Detection of Uric Acid Stones in the Ureter Using Low- and Conventional-dose Computed Tomography

Awareness and implementation of lonizing radiation safety measures among urology community in Egypt: nationwide survey

Background

To assess awareness of ionizing radiation safety measures among Egyptian Urology Trainees and Urologists and see the effect of radiation safety courses on the adoption of these measures.

Methods

This Internet-based survey was conducted via https://www.surveymonkey.com/ after approval by the Egyptian Urological Association (EUA). It was sent to all EUA members via email during December 2019. Participation was voluntary and questions included participants’ demographics such as age, gender, years of experience, level of training and type of practice. Other questions assessed some domains such as whether the participant had radiation safety courses, and the extent to which she/he is adopting these measures during daily practice.

Results

A total of 142 Egyptian urology trainees and urologists responded to this electronic survey. The mean hours of fluoroscopy-guided endourologic procedures per week were 4.3 ± 2.1 h, and only 23% reported that they always wear protective lead aprons. In terms of the thyroid shield, X-ray protective gloves, eye googles, a total of 70% and 89% and 89% reported that they never wore it, respectively. The ALARA principle was known by only 24% of respondents. About 94% denied receiving any radiation safety courses. Participants who received radiation safety course reported significantly shorter FT during URS (p = 0.04), PCNL (p = 0.03) and JJ insertion (p = 0.04) and were significantly more compliant (p = 0.02). In addition, the number of years of experience (< 5y,5-10y,10-15y, > 15y) and the current job level (resident, specialist, consultant, professor) was significantly associated with higher compliance with lead aprons (p = 0.006, p < 0.001, respectively). On regression analysis, previous radiation safety awareness courses were the only predictor of good compliance with radiation safety measures (OR = 2 ± 0.73, p = 0.009).

Conclusion

There was a lack of awareness and implementation of radiation safety measures among all participants. Receiving radiation safety courses was the only predictor of good compliance with radiation safety measures.

Low-dose CT scan in stone detection for stone treatment follow-up: is there a relation between stone composition and radiation delivery? Study on a porcine-kidney model

BACKGROUND

Non-contrast CT scan (NCCT) is becoming the standard imaging modality in urinary stone disease. Radiation dose remains an issue, especially for those patients who may need to undergo several CT scans for this indication during their lifetime. Low-dose and ultra-low-dose protocols exist, but there is limited data on the relationship between the minimum radiation dose capable of detecting stone fragments and stone composition.

METHODS

Seven different kinds of human kidney stone were selected. Fragments of 1, 2, 4 and 7 mm were obtained for each stone. Four fragments of the same material were placed in a porcine kidney. A CT scan was then used to scan the kidney at decreasing dosages of 140, 70, 30, 15 and 7mAs. The scans were repeated for each type of stone. Images were reviewed by two radiologists independently with the intent of identifying the stone composition and providing information on its position, dimensions and Hounsfield units (HU).

RESULTS

All types of stone were visible at all settings. Only the 1-mm uric-acid fragment was not detected by both radiologists at 7 and 15 mAs. Dose Length product (DLP) decreased with the reduction in mAs. In terms of HU a statistically significant difference was observed between calcium-based and non-calcium-based stones. Stone dimensions and HU were not affected by the reductions in mAs.

CONCLUSIONS

Ultra-low-dose CT has a good detection rate for all kinds of stone, even when the fragment size is small. Only small uric acid fragments need higher energy settings in order to be detected. When the stone composition is known after surgery for urolithiasis, the most appropriate CT scan setting could be suggested by the urologist during their follow-up.

Imaging Advances in Urolithiasis

The prevalence of urinary stones in the United States has been described as 1 in 11 persons reporting a history of stones. Imaging plays a crucial role in diagnosis, management, and follow-up for these patients and imaging technology over the last 100 years has advanced as the disease prevalence has increased. CT remains the gold standard for imaging urolithiasis and changes in this technology, with the addition of multidetector CT and dual-energy CT, as well as the changes in utilization of CT, have decreased the radiation dose encountered by patients and allowed for improved stone detection. The use of digital tomography has been introduced for follow-up of recurrent stone formers offering the potential to lower radiation exposure over the course of a patient's lifelong treatment. However, there is still a demand for improved imaging techniques to detect smaller stones and stones in larger patients at lower radiation doses as well as the continued need for the judicious use of all imaging modalities for healthcare cost containment and patient safety.

