A review of applications of MRI in soft tissue and bone tumors

Safe magnetic resonance imaging on biocompatible nanoformulations

Magnetic resonance imaging (MRI) holds promise for the early clinical diagnosis of various diseases, but most clinical MR techniques require the use of a contrast medium. Several nanomaterial (NM) mediated contrast agents (CAs) are widely used as T1- and T2-based MR contrast agents for clinical and non-clinical applications. Unfortunately, most NM-based CAs are toxic or non-biocompatible, restricting their practical/clinical applications. Therefore, the development of nontoxic and biocompatible CAs for clinical MRI diagnosis is highly desired. To this end, several biocompatible and biomimetic strategies have been developed to offer long blood circulation time, significant biocompatibility, in vivo biodistribution and high contrast ability for efficient imaging. However, detailed review reports on biocompatible NMs, specifically for MR imaging have not yet been summarized. Thus, in the present review we summarize  various surface coating strategies (such as polymers, proteins, cell membranes, etc.) to achieve biocompatible NPs, providing a detailed discussion of advances and future prospects for safe MRI imaging.

Compact bunker shielding assessment for 1.5 T MR-Linac

This study evaluated the effect of the 1.5 T magnetic field of the magnetic resonance-guided linear accelerator (MR-Linac) on the radiation leakage doses penetrating the bunker radiation shielding wall. The evaluated 1.5 T MR-Linac Unity system has a bunker of the minimum recommended size. Unlike a conventional Linac, both primary beam transmission and secondary beam leakage were considered independently in the design and defined at the machine boundary away from the isocenter. Moreover, additional shielding was designed considering the numerous ducts between the treatment room and other rooms. The Linac shielding was evaluated by measuring the leakage doses at several locations. The intrinsic vibration and magnetic field were inspected at the proposed isocenter of the system. For verification, leakage doses were measured before and after applying the magnetic field. The intrinsic vibration and magnetic field readings were below the permitted limit. The leakage dose (0.05–12.2 µSv/week) also complied with internationally stipulated limits. The special shielding achieved a five-fold reduction in leakage dose. Applying the magnetic field increased the leakage dose by 0.12 to 4.56 µSv/week in several measurement points, although these values fall within experimental uncertainty. Thus, the effect of the magnetic field on the leakage dose could not be ascertained.

Periosteal osteosarcoma of the calcaneum: a case report

A 30-year-old woman presented with a 6-month history of pain and swelling over the sole of her right foot. Plain radiograph showed a calcified mass in the heel pad, which appeared to be arising from the spur on inferior aspect of calcaneum. Magnetic resonance imaging showed a lesion, hypointense on T1-weighted and hyperintense on T2-weighted images over the plantar aspect of the foot. Open biopsy of the mass was indicative of periosteal osteosarcoma, the variety that has never been reported in calcaneum. Below-knee amputation was done with no recurrence or distance metastasis seen at 24 months of follow up.

Errors in the MRI evaluation of musculoskeletal tumors and tumorlike lesions

Interpretation of an MRI of a suspected musculoskeletal neoplasm can be extremely difficult. Fifty-six MRIs originally evaluated by outside radiologists were independently evaluated by an expert panel consisting of three specialized musculoskeletal radiologists. The outside reports were then graded based upon accuracy and completeness of the differential diagnosis. We compared the expert opinions with those of the outside radiologists. According to the expert panel, only 30 of the 56 (54%) outside reports listed the most likely diagnosis as such and only 35 (63%) listed it at all. A complete appropriate differential diagnosis was listed in only 22 (39%) of the outside reports. Furthermore, 18 (32%) of the outside reports listed diagnoses judged to be extremely unlikely by the experts. In a subset of 15 patients with images that the expert panel had judged diagnostic of specific entities, only nine of the outside reports listed the correct diagnosis as such and only 10 listed it at all. Furthermore, 11 (73%) of the outside reports listed extremely unlikely possibilities for these diagnostic images. We found a substantial difference between the expert and the outside opinions.

Prospective evaluation of soft tissue masses and sarcomas using fluorodeoxyglucose positron emission tomography

BACKGROUND

The differentiation of soft tissue sarcoma (STS) from benign masses is difficult owing to their clinical and radiological similarities. Accurate staging is hindered by the large number of sites at which metastases may be found. This study examined the value of whole-body [18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) in patients presenting with soft tissue masses.

METHODS

Thirty patients with a soft tissue mass suspected to be malignant were evaluated with FDG PET. The images were evaluated qualitatively and quantitatively for uptake of FDG to determine whether benign lesions could be differentiated from malignant tumours, and for the presence of metastases.

RESULTS

Thirty-one masses were removed from 30 patients; 12 were benign and 19 were malignant STSs. Using qualitative assessment of the FDG PET images, all the high-grade STSs (n = 12) were correctly identified, but low-grade STS (n = 7) could not be differentiated from a benign lesion. Using a quantification assessment, there was a 95 per cent sensitivity and a 75 per cent specificity in diagnosing STS. Three patients had metastases at presentation; two were correctly identified by FDG PET.

CONCLUSION

FDG PET has a role in distinguishing high-grade STS from low-grade or benign STS and may have a role in staging malignant tumours.

The use of MRI in the diagnosis of benign and malignant bone and soft tissue tumours

Two hundred and thirty four suspected primary bone and soft tissue tumours were investigated using plain films and MRI. The MR appearance of 200 of these tumours was assessed with respect to the intensity of the lesion, the homogeneity of the tumour, the presence or absence of a capsule or lobulation, whether the tumour was whorled or not and whether it contained either fluid or blood. Apart from benign lipomas and some malignant myxoid liposarcomas, however, it seemed virtually impossible to tell one tumour from another and in many cases to differentiate a benign lesion from a malignant tumour using MRI alone. We recommend that the workup of a suspected soft tissue tumour should be initially by MR scanning and that the workup of a suspected malignant bone tumour should be plain films followed by an MRI scan.

Magnetic resonance imaging of myxoid containing tumors

Myxoid tissue forms part of many benign and malignant soft-tissue tumors. The advent of percutaneous needle biopsy has made it important to be aware of the diagnostic implications of biopsy samples containing myxoid tissue. To determine whether the magnetic resonance imaging (MRI) characteristics could help establish the diagnosis, we compared the MR images of 11 tumors containing myxoid tissue with the resected tumor tissue. In our small series of these rare tumors, the MRI characteristics allowed differentiation of intramuscular myxomas from malignant neoplasms containing myxoid tissue. Intramuscular myxomas meet the following conditions: (a) they are well circumscribed; (b) they arise within muscle; (c) T1-weighted images demonstrate uniform, decreased signal intensity; (d) T2-weighted images demonstrate uniform increased signal intensity; (e) contrast-enhanced images exhibit an inhomogeneous increase in signal intensity. If any of these conditions is not met, then a malignancy containing myxoid tissue should be suspected.