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Background Contrast-unenhanced abdominal CT is the imaging standard for urinary calculi detection; however, studies comparing photon-counting detector (PCD) CT and energy-integrating detector (EID) CT dose-reduction potentials are lacking. Purpose To compare the radiation dose and image quality of optimized EID CT with those of an experimental PCD CT scan protocol including tin prefiltration in patients suspected of having urinary calculi. Materials and Methods This retrospective single-center study included patients who underwent unenhanced abdominal PCD CT or EID CT for suspected urinary caliculi between February 2022 and March 2023. Signal and noise measurements were performed at three anatomic levels (kidney, psoas, and obturator muscle). Nephrolithiasis and/or urolithiasis presence was independently assessed by three radiologists, and diagnostic confidence was recorded on a five-point scale (1, little to no confidence; 5, complete confidence). Reader agreement was determined by calculating Krippendorff α. Results A total of 507 patients (mean age, 51.7 years ± 17.4 [SD]; 317 male patients) were included (PCD CT group, 229 patients; EID CT group, 278 patients). Readers 1, 2, and 3 detected nephrolithiasis in 129, 127, and 129 patients and 94, 94, and 94 patients, whereas the readers detected urolithiasis in 113, 114, and 114 patients and 152, 153, and 152 patients in the PCD CT and EID CT groups, respectively. Regardless of protocol (PCD CT or EID CT) or calculus localization, near perfect interreader agreement was found (α ≥ 0.99; 95% CI: 0.99, 1). There was no evidence of a difference in reader confidence between PCD CT and EID CT (median confidence, 5; IQR, 5-5; P ≥ .57). The effective doses were 0.79 mSv (IQR, 0.63-0.99 mSv) and 1.39 mSv (IQR, 1.01-1.87 mSv) for PCD CT and EID CT, respectively. Despite the lower radiation exposure, the signal-to-noise ratios at the kidney, psoas, and obturator levels were 30%, 23%, and 17% higher, respectively, in the PCD CT group (P < .001). Conclusion Submillisievert abdominal PCD CT provided high-quality images for the diagnosis of urinary calculi; radiation exposure was reduced by 44% with a higher signal-to-noise ratio than with EID CT and with no evidence of a difference in reader confidence. Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Nezami and Malayeri in this issue.
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Tomografía Computarizada por Rayos X , Cálculos Urinarios , Humanos , Masculino , Femenino , Persona de Mediana Edad , Tomografía Computarizada por Rayos X/métodos , Estudios Retrospectivos , Cálculos Urinarios/diagnóstico por imagen , Dosis de Radiación , Adulto , Fotones , Radiografía Abdominal/métodos , AncianoRESUMEN
BACKGROUND. Dual-energy CT pulmonary angiography (CTPA) with energy-integrating detector (EID) technology is limited by the inability to use high-pitch technique. OBJECTIVE. The purpose of this study was to compare the image quality of anatomic images and iodine maps between high-pitch photon-counting detector (PCD) CTPA and dual-energy EID CTPA. METHODS. This prospective study included 117 patients (70 men and 47 women; median age, 65 years) who underwent CTPA to evaluate for pulmonary embolism between March 2022 and November 2022. Fifty-eight patients were randomized to undergo PCD CTPA (pitch, 2.0), and 59 were randomized to undergo EID CTPA (pitch, 0.55). For each examination, 120-kV polychromatic images, 60-keV virtual monogenetic images (VMIs), and iodine maps were reconstructed. One radiologist measured CNR and SNR. Three radiologists independently assessed subjective image quality (on a scale of 1-4, with a score of 1 denoting highest quality). Radiation dose was recorded. RESULTS. SNR and CNR were higher for PCD CTPA than for EID CTPA for polychromatic images and VMIs, for all assessed vessels other than the left upper lobe artery. For example, for PCD CTPA versus EID CTPA, the right lower lobe artery on polychromatic images had an SNR of 34.5 versus 28.0 (p = .003) and a CNR of 29.2 versus 24.4 (p = .001), and on VMIs it had an SNR of 43.2 versus 32.7 (p = .005) and a CNR of 37.4 versus 29.3 (p = .002). For both scanners for readers 1 and 2, the median image quality score for polychromatic images and VMIs was 1, although distributions indicated significantly better scores for PCD CTPA than for EID CTPA for polychromatic images for reader 1 (p = .02) and reader 2 (p = .005) and for VMIs for reader 1 (p = .001) and reader 2 (p = .006). The image quality of anatomic image sets was not different between PCD CTPA and EID CTPA for reader 3 (p > .05). The image quality of iodine maps was not different between PCD CTPA and EID CTPA for any reader (p > .05). For PCD CTPA versus EID CTPA, the CTDIvol was 3.9 versus 4.5 mGy (p = .03), and the DLP was 123.5 mGy × cm versus 157.0 mGy × cm (p < .001). CONCLUSION. High-pitch PCD CTPA provided anatomic images with better subjective and objective image quality versus dual-energy EID CTPA, with lower radiation dose. Iodine maps showed no significant difference in image quality between scanners. CLINICAL IMPACT. CTPA may benefit from the PCD CT technique.
