Inneke Willekens

Evaluation of the radiation dose in micro-CT with optimization of the scan protocol

INTRODUCTION Micro-CT provides non-invasive anatomic evaluation of small animals. Serial micro-CT measurements are, however, hampered by the severity of ionizing radiation doses cumulating over the total period of follow-up. The dose levels may be sufficient to influence experimental outcomes such as animal survival or tumor growth. AIM This study was designed to evaluate the radiation dose of micro-CT and to optimize the scanning protocol for longitudinal micro-CT scans. METHODS AND MATERIALS Normal C57Bl/6 mice were euthanized. Radiation exposure was measured using individually calibrated lithium fluoride thermoluminescent dosimeters (TLDs). Thirteen TLDs were placed in the mice at the thyroid, lungs, liver, stomach, colon, bladder and near the spleen. Micro-CT (SkyScan 1178) was performed using two digital X-ray cameras which scanned over 180 degrees at a resolution of 83 microm, a rotation step of 1.08 degrees , 50 kV, 615 microA and 121 s image acquisition time. The TLDs were removed after each scan. CTDI(100) was measured with a 100 mm ionization chamber, centrally positioned in a 2.7 cm diameter water phantom, and rotation steps were increased to reduce both scan time and radiation dose. RESULTS Internal TLD analysis demonstrated median organ dose of 5.5 +/- 0.6 mGy per mA s, confirmed by CTDI(100) with result of 6.6 mGy per mA s. A rotation step of 2.16 resulted in qualitatively accurate images. At a resolution of 83 microm the scan time is reduced to 63 s with an estimated dose of 2.9 mGy per mA s. At 166 microm resolution, the scan time is limited to 27 s, with a concordant dose of 1.2 mGy per mA s. CONCLUSIONS The radiation dose of a standard micro-CT scan is relatively high and could influence the experimental outcome. We believe that the presented adaptation of the scan protocol allows for accurate imaging without the risk of interfering with the experimental outcome of the study.

Potential Heating Effect in the Gravid Uterus by Using 3-T MR Imaging Protocols: Experimental Study in Miniature Pigs.

Purpose To determine the changes in temperature within the gravid miniature pig uterus during magnetic resonance (MR) imaging at 3 T. Materials and Methods The study received ethics committee approval for animal experimentation. Fiber-optic temperature sensors were inserted into the fetal brain, abdomen, bladder, and amniotic fluid of miniature pigs (second trimester, n = 2; third trimester, n = 2). In the first trimester (n = 2), the sensors were inserted only into the amniotic fluid (three sacs per miniature pig, for a total of six sacs). Imaging was performed with a 3-T MR imager by using different imaging protocols in a random order for animal, each lasting approximately 15 minutes. The first regimen consisted of common sequences used for human fetal MR examination, including normal specific absorption rate (SAR). The second regimen consisted of five low-SAR sequences, for which three gradient-echo sequences were interspersed with two diffusion-weighted imaging series. Finally, a high-SAR regimen maximized the radiofrequency energy deposition (constrained by the 2-W per kilogram of body weight SAR limitations) by using five single-shot turbo spin-echo sequences. Differences in temperature increases between the three regimens and between the three trimesters were evaluated by using one-way analysis of variance. The maximum cumulative temperature increase over 1 hour was also evaluated. Results Low-SAR regimens resulted in the lowest temperature increase (mean ± standard deviation, -0.03°C ± 0.20), normal regimens resulted in an intermediate increase (0.31°C ± 0.21), and high-SAR regimens resulted in the highest increase (0.56°C ± 0.20) (P < .0001). Mean temperature increase in the third trimester was 0.38°C ± 0.27, with no significant differences compared with the first (0.23°C ± 0.27) and second (0.25°C ± 0.32) trimesters (P = .07). The cumulative temperature increase over 1-hour imaging time with high SAR can reach 2.5°C. Conclusion In pregnant miniature pigs, the use of 3-T magnets for diagnostic MR imaging with normal SAR regimens does not lead to temperature increases above 1°C if imaging time is kept below 30 minutes. Longer imaging time, especially with high-SAR regimens, can lead to an increase of 2.5°C. (©) RSNA, 2015 Online supplemental material is available for this article.

