side effects, and one had moderate side effects (bronchospasm); no patient suffered from severe life-threatening conditions. There was only one case of DVT which occurred after an initially negative phlebography. In a subgroup of 40 patients, who underwent iodine-125-fibrinogen scanning after phlebography, the study was positive in 9 cases. None of them presented with any evidence of DVT at follow-up phlebography. Contrast phlebography with iohexol is a safe and comfortable procedure. Low-osmolality nonionic contrast media are well tolerated by the patient.

[High-resolution echography of the neck. Preoperative evaluation of lymph node metastases in patients with thyroid carcinoma]

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.

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.

[Staging of prostatic carcinoma. Accuracy of magnetic resonance]

Twenty-nine prostatic cancer patients were evaluated for staging purpose by Magnetic Resonance (MR). MR findings were correlated with the pathologic examination in 18/29 patients who underwent radical prostatectomy. Four MR staging parameters were evaluated individually: periprostatic fat; periprostatic venous plexus; seminal vesicles and pelvic adenopathy. MR correctly staged 16/18 patients, with one case of overstaging and one case of understaging. The diagnostic accuracy of MR in differentiating intracapsular stage B from extracapsular stage C was 87%, with a sensitivity of 90% and a specificity of 87%. MR and CT results agreed in 4 of the 7 operated patients who were examined with both techniques; in 3 cases there was disagreement, and MR was correct.

Wrist: coronal and transaxial CT scanning

Computed tomography (CT) of the wrist can be useful in selected clinical applications and is generally performed in the transaxial orientation. Coronal and transaxial CT scanning of the wrist were directly compared in three patients and in a normal, isolated cadaveric hand. Twenty other patients with wrist problems who underwent only transaxial or coronal CT examinations were also considered to assess the clinical indications of both techniques. A simple Lucite holder was designed and tested to simplify patient positioning with the coronal CT technique. In most clinical situations, coronal images were superior to transaxial images because the former were more detailed and easier to interpret. In some specific cases, however, especially fracture of the hamate hook and distal radioulnar subluxation, transaxial CT scanning was superior.

[High-resolution echography and angiography in the study of vascular accesses for hemodialysis]

In 23 hemodialytic patients with clinically presumed complications of the vascular access the arteriovenous shunt was studied by high resolution ultrasonography (US) and by angiography. In 21/23 cases US identified the shape of the shunt correctly; in these patients US always showed the alterations of vascular size (stenosis, aneurysm) and complete occlusion, also detecting the intravascular extension of thrombosis. In 3 patients US identified partial venous thrombosis missed on angiography; furthermore, unlike angiography, US gave precise information on the vascular wall and perivascular tissue changes. These findings suggest that US may represent the first imaging procedure in the study of the vascular access in hemodialytic patients; angiography might be performed when US findings are uncertain or when a vascular map is needed for surgery.

Clinical stage B prostate carcinoma: staging with MR imaging

Magnetic resonance (MR) imaging studies were performed in 29 patients with clinical findings of stage B prostatic carcinoma with use of both T1 and T2-weighted spin echo sequences. MR imaging findings were correlated with surgical/pathologic results in 18 patients who underwent an operation. Periprostatic fat, periprostatic venous plexus, seminal vesicles, and lymph nodes were assessed from MR imaging studies. When each was assessed independently, the periprostatic fat signal had a sensitivity of 29%, specificity of 100%, and accuracy of 85% in detecting extracapsular tumor extension, whereas the periprostatic venous plexus had a sensitivity of 57%, specificity of 86%, and accuracy of 80%. MR imaging had a sensitivity of 50%, specificity of 97%, and accuracy of 89% for detecting seminal vesicular involvement. When all four anatomic features were taken into consideration, MR imaging had an accuracy of 89% (16 of 18 patients) in differentiating stage B from stage C or D disease (sensitivity 87%, specificity 90%). Our data indicate that MR imaging is a promising method for staging prostatic carcinoma.

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.

[Magnetic resonance (MR) imaging of the normal mediastinum]

Magnetic Resonance (MR) cross sectional images of the normal mediastinum are presented and discussed. In normal subjects most mediastinal structures visible on Computed Tomography (CT) are also visible using MR. The primary advantages of MR over CT in the evaluation of mediastinum are the greater soft tissues contrast resolution, the multiplanar (axial, coronal and sagittal) display of the mediastinal anatomy and its ability to distinguish vascular from nonvascular structures without injection of contrast media.

[White and black in nuclear magnetic resonance (NMR). Impulse sequences and their significance in the NMR image]

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.

CT appearance of generalized von Recklinghausen neurofibromatosis

Two cases of von Recklinghausen neurofibromatosis (VRN) with thoracic and abdominal involvement are described. Computed tomography demonstrated the typical lesions of this disease: meningoceles, neurofibromas, and skeletal alterations. In both cases lesion morphology and location were similar and characteristic, in particular in the pelvic region. Computed tomography findings in generalized VRN are sufficiently characteristic to be considered diagnostic for this disease.

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 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.

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.

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.

CT demonstration of portal and superior mesenteric vein thrombosis in hepatocellular carcinoma

Three cases of hepatocellular carcinoma in which computed tomography (CT) demonstrated thrombosis of the portal vein are reported. In one patient, extension of the thrombus into the superior mesenteric vein was identified as well. The outstanding CT features of portal vein thrombosis were: (a) enlargement of the vein, (b) intraluminal low density area, and (c) hyperdense peripheral ring due to the enhancement of the venous wall. These findings may be useful in differentiating hepatocellular carcinoma from hepatic metastases.

[Computed tomography in the diagnosis of primary hepatic tumors: comparison with angiography (author's transl)]

The authors expose the CT findings of primitive hepatic neoplasms. There are emphasized the usefulness of CT in detecting hepatic tumors and in the evaluation of its extension. The actual role of angiography in the evaluation of primitive hepatic diseases is stressed.