Suspicion of Recurrent Osteosarcoma in a Patient with Pseudotumour Adjacent To the Endoprosthesis.

Purpose: Pseudotumor is a rare complication after arthroplasty, most often of the hip joint, in response to metal particles present in the implant. There are merely sporadic reports of pseudotumor in patients with bone sarcoma after sparing surgery with endoprosthesis implant. The aim of this study is to present the characteristic imaging features of pseudotumor. Case report: We present a case of a 21-year-old male patient in whom a scheduled follow-up ultrasound revealed a painless lesion suspected of local recurrence at the border of the endoprosthesis and the bone stump 3.5 years after the end of treatment for osteosarcoma of the femur. Histopathology of the biopsy specimen revealed that the lesion was a pseudotumor. Conclusions: Although pseudotumor is sporadic in patients treated with endoprosthesis for bone sarcoma, their prolonged survival could bear the risk of such a complication. Imaging studies, in particular ultrasound, may be helpful in differentiating from local recurrence of sarcoma, however, the histopathology of the specimen obtained by open biopsy at a reference center is crucial for the final diagnosis.

Arterial spin labeling in neonatal magnetic resonance imaging - first experience and new observations.

PURPOSE: Arterial spin labeling (ASL) is a noninvasive non-contrast technique of perfusion imaging that uses endogenous water from the blood as the perfusion tracer, with very scant data on its use in neonates. The authors present the added value of ASL in the examined babies in their own material and discuss it in the light of the existing literature. MATERIAL AND METHODS: During the first 10 months after the purchase of a new magnetic resonance imaging (MRI) scanner, 123 neonates were examined using it in an MR-compatible incubator, 117 of them had brain MRI, and in 104 ASL was incorporated in the routine protocol, which resulted in prolongation of the study time by approximately 4 minutes. 3D ASL sequence uses Pulsed Continuous Arterial Spin Labeling (PCASL; aka pseudo continuous) technique. RESULTS: The quality of the cerebral blood flow (CBF) maps was good in all cases but 2 because all the babies were sedated. Apart from the knowledge about normal perfusion patterns in the preterm and term neonatal brains, the use of ASL sequence provided important additional information in 11 cases (10.8%): increased CBF correlating with electroencephalographic seizure localization in otherwise normal MRI (n = 1), increased CBF in the cortex without clinical information about seizures and with posthaemorrhagic changes (n = 1), increased CBF in the brain stem and decreased in the upper parts of the brain (n = 2), probably reflecting the homeostatic mechanism which allows preferential perfusion of the vital structures of the brain stem, hypoperfusion (n = 1) or hypoperfusion with peripheral hyperperfusion (n = 1) in the area of stroke, hypoperfusion of the posterior areas of the brain in the presence of subarachnoid or epidural haemorrhage (n = 3), significantly increased CBF in the presumed nidus of arteriovenous malformation causing haemorrhage (n = 1), and lack of perfusion in the supratentorial compartment in a case of suspected brain death (n = 1). CONCLUSIONS: Our short experience but relatively large volume of material encourages the use of ASL in routine neonatal MRI as a useful and non-time-consuming tool providing additional important clinical information in a significant percentage of cases.

Neonatal brain and body imaging in the MR-compatible incubator.

BACKGROUND: The use of a specialized MR-compatible incubator (INC) is very poorly described in the literature and only with regard to brain imaging. OBJECTIVES: To present our own experience with brain and body magnetic resonance imaging (MRI) in the INC in a large cohort of neonates. MATERIAL AND METHODS: A total of 555 examinations were performed in 530 newborns with the use of a 1.5T system and Nomag IC 1.5 incubator, equipped with head and body coils. RESULTS: More than half of neonates (54%) were prematurely born at 22 + 6-36 + 6 gestational weeks. They were examined from the first to 153 days of life (median: 18.5, mean: 37.7) with body weights 600-5000 g (mean: 3051 g), 23% of less than 2500 g. The proportion of brain MRIs to other body regions was 533:85 = 86%:14%. In 36.6% of cases, MRI showed more abnormalities than ultrasound (USG), in a further 21.8%, MRI diagnosis was completely different, in 4.7%, a pathology described on a USG was ruled out on MRI. The superiority of MRI over USG was 63.1%. CONCLUSIONS: MR-compatible incubator significantly increased the availability of MRI to newborns, especially to premature and unstable newborns. The integration of body coils into the INC increased the spectrum of examinations and made possible the scanning not only of the brain but also the body. Dedicated neonatal coils improved image quality and allowed more accurate diagnosis than the previously used adult coils. Immobilization of the babies in the INC by means of Velcro belts and head fixation inserts is better than in adult coils. The closed space of the INC isolates newborns to a greater extent from the negative influence of noise in the MR environment.

