Tumor volume or dynamic contrast-enhanced MRI for prediction of clinical outcome of Ewing sarcoma family of tumors

Background. The identification of risk factors that predict poor clinical outcome at the time of diagnosis could lead to intensified early therapy and improved outcome for pediatric patients with Ewing sarcoma family of tumors (ESFT). Objective. To compare the effectiveness of static magnetic resonance (MR) imaging measurements of tumor volume with variables obtained by dynamic contrast-enhanced MR imaging (DEMRI) in predicting ESFT outcome. Methods. MR examinations that included DEMRI were retrospectively reviewed. The analyses included 45 examinations of 21 patients with ESFT (performed from 1992 to 1996). Tumor volumes were measured on the static MR images, and the regions of interest were selected for DEMRI analysis. The relationships of static MR imaging and DEMRI variables with the probability of progression-free survival (PFS) and disease-free survival (DFS) were determined. Results. Larger tumor volume at the time of diagnosis predicted poorer PFS and DFS estimates. No DEMRI variable predicted outcome. Conclusion. Determination of tumor volume by static MR imaging at the time of diagnosis is a simple and reliable method of predicting the clinical outcome of patients with ESFT. DEMRI is not as reliable a technique as static MR imaging for predicting the outcome of these patients. Received: 8 September 2000 Accepted: 28 Feburary 2001     

MR findings of complicated multifetal gestations

This paper presents a review of various complications of multifetal gestations identified on MR imaging and highlights findings of those complications unique to monochorionic twinning. The goal is to illustrate the potential of MR as a useful application in these clinical circumstances. A total of 32 women with multifetal gestations and suspected complication detected initially by US underwent T2-weighted MR imaging. Additional T1-weighted images were obtained when intracranial hemorrhage was suspected. MR and US findings were compared in all cases. Of 32 cases, six demonstrated fetal complications specific to monochorionic twinning; the findings consisted of conjoined twins (n=2), twin-twin transfusion syndrome (n=1), co-twin demise with embolic disease (n=2), and twin-reversed arterial perfusion. (TRAP) syndrome (n=1). MR imaging confirmed US findings in all cases and was particularly helpful in delineating the extent of intracranial complications of monochorionic twins. The technique also showed improved anatomical detail in cases of conjoined twins. MR imaging provided additional information in cases of complicated monochorionic twinning, making it a useful complementary technique when combined with initial sonographic assessment.     

Which MRI sequence of the spine best reveals bone-marrow metastases of neuroblastoma?

Background: MRI is an effective tool in evaluating bone marrow metastases. However, no study has defined which MRI sequences or image characteristics best correlate with bone-marrow metastases in neuroblastoma. Objective: To identify and refine MRI criteria and sequence selection for the diagnosis of bone-marrow metastases in children with neuroblastoma. Materials and methods: Ninety-one children (mean age: 3.2 years; standard deviation: 2.8 years) enrolled in the RDOG IV study participated in our study. Forty-five children had bone metastases determined by bone-marrow aspiration or biopsy (n=4), radionuclide imaging (n=2), or both (n=39). Spine lesions were characterized using coronal T1-weighted (T1W) sagittal short tau inversion recovery (STIR) and coronal gadolinium-enhanced T1-weighted (GAD) MR sequences. Contingency table analysis was performed to determine which MRI sequences and characteristics were associated with metastases. The MRI criteria for metastatic disease were then developed for each imaging sequence. The sensitivity, specificity, predictive values, and accuracy of these criteria were determined for the whole group, children younger than 12 months old, and children 12 months and older. Results: The MR characteristics that had significant (P 0.05) associations with metastases were homogeneous low T1-signal intensity, homogeneous high STIR-signal intensity, and heterogeneous pattern on T1, STIR, or GAD. Homogeneous low T1-signal had the highest sensitivity (88%), but a specificity of 62% for detecting metastases. A heterogeneous pattern on GAD was highly specific (97%), but relatively insensitive (65%) for detecting metastases. These MR characteristics were most accurate in children 12 months and older. Conclusion: The combination of non-contrast-enhanced T1W and GAD sequences can be used to determine the presence of spinal metastases in children with neuroblastoma, particularly those children who are 1 year and older.Presented at the 41st annual meeting of The Society for Pediatric Radiology, Tucson, Arizona, 1998     

