RPS 1407a - Is there any news in CT protocols for renal masses and stones evaluation?

Purpose:

To evaluate the radiation dose exposure, diagnostic performance, and image quality of ultra-low-dose non-contrast CT using an advanced modelled iterative reconstruction (ADMIRE) algorithm with spectral filtration for the detection of urolithiasis.

Methods and materials:

145 consecutive patients underwent non-contrast CT using third-generation dual-source scanner to obtain two datasets: 16.7% (ultra-low-dose CT) and 100% (standard-dose CT) tube loads with spectral filtration. The performance of ultra-low-dose CT for detection of stones was analysed by two readers and compared with that of standard-dose CT. Image quality was measured subjectively and objectively.

Results:

171 stones were detected in 79 patients. The mean effective radiation doses of ultra-low-dose CT was 0.3 mSV. The sensitivity and specificity values for the diagnosis of stones measuring ≥3 mm was 95.1% and 100% for ultra-low-dose CT. The sensitivity and specificity for all stone detection was 74.9% and 97.8% for ultra-low-dose CT. The image quality was lower for ultra-low-dose CT than for standard-dose CT (P<0.01).

Conclusion:

Ultra-low-dose CT can be achieved with radiation doses close to KUB radiography. Ultra-low-dose CT with spectral filtration can be used to detect stones measuring ≥3 mm and be used as a follow-up imaging modality as an alternative to KUB radiography.

Limitations:

The small number of obese patients and the relatively small number of ureteric stones. Due to the difference in image quality between ultra-low-dose and standard-dose CT scans, there was a limit to the extent that the readers could be blinded. The 3 mm slice thickness might impact the ability to detect small stones.

Ethics committee approval

Approval for the study was obtained from the institutional review board of Gil Medical Center.

Funding:

No funding was received for this work.

Purpose:

To evaluate whether the nephro-pyelographic phase of CT-urography alone, without the unenhanced phase, is sufficient to identify and localise urinary calculi.

Methods and materials:

In this single-centre retrospective study, images were acquired using a 64-slice Toshiba multidetector CT scanner. Patients who underwent a CT-urography with split bolus or triphasic technique between 2016 and 2019 were included. Images were evaluated randomly and independently by two radiologists with 7 and 25 years of urogenital imaging experience. Patients with no urinary calculi identified or missing one of the CT-urography phases were excluded. The number of calculi identified on each phase was recorded.

Using Cohen’s method, the intra-reader agreement was calculated comparing the unenhanced and the nephro-pyelographic phases analysed by each radiologist. The inter-reader agreement was calculated comparing the unenhanced phases and the nephro-pyelographic phases analysed by the two radiologists

Results:

Of the 479 enrolled patients, 65 were included in the study (47 M, 18 F). The first radiologist identified 64 calculi in the unenhanced phases and 66 in the nephro-pyelographic phases. The second radiologist identified 76 calculi in the unenhanced phases and 74 in the nephro-pyelographic ones.

The intra-reader agreements were 0.912 and 0.963, respectively. The inter-reader agreements were 0.772 and 0.713, with comparable and reproducible statistical results

Conclusion:

The use of a nephro-pyelographic phase alone has greater sensitivity and specificity than the unenhanced phase in localising urinary calculi and in differentiating them from other calcifications while delivering a lower radiation dose to the patient.

Limitations:

The main limitation of the nephro-pyelographic phase, which occurred in one patient in our series, is in detecting calculi with the same density of iodinated urine, visible only in the unenhanced phase.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

CT is commonly used for evaluating patients with haematuria and renal colic. We assessed variations in radiation doses and CT protocols for the evaluation of haematuria and renal colic in 20 European countries.

Methods and materials:

IAEA surveyed practices in 51 hospitals from 20 European countries and obtained information for three CT protocols (haematuria, renal colic, and routine abdomen-pelvis CT) for 1,276 patients: patient information (weight and clinical indication), scanner information (vendor, scanner name, and number of detector rows), parameters (number of phases, scan start and end locations, mA, and kV), and radiation dose descriptors (CTDIvol and DLP). Two radiologists assessed the appropriateness of clinical indications and scan phases using the ESR referral guidelines and ACR appropriateness criteria. Descriptive statistics and Student’s t tests were performed.

Results:

Most institutions used 3-6 phase CT haematuria protocols (80%, median DLP 1,793-3,618 mGy.cm) which were associated with 2.4-4.9-fold higher dose compared to 2-phase protocol (20%, 740 mGy.cm) (p<0.0001). Likewise, 52% patients were scanned with 3-5 phase routine CT protocol (1,574-2,945 mGy.cm) as opposed to 37% single-phase routine CT (676 mGy.cm). The median DLPs for renal colic CT (516 mGy.cm; 77% had single-phase CT and 23% acquired 2-5-phases for renal colic protocol) were significantly lower than median DLPs with the other two CT protocols (p<0.0001). Most institutions did not change scan parameters (such as kV, mA, scan length) for multiphase protocols.

Conclusion:

Although most institutions use low-dose CT for renal colic, large variations in haematuria and routine abdomen-pelvis CT protocols result in huge radiation doses (up to 2,945-3,618 mGy.cm). Scan parameters are not adjusted when acquiring CT with multiple phases.

Limitations:

Most of the data came from developing nations with a heterogeneous number of patient studies.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

Computed tomography (CT) is the imaging modality of choice in suspected urolithiasis. Information obtained from CT includes the presence, location, and size of the stones, with the latter frequently determining treatment decision. While there is a consensus regarding how to perform measurements, the influence of other factors possibly impairing accurate measurement, including radiation dose and reconstruction techniques, is unknown.

Methods and materials:

47 kidney stones of different composition were scanned using a 256 row MDCT using a 3D-printed, semi-anthropomorphic phantom. The size was measured manually with a digital caliper (Man-M). Stones were imaged with 2 and 10 mGy. Images were reconstructed using filtered-back-projection, hybrid-iterative, and model-based iterative reconstruction algorithms (FBP, HIR, and MBIR) with different kernels and denoising levels. All stones underwent semi-automatic, threshold-based segmentation for computation of maximum diameter. Statistics were conducted using ANOVA ± correction for multiple comparisons.

Results:

Overall stone size as compared to manual measurements was overestimated in CT (8.8±2.9 vs 10.0±3.1 mm, p<0.05) showing a good correlation (R²=0.66). Radiation dose and denoising levels did not significantly influence measurements (p>0.05). MBIR and sharp kernels showed the closest agreement with Man-M (9.3±3.1 vs 8.8±2.9 mm, p<0.05). Differences within single stones were as high as 40% (e.g. Man-M: 5.9 mm, CT: 7.3-12 mm).

Conclusion:

CT-based measurements tend to overestimate stone size as compared to manual measurements. CT-based measurements appear independent of radiation dose and denoising, however, reconstruction algorithms and kernels demonstrate a relevant impact on size measurements. The smallest differences were found when using model-based iterative reconstruction algorithms with a sharp kernel.

Limitations:

This is a retrospective single-centre study only investigating reconstruction techniques of one vendor. Comparisons between reconstruction techniques of different vendors were beyond the scope of this study.

Ethics committee approval

IRB-approval given.

Funding:

No funding was received for this work.