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Yodo , Masculino , Humanos , Femenino , Anciano , Estudios Prospectivos , Fotones , Fantasmas de Imagen , Tomografía Computarizada por Rayos X/métodos , Dosis de RadiaciónRESUMEN
Background Posttraumatic CT imaging of the elbow can be challenging when patient mobility is limited. Gantry-free cone-beam CT (CBCT) with a twin robotic radiography system offers greater degrees of positioning freedom for three-dimensional elbow scans over gantry-based multidetector CT (MDCT), but studies analyzing their clinical value remain lacking. Purpose To investigate the diagnostic performance of gantry-free CBCT versus two-dimensional radiography in adults and children with acute elbow trauma. Materials and Methods In a retrospective study, consecutive patients with elbow trauma and positioning difficulty in a gantry-based MDCT who underwent three-dimensional elbow imaging with a gantry-free CBCT after radiography were enrolled between January 2021 and April 2022 at a tertiary care university hospital. Imaging data sets were independently analyzed for fracture presence, articular involvement, and multi-fragment injuries by three radiologists. Diagnostic performance was calculated individually with surgical reports serving as the reference standard. Differences between radiography and CBCT were compared with the McNemar test. Diagnostic confidence was estimated subjectively by each reader, and results were compared with the Wilcoxon signed-rank test. Results Elbow examinations of 23 adults and children (mean age ± SD, 49 years ± 23; seven women) were included with individual assessment of humerus, radius, and ulna (69 bones; 36 fractured). Multi-fragmentary fracture patterns and involvement of articular surfaces were ascertained in 28 and 30 bones, respectively. CBCT allowed for similar or higher sensitivity compared with radiography in the assessment of fractures (range for three readers, 94%-100% vs 72%-81%; respectively, P ≤ .06-.008), articular surface involvement (90%-97% vs 73%-87%; P ≤ .25), and multi-fragmentary patterns (96%-96% vs 68%-75%; P ≤ .03). Readers' diagnostic confidence improved considerably with access to CBCT data sets versus radiographs (all P ≤ .001). For CBCT, the median dose-length product was 70.9 mGy · cm, and the volume CT dose index was 4.4 mGy. Conclusion In acute elbow injuries, gantry-free cone-beam CT enabled improved detection of fractures, articular involvement, and multi-fragmentary patterns compared with two-dimensional radiography. Published under a CC BY 4.0 license Online supplemental material is available for this article.
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Fracturas Óseas , Procedimientos Quirúrgicos Robotizados , Adulto , Niño , Humanos , Femenino , Dosis de Radiación , Codo , Estudios Retrospectivos , Tomografía Computarizada de Haz Cónico/métodos , Fracturas Óseas/diagnóstico por imagenRESUMEN
OBJECTIVES: While established for energy-integrating detector computed tomography (CT), the effect of virtual monoenergetic imaging (VMI) and iterative metal artifact reduction (iMAR) in photon-counting detector (PCD) CT lacks thorough investigation. This study evaluates VMI, iMAR, and combinations thereof in PCD-CT of patients with dental implants. MATERIAL AND METHODS: In 50 patients (25 women; mean age 62.0 ± 9.9 years), polychromatic 120 kVp imaging (T3D), VMI, T3DiMAR, and VMIiMAR were compared. VMIs were reconstructed at 40, 70, 110, 150, and 190 keV. Artifact reduction was assessed by attenuation and noise measurements in the most hyper- and hypodense artifacts, as well as in artifact-impaired soft tissue of the mouth floor. Three readers subjectively evaluated artifact extent and soft tissue interpretability. Furthermore, new artifacts through overcorrection were assessed. RESULTS: iMAR reduced hyper-/hypodense artifacts (T3D 1305.0/-1418.4 versus T3DiMAR 103.2/-46.9 HU), soft tissue impairment (106.7 versus 39.7 HU), and image noise (16.9 versus 5.2 HU) compared to non-iMAR datasets (p ≤ 0.001). VMIiMAR ≥ 110 keV subjectively enhanced artifact reduction over T3DiMAR (p ≤ 0.023). Without iMAR, VMI displayed no measurable artifact reduction (p ≥ 0.186) and facilitated no significant denoising over T3D (p ≥ 0.366). However, VMI ≥ 110 keV reduced soft tissue impairment (p ≤ 0.009). VMIiMAR ≥ 110 keV resulted in less overcorrection than T3DiMAR (p ≤ 0.001). Inter-reader reliability was moderate/good for hyperdense (0.707), hypodense (0.802), and soft tissue artifacts (0.804). CONCLUSION: While VMI alone holds minimal metal artifact reduction potential, iMAR post-processing enabled substantial reduction of hyperdense and hypodense artifacts. The combination of VMI ≥ 110 keV and iMAR resulted in the least extensive metal artifacts. CLINICAL RELEVANCE: Combining iMAR with VMI represents a potent tool for maxillofacial PCD-CT with dental implants achieving substantial artifact reduction and high image quality. KEY POINTS: ⢠Post-processing of photon-counting CT scans with an iterative metal artifact reduction algorithm substantially reduces hyperdense and hypodense artifacts arising from dental implants. ⢠Virtual monoenergetic images presented only minimal metal artifact reduction potential. ⢠The combination of both provided a considerable benefit in subjective analysis compared to iterative metal artifact reduction alone.
