Standard Low-dose Protocol Research Articles

Pulmonary nodule visualization and evaluation of AI-based detection at various ultra-low-dose levels using photon-counting detector CT.

Radiation dose should be as low as reasonably achievable. With the invention of photon-counting detector computed tomography (PCD-CT), the radiation dose may be considerably reduced. To evaluate the potential of PCD-CT for dose reduction in pulmonary nodule visualization for human readers as well as for computer-aided detection (CAD) studies. A chest phantom containing pulmonary nodules of different sizes/densities (range 3-12 mm and -800-100 HU) was scanned on a PCD-CT with standard low-dose protocol as well as with half, quarter, and 1/40 dose (CTDIvol 0.4-0.03 mGy). Dose-matched scans were performed on a third-generation energy-integrating detector CT (EID-CT). Evaluation of nodule visualization and detectability was performed by two blinded radiologists. Subjective image quality was rated on a 5-point Likert scale. Artificial intelligence (AI)-based nodule detection was performed using commercially available software. Highest image noise was found at the lowest dose setting of 1/40 radiation dose (eff. dose = 0.01mSv) with 166.1 ± 18.5 HU for PCD-CT and 351.8 ± 53.0 HU for EID-CT. Overall sensitivity was 100% versus 93% at standard low-dose protocol (eff. dose = 0.2 mSv) for PCD-CT and EID-CT, respectively. At the half radiation dose, sensitivity remained 100% for human reader and CAD studies in PCD-CT. At the quarter radiation dose, PCD-CT achieved the same results as EID-CT at the standard radiation dose setting (93%, P = 1.00) in human reading studies. The AI-CAD system delivered a sensitivity of 93% at the lowest radiation dose level in PCD-CT. At half dose, PCD CT showed pulmonary nodules similar to full-dose PCD, and at quarter dose, PCD CT performed comparably to standard low-dose EID CT. The CAD algorithm is effective even at ultra-low doses.

Low-Dose CT for Renal Calculi Detection Using Spectral Shaping of High Tube Voltage.

To investigate reduction of radiation exposure in unenhanced CT in suspicion of renal calculi using a tin-filtered high tube voltage protocol compared to a standard low-dose protocol without spectral shaping. A phantom study using 7 human renal calculi was performed to test both protocols. 120 consecutive unenhanced CT examinations performed due to suspicion of renal calculi were included in this retrospective, monocentric study. 60 examinations were included with the standard-dose protocol (SP) (100 kV/130 mAs), whereas another 60 studies were included using a low-dose protocol (LD) applying spectral shaping with tin filtration of high tube voltages (Sn150 kV/80 mAs). Image quality was assessed by two radiologists in consensus blinded to technical parameters using an equidistant Likert scale ranging from 1-5 with 5being the highest score. Quantitative image quality was assessed using regions of interest in abdominal organs, muscles, and adipose tissue to analyze image noise and signal-to-noise ratios (SNR). Commercially available dosimetry software was used to determine and compare effective dose (ED) and size-specific dose estimates (SSDEmean). All seven renal calculi of the phantom could be detected with both protocols. There was no difference regarding calcluli size between the two protocols except for the smallest one. The smallest concretion measured 1.5 mm in LD and1.0 mm in SP (ground truth 1.5 mm). CTDIvol was 3.36 mGy in LD (DLP: 119.3 mGycm) and 8.27 mGy in SP (DLP: 293.6 mGycm). The mean patient age in SP was 47 ± 17 years and in LD 49 ± 13 years. Ureterolithiasis was found in 33 cases in SP and 32 cases in LD. The median concretion size was 3 mm in SP and 4 mm in LD. The median ED in LD was 1.3 mSv (interquartile range (IQR) 0.3 mSv) compared to 2.3 mSv (IQR 0.9 mSv) in SP (p < 0.001). The SSDEmean of LD was also significantly lower compared to SP with 2.4 mGy (IQR 0.4 mGy) vs. 4.8 mGy (IQR 2.3 mGy) (p < 0.001). The SNR was significantly lower in LD compared to SP (p < 0.001). However, there was no significant difference between SP and LD regarding the qualitative assessment of image quality with a median of 4 (IQR 1) for both groups (p = 0.648). Tin-filtered unenhanced abdominal CT for the detection of renal calculi using high tube voltages leads to a significant reduction of radiation exposure and yields high diagnostic image quality without a significant difference compared to the institution's standard of care low-dose protocol without tin filtration. · Tin-filtered CT for the detection of renal calculi significantly reduces radiation dose.. · The application of tin filtration provides comparable diagnostic image quality to that of SP protocols.. · An increase in image noise does not hamper diagnostic image quality.. · Gassenmaier S, Winkelmann MT, Magnus J et al. Low-Dose CT for Renal Calculi Detection Using Spectral Shaping of High Tube Voltage. Fortschr Röntgenstr 2022; 194: 1012 - 1019.

