Paradoxically Decreased Signal Intensity on Postcontrast Short-TR MR Images

Seven lesions are presented in which short TRfshort TE images obtained immediately after IV administration of gadopentetate dimeglumine demonstrated an apparent decrease in signal intensity compared with precontrast short TRfshort TE images. All seven lesions were hyperintense on precontrast short TRfshort TE images. In four cases in which long TRflong TE scans were also obtained, the lesions were hypointense. This phenomenon may be due to a dominant T2 shortening effect by the contrast material that "overwhelms" T1 shortening even on short TRfshort TE scans. Other compounding factors may include variations in scanning variables, receive and transmit attenuations, or a photographic phenomenon due to window widths and center levels. The use of gadopentetate dimeglumine for evaluating CNS disease has become commonplace. With a standard dose of 0.1 mmolfkg , lesions that show contrast enhancement usually become bright on short TRfTE images. The explanation for this phenomenon is the shortening of T1 relaxation by the paramagnetic contrast agent on adjacent protons. As with any dipolar interaction , T2* shortening also occurs; however, its effect is usually inapparent on the short TR/short TE (T1-weighted) scans. We present seven cases in which there was a decrease in signal intensity after IV administration of contrast material in lesions that were hyperintense on precontrast short TR/short TE scans. Materials and Methods In the past 2 years we have observed seven cases in which there appeared to be a decrease in lesion signal intensity on postcontrast short TR (600-850)/short TE (20/30) images compared with precontrast scans. All scans were obtained on high-field 1.5-T scanners. Standard doses of gadopentetate dimeglumine (Magnevist, Berlex Industries , Wayne, NJ) at 0.1 mmolfkg were administered intravenously followed by immediate (i .e. ,< 5 min) postcontrast short TR scans. In three case

Variability in Surgical Treatment of Spondylolisthesis Among Spine Surgeons

Background There are a multitude of treatments for low-grade lumbar spondylolisthesis. There are no clear guidelines for the optimal approach. Objective To identify the surgical treatment patterns for spondylolisthesis among United States spine surgeons. Methods 445 spine surgeons in the United States completed a survey of clinical/radiographic case scenarios on patients with lumbar spondylolisthesis with neurogenic claudication with (S+BP) or without (S−BP) associated mechanical back pain. Treatment options included decompression, laminectomy with posterolateral fusion, posterior lumbar interbody fusion, or none of the above. The primary outcome measure was the probability of 2 randomly chosen surgeons disagreeing on the treatment method. Results There was 64% disagreement (36% agreement) among surgeons for treatment of spondylolisthesis with mechanical back pain (S+BP) and 71% disagreement (29% agreement) for spondylolisthesis without mechanical back pain (S−BP). For S+BP, disagreement was 52% for those practicing 5 to 10 years versus 70% among those practicing more than 20 years. Orthopedic surgeons had greater disagreement than did neurosurgeons (76% vs. 56%) for S+BP. Greater clinical equipoise was seen for S−BP than for S+BP regardless of surgeon characteristics. For spondylolisthesis without mechanical back pain, neurosurgeons were significantly more likely to select decompression-only than were orthopedic surgeons, who more commonly selected fusion. Conclusions Clinical equipoise exists for the treatment of spondylolisthesis. Differences are greater when the patient presents without associated back pain. Surgeon case volume, practice duration, and specialty training influence operative decisions for a given pathologic condition. Recognizing this practice variation will hopefully lead to better evidence and practice guidelines for the optimal and most cost-effective treatment paradigms

Advances in imaging of spinal cord injury: implications for treatment and patient evaluation

Close inspection of MR images in all stages of SCI can reveal alterations which are important for our understanding of the changes which occur in SCI and may be crucial for planning surgical intervention. Importantly also, these observations may assist in the evaluation of novel therapies in SCI, such as cellular transplantation. It is hopeful that MR strategies which are currently in routine use in the brain, such as diffusion weighted imaging, perfusion studies, spectroscopy, and magnetization transfer can be adopted for use in the spine (Schwartz et al., 1999b). Because of the small size of the cord, the magnetic suspectability problems caused by surrounding air and bone, and nearby vascular and CSF flow/pulsations, these techniques are currently very difficult to employ in the cord. They will, however, evolve over time and give us greater insights into the in vivo status of the injured cord