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Artefactos , Implantes Dentales , Humanos , Femenino , Persona de Mediana Edad , Anciano , Reproducibilidad de los Resultados , Metales , Tomografía Computarizada por Rayos X/métodos , AlgoritmosRESUMEN
OBJECTIVE: To evaluate the image quality of an ultra-low contrast medium and radiation dose CT pulmonary angiography (CTPA) protocol for the diagnosis of acute pulmonary embolism using a clinical photon-counting detector (PCD) CT system and compare its performance to a dual-energy-(DE)-CTPA protocol on a conventional energy-integrating detector (EID) CT system. METHODS: Sixty-four patients either underwent CTPA with the novel scan protocol on the PCD-CT scanner (32 patients, 25 mL, CTDIvol 2.5 mGy·cm) or conventional DE-CTPA on a third-generation dual-source EID-CT (32 patients, 50 mL, CTDIvol 5.1 mGy·cm). Pulmonary artery CT attenuation, signal-to-noise ratio, and contrast-to-noise-ratio were assessed as objective criteria of image quality, while subjective ratings of four radiologists were compared at 60 keV using virtual monoenergetic imaging and polychromatic standard reconstructions. Interrater reliability was determined by means of the intraclass correlation coefficient (ICC). Effective dose was compared between patient cohorts. RESULTS: Subjective image quality was deemed superior by all four reviewers for 60-keV PCD scans (excellent or good ratings in 93.8% of PCD vs. 84.4% of 60 keV EID scans, ICC = 0.72). No examinations on either system were considered "non-diagnostic." Objective image quality parameters were significantly higher in the EID group (mostly p < 0.001), both in the polychromatic reconstructions and at 60 keV. The ED (1.4 vs. 3.3 mSv) was significantly lower in the PCD cohort (p < 0.001). CONCLUSIONS: PCD-CTPA allows for considerable reduction of contrast medium and radiation dose in the diagnosis of acute pulmonary embolism, while maintaining good to excellent image quality compared to conventional EID-CTPA. CLINICAL RELEVANCE STATEMENT: Clinical PCD-CT allows for spectral assessment of pulmonary vasculature with high scan speed, which is beneficial in patients with suspected pulmonary embolism, frequently presenting with dyspnea. Simultaneously PCD-CT enables substantial reduction of contrast medium and radiation dose. KEY POINTS: ⢠The clinical photon-counting detector CT scanner used in this study allows for high-pitch multi-energy acquisitions. ⢠Photon-counting computed tomography allows for considerable reduction of contrast medium and radiation dose in the diagnosis of acute pulmonary embolism. ⢠Subjective image quality was rated best for 60-keV photon-counting scans.
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Reducción Gradual de Medicamentos , Embolia Pulmonar , Humanos , Reproducibilidad de los Resultados , Tomografía Computarizada por Rayos X/métodos , Embolia Pulmonar/diagnóstico por imagen , Arteria Pulmonar/diagnóstico por imagen , Fotones , Fantasmas de ImagenRESUMEN
BACKGROUND. Head and neck CT can be limited by dental hardware artifact. Both postprocessing-based iterative metal artifact reduction (IMAR) and virtual monoenergetic imaging (VMI) reconstruction in dual-energy CT (DECT) can reduce metal artifact. Their combination is poorly described for single-source DECT systems. OBJECTIVE. The purpose of this study was to compare metal artifact reduction between VMI, IMAR, and their combination (VMIIMAR) in split-filter single-source DECT of patients with severe dental hardware artifact. METHODS. This retrospective study included 44 patients (nine woman, 35 men; mean age, 66.0 ± 10.4 years) who underwent head and neck CT and had severe dental hardware artifact. Standard, VMI, IMAR, and VMIIMAR images were generated; VMI and VMIIMAR were performed at 40, 70, 100, 120, 150, and 190 keV. ROIs were placed to measure corrected attenuation in pronounced hyperattenuating and hypoattenuating artifacts and artifact-impaired soft tissue and to measure corrected artifact-impaired soft-tissue noise. Two radiologists independently assessed soft-tissue interpretability (1-5 scale), and pooled ratings were analyzed. Readers selected the preferred reconstruction for each patient. RESULTS. Mean hyperattenuating artifact-corrected attenuation was 521.0 HU for standard imaging, 496.4-892.2 HU for VMI, 48.2 HU for IMAR, and 32.8-91.0 HU for VMIIMAR. Mean hypoattenuating artifact-corrected attenuation was -455.1 HU for standard imaging, -408.5 to -679.9 HU for VMI, -37.3 for IMAR, and -17.8 to -36.9 HU for VMIIMAR. Mean artifact-impaired soft tissue-corrected attenuation was 10.8 HU for standard imaging, -0.6 to 24.9 HU for VMI, 4.3 HU for IMAR, and -2.0 to 7.8 HU for VMIIMAR. Mean artifact-impaired soft tissue-corrected noise was 58.7 HU for standard imaging, 38.2 to 129.7 HU for VMI, 11.0 HU for IMAR, and 5.8 to 45.6 HU for VMIIMAR. Median soft-tissue interpretability was 1.2 for standard imaging, 1.1-1.2 for VMI, 3.7 for IMAR, and 2.0-3.8 for VMIIMAR. Artifact-impaired soft tissue-corrected attenuation and soft-tissue interpretability significantly improved (p < .05) for VMIIMAR versus IMAR only at 100 keV. The two readers preferred VMIIMAR at 100 keV in 56.8% and 59.1% of examinations. CONCLUSION. For reducing severe artifact due to dental material, IMAR has greater effect than VMI. Though the results for IMAR and VMIIMAR were similar overall, VMIIMAR had a small benefit at 100 keV. CLINICAL IMPACT. VMI and IMAR techniques in split-filter DECT may be combined for clinical head and neck imaging to reduce artifact from dental hardware and improve image quality.
