A.M. Davies

The value of computed tomographic measurements in Osteosarcoma as a Predictor of Response to Adjuvant chemotherapy

The response to pre-operative adjuvant chemotherapy was assessed with computed tomography (CT) in 41 osteosarcomas of the long bones of the lower limb. Measurements were made of cross-sectional tumour areas and volumes on both the pre- and post-chemotherapy CT examinations. Changes in these measurements were compared with the percentage necrosis determined from examination of the tumour histology from the excised specimen in 39 cases. An increase in the relative size of the tumour (expressed as a ratio of the pretreatment volume) showed a statistically significant correlation with a poor tumour response as judged by the degree of tumour necrosis. Further analysis of the results showed that quantitative assessment of tumour response by CT is able to identify cases with poor response to therapy (negative predictive value = 0.9). This is, however, only achieved with a low specificity (0.5-0.6). These findings are in agreement with other studies of tumour volume changes using MR imaging.

MRI characteristics of chondroblastoma

We report a retrospective study of MR imaging of 16 patients with histologically proven chondroblastoma, 12 at primary presentation and four clinically suspected recurrences. In all the primary cases MR imaging showed a lobulated low signal intensity (SI) rim. Low SI foci within the tumour were present in 11 out of the 12 cases and corresponded to calcification seen on radiographs or CT. Bone marrow oedema was also present in 11 out of 12 cases and an adjacent joint effusion in eight out of 12. The STIR sequence was of particular value, giving optimal delineation of marrow and soft tissue oedema. Of the suspected recurrences one showed peritumoral oedema and was subsequently proven histologically. Three showed no peritumoral oedema and subsequent histology was negative in these cases. The presence or absence of oedema may be a useful indicator of tumour activity although further study is required.

Computed Tomographic Arthrography in the Assessment of Osteochondritis Dissecans of the Elbow

Eleven cases of osteochondritis dissecans of the elbow are reviewed. Computed tomography (CT) accurately identified the abnormality, its extent and its precise location. Computed tomographic arthrography (CTA) allowed accurate delineation of the overlying cartilage in all cases, identifying cartilage defects in four patients, fissuring in two and cartilage thinning in a further two. In those patients who had plain CT, four were shown to have loose bodies, one of which was obscured by contrast medium at subsequent CTA. Two further patients with loose bodies were identified using CTA alone. The possible relevance of these findings to management is discussed.

Glenoid hypoplasia: Assessment by computed tomographic arthrography

Four cases of an uncommon congenital skeletal anomaly, isolated bilateral glenoid hypoplasia, are presented with discussion of the possible pathogenesis and clinical significance. Bilateral computed tomographic arthrography of the shoulder demonstrated thickening of the inferior glenoid cartilage in two cases. The technique was of value in the symptomatic shoulder revealing the location of a contrast medium filled cleft within the posterior cartilage in one case and the true configuration of the glenohumeral joint in the second case, when the degree of deformity had rendered plain radiographs and conventional arthrography uninterpretable.

Signal changes in the intervertebral discs on MRI of the thoracolumbar spine in ankylosing spondylitis

Contrary to standard teaching in magnetic resonance imaging (MRI), recent reports have documented calcification appearing as areas of increased signal intensity (SI) on T1-weighted images. Intervertebral disc calcification is a frequent finding on radiographs in chronic ankylosing spondylitis (AS). This study was performed to investigate the appearance of variable degrees of disc calcification in MRI. Thirty-six patients with AS of variable duration underwent an MRI scan of the thoraco-lumbar spine and the MR appearances, particularly of the discs, were compared with plain radiographs. Increased SI of the discs on T1-weighted images were found in 17 of 36 patients, occurring over a range of disc levels, and correlating with disc calcification on the radiographs in 78% of cases. This group tended to be older and have a longer duration of disease than those with normal appearing discs. Four different patterns of increased signal within the discs termed Type A (marginal), Type B (annular), Type C (central) and Type D (solid) were identified. In those with less than six discs involved Type A was the most common pattern. In those with more than six discs involved Type D was the most common pattern, suggesting a progression of disc involvement with more advanced disease. Although these findings will not affect the management of the disease, they do highlight the recently described phenomenon of calcification appearing as increased SI on T1-weighted images, likely to be related to the surface area of the calcium crystal. This should lead to the consideration of calcium in the differential diagnosis of increased SI on T1-weighted images. End-plate marrow changes were a relatively frequent finding in this study but did not correlate with the signal changes seen within the discs; in a number of cases they related to variable degrees of bony bridging.