The diagnostic value of magnetic resonance urography using a balanced turbo field echo sequence

OBJECTIVES

The aim of the study was to compare the inter-observer variability and the accuracy of magnetic resonance urography (MRU) using a thin sectional balanced-turbo field echo (B-TFE) sequence for detecting ureteral calculi and to determine the effect of additional factors (size, density and location of the calculus) on the sensitivity and specificity of the MRU.

MATERIALS & METHODS

MRU and CT images were evaluated independently by two radiologists according to presence, density and localization of calculi. The degrees of inter-rater agreement for categorical items were evaluated by the Kappa coefficient.

RESULTS

According to the 1st and 2nd observers, the sensitivity of MRU was 65.9 %, 71.8 % and the specificity of MRU was 95.9 %, 100 %, respectively. Inter-observer agreement was 84.6 % for stone detection. The larger size had a better effect on detectability (p < 0.05). Also, the higher density had a better impact on detectability (p < 0.05).

CONCLUSION

Our study has shown that B-TFE MRU was useful to detect ureteral calculi. However, B-TFE MRU has low sensitivity and high specificity in comparison with CT images. MRU is a reasonable alternative imaging technique for follow-up periods of selective groups like patients with large urinary stones, children or pregnant patients when ionizing radiation is undesirable.

KEY POINTS

• According to 1st and 2nd observers, sensitivity of MRU was 65.9 %, 71.8 %, respectively. • According to 1st and 2nd observers, MRU specificity was 95.9 %, 100 %, respectively. • Interobserver agreement was found to be over 84 % for stone detection. • B-TFE sequence provides calculus follow-up without radiation. • Larger calculi and more dense calculi individually have the better effect on detectability.

Focused Dual-energy CT Maintains Diagnostic and Compositional Accuracy for Urolithiasis Using Ultralow-dose Noncontrast CT

OBJECTIVE

To evaluate the diagnostic accuracy of a new energy and radiation dose-reduced protocol for noncontrast computed tomography (NCCT) with dual-energy CT (DECT) analysis and its potential for the compositional analysis of uric acid (UA)- or non-uric acid (N-UA)-containing calculi.

METHODS

A retrospective evaluation was carried out in 61 patients who underwent dose-reduced DECT (tube A: 140 kV/55 mAs; tube B: 80 kV/303 mAs) with a tube current 38.8% lower than that set by the manufacturer. A protocol combining low-dose CT and targeted DE scans was used. Urinary stones were detected and classified as UA- or N-UA-containing or mixed based on DE software results. The accuracy of the compositional analysis was controlled by correlation with conventional infrared-based analysis.

RESULTS

The compositional stone differentiation was correct in 58 of 61 (95.1%) patients. The sensitivity of detecting pure UA-containing and pure N-UA-containing stones was 100%. The specificity of detecting UA- and pure N-UA-containing stones was 100% and 78.57%, respectively, as 3 of 7 mixed urinary stones (small fragments <4 mm) were classified as N-UA calculi. The total radiation dose in patients with body mass index <25 and >25 kg/m(2) was 1.2 and 2.5 mSv, respectively.

CONCLUSION

Lowering the DECT tube current by up to 38% of the manufacturer's recommendations allows a reduced radiation dose without impairing detection accuracy and stone compositional analysis. Compared with previous studies, this protocol might significantly decrease patient radiation exposure without affecting the quality of results.

Advances in CT imaging for urolithiasis

Urolithiasis is a common disease with increasing prevalence worldwide and a lifetime-estimated recurrence risk of over 50%. Imaging plays a critical role in the initial diagnosis, follow-up and urological management of urinary tract stone disease. Unenhanced helical computed tomography (CT) is highly sensitive (>95%) and specific (>96%) in the diagnosis of urolithiasis and is the imaging investigation of choice for the initial assessment of patients with suspected urolithiasis. The emergence of multi-detector CT (MDCT) and technological innovations in CT such as dual-energy CT (DECT) has widened the scope of MDCT in the stone disease management from initial diagnosis to encompass treatment planning and monitoring of treatment success. DECT has been shown to enhance pre-treatment characterization of stone composition in comparison with conventional MDCT and is being increasingly used. Although CT-related radiation dose exposure remains a valid concern, the use of low-dose MDCT protocols and integration of newer iterative reconstruction algorithms into routine CT practice has resulted in a substantial decrease in ionizing radiation exposure. In this review article, our intent is to discuss the role of MDCT in the diagnosis and post-treatment evaluation of urolithiasis and review the impact of emerging CT technologies such as dual energy in clinical practice.