The postsurgical spine. / La columna poscirugía.

Failed back surgery syndrome is the persistence or reappearance of pain after surgery on the spine. This term encompasses both mechanical and nonmechanical causes. Imaging techniques are essential in postoperative follow-up and in the evaluation of potential complications responsible for failed back surgery syndrome. This review aims to familiarize radiologists with normal postoperative changes and to help them identify the pathological imaging findings that reflect failed back surgery syndrome. To interpret the imaging findings, it is necessary to know the type of surgery performed in each case and the time elapsed since the intervention. In techniques used to fuse the vertebrae, it is essential to evaluate the degree of bone fusion, the material used (both its position and its integrity), the bone over which it lies, the interface between the implant and bone, and the vertebral segments that are adjacent to metal implants. In decompressive techniques it is important to know what changes can be expected after the intervention and to be able to distinguish them from peridural fibrosis and the recurrence of a hernia. It is also crucial to know the imaging findings for postoperative infections. Other complications are also reviewed, including arachnoiditis, postoperative fluid collections, and changes in the soft tissues adjacent to the surgical site.

Comparison of image quality and radiation dose in computed tomography angiography of the peripheral arteries using tube voltage of 80 kV versus 100 kV.

OBJECTIVE: To compare the image quality and dose of radiation in two groups of patients undergoing CT angiography of the lower limbs, one with tube voltage of 80 kV and the other with tube voltage of 100 kV. MATERIAL AND METHODS: We performed CT angiography of the lower limbs in 60 patients with suspected peripheral arterial disease. Patients were randomly assigned to one of two groups; in one group, CT angiography was performed using a tube voltage of 80kV, whereas in the other it was performed using 100 kV. The remaining acquisition parameters were the same in both groups. The images were analyzed by quantifying vascular density (VD) and noise (N) and by calculating the quotients density/noise (QVDN) and contrast/noise (QCN). Two radiologists working independently evaluated the subjective quality of the images. We calculated the estimated effective dose (EED) based on the dose-length product (DLP). RESULTS: In the group studied at 80 kV, VD was significantly higher (462.5 UH ± 95.6 vs. 372 UH ± 100.9; P<.001), QVDN was significantly higher (241.9 ± 48.1 vs. 194.3 ± 49.6; P<.001), and there were trends toward higher N (21.3 UH ± 13 vs. 16.3 UH ± 3.5; P=.098) and toward higher QCN (21.4 ± 12.1 vs. 22.9 ± 9.1; P=.15). No significant differences were found in the subjective quality of the images. The EED was significantly lower in the group studied at 80 kV (4.73 mSv ± 1.1 vs. 9.6 mSv ± 2.2; P<.001). CONCLUSION: Using 80 kV instead of 100 kV for CT angiography of the lower limbs reduces the dose of radiation without affecting the diagnostic efficacy of the study.

Strengths, weaknesses, opportunities, and threat analysis of dual-energy CT in head and neck imaging.

Technological development of dual-energy computed tomography (DECT) can play an important role in head and neck area. Multiple innovative applications have evolved, optimizing images, achieving metallic artifact reduction, differentiating materials with better primary tumor delineation, thyroid cartilage and bone invasion. Furthermore, quantification algorithms allow measuring iodine concentration, reflecting the blood supply of a lesion indirectly. DECT enables acquiring images with lower radiation doses and iodine intravenous contrast load to obtain the same CT values.. However, DECT uses ionizing radiation, which does not occur with MRI, and requires long post-processing times. Artifacts on iodine maps may be a potential source of pseudolesions. Besides, photon-counting CT scanners are a promising technique that may displace some DECT advantages. A review analyzing the current status of DECT applied to head and neck imaging from the scope of strengths, weaknesses, opportunities, and threatsanalysis would be very interesting to facilitate a realistic, fact-based, data-driven look of this technique.

Ultralow-dose CT of the petrous bone using iterative reconstruction technique, tin filter and high resolution detectors allows an adequate assessment of the petrous bone structures.

OBJECTIVES: To assess image quality and radiation dose in computed tomography (CT) studies of the petrous bone done with a scanner using a tin filter, high-resolution detectors, and iterative reconstruction, and to compare versus in studies done with another scanner without a tin filter using filtered back projection reconstruction. MATERIAL AND METHODS: Thirty two patients (group 1) were acquired with an ultra-low dose CT (32-MDCT, 130kV, tin filter and iterative reconstruction). Images and radiation doses were compared to 36 patients (group 2) acquired in a 16-MDCT (120kV and filtered back-projection). Muscle density, bone density, and background noise were measured. Signal-to-noise ratio (SNR) was calculated. To assess image quality, two independent radiologists subjectively evaluated the visualization of the different structures of the middle and inner ear (0=not visualized, 3=perfectly identified and delimited). Interobserver agreement was calculated. Effective dose at different anatomical levels with the dose-length product was recorded. RESULTS: In the quantitative analysis, there were no significant differences in image noise between the two groups. In the qualitative analysis, a similar or slightly lower subjective score was obtained in the delimitation of different structures of the ossicular chain and cochlea in the 32-MDCT, compared to 16-MDCT, with statistically significant differences. Mean effective dose (±standard deviation) was 0.16±0.04mSv for the 32-MDCT and 1.25±0.30mSv for the 16-MDCT. CONCLUSIONS: The use of scanners with tin filters, high-resolution detectors, and iterative reconstruction allows to obtain images with adequate quality for the evaluation of the petrous bone structures with ultralow doses of radiation (0.16±0.04mSv).

Brain CT requests from emergency department: Reality.