Microdose protocol stereoradiography has similar reliability to standard low-dose protocol during concurrent Sanders skeletal maturity staging.

Decreasing radiation exposure is important for scoliosis patients who require serial imaging. Microdose protocol stereoradiography is now increasingly utilized. Previous studies have reported similar reliability of concurrent Sanders skeletal maturity staging based on standard low-dose stereoradiography and standard hand radiographs. The purpose of our study was to investigate the reliability and radiation exposure of concurrent Sanders staging using microdose protocol compared to a standard protocol for adolescent idiopathic scoliosis. We hypothesized that surgeon-performed Sanders staging would have similar reliability when comparing microdose and standard-dose imaging protocols. A randomized survey of 30 hand images using standard protocol spinal stereoradiography and an equal number from microdose protocol were distributed to six experienced pediatric orthopaedic spine surgeons. Images were graded by each surgeon according to the Sanders skeletal maturity grading system. Items were again randomized and graded after a 2-week interval. Fleiss' weighted kappa for inter and intraobserver reliability was calculated and an unpaired t test was used to test for significance. Interobserver reliability for all modalities was in the strong to almost perfect agreement (average weighted κ > 0.8) range. For the microdose protocol, κ was 0.82 and 0.84 for each separate round of grading. Standard low-dose protocol κ was 0.83 and 0.79. Intraobserver κ was 0.86 for microdose and 0.82 for standard. Average radiation for microdose was significantly less radiation (82.6%) than standard stereoradiography (0.3 ± 0.1mGy vs. 1.9 ± 0.4mGy, p < 0.001). Sanders staging reliability of a well-positioned hand during scoliosis stereoradiography was similarly excellent for both microdose and standard low-dose protocol. Microdose protocol used less radiation while still preserving the reliability of Sanders staging.

Whole-body ultra-low dose CT using spectral shaping for detection of osteolytic lesion in multiple myeloma.

The aim of this study was to investigate the radiation dose and image quality of a whole-body low-dose CT (WBLDCT) using spectral shaping at 100 kV (Sn 100 kV) for the assessment of osteolytic lesions in patients with multiple myeloma. Thirty consecutive patients were retrospectively selected, who underwent a WBLDCT on a third-generation dual-source CT (DSCT) (Sn 100 kV, ref. mAs: 130). They were matched with patients, who were examined on a second-generation DSCT with a standard low-dose protocol (100 kV, ref. mAs: 111). Objective and subjective image quality, radiation exposure as well as the frequency of osteolytic lesions were evaluated. All scans were of diagnostic image quality. Subjective overall image quality was significantly higher in the study group (p = 0.0003). Objective image analysis revealed that signal intensities, signal-to-noise ratio and contrast-to-noise ratio of the bony structures were equal or significantly higher in the control group. There was no significant difference in the frequency of osteolytic lesions (p = 0.259). The median effective dose of the study protocol was significantly lower (1.45 mSv vs. 5.65 mSv; p < 0.0001). WBLDCT with Sn 100 kV can obtain sufficient image quality for the depiction of osteolytic lesions while reducing the radiation dose by approximately 74%. • Spectral shaping using tin filtration is beneficial for whole-body low-dose CT • Sn 100 kV yields sufficient image quality for depiction of osteolytic lesions • Whole-body low-dose CT can be performed with a median dose of 1.5 mSv.

Coronary CT angiography with a standardized low dose protocol – Image quality and radiation exposure

Coronary CT angiography with a standardized low dose protocol – Image quality and radiation exposure

Low-Dose CT of the Paranasal Sinuses: Minimizing X-Ray Exposure with Spectral Shaping.