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Artefactos , Tomografía Computarizada por Rayos X , Anciano , Algoritmos , Femenino , Humanos , Masculino , Metales , Persona de Mediana Edad , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Estudios Retrospectivos , Tomografía Computarizada por Rayos X/métodosRESUMEN
OBJECTIVES: Trauma evaluation of extremities can be challenging in conventional radiography. A multi-use x-ray system with cone-beam CT (CBCT) option facilitates ancillary 3-D imaging without repositioning. We assessed the clinical value of CBCT scans by analyzing the influence of additional findings on therapy. METHODS: Ninety-two patients underwent radiography and subsequent CBCT imaging with the twin robotic scanner (76 wrist/hand/finger and 16 ankle/foot/toe trauma scans). Reports by on-call radiologists before and after CBCT were compared regarding fracture detection, joint affliction, comminuted injuries, and diagnostic confidence. An orthopedic surgeon recommended therapy based on reported findings. Surgical reports (N = 52) and clinical follow-up (N = 85) were used as reference standard. RESULTS: CBCT detected more fractures (83/64 of 85), joint involvements (69/53 of 71), and multi-fragment situations (68/50 of 70) than radiography (all p < 0.001). Six fractures suspected in radiographs were ruled out by CBCT. Treatment changes based on additional information from CBCT were recommended in 29 patients (31.5%). While agreement between advised therapy before CBCT and actual treatment was moderate (κ = 0.41 [95% confidence interval 0.35-0.47]; p < 0.001), agreement after CBCT was almost perfect (κ = 0.88 [0.83-0.93]; p < 0.001). Diagnostic confidence increased considerably for CBCT studies (p < 0.001). Median effective dose for CBCT was 4.3 µSv [3.3-5.3 µSv] compared to 0.2 µSv [0.1-0.2 µSv] for radiography. CONCLUSIONS: CBCT provides advantages for the evaluation of acute small bone and joint trauma by detecting and excluding extremity fractures and fracture-related findings more reliably than radiographs. Additional findings induced therapy change in one third of patients, suggesting substantial clinical impact. KEY POINTS: ⢠With cone-beam CT, extremity fractures and fracture-related findings can be detected and ruled out more reliably than with conventional radiography. ⢠Additional diagnostic information provided by cone-beam CT scans has substantial impact on therapy in small bone and joint trauma. ⢠For distal extremity injury assessment, one-stop-shop imaging without repositioning is feasible with the twin robotic x-ray system.
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Fracturas Óseas , Procedimientos Quirúrgicos Robotizados , Tomografía Computarizada de Haz Cónico , Fracturas Óseas/diagnóstico por imagen , Fracturas Óseas/terapia , Humanos , Radiografía , Rayos XRESUMEN
BACKGROUND AND AIMS: This study aims to compare the performance of first-generation dual-source photon-counting detector computed tomography (PCD-CT) to third-generation dual-source energy-integrating detector (EID-CT) regarding stent imaging in the femoral arterial runoff. METHODS: Continuous extracorporeal perfusion was established in 1 human cadaver using an inguinal and infragenicular access and peristaltic pump. Seven peripheral stents were implanted into both superior femoral arteries by means of percutaneous angioplasty. Radiation dose-equivalent CT angiographies (high-/medium-/low-dose: 10/5/3 mGy) with constant tube voltage of 120 kVp, matching iterative reconstruction algorithm levels, and convolution kernels were used both with PCD-CT and EID-CT. In-stent lumen visibility, luminal and in-stent attenuation as well as contrast-to-noise ratio (CNR) were assessed via region of interest and diameter measurements. Results were compared using analyses of variance and regression analyses. RESULTS: Maximum in-stent lumen visibility achieved with PCD-CT was 94.48% ± 2.62%. The PCD-CT protocol with the lowest lumen visibility (BV40: 78.93% ± 4.67%) performed equal to the EID-CT protocol with the best lumen visibility (BV59: 79.49% ± 2.64%, P > 0.999). Photon-counting detector CT yielded superior CNR compared with EID-CT regardless of kernel and dose level ( P < 0.001). Maximum CNR was 48.8 ± 17.4 in PCD-CT versus 31.28 ± 5.7 in EID-CT (both BV40, high-dose). The theoretical dose reduction potential of PCD-CT over EID-CT was established at 88% (BV40), 83% (BV48/49), and 73% (BV59/60), respectively. In-stent attenuation was not significantly different from luminal attenuation outside stents in any protocol. CONCLUSIONS: With superior lumen visibility and CNR, PCD-CT allowed for noticeable dose reduction over EID-CT while maintaining image quality in a continuously perfused human cadaveric model.
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Fotones , Tomografía Computarizada por Rayos X , Humanos , Fantasmas de Imagen , Tomografía Computarizada por Rayos X/métodos , Stents , CadáverRESUMEN
OBJECTIVES: The aim of this study was to investigate potential benefits of ultra-high resolution (UHR) over standard resolution scan mode in ultra-low dose photon-counting detector CT (PCD-CT) of the lung. MATERIALS AND METHODS: Six cadaveric specimens were examined with 5 dose settings using tin prefiltration, each in UHR (120 × 0.2 mm) and standard mode (144 × 0.4 mm), on a first-generation PCD-CT scanner. Image quality was evaluated quantitatively by noise comparisons in the trachea and both main bronchi. In addition, 16 readers (14 radiologists and 2 internal medicine physicians) independently completed a browser-based pairwise forced-choice comparison task for assessment of subjective image quality. The Kendall rank coefficient ( W ) was calculated to assess interrater agreement, and Pearson's correlation coefficient ( r ) was used to analyze the relationship between noise measurements and image quality rankings. RESULTS: Across all dose levels, image noise in UHR mode was lower than in standard mode for scan protocols matched by CTDI vol ( P < 0.001). UHR examinations exhibited noise levels comparable to the next higher dose setting in standard mode ( P ≥ 0.275). Subjective ranking of protocols based on 5760 pairwise tests showed high interrater agreement ( W = 0.99; P ≤ 0.001) with UHR images being preferred by readers in the majority of comparisons. Irrespective of scan mode, a substantial indirect correlation was observed between image noise and subjective image quality ranking ( r = -0.97; P ≤ 0.001). CONCLUSIONS: In PCD-CT of the lung, UHR scan mode reduces image noise considerably over standard resolution acquisition. Originating from the smaller detector element size in fan direction, the small pixel effect allows for superior image quality in ultra-low dose examinations with considerable potential for radiation dose reduction.
