[Focal liver lesions. A comparison between magnetic resonance under base conditions and after a superparamagentic contrast medium]

INTRODUCTION

Superparamagnetic iron oxide (Spio) is a negative contrast material which is phagocytosed by reticuloendothelial cells. It significantly decreases the signal intensity of the organs where it is taken up selectively, especially on T2-weighted images. According to previous reports, it improves the visualization of focal liver lesions with(out) a low content of Kupffer's cells. We investigated the yield of Spio-enhanced MRI in the detection and characterization of focal liver lesions.

MATERIALS AND METHODS

Eighteen patients underwent MRI before and after the administration of Spio particles. T1, PD, T2 SE and T2* GE images were acquired with a .5 T superconductive unit. The Spio dose was .075 mL/kg which was administered i.v. in 35-45 minutes' infusions. Images were acquired about 30-90 minutes after the end of administration. Scanning was repeated in one patient about 8 hours after the end of Spio administration.

RESULTS

Baseline MRI showed hepatocellular carcinoma (HCC) in 10 patients, metastases in 4, 1 dysplastic lesion, 1 single and 1 multiple hemangioma, 1 focal nodular hyperplasia (FNH) and 1 intrahepatic cholangiocarcinoma. No lesion was detected in one patient. Spio-enhanced MRI detected 7 more lesions that baseline MRI, with 11.47% sensitivity improvement. Moreover, Spio-enhanced MRI detected more lesions that baseline MRI in 5/18 patients (27.78%). PD/T2 SE images were the most sensitive ones, followed by T2* GE and finally by T1 SE. Nearly all HCC nodules (17/18), all metastatic lesions and the cholangiocarcinoma did not take up iron oxide and were relatively hyperintense to the liver. However, in one well-differentiated HCC, the nodule partially took up the contrast agent and became isointense, with high-signal borders on PD/T2 SE images. Both the dysplastic lesion and FNH took up iron oxide; the former was isointense to the liver, while the latter appeared slightly hyperintense, with a high-signal central scar. Finally, hemangiomas became hyperintense on Spio-enhanced T1 SE images and had slightly decreased signal intensity on Spio-enhanced T2 SE images.

CONCLUSIONS

In our experience iron oxide was an effective contrast material. Spio-enhanced MRI improved the detection and characterization of focal liver lesions relative to baseline MRI. Several liver-specific contrast agents are now available or in an advanced experimental stage. Therefore, future studies could be aimed at assessing the effectiveness of iron oxide versus other contrast agents and at establishing the role of Spio-enhanced MRI versus spiral CT and CT during arterial portography.

[The assessment of skin tumors with magnetic resonance with high resolution and a paramagnetic contrast medium]

INTRODUCTION

The technologic improvement of surface coils in MRI has allowed better visualization of the skin and thus permitted the clinical use of this technique in dermatology. MRI allows to assess the depth and extent of skin tumors and to detect any malignant transformation. The MR differentiation between benign and malignant skin lesions relies on morphological criteria which however do not have an absolute diagnostic value. We investigated the role of paramagnetic contrast agents in the differentiation between benign and malignant skin lesions.

MATERIAL AND METHODS

Forty-one patients, 33 with benign and 8 with malignant skin tumors, were submitted to MRI. All the examinations were performed with a 1.5 T superconductive unit, with a 2.5 cm surface coil. Axial T1- and T2-weighted SE images were acquired with 2 mm slice thickness. Paramagnetic contrast material was administered to all patients. The signal intensity of the skin lesions was calculated before and after paramagnetic contrast agent administration positioning a region of interest. A percentage ratio of contrast enhancement was calculated to quantify contrast agent uptake and the relative values were compared between benign and malignant lesions. A qualitative analysis was also performed rating the contrast enhancement of each lesion as high, intermediate, or absent.