Reconversion of bone marrow in Gaucher disease treated with enzyme therapy documented by MR

Background. Skeletal complications are responsible for significant morbidity in Gaucher patients. Plain radiographs have been unreliable in assessing bone marrow infiltration and activity. A way to assess bone marrow improvement is needed during enzyme therapy. Objective. The purpose of this paper is to assess the usefulness of MR in following improvement of abnormal bone marrow in Gaucher patients on enzyme therapy. Materials and methods. Three patients aged 2, 7, and 24 years underwent serial MR scans of the lower extremities before and during treatment with Alglucerase (two patients) and Imiglucerase (one patient). T1-weighted, T2-weighted, STIR and FSE T2-weighted images were utilized. Two patients were imaged after 16 months of therapy, and one patient was imaged after 6 months of therapy. Results. All patients had improvement in marrow signal consistent with partial reconversion to fatty marrow during treatment. The findings were more marked after prolonged therapy. T1-weighted images demonstrated findings most clearly. Conclusion. MR consistently showed improvement in marrow signal in Gaucher patients on enzyme therapy. As smaller doses of enzyme therapy are the trend, MR can be utilized to determine if therapy is effecting a change in the bone marrow. Received: 20 June 1997 Accepted: 7 November 1997     

Ewing's sarcoma recurrence vs radiation necrosis in dynamic contrast-enhanced MR imaging: a case report

Purpose. We report a case of Ewing's sarcoma in the right distal femur in a 6-year-old male to demonstrate how dynamic contrast-enhanced magnetic resonance imaging (DEMRI) findings predicted histopathology. Materials and methods. DEMRI was performed at presentation and during and after completion of chemotherapy and radiation therapy. Histopathologic studies were done at presentation, at 77 weeks (20 weeks after a pathological fracture), and from the en bloc resection at 104 weeks. Results. DEMRI predicted the early tumor response, absence of tumor recurrence, presence of necrosis and lack of fracture healing, confirmed by histopathology. Conclusion. DEMRI is a clinically useful tool in managing Ewing's sarcoma. Received: 31 July 1998 Accepted: 9 November 1998     

Myofibromatosis: imaging characteristics

Background: Infantile myofibromatosis is the most common fibrous tumor of infancy. It can involve the skin, muscle, bone, and viscera. This uncommon entity is subdivided into solitary and multicentric forms, with or without visceral involvement. Objective: To describe the imaging characteristics of extracranial myofibromatosis. Materials and methods: Six infants, aged 1 day–1 week, were evaluated by imaging. All six patients had evaluation of one of the masses by US; four patients had CT evaluation of at least one of the masses; and five patients had evaluation by MRI. Results: The US appearance of the myofibromas included a mass with a purely anechoic center with a thick wall, a mass with a partially anechoic center, and a mass without anechoic components. On enhanced CT, the masses had lower or similar attenuation compared to adjacent muscle, with some masses exhibiting peripheral enhancement. The MR appearance consisted of low signal on T1-weighted imaging. On T2-weighted imaging, two had low signal of the center and the other three had high signal. All masses showed peripheral enhancement after gadolinium administration. Conclusions: Myofibromas have variable appearance on US, with a mass with an anechoic center being the most common feature. On CT, the mass can exhibit peripheral enhancement, calcifications, and erosion of adjacent bone. The MR appearance consisted of low signal on T1-weighted imaging and high or low signal of the center on T2-weighted imaging. All masses showed peripheral enhancement after gadolinium administration.     