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Fotones , Tomografía Computarizada por Rayos X , Humanos , Fantasmas de Imagen , Tomografía Computarizada por Rayos X/métodos , Pulmón/diagnóstico por imagen , TóraxRESUMEN
PURPOSE: To investigate the metal artifact suppression potential of combining tin prefiltration and virtual monoenergetic imaging (VMI) for osseous microarchitecture depiction in ultra-high-resolution (UHR) photon-counting CT (PCCT) of the lower extremity. METHOD: Derived from tin-filtered UHR scans at 140 kVp, polychromatic datasets (T3D) and VMI reconstructions at 70, 110, 150, and 190 keV were compared in 117 patients with lower extremity metal implants (53 female; 62.1 ± 18.0 years). Three implant groups were investigated (total arthroplasty [n = 48], osteosynthetic material [n = 43], and external fixation [n = 26]). Image quality was assessed with regions of interest placed in the most pronounced artifacts and adjacent soft tissue, measuring the respective attenuation. Additionally, artifact extent, bone-metal interface interpretability and overall image quality were independently evaluated by three radiologists. RESULTS: Artifact reduction was superior with increasing keV level of VMI. While T3D was superior to VMI70keV (p ≥ 0.117), artifacts were more severe in T3D than in VMI ≥ 110 keV (all p ≤ 0.036). Image noise was highest for VMI70keV (all p < 0.001) and lowest for VMI110keV with comparable results for VMI110keV - VMI190keV. Subjective image quality regarding artifacts was superior for VMI ≥ 110 keV (all p ≤ 0.042) and comparable for VMI110keV - VMI190keV. Bone-metal interface interpretability was superior for VMI110keV (all p ≤ 0.001), while T3D, VMI150keV and VMI190keV were comparable. Overall image quality was deemed best for VMI110keV and VMI150keV. Interreader reliability was good in all cases (ICC ≥ 0.833). CONCLUSIONS: Tin-filtered UHR-PCCT scans of the lower extremity combined with VMI reconstructions allow for efficient artifact reduction in the vicinity of bone-metal interfaces.
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Estaño , Tomografía Computarizada por Rayos X , Humanos , Femenino , Reproducibilidad de los Resultados , Tomografía Computarizada por Rayos X/métodos , Prótesis e Implantes , Procesamiento de Imagen Asistido por Computador/métodos , Metales , Artefactos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Relación Señal-Ruido , Estudios RetrospectivosRESUMEN
The goal of this experimental study was to quantify the influence of helical pitch and gantry rotation time on image quality and file size in ultrahigh-resolution photon-counting CT (UHR-PCCT). Cervical and lumbar spine, pelvis, and upper legs of two fresh-frozen cadaveric specimens were subjected to nine dose-matched UHR-PCCT scan protocols employing a collimation of 120 × 0.2 mm with varying pitch (0.3/1.0/1.2) and rotation time (0.25/0.5/1.0 s). Image quality was analyzed independently by five radiologists and further substantiated by placing normed regions of interest to record mean signal attenuation and noise. Effective mAs, CT dose index (CTDIvol), size-specific dose estimate (SSDE), scan duration, and raw data file size were compared. Regardless of anatomical region, no significant difference was ascertained for CTDIvol (p ≥ 0.204) and SSDE (p ≥ 0.240) among protocols. While exam duration differed substantially (all p ≤ 0.016), the lowest scan time was recorded for high-pitch protocols (4.3 ± 1.0 s) and the highest for low-pitch protocols (43.6 ± 15.4 s). The combination of high helical pitch and short gantry rotation times produced the lowest perceived image quality (intraclass correlation coefficient 0.866; 95% confidence interval 0.807-0.910; p < 0.001) and highest noise. Raw data size increased with acquisition time (15.4 ± 5.0 to 235.0 ± 83.5 GByte; p ≤ 0.013). Rotation time and pitch factor have considerable influence on image quality in UHR-PCCT and must therefore be chosen deliberately for different musculoskeletal imaging tasks. In examinations with long acquisition times, raw data size increases considerably, consequently limiting clinical applicability for larger scan volumes.
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Fotones , Humanos , Tomografía Computarizada por Rayos X/métodos , Cadáver , Rotación , Dosis de Radiación , Tomografía Computarizada Espiral/métodosRESUMEN
RATIONALE AND OBJECTIVES: This study investigates the dose burden of photon-counting detector (PCD) lung CT with ultra-high-resolution (UHR) and standard mode using organ-based tube current modulation (OBTCM). MATERIALS AND METHODS: An anthropomorphic Alderson-Rando phantom was scanned in UHR and standard mode with and without OBTCM on three dose levels (IQ 5, 20, 50). Effective radiation dose was determined by thermoluminescent dosimetry in 13 measurement sites and compared with the calculated effective dose derived from the dose-length product. Image quality was evaluated subjectively by six radiologists using an equidistant 7-point scale and objectively by means of modulation transfer function analysis. RESULTS: Measured effective radiation exposure was lower in UHR and OBTCM studies than in standard mode (IQ 5: 0.34-0.36, IQ 20: 1.57-1.70, IQ 50: 3.76-3.99 mSv). Compared with the calculated effective dose, the radiation exposure measured with thermoluminescence dosimetry was 131-170% higher. Noise in UHR mode was rated lower than in standard (all p ≤ 0.042) and OBTCM images (all p ≤ 0.028) for all dose levels, while image sharpness was deemed highest for UHR protocols (all p ≤ 0.042). The use of OBTCM had no significant effect on either dimension of subjective image quality (all p ≥ 0.999). Modulation transfer function analysis confirmed the highest spatial frequency in UHR datasets (all p ≤ 0.016). CONCLUSION: In PCD-CT of the lung, full field-of-view UHR imaging entails no dose disadvantage over standard mode despite superior image quality. OBTCM possesses moderate dose saving potential. Thermoluminescence dosimetry yielded considerably higher effective doses than those calculated from dose-length products.