Seventeen years of prenatal magnetic resonance imaging at the Institute of Mother and Child in Warsaw.

PURPOSE: The purpose of this paper is to summarise and to present the experience of the main Polish centre for prenatal magnetic resonance imaging (MRI) and to discuss the place and role of MRI in antenatal diagnosis, management, and counselling. MATERIAL AND METHODS: Retrospective analysis of the examinations performed in the years 2001-2017. RESULTS: In total, 1221 medical records and/or image files were collected. The full documentation of ultrasonography and MRI referrals, reports, and images was not available in every case. During the first three years 98 pregnant women were examined (approximately 33 per year, one study per fortnight). After purchase of own MR scanner, the number of examinations grew constantly, reaching 208 in 2017, which means almost one per day, and the highest number was eight in one day. We examined 45 pairs of twins, including three pairs of conjoined twins. CONCLUSIONS: MRI at our Institute is a practically used second-line foetal imaging tool, necessary to confirm, complete, or correct sonographic diagnoses, with important impact on clinical decisions concerning management of pregnancy and of the neonate, termination of pregnancy, choice of the time, place, and mode of delivery, and neonatal care, as well as on counselling. In experienced hands, MRI is to date the last and the best non-invasive method of diagnosis in utero. It is frequently requested by the interdisciplinary team for foetal diagnosis and therapy and routinely performed in everyday practice.

Neuroimaging results, short-term assessment of psychomotor development and the risk of autism spectrum disorder in extremely premature infants (≤28 GA) - a prospective cohort study (preliminary report).

OBJECTIVE: Infants ≤28 GA are at particular risk of psychomotor and neurological developmental disorder. They also remain at a higher risk of developing autism spectrum disorder (ASD), characterized by persistent deficits in communication/social interactions and restricted, repetitive behaviors, activities and interests. Monitoring their development by a team of specialists (a neurologist, psychologist, psychiatrist) allows us to make an early diagnosis and to implement appropriate therapy. Neuroimaging studies during the neonatal period may be helpful in clarifying diagnosis and prognosis. Objective: The aim of the study was to search for the interrelation between the results of neuroimaging and the neurological, psychological and psychiatric evaluation at the age of 2. PATIENTS AND METHODS: Material and methods: Neonates born at ≤28 weeks between 01.06.2013 and 31.12.2015 and hospitalized at NICU were enrolled. We present the results of the first 12 children who have attained 2 years of corrected age and have undergone both neuroimaging, and neurological, psychological and psychiatric assessments. Transfontanel ultrasound was performed according to general standards, MRI between 38 and 42 weeks of corrected age. Neurological examination based on the Denver scale, ASD screening with use of the STAT test and psychological DSR assessment were performed at 2 years of corrected age. RESULTS: Results: Median GA was 26 weeks and median weight 795 g. The ultrasound examination was normal in 9 cases (75%) and MRI in 4 (33%). Abnormalities in the cerebellum were the main additional information found in MRI as compared to US. Neurological examination was normal in 8 infants (67#37;), in 4 of whom neuroimaging was normal. In 4 (33%) infants the neurological examination was abnormal. Psychomotor development at an average level or above was found in seven (58#37;) children. In 4 of them neuroimaging was normal, whereas 3 had ventricular dilatation and haemorrhagic infarct. There were no abnormalities within the cerebellum in this group. In the remaining 5 children (42#37;) psychomotor development was rated as delayed. All of them had cerebellar haemorrhage. An increased risk of ASD was observed in 4 children who developed cerebellar hemorrhage. CONCLUSION: Conclusions: 1. The use of MRI at a term-equivalent age may contribute to the prognosis of neurodevelopmental outcomes in extremely premature infants, allowing risk stratification and thus enhancing early monitoring of a child's development and functional status 2. There is a clear tendency towards abnormal psychomotor development and positive screening for ASD to co-occur with abnormal MRI findings in the cerebellum.