Physeal and epiphyseal extent of primary malignant bone tumors in childhood

Twenty-two patients with metaphyseal primary malignant bone tumors (17 osteosarcomas, 5 Ewing's tumors) occurring before closure of the growth plate were examined with plain radiographs and MRI in order to determine the physeal or epiphyseal extent of the tumor. Results were correlated with the pathologic examination. Transphyseal spread was pathologically proven in 13 cases (59%): 12 cases of osteosarcoma and 1 case of Ewing's tumor (70% and 20%, respectively). There was no significant relation between epiphyseal invasion, age of patient, length of tumor or, in the cases of osteosarcoma, response to chemotherapy. Plain radiographs showed epiphyseal involvement in 4 cases and there were 10 false negatives. MRI revealed epiphyseal involvement in all cases; there were no false positives or false negatives. T1-weighted images in coronal or sagittal planes appeared to be sufficient. These findings are very useful in planning surgical limb salvage procedures and stress the ineffectiveness of the barrier effect of the growth plate against tumor spread.     

MR imaging differentiation of benign and malignant peripheral nerve sheath tumors: use of the target sign

Background. T2-weighted MR imaging of soft tissue tumors of neural origin may show round lesions with a central hypointensity and a hyperintense rim resembling a target. We define the “target sign” as a mass consisting of a solitary target, or a multicompartmental mass in which the largest component consists of multiple targets. Objective. The objective of this study was to determine whether the target sign can differentiate benign neurofibromas and their malignant counterparts, malignant peripheral nerve sheath tumors. Materials and methods. Preoperative T2-weighted MR images of 23 neurofibromas or malignant peripheral nerve sheath tumors were retrospectively reviewed in 16 patients, aged 3 weeks to 20 years (median 15 years), without knowledge of the pathologic diagnosis. The presence or absence of a target sign was noted. Results. The target sign was seen in all 12 neurofibromas and 1 of the 11 malignant peripheral nerve sheath tumors. Statistical analysis showed good differentiation of benign and malignant tumors using this sign (ϰ = 0.91). Conclusion. The target sign on T2-weighted MR imaging is helpful in differentiating neurofibromas from malignant peripheral nerve sheath tumors. Received: 10 January 1996 Accepted: 14 June 1996     

Application of a three-point method for water-fat MR imaging in children

Background. Effective fat suppression is desirable in clinical magnetic resonance imaging. Conventional frequency selective fat suppression is dependent on accurate prescan shimming and is subject to artifacts due to magnetic field inhomogeneity. Quadrature three-point water-fat imaging with direct phase encoding is an alternative technique for fat suppression that has been previously described in adult volunteers and patients. Objective. To evaluate the use of three-point water-fat imaging with direct phase encoding for fat-suppressed MR scans in children. Materials and methods. Sixty-two three-point water-fat imaging studies were performed in 55 children 2 months to 18 years old. T 1-weighted fat-suppressed (water) images from this sequence were compared with frequency selective fat-suppressed images obtained in 15 patients. The reliability and subjective quality of the sequence were assessed in the remaining 47 cases. Results. High-quality fat suppression was achieved in all anatomic sites studied, even where frequency selective fat-suppression failed due to magnetic susceptibility artifact. The three-point water-fat sequence was visually preferred to the frequency selective fat saturation technique in 15/15 cases. Conclusion. Three-point water-fat imaging has replaced the conventional frequency selective technique for fat suppression on T 1-weighted MR imaging at our institution. Received: 27 July 1998 Accepted: 23 December 1998     

US, CT and MR imaging characteristics of nephroblastomatosis

Objectives. To describe the imaging features of nephroblastomatosis with US, CT and MR, to point out characteristics of differentiation between nephrogenic rests (NR) and Wilms' tumour (WT) and to determine the most appropriate imaging modality. Materials and methods. We reviewed the US, CT and MR images of 29 cases of histopathologically confirmed nephroblastomatosis sent to our department for reference evaluation (German nephroblastoma study). The series included 17 kidneys with NR, 6 kidneys with WT and 32 kidneys with both NR and WT. Results. NR presented as multinodular, peripheral, cortical lesions, the diffuse form of distribution being less common. Foci were homogeneous and of low echogenicity, density or signal intensity. The lesions were most clearly depicted with contrast-enhanced CT and T1-weighted (T1-W) MR images. Lesions smaller than 1 cm were rarely identified by US. The most reliable criterion to differentiate NR from WT was their homogeneity. Conclusions. Contrast-enhanced CT and T1-W MR images are of similar potential and superior to US in the diagnosis of nephroblastomatosis. Due to the significant radiation dose of serial CT, MR imaging should be the method of choice wherever it is available. The cost-effectiveness and availability of US makes it ideal for serial follow-up of known lesions. Received: 6 June 1997 Accepted: 9 January 1998     