RESULTS

The quantitative analysis showed a statistically significant difference (p < .5) between the contrast enhancement values of benign and malignant lesions. In particular, malignancies had values ranging 117.3 (+/- 28.7) to 125 (+/- 32.4), while benign lesions had -20.6 to 99.8 (+/- 21.1). Conversely, no difference in contrast enhancement was found at qualitative analysis.

CONCLUSIONS

MRI is a promising tool for characterizing skin tumors. Our preliminary results should be confirmed on larger series of patients with the use of high temporal resolution imaging sequences.

Nocardial adrenal abscess: CT and MR findings

To our knowledge, four bacterial adrenal abscesses in adults have already been reported in the international literature, but an adrenal Nocardia abscess has never been described previously. In this report the CT and MR imaging appearances and the differential diagnosis of the entity are discussed. The mass could resemble a malignancy. The observation of a rapid growth and colliquation of the mass helped in distinguishing it from a malignancy. The associated pulmonary infection provided a further clue to the diagnosis. The diagnosis was confirmed by surgery.

Image quality control in breast ultrasound

Sonography is well suited for breast studies. Adequate equipment is needed to acquire high quality images because several technical factors influence ultrasound images. Thus, the use of high frequency dynamic scanning probes, the ultrasound beam focusing corrected for the near field, the adjustment of the gain and image contrast may all interfere with ultrasound beam reflection and scattering, determined by the heterogeneity of the gland parenchyma. In the last few years, a line of ultrasound equipment dedicated to this kind of application has been developed with 'small parts' transducers and frequencies ranging 10-13 MHz. These units can improve the evaluation of superficial structures and provide diagnostic results that conventional equipment cannot achieve. The higher the quality, the more a sonographic image corresponds to real anatomy. This capability depends on the different kinds of system resolution. Axial spatial resolution is the capability to resolve discrete structures along the beam axis. Pulse length is inversely proportional to frequency and thus, the higher the transducer frequency, the better the axial resolution. However, the increase in frequency reduces the depth of penetration of the ultrasound beam. The spectrum of frequencies emitted by the crystal has been recently modified in order to obtain a good trade-off between the beam resolution and its penetration. Indeed, the development of the multifrequency technology allowed to improve the near field resolution while retaining a good penetration into the distant field. Furthermore, the use of compound ceramics with a broad bandwidth helps Doppler analysis because flow studies are optimized by low frequencies, whereas two-dimensional morphologic imaging is optimized by high frequencies. Lateral spatial resolution is the capability to resolve discrete structures perpendicular or lateral to the beam axis. This parameter strictly depends on the size of the ultrasound beam section and it is optimal only in the focal area. Therefore, it improves with narrow beams. Several transducers are available in breast sonography, but the most adequate one is currently the annular transducer. The equipment should be able to detect even slight differences in acoustic impedance between the several breast tissues. This may be obtained by optimizing the dynamic range and the pre- and postprocessing setting. Apart from equipment, two other technical factors should be optimized to obtain high quality images, namely beam intensity and gain curve. A new Doppler technique has been recently introduced: power Doppler, which allows the demonstration of breast nodule vascularization with higher sensitivity than color Doppler. Finally, a rigorous examination technique is required to obtain high quality images. In the last few years, several quality assurance programs have been introduced. Dedicated phantoms are generally used. Recently, computer systems have been also developed.

MR imaging technique for the diagnosis of pituitary iron overload in patients with transfusion-dependent beta-thalassemia major

To identify the optimal MR imaging technique for diagnosing pituitary iron overload, we compared spin-echo and gradient-echo MR imaging with measurements of pituitary T2 relaxation times in 30 patients with secondary hemochromatosis due to transfusion-dependent beta-thalassemia major and in 10 healthy volunteers. We found that the optimal MR imaging technique to evaluate pituitary iron overload is the gradient-echo T2*-weighted technique, as it best demonstrated signal reduction in the anterior lobe of the pituitary gland.