Imaging of Complications After Limb Prostheses Implantation in Children with Bone Tumors.

BACKGROUND: Tumors of the developmental age are an important problem in clinical practice. Primary bone tumors constitute 1-1.5% of all tumors, and 7% of all tumors diagnosed in the developmental age. The aim of the study was to assess the capabilities of imaging methods in diagnosing complications of limb endoprostheses in children with osteoarticular tumors. MATERIAL/METHODS: We included 155 patients with limb endoprostheses, aged 7-26 years. There were 113 patients with knee prostheses, 1 patient with bilateral knee prostheses, 16 patients with shoulder prostheses, 14 patients with hip prostheses, 11 patients with hip and knee prostheses, and 1 patient with a femoral prosthesis. All patients underwent plain radiography and an ultrasound study. RESULTS: Complications were found in 50 patients (32% of all patients). The following complications were seen - inflammatory changes in soft tissues and bones (12 patients, 7.7%), stump fractures (11 patients, 7%), lack of elongation effect or shortening of the prosthesis (7 patients, 4.5%), prosthesis fractures (4 patients, 2.5%), crural fractures (4 patients, 2.5%), loosening of the prosthesis (3 patients, 1.9%), joint dislocation (2 patients, 1.3%), stump and prosthesis fracture (1 patient, 0.6%) and local recurrence (6 patients, 3.9%). Prostheses were exchanged for the following reasons - fractures (5 patients, 3.2%), inflammation (2 patients with 3 exchanges, 1.9%). Local recurrence and inflammation were confirmed by a biopsy. CONCLUSIONS: Radiography and ultrasonography are of crucial importance in monitoring patients after implantation of limb endoprostheses. The findings did not require confirmation in additional studies: CT and MRI. Suspicion of local recurrence and inflammation required a biopsy confirmation.

Diagnostic Imaging of Pregnant Women - The Role of Magnetic Resonance Imaging.

BACKGROUND: Presentation of magnetic resonance imaging (MRI) findings in pregnant women in the Department of Diagnostic Imaging, Institute of Mother and Child, Warsaw, Poland. MATERIAL/METHODS: Forty-three symptomatic pregnant women underwent MRI between 9 and 33 weeks of gestation (mean of 23 weeks). Moreover, we included 2 pregnant women who underwent fetal MRI and had incidental abnormalities. RESULTS: In 9 cases, we excluded the suspected brain abnormalities. In 4 cases, we found unremarkable changes in the brain without clinical significance. One patient was diagnosed with multiple sclerosis, one with cortical dysplasia, one with pineal hemorrhage and one with a brain tumor. On abdominal MRI, 2 patients had normal findings, one patient had colon cancer with a hepatic metastasis, one patient had a hepatic angioma, one patient had an extraadrenal pheochromocytoma, one patient had an abscess in the iliopsoas muscle, 9 patients had myomas, two patients had ovarian simple cysts, two endometrial cysts, three dermoid cysts, one patient had sacrococcygeal teratoma, one patient had a cystadenofibroma (partial borderline tumor), one patient had an androgenic ovarian tumor and two patients had hyperreactio luteinalis. One patient was diagnosed with transient osteoporosis of the hip and one with a stress fracture of the sacral bone. CONCLUSIONS: Magnetic resonance imaging is the best imaging modality for pregnant women. Although ultrasonography is the method of choice, doubtful cases as well as structures that cannot be examined with ultrasonography can be non-invasively evaluated with MRI.