Imaging findings in primary intracranial atypical teratoid/rhabdoid tumors

Background: Intracranial atypical teratoid/rhabdoid tumors (AT/RT) are rare and extremely aggressive neoplasms seen primarily in childhood. Imaging features are often considered non-specific. However, correct diagnosis of AT/RT is important because these tumors have a markedly different clinical prognosis and require more aggressive therapy.Objective: To determine the imaging features of AT/RT.Materials and methods: We retrospectively analyzed imaging findings in 11 patients with primary intracranial AT/RT presenting over a period of 5 years. CT (n=11), MR (n=7), clinical (n=11) and pathological (n=11) features were evaluated. FISH analysis showing monosomy of chromosome 22 (absence of bcr 22q11 locus) was available for three patients. Immunohistochemical staining for INI-1 (BAF47) was performed on all tumors. Results: There were 11 patients, 6 boys and 5 girls. The age of presentation varied from 1 month to 15 years (average age 3 years 8 months). Six tumors were located in the posterior fossa and five in the supratentorial compartment. The tumors showed a hyperdense solid component (64%) that showed moderate to marked enhancement with contrast medium. On MR imaging, the predominant signal pattern was isointensity on T1-weighted images (57%) and T2 shortening with heterogeneity on T2-weighted images (86%). All tumors were large in size (average 4.2×3.7 cm), and there was a tendency for calcification (36%), hemorrhage (46%), necrosis (46%) and perifocal edema (100%). There was also a high tendency for subarachnoid dissemination, with five patients (46%) demonstrating brain and/or spinal metastasis. At follow-up (n=7), six patients showed local recurrence. At the time of recurrence, all these patients showed extensive leptomeningeal spread of the disease in both intracranial and intraspinal compartments. Conclusion: There are no specific imaging features for intracranial AT/RT. But a high tendency toward large size, a hyperdense solid component on CT scan with calcification, hemorrhage, necrosis and subarachnoid spread suggest that this tumor should be considered in the differential diagnosis of large pediatric intracranial tumors.     

Gadolinium-enhanced MR imaging demonstrates abduction-caused hip ischemia and its reversal in piglets

Purpose To determine whether gadoliniumenhanced MR imaging can detect early reversible ischemia of the capital femoral epiphysis and physis induced by hip hyperabduction in piglets.Materials and methods Thirteen 1-to 3-week-old piglets were placed in maximal abduction of both hips and studied with dynamic gadolinium-enhanced MR imaging 1–6 h later to assess ischemia of the 26 femoral heads. They were then allowed to ambulate freely for 1 or 7 days, and reimaged in neutral position to assess reperfusion. Enhancement was evaluated on MR images and compared with histologic findings.Results Ischemia after hyperabduction developed in all 26 cartilaginous epiphyses and in 85% of the physes. The most frequent abnormality was a sharply marginated nonenhancing area in the anterior part of the femoral head. A smaller area of ischemia developed in the posterior part of the femoral head, adjacent to the acetabular rim. The secondary center of ossification was ischemic in 56% of the hips after 1 h of abduction and in all hips after 4 or 6 h (p=0.02). The overall severity of ischemia was greater with increasing abduction time (p<0.001) and increasing degree of abduction (p<0.01). There was partial reperfusion in 83% of the hips after 1 day of ambulation and complete reperfusion in all 26 hips (100%) after 1 week.Conclusion Enhanced MRI detects early ischemia of the epiphyseal and physeal cartilage and the epiphyseal marrow. In piglets, ischemia due to hyperabduction is reversible if corrected within 6 h.Editor's note The publication by Dr. Jaramíllo et al.Gadolinium-enhanced MR imaging demonstrates abduction-caused hip ischemia and its reversal in piglets, represents the 1995 Caffey Award winning paper at The Society for Pediatric Radiólogy annual meeting. This paper will be published in bothPediatric Radiology and theAmerican Journal of Roentgenology in recognition of its award winning excellence. This joint publication is an honor andnot a double publication. From now on, each year's Caffey Award winning paper will be so honored in both journals.     