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BACKGROUND AND AIMS: The aim of this study was to investigate the imaging performance and quality differences of PCD-CT in standard resolution mode (SR) versus ultra-high resolution mode (UHR) in the lower extremity runoff of dose-matched CTAs in a human cadaveric model. METHODS: Extracorporeal perfusion of the upper leg was established in one fresh-frozen human cadaver via inguinal and popliteal accesses using a peristaltic pump. Seven peripheral stents were deployed in the SFA. Photon-counting CTAs were performed under contrast perfusion in SR and UHR mode with dose-equivalent 120kVp acquisition protocols (low-/ medium-/ high-dose: CTDIVol=3, 5, 10 mGy) and reconstructed with four vascular convolution kernels. Lumen visibility and contrast-to-noise ratio were compared using analyses of variance. Subjective image quality was assessed using a pairwise, forced-choice comparison software. RESULTS: Lumen visibility was equal for SR and UHR at the used dose levels. CNR increase by UHR was significant for (ultra-)sharp convolution kernels BV60 (3 mGy; UHR vs. SR, 19.9 ± 1.9 vs. 15.7 ± 1.6, p < 0.046) and BV76 (8.0 ± 0.6 vs. 5.4 ± 0.3, p < 0.001). The relative CNR increase was higher for low-dose than high-dose scans (BV76: 48% vs. 36% at high dose, p < 0.033). The CNR of the low-dose scan in UHR mode was comparable to the high-dose scan in SR mode when the ultra-sharp kernel was used (8.0 ± 0.6 vs. 9.1 ± 1.1, p > 0.760). Among UHR examinations, a significant increase in CNR could only be measured in BV76 (8.0 ± 0.6 (3 mGy) vs. 12.4 ± 0.9 (10 mGy), p < 0.001). Readers preferred subjective image quality of UHR for all kernels with BV76 being ranked highest. CONCLUSION: The CNR increase in UHR mode is highest when combining low radiation dose and ultra-sharp reconstructions. Meanwhile, the subjective image quality in UHR mode generally supersedes SR images, suggesting further dose reduction potential.
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RATIONALE AND OBJECTIVES: This study aims to compare the diagnostic confidence of photon-counting detector CT angiography (PCD-CTA) depending on the used vascular reformatting kernels with digital subtraction angiography (DSA) as diagnostic reference standard in peripheral arterial occlusive disease (PAOD). MATERIAL AND METHODS: In 39 patients, 45 lower extremity PCD-CTA with subsequent DSA were analyzed. Advanced PAOD (Fontaine stage 4) was ascertained in 77.8% of patients. CTA post-processing comprised three vascular kernels (Bv36/48/56). Objective image quality assessment included vessel attenuation, image noise, contrast-to-noise (CNR) and signal-to-noise ratios (SNR). Subjective evaluation of calcium blooming, vessel sharpness, luminal attenuation and image noise was performed by three radiologists. Diagnostic performance and concordance to DSA were assessed. RESULTS: The luminal attenuation remained kernel-independent constant. With sharper kernels, image noise increased substantially, while SNR and CNR decreased. Subjective reduction of calcium blooming and increased vessel sharpness were noted for the sharp Bv56 kernel. While sensitivity in stenosis quantification was comparable between kernels (81.6% vs. 81.5% vs. 81.0%, p = 0.797), specificity increased slightly higher sharpness (71.1% vs. 76.9% vs. 79.6%, p = 0.067). Diagnostic concordance of stenosis ratings compared to DSA increased likewise (Bv36 vs. Bv56, p = 0.002). Severe crural vessel calcifications had no influence on sensitivity, regardless of kernel selection. Contrarily, specificity was substantially worse in severely calcified tibial vessels but could be improved by using the sharp Bv56 kernel (Bv36 vs. Bv56 p = 0.024). Diagnostic confidence was highest for Bv56. CONCLUSION: In lower leg PCD-CTA, sharp convolution kernels increase diagnostic confidence compared to DSA by improved vessel delineation and reduced calcium blooming with acceptable image noise.
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Angiografía de Substracción Digital , Angiografía por Tomografía Computarizada , Enfermedad Arterial Periférica , Sensibilidad y Especificidad , Humanos , Angiografía de Substracción Digital/métodos , Femenino , Masculino , Enfermedad Arterial Periférica/diagnóstico por imagen , Anciano , Angiografía por Tomografía Computarizada/métodos , Persona de Mediana Edad , Anciano de 80 o más Años , Relación Señal-Ruido , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Fotones , AdultoRESUMEN
PURPOSE: The aim of this study was to evaluate the usability of a recently developed extracorporeally-perfused cadaver model for training the angiographic management of acute arterial diseases and periprocedural complications that may occur during endovascular therapy of the lower extremity arterial runoff. MATERIALS AND METHODS: Continuous extracorporeal perfusion was established in three fresh-frozen body donors via inguinal and infragenicular access. Using digital subtraction angiography for guidance, both arterial embolization (e.g., embolization using coils, vascular plugs, particles, and liquid embolic agents) and endovascular recanalization procedures (e.g., manual aspiration or balloon-assisted embolectomy) as well as various embolism protection devices were tested. Furthermore, the management of complications during percutaneous transluminal angioplasty, such as vessel dissection and rupture, were exercised by implantation of endovascular dissection repair system or covered stents. Interventions were performed by two board-certified interventional radiologists and one resident with only limited angiographic experience. RESULTS: Stable extracorporeal perfusion was successfully established on both thighs of all three body donors. Digital subtraction angiography could be performed reliably and resulted in realistic artery depiction. The model allowed for repeatable training of endovascular recanalization and arterial embolization procedures with typical tactile feedback in a controlled environment. Furthermore, the handling of more complex angiographic devices could be exercised. Whereas procedural success was be ascertained for most endovascular interventions, thrombectomies procedures were not feasible in some cases due to the lack of inherent coagulation. CONCLUSION: The presented perfusion model is suitable for practicing time-critical endovascular interventions in the lower extremity runoff under realistic but controlled conditions.