CNS Metastases from Bone and Soft Tissue Sarcomas in Children, Adolescents, and Young Adults: Are They Really So Rare?

Purpose. To check whether primary involvement of brain/spinal cord by bone/soft tissue sarcomas' metastases in children is as rare as described and to present various morphological forms of bone/soft tissue sarcomas' CNS metastases. Methods. Patients with first diagnosis in 1999-2014 treated at single center were included with whole course of disease evaluation. Brain/spinal canal magnetic resonance imaging (MRI)/computed tomography were performed in cases suspicious for CNS metastases. Extension from skull/vertebral column metastases was excluded. Results. 550 patients were included. MRI revealed CNS metastases in 19 patients (incidence 3.45%), 14 boys, aged 5-22 years. There were 12/250 osteosarcoma cases, 2/200 Ewing's sarcoma, 1/50 chondrosarcoma, 3/49 rhabdomyosarcoma (RMS), and 1/1 malignant mesenchymoma. There were 10 single metastases and 7 cases of multiple ones; in 2 RMS cases only leptomeningeal spread in brain and spinal cord was found. Calcified metastases were found in 3 patients and hemorrhagic in 4. In one RMS patient there were numerous solid, cystic, hemorrhagic lesions and leptomeningeal spread. Conclusions. CNS metastases are rare and late in children with bone/soft tissue sarcomas, although in our material more frequent (3.45%) than in other reports (0.7%). Hematogenous spread to brain and hemorrhagic and calcified lesions dominated in osteosarcoma. Ewing sarcoma tended to metastasize to skull bones. Soft tissue sarcomas presented various morphological forms.

Diffusion restriction in the corticospinal tracts and the corpus callosum in neonates after cerebral insult.

BACKGROUND: In neonatal brains diffusion restriction, which is not limited to the region of insult, but is also found in distant locations from it seems to be a frequent finding, called pre-Wallerian degeneration. OBJECTIVES: The purpose of this study was to describe these findings and to estimate the frequency of their occurrence with an attempt to determine their clinical significance. METHODS: 125 brain MRI examinations of neonates with confirmed brain damage performed or consulted in our Institute were retrospectively reviewed, focusing on the presence of restricted diffusion in corticospinal tracts (CST) and corpus callosum (CC). Apparent diffusion coefficients (ADC) were measured in callosal splenium and compared to normal neonatal brains. RESULTS: Restricted diffusion was found in 21 newborns (16.8%): in 4 in CST (3.2%), in 5 in CC (4.0%), in 12 in both (9.6%). Mean ADC value in CC was 0.638, standard deviation (SD): 0.211µm2/s and in the control group 0.995, SD: 0.162µm2/s (p=0,001). CONCLUSIONS: Neonatal brain MRI should be searched for DWI abnormalities which are not rare and require careful studying of ADC maps. Diffusion restriction in the corpus callosum and/or corticospinal tracts below the region of insult should not be mistaken for acute ischemia as it most likely reflects early phase of secondary neuronal degeneration called pre-Wallerian degeneration. This finding helps in prognostication and guides the management of the affected neonates.

Fetal MRI versus postnatal imaging in the MR-compatible incubator.

INTRODUCTION: One of the aims of fetal magnetic resonance imaging (MRI) is to avoid postnatal scanning. However, clinicians sometimes wish to have postnatal confirmation of prenatal findings. This study's purpose was to check whether there was indeed the added value of neonatal MRI performed in the MR-compatible incubator (INC) after fetal examination. MATERIALS AND METHODS: Material consists of 25 neonates (14 girls) who underwent prenatal and postnatal MRI in a 1.5 T scanner, the latter in INC. Mean time of prenatal MRI was 30th gestational week, of postnatal MRI-16th day of life. RESULTS: In 14 cases (56 %) postnatal findings were the same as prenatal ones. In 11 (44 %) postnatal MRI showed some different/new/more precise results, in two the differences were attributed to other factors than the advantage of postnatal MRI over prenatal one. Altogether then postnatal results were partly discordant with prenatal ones in 9/25 cases (36 %). CONCLUSIONS: In most cases there was no added value of postnatal MRI as compared to prenatal one. This value lied in small details that could not have been noticed on prenatal MRI or required contrast medium administration to be noticed. On the other hand, MR examination performed with use of the dedicated neonatal coils in the MR-compatible incubator is a safe and reliable method of visualization of these small details with better spatial resolution thus helping to establish final diagnosis, treatment plan and prognosis.