Shaping the energy spectrum of the X-ray beam has been shown to be beneficial in low-dose CT. This study's aim was to investigate dose and image quality of tin filtration at 100kV for pre-operative planning in low-dose paranasal CT imaging in a large patient cohort. In a prospective trial, 129 patients were included. 64 patients were randomly assigned to the study protocol (100kV with additional tin filtration, 150mAs, 192x0.6-mm slice collimation) and 65 patients to the standard low-dose protocol (100kV, 50mAs, 128 × 0.6-mm slice collimation). To assess the image quality, subjective parameters were evaluated using a five-point scale. This scale was applied on overall image quality and contour delineation of critical anatomical structures. All scans were of diagnostic image quality. Bony structures were of good diagnostic image quality in both groups, soft tissues were of sufficient diagnostic image quality in the study group because of a high level of noise. Radiation exposure was very low in both groups, but significantly lower in the study group (CTDIvol 1.2mGy vs. 4.4mGy, p < 0.001). Spectral optimization (tin filtration at 100kV) allows for visualization of the paranasal sinus with sufficient image quality at a very low radiation exposure. • Spectral optimization (tin filtration) is beneficial to low-dose parasinus CT • Tin filtration at 100kV yields sufficient image quality for pre-operative planning • Diagnostic parasinus CT can be performed with an effective dose <0.05mSv.

Seventy kilovolt ultra-low dose CT of the paranasal sinus: first clinical results

To evaluate the diagnostic image quality and radiation dose of low-dose 70 kV computed tomography (CT) of the paranasal sinus in comparison to 100 and 120 kV CT. CT of the paranasal sinus was performed in 127 patients divided into three groups using different tube voltages and currents (70 kV/75 mAs, ultra-low dose protocol, n = 44; 100 kV/40 mAs, standard low-dose protocol, n = 42; 120 kV/40 mAs, standard protocol, n = 41). CT dose index (CTDIvol), dose-length product (DLP), attenuation, image noise and signal-to-noise ratio (SNR) were compared between the groups using Wilcoxon-Mann-Whitney U-test. Subjective diagnostic image quality was compared by using a five-point scale (1 = non-diagnostic, 5 = excellent, read by two readers in consensus) and Cohen's weighted kappa analysis for interobserver agreement. Radiation dose was significantly lower with 70 kV acquisition than 100 and 120 kV (DLP: 31 versus 52 versus 82 mGy·cm; CTDI 2.33 versus 3.95 versus 6.31 mGy, all p < 0.05). Mean SNR (70 kV: 0.37; 100 kV: 0.21; 120 kV: 0.13; p < 0.05) and organ attenuation increased significantly with lower voltages. All examinations showed diagnostic image quality. Subjective diagnostic image quality was higher with standard protocols than the 70 kV protocol (120 kV: 5.0; 100 kV: 4.5; 70 kV: 3.5, p < 0.05) without significant differences with substantial interobserver agreement (κ > 0.59). The ultra-low dose (70 kV) CT imaging of the paranasal sinus allowed for significant dose reduction by 61% and an increased attenuation of organ structures in comparison to standard acquisition while maintaining diagnostic image quality with a slight reduction in subjective image quality.

Ultrasound-Accelerated Catheter-Directed Thrombolysis for Acute Submassive Pulmonary Embolism

PurposeTo evaluate the safety and efficacy of ultrasound-accelerated catheter-directed thrombolysis (USAT) in patients with submassive pulmonary embolism (PE). Materials and MethodsThis retrospective study comprised 45 consecutive patients (15 prospective, 30 retrospective) who underwent USAT for submassive PE from June 2012–May 2014. Inclusion criteria were right ventricular dysfunction (RVD) as indicated by right ventricle-to-left ventricle (RV:LV) ratio > 0.9, symptoms of < 2 weeksʼ duration, and absence of absolute contraindication to thrombolysis. All patients underwent pulmonary artery catheterization with a standardized protocol (24 mg recombinant tissue plasminogen activator). Hemodynamic evaluation immediately after USAT, RV:LV ratio evaluation at 48–72 hours after USAT by computed tomography angiography and echocardiography, and adverse event reporting for a minimum of 30 days were performed. Outcomes and complications are reported as per the Society of Interventional Radiology Reporting Standards for Endovascular Treatment of Pulmonary Embolism. ResultsUSAT was technically successful in 100% (n = 45) of patients. Main pulmonary artery pressure significantly decreased from 49.8 mm Hg to 31.1 mm Hg (P < .0001). RVD significantly improved with mean RV:LV ratios decreasing from 1.59 to 0.93 (P < .0001). There were 6 complications: 4 minor bleeding episodes at access sites and 2 major bleeding complications (flank and arm hematoma). All-cause mortality at 30 days was 0%. There were no readmissions for PE at 30 days after discharge. ConclusionsUltrasound-accelerated catheter-directed thrombolysis using a standardized low-dose protocol is a safe and efficacious method of treatment of submassive PE to reduce acute pulmonary hypertension and RVD.