[Potential uses of color Doppler in periskeletal soft tissue neoplasms]

Integrated imaging plays a fundamental role in the study of periskeletal soft tissue tumors, for both diagnosis and treatment planning. The steady and progressive technologic progress of color Doppler US equipment now permits the integration of conventional morphostructural parameters with the biofunctional data of lesion flow patterns and relative qualitative features. To assess color Doppler capabilities in differentiating benign from malignant soft tissue tumors, we reviewed the B-mode and color Doppler findings of 43 consecutive patients with a palpable periskeletal soft tissue mass. All patients were examined with a real time unit (Ultramark 9 HDI), with a broadband (5-10 MHz) linear transducer operating at 6.5 MHz for Doppler measurements. The PRF was set at 1500 to 800 Hz with 70% color gain; a 100 Hz wall filter was used. We kept the color box in the area of interest as small as possible to keep the frame rate high; pulsed Doppler studies were performed with a small sample volume and 2000 Hz PRF. The following signs were considered: morphostructural features; the presence/absence of color signals; the (peripheral/internal) site of vascular branches, their caliber and course; the number of afferent vascular poles; resistance index. As a rule, malignant masses tend to differ from benign masses for the presence of multiple vascular afferent branches, especially if they have an irregular pattern and caliber, and for the variability of the resistance index measured in different parts of the same mass. Further examinations, performed with second level imaging (CT and MRI) and microhistologic tests, respectively after biopsy and surgical resection, confirmed the high predictive value of color Doppler US, with only 1 false negative and 2 false positives; color Doppler sensitivity and specificity were 94.7% and 91.6%, respectively, which are higher values than those obtained with US alone (63% and 66.6%). Therefore, we believe that color Doppler US can be systematically applied to the study of periskeletal soft tissue masses, integrating conventional US for the correct selection of the patients to be submitted to second level investigations.

Serum and fecal pancreatic enzymes in beta-thalassemia major

CONCLUSION

This study, using indirect tests, demonstrated that exocrine pancreatic function is impaired in a proportion of patients with beta-thalassemia major (TM), though this impairment is generally mild or moderate.

BACKGROUND

Impaired structure and function of the exocrine pancreas has been reported in patients with Beta-thalassemia major.

METHODS

In this study we measured fecal fats and serum and fecal pancreatic enzymes in 30 patients (13 M, 17 F) with TM, mean age 22.1 yr (range 14-39) and compared them with those of a matched group of healthy controls. Results were correlated with age, serum ferritin, blood transfusion, and various nutritional parameters. Enzymes assays included: serum pancreatic amylase (PA), lipase (L), trypsin (T), fecal chymotrypsin (FCT), and fecal elastase (FE).

RESULTS

No patient was positive for steatorrhea. Comparison of the mean values showed a significant difference only for FE (p < 0.002). Using only the fecal tests as a reference, we found that 12 patients had FE values below the cutoff limit; of these, five had values between 100 and 185 micrograms/g, three between 50 and 99 micrograms/g and four below 50 micrograms/g. Ten patients had FCT values below the cutoff limit; seven presented impairment in both tests and six of them had FE values below 100 micrograms/g (including four diabetics). No correlations were found between enzyme values and mean serum ferritin values or mean blood consumption over the previous 3 yr. No correlation was found between FE and FCT levels or between enzymes and age.

Perfusion MRI in normal and abnormal pituitary gland. A preliminary study

Perfusion MRI (magnetic resonance imaging) of the pituitary gland was performed in 20 healthy volunteers and 63 patients with various lesions involving the pituitary gland. All patients underwent sequential contrast-enhanced MRI using spoiled gradient recalled sequences with high temporal resolution (7 seconds). Four pituitary areas (pituitary stalk, posterior lobe, postero-superior, and antero-inferior adenohypophysis) were tested with a selected region of interest. Maximal contrast percentual variation was calculated. The timing of enhancement in normal patients matched perfectly with normal pituitary vascularization. Abnormal timing in pathological condition was investigated.