First Experience with Neonatal Examinations with the Use of MR-Compatible Incubator.

BACKGROUND: Since 2003, very few publications have described brain examinations using neonatal MR-compatible incubator (INC). The authors present their first experience in these examinations, not limited to brain scans, with the use of an incubator equipped not only with head coil, but also with a coil designed for examinations of the spinal canal and spinal cord as well as the whole body, at the Institute of Mother and Child in Warsaw. MATERIAL/METHODS: Examinations were performed in 27 newborns (12 girls, 15 boys). Most of the neonates were prematurely born: 19 (70.4%) were born at gestational age of 23-37 weeks, mean of 30 weeks. They were examined at the corrected age of 26 weeks-1 month, mean of 36 weeks. Body weight of the newborns on the day of the study was 600-4,300 g, mean of 2,654 g. The study was performed with a GE Signa HDxT 1.5 T system with the use of a Nomag IC 1.5 incubator by Lammers Medical Technology Co., equipped with three coils: an eight-channel, phased-array head coil and a twelve-channel phased-array coil for the whole body, consisting of an eight-channel coil integrated in the incubator and a separate four-channel surface coil. RESULTS: Of the 27 children, 25 (92.6%) required a brain scan. Two children (7.4%) were referred to MRI for assessment of the spinal canal and the abdomen. We compared the results of transfontanelle ultrasound and MRI scans in 21 children. MRI provided significantly more diagnostic information in 18 cases (85.7%); in 3 cases (14.3%), no additional knowledge about the pathology was provided by the exam. CONCLUSIONS: The MR-compatible incubator increases the availability of MRI to newborns, especially premature newborns and those with low and extremely low body weight, for whom MR examinations are necessary to determine the extent of changes, not limited to the central nervous system, as well as to establish prognosis. Dedicated neonatal coils integrated with the incubator permit more accurate diagnosis than the previously used adult coils.

Circle of Willis abnormalities in children with neurofibromatosis type 1.

BACKGROUND AND PURPOSE: The aim of the study was to assess anatomical variants and abnormalities in cerebral arteries on magnetic resonance angiography in 67 children with neurofibromatosis type 1 (NF1). MATERIALS AND METHODS: The study included 67 children aged 9 months to 18 years (mean 6.6 years). Control group comprised 90 children aged 2-18 years (mean: 11.8 years). All patients were examined at 1.5T scanner. RESULTS: We found cerebral arteriopathy (moyamoya disease) in one child (1.5%) in the study group. No aneurysms were found. Twenty-nine NF1 children (43.3%) had arterial anatomical variants. In 13 of them, more than one variant was diagnosed (44.8% of group with variants, 19.4% of study group). In control group, 19 children (21.1%) had variants, including four children with more than one variant (21% of group with variants, 4.4% of control group). Arterial variants were more common in NF1 patients compared with control group (p=0.026, binomial test for two proportions). Percentage of multiple variants was higher in study group than in control group, but this difference was not significant. Variants were more frequent on left side than on the right one (significant difference in control group; p=0.022, McNemara test). In study group, the number of left-sided anomalies (25) was similar to that of right-sided ones (22). There was no correlation between gender and variants, unidentified bright objects and variants or between optic gliomas and variants. CONCLUSIONS: Occurrence of arterial variants in NF1 patients was twofold higher than in control group. Multiple variants were more frequent in the study group although the difference did not reach statistical significance. Features of cerebral arteriopathy were found in one child with NF1.

Rhombencephalosynapsis - isolated anomaly or complex malformation?

