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The frequency of abdominal computed tomography examinations is increasing, leading to a significant level of patient dose. This study aims to quantify and evaluate the effects of automatic tube current modulation (ATCM) technique on patient dose and image quality in contrast-enhanced biphasic abdominal examinations.Two different scan protocols, based on constant tube current and ATCM technique, were used on 64 patients who visited our radiology department periodically. For three patient groups with different patient size, results from two protocols were compared with respect to patient dose and image quality. Dosimetric evaluations were based on the Computed Tomography Dose Index, dose length product, and effective dose. For the comparison of image qualities between two protocols, Noise Index (NI) and Contrast to Noise Ratio (CNR) values were determined for each image. Additionally, the quality of each image was evaluated subjectively by an experienced radiologist, and the results were compared between the two protocols.Dose reductions of 31% and 21% were achieved by the ATCM protocol in the arterial and portal phases, respectively. On the other hand, NI exhibited an increase between 9% and 46% for liver, fat and aorta. CNR values were observed to decrease between 5% and 19%. All images were evaluated by a radiologist, and no obstacle limiting a reliable diagnostic evaluation was found in any image obtained by either technique.These results showed that the ATCM technique reduces patient dose significantly while maintaining a certain level of image quality.Abdominal bilgisayarlı tomografi incelemelerinin sıklığı artmakta ve önemli miktarda hasta dozuna yol açmaktadır. Bu çalışma, kontrastlı, çift fazlı abdomen incelemelerinde otomatik tüp akım modülasyon tekniğinin hasta dozu ve görüntü kalitesi üzerine etkilerini ölçmeyi ve değerlendirmeyi amaçlamaktadır.Radyoloji anabilim dalını periyodik olarak ziyaret eden 64 hastaya sabit tüp akımı ve otomatik tüp akımı modülasyonu tekniğine dayanan iki farklı tarama protokolü uygulandı. Farklı hasta boyutlarına sahip üç hasta grubu için, iki protokolden elde edilen sonuçlar hasta dozu ve görüntü kalitesi açısından karşılaştırıldı. Dozimetrik değerlendirmeler, Bilgisayarlı Tomografi Doz İndeksi, doz uzunluk çarpımı ve etkin doza dayandırıldı. İki protokol arasındaki görüntü kalitesinin karşılaştırılması amacıyla her görüntü için Gürültü İndeksi (NI) ve Kontrast Gürültü Oranı (CNR) değerleri belirlendi. Ek olarak, her görüntü deneyimli bir radyolog tarafından öznel olarak değerlendirildi ve sonuçlar iki protokol arasında karşılaştırıldı.Otomatik tüp akım modülasyon protokolü ile arteriyel ve portal fazlarda sırasıyla %31 ve %21 doz düşüşleri sağlandı. Öte yandan, NI karaciğer, yağ ve aort için %9 ile %46 arasında bir artış gösterdi. CNR değerlerinin ise %5 ile %19 arasında azaldığı gözlendi. Tüm görüntüler bir radyolog tarafından değerlendirildi ve herhangi bir teknikle elde edilen görüntülerde güvenilir bir tanısal değerlendirmeyi sınırlayan bir engel bulunmadı.Bu sonuçlar, otomatik tüp akım modülasyon tekniğinin, belirli bir görüntü kalitesi seviyesini korurken hastanın dozunu önemli ölçüde azalttığını göstermiştir.

Objective: To assess the efficacy of high-resolution magnetic resonance imaging (HRMRI) for preoperative local staging in patients with rectal cancer who did not receive preoperative radiochemotherapy. Methods: In this retrospective study, 30 patients with biopsy proved primary rectal cancer were evaluated by HRMRI. Two observers independently scored the tumour and lymph node stages, and circumferential resection margin (CRM) involvement. The sensitivity, specificity, the negative predictive value and the positive predictive value of HRMRI findings were calculated within the 95% confidence interval. The area under the curve was measured for each result. Agreement between two observers was assessed by means of the Kappa test. Results: In T staging the accuracy rate of HRMRI was 47-67%, overstaging was 10-21%, and understaging was 13-43%. In the prediction of extramural invasion with HRMRI, the sensitivity was 79-89%, the specificity was 72-100%, the PPV was 85-100%, the NPV was 73-86%, and the area under the curve was 0.81-0.89. In the prediction of lymph node metastasis, the sensitivity was 58-58%, the specificity was 50-55%, the PPV was 43-46%, and the NPV was 64-66%. The area under the curve was 0.54-0.57. When the cut off value was selected as 1 mm, the sensitivity of HRMRI was 38-42%, the specificity was 73-82%, the PPV was 33-42%, and NPV was 79-81% in the prediction of the CRM involvement. The correlation between the two observers was moderate for tumour staging, substantial for lymph node staging and predicting of CRM involvement. Conclusion: Preoperative HRMRI provides good predictive data for extramural invasion but poor prediction of lymph node status and CRM involvement. Conflict of interest:None declared.