[Biomechanics and semiology of transient lateral patellar dislocation: reliability of magnetic resonance diagnosis]

Transient patellar dislocation is a rare finding. It is usually due to direct trauma in mediolateral direction or to indirect trauma related to violent quadriceps muscle contraction. The clinical diagnosis of transient forms is usually rather difficult because the associated signs (hemarthros and pain at the joint and/or at the vastus medialis insertion) are not specific. Conventional radiography and CT are very accurate in bone studies, but exhibit major limitations in the detection of capsular injuries with intramedullary and/or cartilaginous bone involvement. We investigated MR diagnostic reliability in the study of the injuries caused by transient patellar dislocation. 526 MR examinations of the knee were reviewed retrospectively; fifteen of them were positive for transient patellar dislocation. We used a .5 T superconductive MR unit with a circumferential extremity coil. Axial, coronal and sagittal T1-weighted spin echo, T2*-weighted gradient echo and axial STIR images were acquired. The following criteria were considered specific for the diagnosis of former lateral patellar dislocation: retinacular changes; patella site; signal intensity changes in femoral and patellar intramedullary bone; joint effusion; cartilage and subchondral bone changes. All the patients with transient patellar dislocation had hemarthros with inner retinaculum involvement. The femoropatellar joint was incongruous in 115 cases; patellar subluxation was external in 8/11 patients and lateral in the remaining 3 patients. Medullary bruises were found in 8/15 cases and cartilage injuries in 13/15. Finally, other joint components, such as the posterior horn of the medial meniscus or the anterior cruciate ligament were involved in 6/13 cases. Arthroscopy was performed in 6 patients with associated injuries and confirmed all MR findings (100% agreement). To conclude, in our experience MRI was a very reliable tool to study the injuries due to transient patellar dislocation because it showed specific changes and possible associated traumas, which helps choose the most suitable treatment.

Magnetic resonance findings in scuba diving-related spinal cord decompression sickness

Scuba diving is associated with risk of severe decompression sickness (DCS type II), which results from rapid reduction of the environmental pressure sufficient to cause the formation into tissue or blood of inert gas bubbles previously loaded within tissues as a soluble phase. DCS type II constitutes a unique subset of ischemic insults to the central nervous system (CNS) with primarily involvement of the spinal cord. Ten patients with diving-related barotrauma underwent neurologic examination. Two of them presented progressive sensory and motor loss in the extremities at admission and were presumed affected by spinal cord DCS. Magnetic resonance imaging (MRI) demonstrated abnormalities in the white-matter tracts of the spinal cord in these patients, in each case corresponding to an area of the cord believed to be clinically involved. After a course of therapeutic recompressions, one patient was able to stand and walk a short distance, and MRI revealed a decreased extension of areas of spinal cord abnormalities. MRI has proved to be reliable in the detection of pathologic changes of spinal cord decompression sickness that were previously undetectable by other neuroimaging methods and also has proved to be useful in the follow-up during therapeutic hyperbaric recompressions.

[Normal anatomy and pathologic features of the supraspinatus muscle: comparison between ultrasonography and surgery. Analysis of the potential sources of diagnostic errors]

The supraspinatus muscle performs about 60% of the elevation-abduction motion of the arm; therefore, it has a prominent functional role among the extrarotational muscles of the shoulder and is the most injured in subacromial space conditions. Seventy-four patients, aged 21-64 years, were examined to compare ultrasonography (US) results with surgical findings in supraspinatus conditions and to analyze the possible pitfalls in US diagnosis. All the patients underwent conventional X-ray, US and then surgery or arthroscopy. The following criteria were considered: morphology, thickness, echotexture, the convexity of the superior border of supraspinatus tendon, the relationships with the subacromial bursa and the tendon of the biceps long head, the regularity of the bone cortex of the humeral head. US showed: chronic degenerative tendinopathy in 10 patients; perforating focal injuries in 21 patients; deep focal injuries in 10 patients; intramural focal injuries in 6 patients; superficial focal injuries in 8 patients; complete tendon tear with detachment in 19 cases. 62/74 US diagnoses were surgically confirmed, with a specificity of 83.7%. In our experience, US provided very useful information about the pattern, size and site of the injuries and was very helpful in the surgical planning.

