Patient safety in magnetic resonance imaging

Image acquisition involves the use of static magnetic fields, field gradients and radiofrequency waves. These elements make the MRI a different modality. More and more centers work with 3.0 T equipment that present higher risks for the patient, compared to those of 1.5 T. Therefore, there is a need for updating for radiology staff that allows them to understand the risks and reduce them, since serious and even fatal incidents can occur. The objective of this work is to present a review and update of the risks to which patients are subjected during the performance of a magnetic resonance imaging (MRI) study.

Usefulness of dynamic contrast-enhanced magnetic resonance imaging in characterizing ovarian tumors classified as indeterminate at ultrasonography

OBJECTIVES

To determine whether there is a significant relationship between the shape of the time-intensity curve on dynamic gadolinium-enhanced magnetic resonance imaging (MRI) of ovarian tumors classified as indeterminate at ultrasonography and the type of lesion (benign, borderline, or malignant) to enable an accurate presurgical diagnosis.

MATERIAL AND METHODS

We used dynamic contrast-enhanced MRI to study 68 ovarian tumors that were classified as indeterminate at ultrasonography. We included only cases for which a definitive diagnosis (histologic diagnosis or ≥1 year stability on imaging tests) was available. Each case was classified as benign, borderline, or malignant. To analyze the MRI studies, we marked regions of interest in the lesion and in the myometrium (as a reference). We obtained a curve defined by the relation between the intensity of enhancement and time and classified each tumor according to four predefined curve types. We also analyzed semiquantitative parameters. Finally, we compared the results for each of the three groups of tumors.

RESULTS

We found significant associations (p <0.001) between the curves without early enhancement and benign and borderline lesions as well as between the curves with early enhancement and malignant lesions. Malignant lesions were significantly associated with the semiquantitative enhancement parameters: maximum (p=0.002), maximum relative (p=0.006), and relative (p=0.018).

CONCLUSIONS

In ovarian tumors classified as indeterminate at ultrasonography, dynamic contrast-enhanced MRI can be useful for classification as benign, borderline, or malignant because the malignant lesions are significantly associated with early enhancement curves.

Evaluation of upper tract urothelial carcinomas by contrast-enhanced ultrasound

AIM

To describe the findings and behaviour of contrast-enhanced ultrasound in the study of upper tract urothelial tumours and to assess its usefulness for diagnosis.

MATERIAL AND METHODS

We reviewed our hospital's database over a period of 45 months to identify patients diagnosed with upper tract urothelial carcinomas. We reviewed the findings on mode B-ultrasound, contrast-enhanced ultrasound (location and qualitative assessment of intensity and washout of enhancement), and made a comparison with other techniques (computed tomography or magnetic resonance), and with the surgical specimen.

RESULTS

We found 42 patients with a diagnosis of upper tract urothelial carcinoma confirmed with surgery over the period reviewed. Twenty-eight (67%) patients underwent contrast-enhanced ultrasound. Baseline ultrasound showed hydronephrosis with or without ureteral dilatation with echogenic content occupying the renal calyx (6), pelvis (10) or ureter (12). After injection of contrast, enhancement was noticed in 100% of the lesions, with similar intensity to the cortex in 23, and less in 5. Twenty-four lesions showed early washout, before the cortex, between 40 and 55seconds after the injection. The diagnosis was correct in 27 cases. Localisation coincided with the histological specimen in 28 cases, and 3 patients had additional distal carcinoma foci.

CONCLUSION

Contrast-enhanced ultrasound is a useful technique for diagnosing upper tract urothelial tumours that increases confidence in the diagnosis.

Optimization of the protocols for the use of contrast agents in PET/CT studies

The introduction of PET/CT scanners in clinical practice in 1998 has improved care for oncologic patients throughout the clinical pathway, from the initial diagnosis of disease through the evaluation of the response to treatment to screening for possible recurrence. The CT component of a PET/CT study is used to correct the attenuation of PET studies; CT also provides anatomic information about the distribution of the radiotracer. CT is especially useful in situations where PET alone can lead to false positives and false negatives, and CT thereby improves the diagnostic performance of PET. The use of intravenous or oral contrast agents and optimal CT protocols have improved the detection and characterization of lesions. However, there are circumstances in which the systematic use of contrast agents is not justified. The standard acquisition in PET/CT scanners is the whole body protocol, but this can lead to artifacts due to the position of patients and respiratory movements between the CT and PET acquisitions. This article discusses these aspects from a constructive perspective with the aim of maximizing the diagnostic potential of PET/CT and providing better care for patients.

[Extravasation of contrast media at the puncture site: Strategies for managment]

The incidence of contrast medium extravasation at the venipuncture site has increased with the generalized use of automatic injectors. Most extravasations only cause slight edema and erythema. Nevertheless, in some cases extravasation can result in severe skin lesions or even in compartment syndrome. Lesions caused by extravasation usually resolve spontaneously with conservative treatment. Although the complications of extravasation are well known, institutional protocols are normally lacking and the criteria for taking action and the type of treatment, whether based on the literature or personal preferences, tend to vary. In this article, we review the incidence, risk factors, clinical manifestations, and options for preventing and treating contrast medium extravasation in soft tissues. Finally, we present the protocol we use to manage extravasation at our hospital.