OBJECTIVES: To evaluate the most common reasons for requesting brain CT studies from the emergency department and to calculate the prevalence of urgent acute pathology on this population group. MATERIAL AND METHODS: We reviewed brain CT studies requested from the emergency department during October and November 2018. We recorded the following variables: age, sex, reason for requesting the study, CT findings, use of contrast agents and reasons for using them, and, in patients who had undergone previous head CT studies, whether the findings had changed. SPSS was used for statistical analyses. RESULTS: A total of 507 urgent brain CT studies were done (41.4% in men, 58.6% in women; mean age, 65.4±20 years). The most common reason for requesting the study was head trauma (40.5%); only 15.6% of these studies showed acute posttraumatic intracranial lesions. The second most common reason was focal neurologic symptoms (16%); only 16% of these studies showed recent ischemic infarcts or acute bleeding. No pathological findings were reported in 43.2% of the studies. The most common abnormal finding was ischemic lesions in small vessels (20%). Space-occupying lesions (both benign and malignant) were found in 3.9% of all patients. CONCLUSIONS: Most brain CT studies requested from the emergency department showed no findings that would modify the management of the patient. Overuse of urgent brain CT increases the radiology department's workload and exposes patients to radiation unnecessarily.

Ultralow-dose CT of the petrous bone using iterative reconstruction technique, tin filter and high resolution detectors allows an adequate assessment of the petrous bone structures. / La tomografía computarizada de peñascos con dosis ultrabaja, utilizando filtro de estaño, detectores de alta resolución y reconstrucción iterativa, permite una adecuada valoración de las estructuras del peñasco.

OBJECTIVES: To assess image quality and radiation dose in computed tomography (CT) studies of the petrous bone done with a scanner using a tin filter, high-resolution detectors, and iterative reconstruction, and to compare versus in studies done with another scanner without a tin filter using filtered back projection reconstruction. MATERIAL AND METHODS: Thirty two patients (group 1) were acquired with an ultra-low dose CT (32-MDCT, 130 kV, tin filter and iterative reconstruction). Images and radiation doses were compared to 36 patients (group 2) acquired in a 16-MDCT (120 kV and filtered back-projection). Muscle density, bone density, and background noise were measured. Signal-to-noise ratio (SNR) was calculated. To assess image quality, two independent radiologists subjectively evaluated the visualization of the different structures of the middle and inner ear (0 = not visualized, 3 = perfectly identified and delimited). Interobserver agreement was calculated. Effective dose at different anatomical levels with the dose-length product was recorded. RESULTS: In the quantitative analysis, there were no significant differences in image noise between the two groups. In the qualitative analysis, a similar or slightly lower subjective score was obtained in the delimitation of different structures of the ossicular chain and cochlea in the 32-MDCT, compared to 16-MDCT, with statistically significant differences. Mean effective dose (± standard deviation) was 0.16 ± 0.04 mSv for the 32-MDCT and 1.25 ± 0.30 mSv for the 16-MDCT. CONCLUSIONS: The use of scanners with tin filters, high-resolution detectors, and iterative reconstruction allows to obtain images with adequate quality for the evaluation of the petrous bone structures with ultralow doses of radiation (0.16±0.04 mSv).

Brain CT requests from emergency department: reality. / Tomografía computarizada cerebral solicitada desde Urgencias: la realidad.

OBJECTIVES: To evaluate the most common reasons for requesting brain CT studies from the emergency department and to calculate the prevalence of urgent acute pathology on this population group. MATERIAL AND METHODS: We reviewed brain CT studies requested from the emergency department during October and November 2018. We recorded the following variables: age, sex, reason for requesting the study, CT findings, use of contrast agents and reasons for using them, and, in patients who had undergone previous head CT studies, whether the findings had changed. SPSS was used for statistical analyses. RESULTS: A total of 507 urgent brain CT studies were done (41.4% in men, 58.6% in women; mean age, 65.4±20 years). The most common reason for requesting the study was head trauma (40.5%); only 15.6% of these studies showed acute posttraumatic intracranial lesions. The second most common reason was focal neurologic symptoms (16%); only 16% of these studies showed recent ischemic infarcts or acute bleeding. No pathological findings were reported in 43.2% of the studies. The most common abnormal finding was small vessel disease (20%). Space-occupying lesions (both benign and malignant) were found in 3.9% of all patients. CONCLUSIONS: Most brain CT studies requested from the emergency department showed no findings that would modify the management of the patient. Overuse of urgent brain CT increases the radiology department's workload and exposes patients to radiation unnecessarily.

Should susceptibility-weighted imaging be included in the basic protocol for magnetic resonance imaging of the brain? / ¿Se debe incluir la secuencia de susceptibilidad magnética en el protocolo de resonancia magnética cerebral básico?

OBJECTIVE: To analyze the clinical impact of routine acquisition of susceptibility-weighted imaging (SWI) in magnetic resonance imaging (MRI) studies of the brain. MATERIAL AND METHODS: This prospective observational study included all patients undergoing brain MRI including SWI during a 6-month period. Patients were divided into two groups based on the clinical information provided: Group 1 comprised patients in whom SWI acquisition formed part of the brain MRI protocol, and Group comprised patients who underwent SWI without these sequences being included in the protocol. We recorded patients' age, sex, and risk factors (hypertension, history of brain trauma or intracranial vascular malformations). We analyzed the SWI findings, whether these findings were visible on the other sequences, and whether identifying these findings resulted in substantial changes to the radiological report. RESULTS: There were 62 patients in Group 1 and 79 in Group 2. The groups were similar in age and risk factors. SWI findings resulted in substantial changes to the radiological report in 34% of the patients in Group 1 and in 14% of those in Group 2; this difference was statistically significant. CONCLUSION: SWI can help radiologists detect findings not seen on conventional brain MRI that sometimes result in substantial changes to the radiological report.