Myelography Using Energy-Integrating Detector CT Versus Photon-Counting Detector CT for Detection of CSF-Venous Fistulas in Patients With Spontaneous Intracranial Hypotension

Abstract

BACKGROUND. CSF-venous fistulas (CVFs), which are an increasingly recognized cause of spontaneous intracranial hypotension (SIH), are often diminutive in size and exceedingly difficult to detect by conventional imaging. OBJECTIVE. This purpose of this study was to compare energy-integrating detector (EID) CT myelography and photon-counting detector (PCD) CT myelography in terms of image quality and diagnostic performance for detecting CVFs in patients with SIH. METHODS. This retrospective study included 38 patients (15 men and 23 women; mean age, 55 ± 10 [SD] years) with SIH who underwent both clinically indicated EID CT myelography (slice thickness, 0.625 mm) and PCD CT myelography (slice thickness, 0.2 mm; performed in ultrahigh-resolution mode) to assess for CSF leak. Three blinded radiologists reviewed examinations in random order, assessing image noise, discernibility of spinal nerve root sleeves, and overall image quality (each assessed using a scale of 0-100, with 100 denoting highest quality) and recording locations of the CVFs. Definite CVFs were defined as CVFs described in CT myelography reports using unequivocal language and having an attenuation value greater than 70 HU. RESULTS. For all readers, PCD CT myelography, in comparison with EID CT myelography, showed higher mean image noise (reader 1: 69.9 ± 18.5 [SD] vs 37.6 ± 15.2; reader 2: 59.5 ± 8.7 vs 49.3 ± 12.7; and reader 3: 57.6 ± 13.2 vs 42.1 ± 16.6), higher mean nerve root sleeve discernibility (reader 1: 81.6 ± 21.7 [SD] vs 30.4 ± 13.6; reader 2: 83.6 ± 10 vs 70.1 ± 18.9; and reader 3: 59.6 ± 13.5 vs 50.5 ± 14.4), and higher mean overall image quality (reader 1: 83.2 ± 20.0 [SD] vs 38.1 ± 13.5; reader 2: 80.1 ± 10.1 vs 72.4 ± 19.8; and reader 3: 57.8 ± 11.2 vs 51.9 ± 13.6) (all p < .05). Eleven patients had a definite CVF. Sensitivity and specificity of EID CT myelography and PCD CT myelography for the detection of definite CVF were 45% and 96% versus 64% and 85%, respectively, for reader 1; 36% and 100% versus 55% and 96%, respectively, for reader 2; and 57% and 100% versus 55% and 93%, respectively, for reader 3. The sensitivity was significantly higher for PCD CT myelography than for EID CT myelography for reader 1 and reader 2 (both p < .05) and was not significantly different between the two techniques for reader 3 (p = .45); for all three readers, specificity was not significantly different between the two modalities (all p > .05). CONCLUSION. In comparison with EID CT myelography, PCD CT myelography yielded significantly improved image quality with significantly higher sensitivity for CVFs (for two of three readers), without significant loss of specificity. CLINICAL IMPACT. The findings support a potential role for PCD CT myelography in facilitating earlier diagnosis and targeted treatment of SIH, avoiding high morbidity during potentially prolonged diagnostic workups.

Keywords: CSF-venous fistula; photon-counting detector CT; spectral CT; spontaneous intracranial hypotension.

Figure 1:

Flow chart showing patient selection process. EID: energy-integrating detector; PCD = photon-counting detector; CVF = CSF-venous fistula; ICHD3 = International Classification of Headache Disorders-3

Figure 2:

59-year-old woman with symptoms of SIH for 1.5 years, with prior temporary symptom relief after fibrin blood patch. (A,B) Images from EID-CT myelogram, performed to assess for CSF leak. (A) Axial image with slice thickness of 0.625 mm. (B) Coronal maximum intensity projection (MIP) image with slice thickness of 6 mm. Nerve root sleeve diverticulum is visualized at right T12 level (arrow, A and B). (C,D) Images from PCD-CT myelogram performed 5 months later; during this interval, patient received no interventions, and symptoms remained similar. (C) Axial image with slice thickness of 0.2 mm. (D) Coronal MIP image with slice thickness of 6 mm. Nerve root sleeve diverticulum is visualized at right T12 level (white arrow, C and D). Course of CVF is also visualized at this level (red arrows, C and D). All images for both examinations were acquired in right lateral decubitus position and are presented in figure with window center of 460 and window width of 1530. CVF was classified as definite based on study criteria. CVF was detected by one reader by EID-CT myelogram and by all three readers by PCD-CT myelogram. Coronal MIP images are shown for illustrative purposes and were not assessed by readers. After PCD-CT myelogram, patient was treated by embolization, leading to symptom relief. SIH = spontaneous intracranial hypotension; EID = energy-integrating detector; PCD = photon-counting detector; CVF = CSF-venous fistula

Figure 3:

57-year-old man with symptoms of SIH for 2 years. (A,B) Images from EID CT myelogram, performed to assess for CSF leak. (A) Axial image with slice thickness of 0.625 mm. (B) Coronal maximum intensity projection (MIP) image with slice thickness of 3.1 mm. Nerve root sleeve diverticulum is visualized at right T14 level (arrow, A and B). (C,D) Images from PCD-CT myelogram performed 1.5 years later; during this interval, patient received no interventions, and symptoms remained similar. (C) Axial image with slice thickness of 0.2 mm. (D) Coronal MIP image with slice thickness of 4 mm. Nerve root sleeve diverticulum is visualized at right T4 level (white arrow, C and D). Course of CVF is also visualized at this level (red arrows, C and D). All images for both examinations were acquired in right lateral decubitus position and are presented in figure with window center of 460 and window width of 1530. CVF was classified as definite based on study criteria. CVF was detected by no reader by EID-CT myelogram and by all three readers by PCD-CT myelogram. Coronal MIP images are shown for illustrative purposes and were not assessed by readers. After PCD-CT myelogram, patient was treated by embolization, leading to symptom relief. SIH = spontaneous intracranial hypotension; EID = energy-integrating detector; PCD = photon-counting detector; CVF = CSF-venous fistula