BACKGROUND: Rhombencephalosynapsis (RES) is a rare malformation of the posterior cranial fossa, characterized by fusion of the cerebellar hemispheres, medial cerebellar peduncles and dentate nuclei. Over the period of 7 years 8 cases of this anomaly have been diagnosed in two pediatric centers in Warsaw including one on the prenatal magnetic resonance imaging (MRI). MATERIAL/METHODS: Material consists of involves one fetus examined at the gestational age of 27 and 33 weeks and 7 children (5 girls and 2 boys) aged 8 months - 16 years. All of them underwent brain MRI with the use of 1.5T scanners. RESULTS: In 1 case RES was an isolated anomaly, in 1 case it was accompanied by hydrocephalus only, in the remaining 6 cases RES was an element of a complex malformation. The additional anomalies were as follows: callosal hypoplasia in 3 children, abnormalities of gyration in 2, brainstem hypoplasia in 2, isolated fourth ventricle in 1, abnormal white matter signal intensity in 4 (in 2 cases in supratentorial compartment, in 1 in the cerebellum and in 1 in the pons), abnormally dilated extraaxial fluid collections in 2, syringohydromyelia in 2. In 5 cases RES was total, in 3 - partial. CONCLUSIONS: Rhombencephalosynapsis has a very characteristic appearance on magnetic resonance imaging which allows diagnosis of this malformation at any age, including prenatal period.

MR images of bone lesions in children treated due to leukemia.

Leukemia is the most frequent malignancy in children (30-40%); acute lymphoblastic leukemia (ALL) accounts for 85% of cases of this leukemia. Apart from bone marrow infiltration, MR imaging reveals other lesions in the bones of these children, that may be a complication of the disease or of its therapy and do not require referral to the oncologist unless they are misinterpreted. These lesions include osteonecrosis, stress fractures due to osteopenia, osteomyelitis - often resulting from administration of corticosteroids. The authors present MR images of these lesions, often misinterpreted as leukemic infiltration.

[Sonography of small bowel, colon and appendix in children with cystic fibrosis]. / Ocena ultrasonograficzna jelita cienkiego, grubego i wyrostka robaczkowego u pacjentów z mukowiscydoza.

AIM: To assess the utility of sonographic examination in estimation of the incidence and character of pathological changes in different parts of the intestine and other abdominal organs in children with cystic fibrosis (CF). MATERIAL AND METHOD: The study group consisted of 182 children (94 girls, 88 boys), aged from 2 months up to 22 yrs, with diagnosed cystic fibrosis or its suspicion, confirmed later. The control group consisted of 20 children with mean age 8 yrs. Sonography was performed with Philips equipment: 4000 HDI and iU 22 using convex, microconvex and linear probes. 329 examinations were performed in 182 children in 2.5 years, 109 underwent second US and 38 patients were examined for the third time. RESULTS: In children with CF, changes in the intestines were observed in 108 patients (59.3%), in the colon in 97 patients (53.3%), and in the small intestine in 49 patients (26.9%). In the control group the wall thickness of large intestine did not surpass 1.6 mm, of small intestine--1.4 mm. In the tested group the maximum thickness of large intestine wall was 7 mm and of small intestine--4.3 mm. Layer structure of the ileum wall was found in 46 children (25%), enlarged appendix in 21 patients (11.6%). Enlarged mesenteric lymph nodes were observed in 84 pts (46%). Hyperaemia of the bowel wall was not observed on Power Doppler examination. In 71 patients (39%) changes in the structure of the liver were observed (cirrhosis, steatosis, enlargement) and in 114 (62.6%) there were changes in the pancreas. CONCLUSIONS: Sonographic examination in patients with cystic fibrosis revealed a high frequency of intestinal changes which confirms the need of including this examination in the annual follow-up of children with CF. In cases of unidentified CF, abdominal sonography leads to the diagnosis.

Brain development of the human fetus in magnetic resonance imaging.