Ultrasound follow-up of posttraumatic injuries of the sagittal band of the dorsal hood treated by a conservative approach

Traumatic dislocation of the extensor tendon over the metacarpophalangeal (MCP) joint is a rare problem in patients without rheumatoid disorders. The common extensor tendon is stabilized on the metacarpal head by components of the dorsal hood (DH). A tear in the sagittal bands, allows (sub)luxation of the tendon. To ensure appropriate treatment, the identification of the damaged structures is essential. Ultrasound (US) is a valuable method in the evaluation of DH injuries and in the follow-up for evaluation of healing or lack of healing of the lesions. We report three cases with partial rupture of the sagittal band of the DH: two cases in the index finger and one case in the long finger, which caused pain and swelling and was diagnosed with US. The patients were treated conservatively and the pain resolved after 9 months in case 1, 3 months in case 2 and 6 months in case 3. The follow-up at one year revealed painless full range of motion and no residual subluxation during the dynamic ultrasound.

The Normal Appendix on CT: Does Size Matter?

Purpose (1) To evaluate the frequency of visualisation and measurements of the normal appendix. (2) To correlate Body Mass Index (BMI) and gender with visualisation of the normal appendix. (3) To correlate age, gender and body length with appendiceal length. Materials and Methods A retrospective review of 186 patients undergoing abdominal CT without suspicion of acute appendicitis was done. Frequency of visualisation and measurements (including maximal outer diameter, wall thickness, length, content, location of base and tip) of normal appendices were recorded. Results Prevalence of appendectomy was 34.4%. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of visualisation of the normal appendix were 76%, 94%, 96%, 67%, and 82% respectively. The mean maximal diameter of the appendix was 8.19 mm±1.6 (SD) (range, 4.2–12.8 mm). The mean length of the appendix was 81.11 mm±28.44 (SD) (range, 7.2–158.8 mm). The mean wall thickness of the appendix was 2.22 mm±0.56 (SD) (range, 1.15–3.85 mm). The most common location of the appendiceal tip was pelvic in 66% appendices. The most common location of the appendiceal base was inferior, medial, and posterior in 37%. The normal appendix contained high-density material in 2.2%. There was a significant correlation between gender and appendiceal length, with men having longer appendices than women. Conclusion Most normal appendices are seen at multislice CT using IV contrast. The maximal outer diameter of the normal appendix overlaps with values currently used to diagnose appendicitis on CT.

Quality control of micro-computed tomography systems

The rapid proliferation of micro-computed tomography (micro-CT) scanners in preclinical small animal studies has created a need for a method on scanner performance evaluation and scan parameter optimisation. The purpose of this study was to investigate the performance of the scanner with a dedicated micro-CT phantom. The phantom was developed with different independent sections that allow for measurement of major scanner characteristics such as uniformity, linearity, contrast response, dosimetry and resolution. The results of a thorough investigation are discussed.

Use of eXIA 160 XL for contrast studies in micro-computed tomography: experimental observations.

The purpose of this study was to evaluate the time course of contrast enhancement of spleen, liver, and blood using eXIA 160 XL in healthy mice. eXIA 160 XL was intravenously injected in C57bl/6 mice (n = 12) at a dose of 0.1 mL/20 g (16 mg iodine [I]/20 g) (n = 6) or 0.2 mL/20 g (32 mg I/20 g) (n = 6). The distribution was analyzed by repeated micro–computed tomographic scans up to 48 hours after contrast administration. Images were analyzed using Amide software. Regions of interest were drawn in the spleen, liver, and left ventricle. Contrast enhancement was measured and expressed as a function of time. Peak contrast enhancement of the spleen was reached at 30 minutes, and peak contrast enhancement of the liver occurred 45 minutes after 16 mg I/20 g. Given that this contrast was found to be rather low in the spleen in comparison with former eXIA 160 products, experiments were done at a higher dose. However, the 32 mg I/20 g dose was lethal for mice. Enhancement inside the heart lasts for 1 hour. Administration of eXIA 160 XL results in long-lasting blood pool contrast with higher contrast enhancement in heart and liver in comparison with eXIA 160; however, the administered dose should be limited to 16 mg I/20 g.