Arrhythmogenic right ventricular dysplasia: MR features

Arrhythmogenic right ventricular dysplasia (ARVD) is a heart disease characterized by a total or partial fat replacement of the myocardium. A total of 30 patients were studied with a suspected diagnosis of ARVD. Clinical criteria used for evaluation of ARVD were: (a) ventricular origin arrhythmias with a left bundle branch block configuration, (b) T-wave inversion in the anterior precordial leads, (c) ventricular kinetic alterations observed using echocardiography and angiography and (d) cardiac failure when there are no pathologies attributable to other heart diseases. All patients had serial EKG and echocardiography tests. One third of patients underwent angiocardiography; 7 of 30 had Holter; 7 of 30 had exercise test just to evaluate the effectiveness of the anti-arrhythmic therapy. All patients underwent MRI examination. The following MRI criteria were used: (a) high-intensity areas indicating the fatty substitution of the myocardium, (b) ectasia of the right ventricular outflow tract, (c) dyskinetic bulges, (d) dilation of the right ventricle and (e) enlargement of the right atrium. The diagnosis of ARVD was classified as highly probable for patients manifesting at least three positive criteria, probable with two positive criteria, dubious with one and negative in the absence of all criteria. Highly probable diagnosis of ARVD was made in 8 patients, probable in 4, dubious in 7 and negative in 11. The MRI technique is very effective in the assessment of ARVD. The MRI criteria may be helpful in the diagnosis of this condition.

Blood-ocular barrier damage: use of contrast-enhanced MRI

The blood-ocular barrier (BOB) shares similar neuroepithelial origin, microanatomy and functions with the blood-brain barrier. There are many natural (e. g. diabetes, hypertension) or iatrogenic (chemotherapy, retinal photocoagulation) conditions which can cause a BOB breakdown, resulting in visual acuity impairment or loss. The authors examined 42 patients affected by BOB damage in different pathological conditions. All patients previously underwent a conventional fluoroangiographic (FA) study. Nine patients with normal FA exam were evaluated also. Despite normal MRI findings immediately after Gd-DTPA injection, contrast leakage into the vitreous body or into the aqueous fluid was demonstrated in delayed scans (40-50 min after contrast administration), proving the existence of a BOB damage (sensitively 94 %). Although FA exam remains the choice modality in BOB breakdown demonstration, we propose MRI as a useful diagnostic tool when optic media opacity (cataract, haemovitreous, intraocular silicon oil) occurs, preventing direct retinal fundus imaging and/or an early screening tool.

[Stener lesions: ultrasonography assessment in 12 cases]

We investigated the ultrasonographic (US) features of Stener injury and thus the role of US in the diagnosis of this condition. Stener injuries are characterized by the tear of the cubital ligament system of the first metacarpophalangeal joint during hyperabduction. This condition may be associated with the displacement of the ligament proximal stump above the thumb adductor muscle. We examined 12 patients (9 men and 3 women) with a clinical diagnosis of joint instability due to hyperabduction of the first metacarpophalangeal joint. All the US exams were performed with a linear probe (7.5-10 MHz); a 13-MHz probe was also used in 7 patients. All the patients were submitted to radiography in the standard projections, to detect associated bone injuries. US allowed the identification of a round lesion surrounded by a hypoechoic halo, between the distal edge of the dorsal interosseous muscle of the first finger and the first metacarpal bone (the proper Stener injury) in 4/12 patients. In contrast, no typical sign was shown in the other 8 patients. US results were then compared with surgical findings. The diagnosis of proper Stener injury was surgically confirmed in 4 patients. Only 2 patients with clinical signs of thumb instability, who were negative for Stener injuries at US, were submitted to surgery which demonstrated the ligament tear responsible for joint instability, but ruled out the displacement. To conclude, US must be integrated with clinical signs because this imaging method accurately shows complete tears with displaced proximal stump of the cubital ligament.