Bildgebung beim primären Osteosarkom

ZusammenfassungDas Osteosarkom ist abgesehen vom Myelom der häufigste primäre bösartige Knochentumor. Die überwiegende Mehrzahl der Osteosarkome kommen innerhalb des Knochens vor und werden „konventionelle Osteosarkome” genannt. Die im Knochen vorkommenden Varianten beinhalten teleangiektatische, kleinzellige, niedrig differenzierte intraossäre und kortikale Osteosarkome. Weniger als 10% der Osteosarkome treten an der Knochenoberfläche auf. Diese werden in periosteale, hochgradig differenzierte, oberflächliche und paraostale Varianten unterteilt. Im folgenden werden Osteosarkom-Bildgebungsmethodik und ihr Einfluß auf Diagnose und Therapie diskutiert. Basis dafür sind 750 Osteosarkomen, die am klinischen Zentrum des Autors behandelt wurden.Die Erkennung des Tumors beruht immer noch auf konventionellen Röntgenaufnahmen, während Knochenszintigraphie und Kernspintomographie helfen, diskrete Tumoren aufzuspüren. Die radiologische Diagnose gründet sich auf sorgfältigen Röntgenbildanalysen, unter spezieller Berücksichtigung von Natur und Ausdehnung der Knochendestruktionen, periostalen Knochenneubildungen und Matrixverkalkungen. Streßfrakturen und Osteomyelitiden können differentialdiagnostische Probleme aufwerfen. Die chirurgische Stadieneinteilung beruht auf der kernspintomographischen Darstellung des Primärtumors. Mit ihrer Hilfe kann das Ausmaß des Tumors in Knochen und Weichteilen erkannt, Metastasen bestätigt oder ausgeschlossen sowie der Befall regionärer Lymphknoten abgegrenzt werden. In die Stadieneinteilung sollte auch Knochenszintigraphie sowie Thoraxcomputertomographie mit einbezogen werden, um multiple Läsionen bzw. Lungenmetastasen auszuschließen. Anschließend an die chirurgische Behandlung wird die Bildgebung in Nachsorgeuntersuchungen eingesetzt, um Lokalrezidive und Lungen- bzw. Knochenmetastasen zu erfassen.SummaryOsteosarcoma is the most common primary malignant bone tumour with the exception of myeloma. The majority of osteosarcoma cases arise within bone and are called conventional osteosarcoma. Intraosseous variants include telangiectatic, small-cell, low-grade intraosseous and cortical osteosarcoma. Less than 10% of osteosarcomas arise on the surface of bone and are subdivided into periosteal, high-grade surface and parosteal varieties. The imaging features of these subtypes of osteosarcoma are described and the impact on diagnosis highlighted. Using material from over 750 osteosarcomas treated at the author’s centre, this article reviews the role of imaging in the management of this condition. Detection still relies principally on the conventional radiograph with bone scintigraphy and MR imaging useful in occult tumours. Establishing the radiological diagnosis depends on careful analysis of the radiographs, with particular attention paid to the nature and extent of bone destruction, periosteal new bone formation and matrix mineralization. The prudent radiologist will be wary of those bone conditions, such as stress fractures and osteomyelitis, which are frequently mistaken for osteosarcoma. Appropriate surgical staging requires MR imaging of the primary tumour to show the bony and soft tissue extent of the lesion and to confirm/exclude skip metastases and local lymph-node involvement. Staging should also include bone scintigraphy to confirm/exclude multiple lesions and chest CT to confirm/exclude pulmonary metastases. Following definitive surgery, imaging is used in the follow-up to monitor potential local recurrence and the development of pulmonary or osseous metastases.

Out-patient lumbar radiculography with iohexol

A prospective study of 200 patients undergoing lumbar radiculography using 10 ml iohexol (240 mgI/ml) was undertaken to determine whether the procedure could be safely performed on an out-patient basis. No statistically significant differences in the incidence and severity of side-effects were found between the 99 out-patients and 101 in-patient controls. Three out-patients had to be kept in hospital at the end of the observation period and a further three out-patients were re-admitted to hospital because of severe side-effects. Out-patient lumbar radiculography is a safe procedure provided there is careful patient selection, adequate advice and easy access to medical help should problems arise following the examination. Adopting this practice considerably reduces the cost of lumbar radiculography and indirectly increases the availability of orthopaedic beds.