Liver Abscess Due to Dropped Appendicolith after Laparoscopic Appendectomy

The lifetime risk of appendicitis is 6 to 7 % [1]. When appendicitis is clinically suspected, an appendicolith can be found in 30% of the patients [2]. An appendicolith may be retained post-operatively (‘dropped appendicolith’) due to previous perforation, non-recognition during surgery or the impossibility to remove it. Abscesses that result from ectopic appendicoliths tend to occur paraceacally in the vicinity of Morrison’s pouch and should be removed to prevent abscess development and possible overt sepsis [3]. As far as we know, we describe the first documented case of an intrahepatic localization of a dropped appendicolith causing a liver abscess.

Ileocolic invagination as a complication of a cecal adenocarcinoma

Ileocolic invagination in the adult may be caused by adenocarcinoma and lead to intestinal obstruction. We report a case of a cecal adenocarcinoma that was complicated by an ileocolic invagination in a 38 year old female, diagnosed on a contrast enhanced CT scan of the abdomen and highlights the importance of contrast enhanced CT for diagnosis of ileocolic invagination.

Ultrasonographic Evaluation of the Anatomy of the Foal Foot From 0 to 7 Months

Abstract This study aimed to provide an ultrasonographic description of the anatomical development of the foal foot from 7 months pre‐ to 7 months postpartum. The right forelimbs of 20 foals (age range, 7‐month fetus to 7‐month foal) without orthopedic disease and which died for reasons unrelated to this study were examined by an experienced ultrasound operator, and reference images were obtained for every age. A 4‐step protocol was used to assess images of the complete foal foot, and these were compared with macroscopic dissection, performed using a standardized protocol. It was concluded that ultrasound images correlated well with macroscopic dissection.

Splenic rupture, a rare complication following extracorporeal shock-wave lithotripsy

“Splenic laceration is a rare complication of abdominal procedures, occurring as such most often after colonoscopy. It has been described as an exceedingly rare complication of ESWL as well. Special care should be taken in those patients undergoing ESWL under general anaesthesia, especially if known with splenic abnormalities. In case of Kehr’s sign or generalized upper-quadrant pain after ESWL, splenic rupture should always be ruled out. Splenectomy is often warranted in these cases, however if the patient is hemodynamically stable a more conservative approach may be attempted with close follow-up in the ICU.” – Anonymous A 41-year-old man presented at the emergency department of our hospital with complaints of intolerable pain in the left upper quadrant. He had undergone extracorporeal shock-wave lithotripsy (ESWL) eight hours prior as treatment for a left-sided kidney stone. This procedure had been performed in another hospital under general anaesthesia. The stone was to be found in the upper pole of the left kidney; in total an estimated energy of 250J was administered. No relevant medical history was withheld, and there was no notion of anticoagulant therapy. In our hospital a bedside ultrasound (Figure 1) was immediately performed which demonstrated a large subcapsular hyperechoic collection in the spleen. A subsequent contrast-enhanced computed tomography (CT) (Figure 2(a) and (b)) identified a laceration of the lower lobe of the spleen with a subcapsular haematoma and a discrete amount of surrounding free fluid. Adjacent to the laceration, a smaller subcapsular haematoma was also present in the left kidney. The therapy was conservative with haemodynamic followup in the intensive care unit (ICU). The initial haemoglobin count proved rather low (9.9 g/dl), with subpar haematocrit levels as well (29.4%). The patient spent three days in the ICU without significant changes and manageable pain. No transfusion was required. After this period the patient was kept for observation another four days on the surgical ward. Haemoglobin count and haematocrit levels remained stable; a follow-up CT scan revealed no enlargement of the subcapsular haematoma. The patient was then discharged. ESWL is a widely used non-invasive procedure for urolithiasis. By use of a focused, high-intensity acoustic pulse, attempts are made to pulverise the stones. The power levels of the pulse are usually gradually increased, limited in maximum power by the patient’s pain threshold. The procedure can be performed under general anaesthesia, enabling higher power output and pulse frequency, thereby speeding up the process. The patient then, however, can no longer provide the clinician with feedback concerning pain Splenic rupture, a rare complication following extracorporeal shock-wave lithotripsy