INTRODUCTION: Ultrasonography is the first step in the in vivo evaluation of fetal central nervous system. However, it is not always easy--or even possible--to carry out this examination because of maternal obesity, oligo- or ahydramnios or fetal position. Magnetic resonance imaging becomes then the only method of assessment. Recognition of cerebral and cerebellar abnormalities requires detailed knowledge of normal development and morphology of the fetal brain. AIM: To show the sequence of fetal brain maturation on MR images on the basis of own material and equipment. MATERIAL AND METHOD: Seventy five fetuses without cerebral abnormalities were selected for the analysis of T2-weighted images of the brain obtained with use of GE Signa 1.5T scanners. No maternal sedation was used. Single-Shot Fast Spin Echo sequence (SSFSE) was applied in T2-weighted images in axial, sagittal and coronal planes in all fetuses. Fast Spoiled Gradient Echo (FSPGR) T1-weighted images were also obtained. RESULTS: The sequence of fetal brain maturation during the second half of pregnancy was elaborated and discussed. CONCLUSIONS: Magnetic resonance imaging is the most useful method of the evaluation of normal fetal brain development. It should be used as an additional tool in every case of diagnostic difficulties or uncertainty.

Postradiotherapeutic changes and their evolution in MRI in children with aggressive soft tissue tumors.

BACKGROUND: Magnetic resonance imaging is a commonly used method of monitoring of soft tissue tumours. The aim of the work was to describe precisely the typical changes within soft tissues and bones occurring after radiotherapy in children treated for sarcomas and other soft tissue tumours. With time, the changes undergo evolution and their characteristics and comparison with previous examinations help in a difficult differentiation between tumour lesions and posttherapeutic changes. MATERIAL/METHODS: Fifteen children and young adolescents (9 boys and 6 girls) aged between 2 and 22 years (mean age of 13.4 years) with diagnosed aggressive soft tissue tumours, were treated with radiotherapy. There were 102 MRI examinations analysed in the period from February 2004 to February 2008. The examinations were performed with a 1.5T MRI scanner in the following sequences: SE T1, SE T1+fatsat, before and after gadolinium administration (Gd), FSE T2 and STIR in three planes, and, in some selected cases, a dynamic gadolinium-enhanced (DCE MRI) examination with FAME sequence. HISTOPATHOLOGICAL EXAMINATIONS SHOWED: rhabdomyosarcoma (RMS) in 8 cases, synovial sarcoma - 3, agressive desmoid fibroma - 3, mesenchymoma mal. - 1. MRI examinations were performed at different postradiotherapeutic stages, several times in one patient (12 times at the most). RESULTS: Every postirradiation stage revealed a typical picture of posttherapeutic changes. We distinguished four stages and described changes in different sequences within soft tissues and bones, as well as features of contrast enhancement and enhancement curves in a dynamic study. The stages included: I stage - early, up to 3 months after rth, II stage - chronic, from 3 months to 12 months after rth, with some differences between the following periods: • 3-9 months; 9-12 months; III stage - late, from 1 to 3 years after rth, IV stage - distant, more than 3 years after rth. In the early stage, there were 2 cases with a suspicious, equivocal image of postradiotherapeutic changes. In the chronic stage, there was one recurrence and one case of increasing changes after the therapy. However, the changes resolved in subsequent examinations. In the distant stage, we found two cases of a local recurrence. CONCLUSIONS: 1. MRI is a method of choice in the monitoring of treatment of aggressive soft tissue tumours and in diagnosis of recurrence. 2. To interpret the examination results, it is very important to know the MRI characteristics of changes after radiotherapy and their evolution with time. 3. Interpretation of MRI images and differentiation between postradiotherapeutic and neoplastic changes is difficult, especially at an early postradiotherapeutic stage. 4. A dynamic MRI examination may be useful in the differentiation between postradiotherapeutic and neoplastic changes but it may be unreliable at an early postradiotherapeutic stage. 5. When interpreting the results, it is very important to compare the image with the previous ones. It is therefore indicated to carry out a baseline MRI in the early postradiotherapeutic stage, and then further follow-up images, at several-month intervals.