Recognize and classify pneumoconiosis

In the year 2012, out of the 10 most frequently recognized occupational diseases 6 were forms of pneumoconiosis. With respect to healthcare and economic aspects, silicosis and asbestos-associated diseases are of foremost importance. The latter are to be found everywhere and are not restricted to large industrial areas. Radiology has a central role in the diagnosis and evaluation of occupational lung disorders. In cases of known exposure mainly to asbestos and quartz, the diagnosis of pneumoconiosis, with few exceptions will be established primarily by the radiological findings. As these disorders are asymptomatic for a long time they are quite often detected as incidental findings in examinations for other reasons. Therefore, radiologists have to be familiar with the pattern of findings of the most frequent forms of pneumoconiosis and the differential diagnoses. For reasons of equal treatment of the insured a quality-based, standardized performance, documentation and evaluation of radiological examinations is required in preventive procedures and evaluations. Above all, a standardized low-dose protocol has to be used in computed tomography (CT) examinations, although individualized concerning the dose, in order to keep radiation exposure as low as possible for the patient. The International Labour Office (ILO) classification for the coding of chest X-rays and the international classification of occupational and environmental respiratory diseases (ICOERD) classification used since 2004 for CT examinations meet the requirements of the insured and the occupational insurance associations as a means of reproducible and comparable data for decision-making.

WE-G-141-06: Progressive Cone Beam CT Dose Control in Image-Guided Radiation Therapy

Purpose: In image-guided radiotherapy (IGRT), currently cone beam CT (CBCT) offers the best solution for patient setup. Yet its associated imaging dose is a clinical concern. One unique feature of CBCT-based IGRT is that, the same patient is often repeatedly scanned during a treatment course, and the sequence of CBCT images at different fractions share a large amount of redundant information. We propose a progressive dose control (PDC) scheme to utilize this temporal correlation for imaging dose reduction. Methods: A dynamic CBCT scan protocol, as opposed to the static one in the current practice, is proposed to gradually reduce the imaging dose at each fraction. The CBCT image at each day is processed by a prior image based non-local means (PINLM) module to enhance its quality using previous CBCT images as prior information. The increasing amount of prior information prevents the loss of image quality due to dose reduction. Two proof-of-principle experiments have been conducted using measured phantom data and synthetic patient data simulated by a Monte Carlo method. Results: In the measured phantom case, PINLM is able to improve the image quality of a CBCT acquired at 0.2 mAs by reducing the noise level from 34.95 HU to 12.45 HU, utilizing a prior image acquired at 0.4 mAs (standard low-dose protocol). In the synthetic patient case, acceptable image quality is maintained at four consecutive fractions with gradually decreased exposure level at 0.4, 0.1, 0.07 and 0.05 mAs. Compared with the standard low-dose protocol with a constant 0.4 mAs for all fractions, an overall imaging dose reduction of over 60% is achieved. Conclusion: PINLM-PDC is able to reduce CBCT imaging dose in IGRT utilizing the temporal correlations among the sequence of CBCTs while maintaining the image quality. This work is supported in part by NIH (1R01CA154747-01), Varian Medical Systems through a Master Research Agreement, the Early Career Award from Thrasher Research Fund, and the University of California Lab Fees Research Program.

Progressive cone beam CT dose control in image‐guided radiation therapy

Cone beam CT (CBCT) in image-guided radiotherapy (IGRT) offers a tremendous advantage for treatment guidance. The associated imaging dose is a clinical concern. One unique feature of CBCT-based IGRT is that the same patient is repeatedly scanned during a treatment course, and the contents of CBCT images at different fractions are similar. The authors propose a progressive dose control (PDC) scheme to utilize this temporal correlation for imaging dose reduction. A dynamic CBCT scan protocol, as opposed to the static one in the current clinical practice, is proposed to gradually reduce the imaging dose in each treatment fraction. The CBCT image from each fraction is processed by a prior-image based nonlocal means (PINLM) module to enhance its quality. The increasing amount of prior information from previous CBCT images prevents degradation of image quality due to the reduced imaging dose. Two proof-of-principle experiments have been conducted using measured phantom data and Monte Carlo simulated patient data with deformation. In the measured phantom case, utilizing a prior image acquired at 0.4 mAs, PINLM is able to improve the image quality of a CBCT acquired at 0.2 mAs by reducing the noise level from 34.95 to 12.45 HU. In the synthetic patient case, acceptable image quality is maintained at four consecutive fractions with gradually decreasing exposure levels of 0.4, 0.1, 0.07, and 0.05 mAs. When compared with the standard low-dose protocol of 0.4 mAs for each fraction, an overall imaging dose reduction of more than 60% is achieved. PINLM-PDC is able to reduce CBCT imaging dose in IGRT utilizing the temporal correlations among the sequence of CBCT images while maintaining the quality.

