Confidence in Assessment of Lumbar Spondylolysis Using Three-Dimensional Volumetric T2-Weighted MRI Compared With Limited Field of View, Decreased-Dose CT.

BACKGROUND: Limited z-axis-coverage computed tomography (CT) to evaluate for pediatric lumbar spondylolysis, altering the technique such that the dose to the patient is comparable or lower than radiographs, is currently used at our institution. The objective of the study was to determine whether volumetric 3-dimensional fast spin echo magnetic resonance imaging (3D MRI) can provide equal or greater diagnostic accuracy compared with limited CT in the diagnosis of pediatric lumbar spondylolysis without ionizing radiation. HYPOTHESIS: Volumetric 3D MRI can provide equal or greater diagnostic accuracy compared with low-dose CT for pediatric lumbar spondylolysis without ionizing radiation. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 2. METHODS: Three pediatric neuroradiologists evaluated 2-dimensional (2D) MRI, 2D + 3D MRI, and limited CT examinations in 42 pediatric patients who obtained imaging for low back pain and suspected spondylolysis. As there is no gold standard for the diagnosis of spondylolysis besides surgery, interobserver agreement and degree of confidence were compared to determine which modality is preferable. RESULTS: Decreased-dose CT provided a greater level of agreement than 2D MRI and 2D + 3D MRI. The kappa for rater agreement with 2D MRI, 2D + 3D MRI, and CT was 0.19, 0.32, and 1.0, respectively. All raters agreed in 31%, 40%, and 100% of cases with 2D MRI, 2D + 3D MRI, and CT. Lack of confidence was significantly lower with CT (0%) than with 2D MRI (30%) and 2D + 3D MRI (25%). CONCLUSION: For diagnosing spondylolysis, radiologist agreement and confidence trended toward improvement with the addition of a volumetric 3D MRI sequence to standard 2D MRI sequences compared with 2D MRI alone; however, agreement and confidence remain significantly greater using decreased-dose CT when compared with either MRI acquisition. CLINICAL RELEVANCE: Decreased-dose CT of the lumbar spine remains the optimal examination to confirm a high suspicion of spondylolysis, with dose essentially equivalent to radiographs. If clinical symptoms are not classic for spondylolysis, 2D MRI is still very good at detecting spondylolysis while remaining sensitive for detection of alternative diagnoses such as disc abnormalities and pars stress reaction. The data suggest that standard 2D MRI sequences should not be entirely replaced by a volumetric T2-weighted 3D sequence (despite promising features of rapid acquisition time, increased spatial resolution, and reconstruction capability).

Gemcitabine-induced radiation recall myositis.

Radiation recall is an uncommon phenomenon in which administration of a chemotherapeutic agent induces an acute inflammatory reaction in previously irradiated tissues, often weeks to years after completion of radiotherapy. This entity is well known to medical and radiation oncologists, however only three cases have been reported in radiology journals. We present a case of gemcitabine-induced radiation recall that manifested as myositis with associated dermatitis in the posterior thigh of a patient with remote history of localized radiotherapy for biopsy-proven breast cancer metastasis. We also present a brief literature review to update the topic of radiation recall in imaging, and emphasize the importance of knowledge of this phenomenon when considering the differential diagnosis of myositis/dermatitis in a patient who has received cancer treatment.