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Procedimientos Endovasculares , Enfermedades Vasculares , Humanos , Procedimientos Endovasculares/métodos , Arterias , Angioplastia/métodos , Stents , Cadáver , Resultado del Tratamiento , Estudios RetrospectivosRESUMEN
RATIONALE AND OBJECTIVES: To assess image quality and radiation dose of ultra-high-pitch CT pulmonary angiography (CTPA) with free-breathing technique for diagnosis of pulmonary embolism using a photon-counting detector (PCD) CT compared to matched energy-integrating detector (EID)-based single-energy CTPA. MATERIALS AND METHODS: Fifty-one PCD-CTPAs were prospectively compared to 51 CTPAs on a third-generation dual-source EID-CT. CTPAs were acquired with an ultra-high-pitch protocol with free-breathing technique (40 mL contrast medium, pitch 3.2) at 140 kV (PCD) and 70-100 kV (EID). Iodine maps were reconstructed from spectral PCD-CTPAs. Image quality of CTPAs and iodine maps was assessed independently by three radiologists. Additionally, CT attenuation numbers within pulmonary arteries as well as signal-to-noise and contrast-to-noise ratios (SNR, CNR) were compared. Administered radiation dose was compared. RESULTS: CT attenuation was higher in the PCD-group (all P < 0.05). CNR and SNR were higher in lobar pulmonary arteries in PCD-CTPAs (P < 0.05), whereas no difference was ascertained within the pulmonary trunk (P > 0.05). Image quality of PCD-CTPA was rated best by all readers (excellent/good image quality in 96.1% of PCD-CTPAs vs. 50.9% of EID-CTPAs). PCD-CT produced no non-diagnostic scans vs. three non-diagnostic (5.9%) EID-CTPAs. Radiation dose was lower with PCD-CT than with EID-CT (effective dose 1.33 ± 0.47 vs. 1.80 ± 0.82 mSv; all P < 0.05). CONCLUSION: Ultra-high-pitch CTPA with free-breathing technique with PCD-CT allows for superior image quality with significantly reduced radiation dose and full spectral information. With the ultra-high pitch, only PCD-CTPA enables reconstruction of iodine maps containing additional functional information.
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This study was designed to investigate the image quality of ultra-high-resolution ankle arthrography employing a photon-counting detector CT. Bilateral arthrograms were acquired in four cadaveric specimens with full-dose (10 mGy) and low-dose (3 mGy) scan protocols. Three convolution kernels with different spatial frequencies were utilized for image reconstruction (ρ50; Br98: 39.0, Br84: 22.6, Br76: 16.5 lp/cm). Seven radiologists subjectively assessed the image quality regarding the depiction of bone, hyaline cartilage, and ligaments. An additional quantitative assessment comprised the measurement of noise and the computation of contrast-to-noise ratios (CNR). While an optimal depiction of bone tissue was achieved with the ultra-sharp Br98 kernel (S ≤ 0.043), the visualization of cartilage improved with lower modulation transfer functions at each dose level (p ≤ 0.014). The interrater reliability ranged from good to excellent for all assessed tissues (intraclass correlation coefficient ≥ 0.805). The noise levels in subcutaneous fat decreased with reduced spatial frequency (p < 0.001). Notably, the low-dose Br76 matched the CNR of the full-dose Br84 (p > 0.999) and superseded Br98 (p < 0.001) in all tissues. Based on the reported results, a photon-counting detector CT arthrography of the ankle with an ultra-high-resolution collimation offers stellar image quality and tissue assessability, improving the evaluation of miniscule anatomical structures. While bone depiction was superior in combination with an ultra-sharp convolution kernel, soft tissue evaluation benefited from employing a lower spatial frequency.