[Chronic osteomyelitis of the long bones: magnetic resonance imaging]

To investigate MR capabilities in assessing the extent of disease in chronic osteomyelitis of long bones, we examined 6 consecutive patients, 4 men and 2 women (age range: 27-67 years; mean: 42 years), with posttraumatic chronic osteomyelitis diagnosed at clinics, US, CT and radiography. The diagnosis had surgical or bioptical confirmation. MR studies were performed with an 0.5 T superconducting magnet, a surface coil and T1-weighted SE sequences-before and after Gd-DTPA administration-STIR and T2-weighted SE sequences, on the axial and coronal or sagittal planes. The signal intensity of the inflammation area was hypointense on short TR and TE images and hyperintense on long TR and TE images. After Gd-DTPA administration, granulation tissue surrounding the infection was enhanced in all cases and also the areas of vascularized inflammation within bone marrow were enhanced in two cases. MRI provided accurate and detailed information as to soft tissue and medullary canal involvement depicted sinus tracts in 5 cases and confirmed the presence of sequestrum in 5 cases, in agreement with previous CT findings. In our experience, MRI proved to be a reliable tool to assess the intramedullary and extracompartmental extent of osteomyelitis and also to plan surgery. MR specificity, which is often affected by post-traumatic or postoperative changes, improves markedly if some morphological features typical of the condition are also considered, such as sequestrum and sinus tracts.

[Biomechanics and semeiotics of traumatic lesions of the posterior cruciate ligament using magnetic resonance]

The authors reviewed 458 MR examinations of the knee to assess the potentials of this technique in the study of traumatic injuries of the posterior cruciate ligament (PCL) and to investigate the frequency of their association with injuries of other knee joints. MR images were acquired with an 0.5-T super-conductive unit with an extremity coil. T1-weighted spin-echo (SE) and T2*-weighted gradient-echo (GE) sequences were used on sagittal, coronal and, in some cases, axial planes, with 3-mm slice thickness and 0-1 mm slice gap. The following parameters were studied to diagnose partial or complete PCL tears: PCL thickness and outline, disruption of ligamentous fasci and signal intensity features. The injuries were classified as proximal, intermediate and distal according to their site. Thirteen PCL tears were detected, 5 of them complete and 8 partial. Complete tears were found in 4/5 patients in the middle third and one patient had a distal intersection tear with tibial bone avulsion. Partial tears were found in the distal tract in 5/8 patients, in the proximal tract in one patient and in the middle third in 2 patients. In 12/13 patients capsuloligamentous knee tears were associated. Overall MR rate of PCL tears was 2.8%; of them, 92.3% were associated with other capsuloligamentous injuries. MR diagnosis was confirmed at arthroscopy in 12/13 patients. The sagittal plane was best in optimally demonstrating the whole PCL and its injuries. GE T2* sagittal sequences demonstrated the site of PCL tears better than SE sagittal ones. Relative to other authors, we found MRI an extremely reliable method to distinguish partial from complete PCL tears. This was probably due to the thinner slices (3 mm) we used. MRI can accurately assess the extent of traumatic injuries of the PCL and of other capsuloligamentous parts of the knee, which is relevant from the clinical point of view. Indeed, MRI allows useless diagnostic arthroscopy to be avoided and yields major indications to choose the correct treatment.

[Aortic isthmic stenosis: clinical study and postoperative follow-up by MRI. Report of a case]

A case report. Nuclear Magnetic Resonance (NMR) is the most recent non-invasive diagnostic technique which can provide high quality anatomic and functional data. The absolute safety of the method make it suitable for follow-up of patients who have undergone aortic surgery. The authors report the case of a 12-year-old girl suffering from isthmic coarctation of the aorta for which both traditional methods (echocardiography and angiography) and NMR were used. Following bypass surgery with a dacron implant in the stenotic tract of the aorta, the patient was followed up using transthoracic echocardiogram and NMR. The latter method was found to be most efficacious in providing anatomic and functional information after surgery, enabling an optimal follow-up of these patients.