MR marrow signs of iron overload in transfusion-dependent patients with sickle cell disease

Magnetic resonance (MR) marrow signal in the axial and appendicular skeleton of 13 transfusiondependent and chelated pediatric patients with sickle cell anemia (SSD) was compared with marrow signal in six non-transfusion-dependent patients with SSD. Hepatic, pancreatic, and renal MR signal were also evaluated. Indication for hypertransfusion therapy was primarily prior history of stroke. Transfusion-dependent patients had evidence of iron deposition throughout the imaged marrow and the liver, despite deferoxamine chelation therapy. Non-transfusion-dependent patients did not demonstrate grossly apparent signs of iron overload. Red marrow restoration was present in the spine, pelvis and long bones and, in some patients, within the epiphyses. Marrow edema secondary to vaso-occlusive crises was evident in the metaphyses and diaphyses of long bones in areas of both red and fatty marrow and was best seen using fat-saturated T2-weighted imaging techniques.     

Imaging of arteriovenous malformation following stereotactic radiosurgery

Background. Stereotactic radiosurgery allows for a high dose of focused radiation to be delivered to a small lesion such as an arteriovenous malformation (AVM). The clinical change and brain response over time to this localized high-dose radiation can be quite striking. Objective. The objective of this study to describe and analyse the imaging changes following radiotherapy for AVMs. Materials and methods. The clinical presentation and the imaging changes following radiotherapy in two patients were studied over the course of 1–2 years. Results. The imaging findings include diffuse low attenuation and contrast enhancement on CT. High-signal lesions were apparent on T2-weighted MR images with prominent contrast enhancement on T1-weighted images. Ring enhancement occurred over time. While new changes appeared over 12 months, these changes diminished during the second year. Conclusion. Radiotherapy induces inflammatory changes that are generally reversible but can lead to parenchymal destruction. These imaging changes are often nonspecific and therefore must be interpreted in light of clinical symptomatology and the time course since treatment. These patients should receive routine MR imaging within 3 months after radiosurgery with follow-up imaging at 6, 12, and 18 months. Received: 13 February 1996 Accepted: 29 June 1996     

Pilomatricomas in children: imaging characteristics with pathologic correlation

Background Although pilomatricoma commonly occurs in children, there is still a poor understanding of the imaging characteristics of pilomatricoma and lack of agreement regarding its imaging findings and histopathologic features. Objectives To characterize the radiologic appearance of pilomatricomas on US, CT, and MR and to correlate the imaging findings with histopathologic features. Materials and methods The imaging findings of 47 pilomatricomas on US (n = 17), CT (n = 31), and MR (n = 5) were retrospectively evaluated. Pathologic specimens of all cases were reviewed and compared with imaging findings. Results All lesions were well-circumscribed, subcutaneous nodules with partial attachment to the overlying skin. On US, the lesions were mostly hyperechoic with posterior acoustic shadowing and hypoechoic rim. On CT, they appeared as enhancing soft-tissue masses with varying amounts of calcification. MR findings were internal reticulations and patchy areas on T2-weighted images and contrast-enhanced T1-weighted images, corresponding to edematous stroma on pathology. Peritumoral inflammatory changes and connective capsule on pathology were well correlated with imaging findings. Conclusion Pilomatricoma should be considered when US or CT shows a well-defined hyperechoic or calcific nodule in subcutaneous fat attached to the skin in children. MR images may be helpful in diagnosis. Pathologic findings are well correlated with imaging findings.     