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This study evaluated the influence of different vascular reconstruction kernels on the image quality of CT angiographies of the lower extremity runoff using a 1st-generation photon-counting-detector CT (PCD-CT) compared with dose-matched examinations on a 3rd-generation energy-integrating-detector CT (EID-CT). Inducing continuous extracorporeal perfusion in a human cadaveric model, we performed CT angiographies of eight upper leg arterial runoffs with radiation dose-equivalent 120 kVp acquisition protocols (CTDIvol 5 mGy). Reconstructions were executed with different vascular kernels, matching the individual modulation transfer functions between scanners. Signal-to-noise-ratios (SNR) and contrast-to-noise-ratios (CNR) were computed to assess objective image quality. Six radiologists evaluated image quality subjectively using a forced-choice pairwise comparison tool. Interrater agreement was determined by calculating Kendall's concordance coefficient (W). The intraluminal attenuation of PCD-CT images was significantly higher than of EID-CT (414.7 ± 27.3 HU vs. 329.3 ± 24.5 HU; p < 0.001). Using comparable kernels, image noise with PCD-CT was significantly lower than with EID-CT (p ≤ 0.044). Correspondingly, SNR and CNR were approximately twofold higher for PCD-CT (p < 0.001). Increasing the spatial frequency for PCD-CT reconstructions by one level resulted in similar metrics compared to EID-CT (CNRfat; EID-CT Bv49: 21.7 ± 3.7 versus PCD-CT Bv60: 21.4 ± 3.5). Overall image quality of PCD-CTA achieved ratings superior to EID-CTA irrespective of the used reconstruction kernels (best: PCD-CT Bv60; worst: EID-CT Bv40; p < 0.001). Interrater agreement was good (W = 0.78). Concluding, PCD-CT offers superior intraluminal attenuation, SNR, and CNR compared to EID-CT in angiographies of the upper leg arterial runoff. Combined with improved subjective image quality, PCD-CT facilitates the use of sharper convolution kernels and ultimately bears the potential of improved vascular structure assessability.
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Angiografía por Tomografía Computarizada , Pierna , Humanos , Angiografía por Tomografía Computarizada/métodos , Fantasmas de Imagen , Fotones , Tomografía Computarizada por Rayos X/métodos , AngiografíaRESUMEN
OBJECTIVES: Detailed visualization of the arterial runoff is mandatory for the assessment of peripheral arterial occlusive disease. This study aims to compare the performance of a first-generation photon-counting detector computed tomography (PCD-CT) to a third-generation energy-integrating detector CT (EID-CT). MATERIALS AND METHODS: Computed tomography angiographies of 8 upper leg arterial runoffs were performed on human cadaveric models with continuous extracorporeal perfusion. For both PCD-CT and EID-CT, radiation dose-equivalent 120 kVp acquisition protocols (low-/medium-/high-dose: CTDI Vol = 3/5/10 mGy) were used. All scans were performed with standard collimation (PCD-CT: 144 × 0.4 mm; EID-CT: 96 × 0.6 mm), a pitch factor of 0.4, and a gantry rotation time of 1.0 second. Reformatting of data included the use of comparable vascular kernels (Bv 48/49), a slice thickness and increment of 1.0 mm, and a field of view of 150 × 150 mm. Eight radiologists evaluated image quality independently using a browser-based pairwise forced-choice comparison setup. Kendall concordance coefficient ( W ) was calculated to estimate interrater agreement. Signal-to-noise ratio and contrast-to-noise ratio (CNR) were compared based on 1-way analyses of variance and linear regression analysis. RESULTS: Low-dose PCD-CT achieved superior signal-to-noise ratio/CNR values compared with high-dose EID-CT ( P < 0.001). Linear regression analysis suggested that an EID-CT scan with a CTDI Vol of at least 15.5 mGy was required to match the CNR value of low-dose PCD-CT. Intraluminal contrast attenuation was higher in PCD-CT than EID-CT, irrespective of dose level (415.0 ± 31.9 HU vs 329.2 ± 29.4 HU; P < 0.001). Subjective image quality of low-dose PCD-CT was considered superior to high-dose EID-CT ( P < 0.001). Interrater agreement was high ( W = 0.989). CONCLUSIONS: Using cadaveric models with continuous extracorporeal perfusion allows for intraindividual image quality comparisons between PCD-CT and EID-CT on variable dose levels. With superior luminal contrast attenuation and denoising in angiographies of the peripheral arterial runoff, PCD-CT displayed potential for radiation saving of up to 83% compared with EID-CT.
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Angiografía por Tomografía Computarizada , Tomografía Computarizada por Rayos X , Humanos , Angiografía por Tomografía Computarizada/métodos , Fantasmas de Imagen , Tomografía Computarizada por Rayos X/métodos , Relación Señal-Ruido , Fotones , CadáverRESUMEN
OBJECTIVES: We developed a novel human cadaveric perfusion model with continuous extracorporeal femoral perfusion suitable for performing intra-individual comparison studies, training of interventional procedures and preclinical testing of endovascular devices. Objective of this study was to introduce the techniques and evaluate the feasibility for realistic computed tomography angiography (CTA), digital subtraction angiography (DSA) including vascular interventions, and intravascular ultrasound (IVUS). METHODS: The establishment of the extracorporeal perfusion was attempted using one formalin-fixed and five fresh-frozen human cadavers. In all specimens, the common femoral and popliteal arteries were prepared, introducer sheaths inserted, and perfusion established by a peristaltic pump. Subsequently, we performed CTA and bilateral DSA in five cadavers and IVUS on both legs of four donors. Examination time without unintentional interruption was measured both with and without non-contrast planning CT. Percutaneous transluminal angioplasty and stenting was performed by two interventional radiologists on nine extremities (five donors) using a broad spectrum of different intravascular devices. RESULTS: The perfusion of the upper leg arteries was successfully established in all fresh-frozen but not in the formalin-fixed cadaver. The experimental setup generated a stable circulation in each procedure (ten upper legs) for a period of more than six hours. Images acquired with CT, DSA and IVUS offered a realistic impression and enabled the sufficient visualization of all examined vessel segments. Arterial cannulating, percutaneous transluminal angioplasty as well as stent deployment were feasible in a way that is comparable to a vascular intervention in vivo. The perfusion model allowed for introduction and testing of previously not used devices. CONCLUSIONS: The continuous femoral perfusion model can be established with moderate effort, works stable, and is utilizable for medical imaging of the peripheral arterial system using CTA, DSA and IVUS. Therefore, it appears suitable for research studies, developing skills in interventional procedures and testing of new or unfamiliar vascular devices.