Contrast dynamics during CT pulmonary angiogram: analysis of an inspiration associated artifact.

OBJECTIVE: Several artifacts have been observed during contrast-enhanced CT of the pulmonary arteries. We describe a physiological artifact caused by a transient interruption of the contrast column in the pulmonary arteries associated with inspiration immediately prior to imaging. This results from a variable inflow of unopacified blood from the inferior vena cava (IVC). MATERIALS AND METHODS: From 327 consecutive pulmonary CT-angiograms, all performed on a single detector scanner at 3 mm collimation (1.5 mm incremental reconstruction), 50 positive studies, 46 indeterminate studies, and 33 negative studies (129 exams) were retrospectively reviewed by a blinded observer to determine the frequency of the described contrast interruption, its severity (mild, moderate, or severe), and its possible contribution to misinterpretation of studies. The numerical change in Hounsfield units was assigned within the right ventricular chamber for each examination to correlate with the subjective evaluation of severity. Statistical significance was determined with P = 0.05%. RESULTS: The artifact was present in 48 (37.2%) of the 129 evaluated studies. It was greater in frequency (50.0%) with the negative studies. The presence was 25% with positive studies and 36.7% with indeterminate exams. The interruption was more often mild (<100 HU change) in severity (45.8%). Three (6.6%) definite false positives were detected where the misinterpretation was directly attributed to the artifact. Three (6.6%) other examinations called positive were also directly related to the interrupted contrast column. However, since no further pulmonary vascular evaluation was performed, these examinations can only be considered indeterminate. Two of the latter 3 studies demonstrated a severe (>150 HU change) and the other study demonstrated a moderate (100-150 HU) interruption of contrast opacification. CONCLUSIONS: During inspiration, there is a variable increase in unopacified venous blood from the IVC, briefly diluting the contrast column entering from the SVC. This interruption is common, though usually mild in severity. However, a short severe interruption of vascular opacification can lead to misinterpretation as a pulmonary embolus or contribute to an indeterminate examination.

Selective dorsal rhizotomy in children with spastic hemiparesis.

OBJECT: Neurological conditions including cerebral palsy, brain injury, and stroke often result in severe spasticity, which can lead to significant deformity and interfere with function. Treatments for spasticity include oral medications, intramuscular botulinum toxin type A injections, orthopedic surgeries, intrathecal baclofen pump implantation, and selective dorsal rhizotomy (SDR). Selective dorsal rhizotomy, which has been well studied in children with spastic diplegia, results in significant reduction in spasticity and improved function in children. To the authors' knowledge, there are no published outcome data for SDR in patients with spastic hemiparesis. The object of this study was to examine the effects of SDR on spastic hemiparesis. METHODS: A 2-year study was undertaken including all children with spastic hemiparesis who underwent SDR at the authors' institution. The degree of spasticity, as measured by the Modified Ashworth Scale or quality of gait rated using the visual gait assessment scale, the gait parameters, and velocity were compared in patients before and after undergoing SDR. RESULTS: Thirteen children (mean age 6 years 7 months) with spastic hemiparesis underwent SDR performed by the same surgeon during a 2-year period. All of the patients had a decrease in tone in the affected lower extremity after the procedure. The mean reduction in tone in 4 muscle groups (hip adductors, knee flexors, knee extensors, and ankle plantar flexors) according to the modified Ashworth scale score was 2.6 ± 1.26 (p < 0.0001). The quality of gait was assessed in 7 patients by using the visual gait assessment scale. This score improved in 6 patients and remained the same in 1. Stride length and gait velocity were measured in 4 children. Velocity increased in 3 patients and decreased in a 3-year-old child. Parents and clinicians reported an improvement in quality of gait after the procedure. Stride length increased bilaterally in 3 patients and increased on one side and decreased on the other in the other patient. CONCLUSIONS: Selective dorsal rhizotomy showed efficacy in the treatment of spastic hemiparesis in children. All of the patients had decreased tone after SDR as measured by the modified Ashworth scale. The majority of patients had qualitative and quantitative improvements in gait.