MR findings of bowlegs in toddlers

Background. Toddlers with severe physiologic tibial bowing are considered to be at risk for the development of Blount's disease. Objective. To correlate MR findings of the knee with the clinical outcome in toddlers with severe physiological tibial bowing. Materials and methods. MR findings were evaluated in 22 affected legs of 14 children with severe tibial bowing (mean age 1.9 years). In 18 affected legs, MR findings were compared with the transition of the tibial metaphyseal-diaphyseal angle (MDA) and tibiofemoral angle (TFA) measured serially between 2 and 3 years of age. Results. MR findings of severe tibial bowing comprised undulation of the posteromedial physis of the tibia (3/22), signal alterations in the medial tibial metaphysis (10/22), T2 prolongation in the posteromedial tibial epiphyseal cartilage (14/22) and signal changes in the medial menisci (18/22). The decrease in the TFA was different in the legs with and without increased signal in the epiphyseal cartilage, and the decrease in the MDA was different in the legs with and without physeal undulation. Conclusion. MR imaging findings can predict the retarded resolution of tibial bowing, which may be a risk factor for the development of Blount's disease. Received: 16 December 1998 Accepted: 20 May 1999     

Potential utility of MRI in the evaluation of children at risk of renal scarring

Background. Gadolinium-enhanced MRI has recently been employed in the diagnosis of acute pyelonephritis. Its potential utility in the diagnosis of renal scars in children is unknown. Objective. To evaluate the potential utility of MRI using fat-saturated T1-weighted (T1-W) and post-gadolinium, short-tau inversion-recovery (STIR) sequences in detecting renal scarring by comparison with technetium dimercaptosuccinic acid (^{99 m}Tc-DMSA) renal scintigraphy in children at risk of renal scarring. Materials and methods. A group of 24 children with spina bifida and neurogenic bladder or anorectal anomaly was studied. No patient had a history of acute pyelonephritis. Documented urinary tract infection (UTI) was present in 10 children (42 %). The remaining 14 (58 %) children had a history of asymptomatic bacteriuria. None had clinical signs or symptoms of acute UTI at the time of the study. ^{99 m}Tc-DMSA and MRI were performed to detect renal scarring. ^{99 m}Tc-DMSA scans were supplemented with pinhole imaging. MRI of the kidneys employed a fat-saturated T1-W sequence and a post-gadolinium STIR sequence employing a short echo time. Results. Of the kidneys studied, 33 % (n = 16) had evidence of a renal parenchymal defect suggestive of scarring on ^{99 m}Tc-DMSA. The concordance in the detection of a scarred kidney by post-gadolinium STIR sequence and ^{99 m}Tc-DMSA is 94 %; that by fat-saturated T1-W sequence and ^{99 m}Tc-DMSA is 82 %; that by both sequences (positive result on either sequence) and ^{99 m}Tc-DMSA is 100 %. Using ^{99 m}Tc-DMSA as the gold standard, MRI had a sensitivity of 100 % and a specificity of 78 % in the diagnosis of a scarred kidney. The concordance in the detection of a scarred zone by post-gadolinium STIR sequence and ^{99 m}Tc-DMSA is 68 %; that by fat-saturated T1-W sequence and DMSA is 44 %; that by both sequences (positive result on either sequence) and ^{99 m}Tc-DMSA is 84 %. MRI had a sensitivity of 84 % and a specificity of 86 % in the diagnosis of a scarred zone, using ^{99 m}Tc-DMSA as the gold standard. Conclusion. The detection rate for renal scarring on MRI using the fat-saturated T1-W and post-gadolinium STIR sequences is comparable to planar ^{99 m}Tc-DMSA. MRI is of potential utility in the evaluation of children at risk of renal scarring. Received: 9 September 1998 Accepted: 10 May 1999     

MRI evaluation of infectious and non-infectious synovitis: preliminary studies in a rabbit model