The importance of combined hematologic and CT diagnosis for monitoring response in patients with multiple myeloma treated with Bortezomib based therapy

8597 Background: To assess the potential role of radiological monitoring (conventional CT) of lytic bone lesions for diagnosis of progressive (PD) or relapsing (R) multiple myeloma (MM) in comparison with laboratory-based diagnosis, soft-tissue based CT-diagnosis and combined hematologic-radiological diagnosis. Materials and Methods: Between 3/03 and 12/07, 201 patients with MM underwent nonenhanced whole-body low-dose multidetector-CT (WBLD-MDCT) survey parallel to hematological follow up (582 investigations). CT-scans were performed using a standardized low-dose protocol assessing number and size of lytic bone lesions (bone window setting, bW) similar to conventional X-ray diagnosis. In addition, number, size and density of medullary and extra-medullary lesions (soft-tissue window setting, s-tW) were analyzed. Progressive or relapsing myeloma was defined by progression of lytic bone lesions, medullary and extra-medullary tumor infiltration and/or of established basic hematologic parameters. Results: 210/582 investigations showed PD or R. 50/210 (24%) yielded the correct diagnosis by all three methods, 50/210 (24%) were diagnosed correctly by WBLD-MDCT (bW), 133/210 (63%) by laboratory-based testing and 195/210 (93%) by WBLD-MDCT (s-tW) as well as by the combination of the latter two. 8/26 assessments of R were biomarker negative. Only 1 of these examinations proved positive on WBLD-MDCT (bW) while the other 7 were correctly diagnosed by WBLD-MDCT (s-tW) due to progress of medullary infiltration and/or extra-medullary manifestation. Of the biomarker-negative assessments of PD (84/210), only 24 (24/84) showed progress of osteolysis on WBLD-MDCT (bW) while all were correctly assessed by WBLD-MDCT (s-tW). Discussion: This retrospective analysis indicates that monitoring of lytic bone lesions in patients with MM is inaccurate for assessment of progression or relapse of multiple myeloma. Due to the effects of specific chemotherapy and accompanying bisphosphonates therapy, progression of lytic bone lesions seems to occur much later in the course of the disease showing slower growth kinetics compared with medullary and extra-medullary myeloma manifestations. No significant financial relationships to disclose.

The benefit of whole-body low-dose unenhanced multidetector computer tomography (WBLD-MDCT) for follow up and therapy response monitoring in patients with multiple myeloma: Correlation with hematologic parameters

7607 Background: To assessthe value of whole-body low-dose multidetector computer tomography (WBLD-MDCT) as diagnostic and survey modality in multiple myeloma (MM), and as a one-stop alternative (Horger et al. EJR 2005;54:289–297) to established imaging techniques (e.g. x-ray and MRI). Methods: Between 7/2001 and 2/2005, WBLD-MDCT scans were obtained in 90 consecutive patients with histologically proven stage II-III MM, all patients having 2 or more scans (mean = 3,8; range = 2–6). CT-scans were performed using a standardized low-dose protocol and the number, size and density of focal or diffuse medullary (in the appendicular skeleton and pelvis) and extra-medullary lesions as well as osteolysis were analysed for each examination and at follow up. Results were correlated with current standard MM laboratory data and at follow up in order to assess correct temporal recognition of significant myeloma changes by both methods. Results: Detection and follow up of medullary and extra-medullary MM lesions and osteolysis by WBLD-MDCT resulted in a sensitivity of 92%, a specificity of 93%, a NPV of 95%, a PPV of 85% and a likelihood ratio for patients with CT-abnormalities to present changes in the course of their disease of 12. Results of radiologic and hematologic analysis showed high agreement at follow up (median, 3 mo). However, agreement of both techniques at the time of investigation was only moderate (κ = 0.629), with CT being correct in 60% of mismatching cases. Thus, CT enabled earlier detection of MM changes. WBLD-MDCT assessed correctly the course of disease in all 4 patients with nonsecretory MM. Evaluation of stability was optimal in all patients. Conclusions: WBLD-MD represents a reliable, widespread, quick (75s acquisition time), and cost-effective imaging technique in MM, allowing detection of bone marrow involvement, extra-medullary tumors and lytic bone lesions in different clinical settings (staging, follow up, therapy monitoring, evaluation of stability). WBLD-MDCT repeatedly allowed detection of changes in the course of the disease prior to laboratory data, especially in extramedullary MM relapse and nonsecretory MM. No significant financial relationships to disclose.