Background. Literature on magnetic resonance imaging (MR) evaluation of inflammatory joint effusions is sparse. Objective. To describe an animal model for studying infectious and non-infectious joint effusions with magnetic resonance imaging. Materials and methods. Ten rabbit knees with septic arthritis and four with talc synovitis were imaged with MR. Contralateral knees injected with saline served as controls. Fat saturation T2-weighted and gadolinium-enhanced T1-weighted images were assessed for joint effusion, and periarticular and adjacent intraosseous increased signal or enhancement. Each knee was cultured and underwent pathologic examination. Results. Both Staphylococcus aureus and talc produced effusions in all knees. The degree of periarticular signal and enhancement was greater in infected knees than talc-injected knees. No abnormal enhancement was seen within bone. Pathologic examination showed a greater degree of inflammation and joint destruction in the infected knees, but no evidence of osteomyelitis. Conclusion. A greater degree of abnormal signal and enhancement seen on MR suggests a more vigorous inflammatory process, as seen with septic arthritis. In spite of advanced septic arthritis, no enhancement was evident within bone, suggesting that enhancement within bone is not an expected finding in isolated septic arthritis and should raise concern for osteomyelitis. Received: 8 May 1998 Accepted: 27 October 1998     

Imaging following allograft reconstruction in children with malignant bone tumours

Purpose. To determine the nature of the imaging findings following reconstructive surgery using massive allografts in children with malignant bone tumours. Materials and methods. A retrospective review of the imaging studies and medical charts of 25 consecutive children who received an allograft as part of the management of a malignant bone tumour. Results. Uncomplicated allografts were sclerotic relative to native bone on radiographs and showed a typical ’tramline' appearance on bone scintigraphy. On MR, the medullary canal of the allograft showed low signal, similar to or greater than skeletal muscle, but less than subcutaneous fat, on 91 % of T1-weighted images. On short-tau inversion recovery images, the medullary canal was inhomogeneous and hyperintense to subcutaneous fat in 70 % and hyperintense to muscle in the remainder. Complications occurred in 68 % of patients and included allograft fractures (36 %), recurrent tumour (20 %), infection (8 %), and non-union or delayed union (8 %). The radiographic findings alone permitted accurate diagnosis of most serious complications. Infection and rejection were difficult to distinguish with any technique. All complications were suspected on clinical and/or radiological grounds before being shown by MR or scintigraphy. Conclusions. Allografts, whether normal or complicated, have characteristic imaging findings, except that infection and bone resorption related to rejection and revascularisation are difficult to distinguish. Routine MR and bone scintigraphy appear to contribute little to the management of these patients. Received: 6 October 1998 Accepted: 22 March 1999     

Fast fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging of the brain: a comparison of multi-shot echo-planar and fast spin-echo techniques

Purpose. To evaluate fast spin-echo and multi-shot echo-planar fluid-attenuated inversion recovery (FLAIR) sequences in paediatric brain imaging. Materials and methods. Matched images from 32 patients with suspected tumour or white matter disease were independently evaluated by two paediatric neuroradiologists. The observer preferences for image quality and lesion detection were analysed for differences between fast spin-echo FLAIR and multi-shot echo-planar FLAIR. Diagnostic quality was compared with that of fast spin-echo T2-weighted images. Results. Images of a diagnostic quality equivalent to that of fast spin-echo T2-weighted images were achieved with both FLAIR techniques. Grey and white matter differentiation and cerebrospinal fluid (CSF) nulling were significantly better on fast spin-echo FLAIR sequences. CSF flow artefact was reduced on multi-shot echo-planar FLAIR. There was no difference in lesion detection. Fast spin-echo FLAIR images were visually preferred at the expense of longer imaging time. Conclusion. Fast FLAIR techniques are complementary to fast spin-echo T2-weighted sequences in imaging of the paediatric brain. We find that the fast spin-echo FLAIR sequence is preferable to the multi-shot echo-planar technique. Received: 20 August 1996 Accepted: 6 November 1996