Erhan T. Ilgit

Lowering the Dose in Head CT Using Adaptive Statistical Iterative Reconstruction

To avoid increased radiation exposure and subsequent long-term risk of cancer, iterative reconstruction is a means of lowering the dose on CT studies. Here, the authors compared head CT scans obtained via standard dose with low-dose (31% less) iterative reconstruction. Signal-to-noise and contrast-to-noise ratios as well as image noise, sharpness, artifacts, and diagnostic acceptability were assessed. Overall these parameters were judged to be better in the standard-dose CT, but those obtained with the lower dose and iterative reconstruction were judged acceptable. Thus, iterative reconstruction appears to be useful in adult head CT examinations. (Editors Note: This technique would be ideal in children where radiation dosage is of utmost concern. At my institution we use it for all head and neck studies, but not for temporal bone or paranasal sinus studies as we have found that bone detail may be less than optimal.) BACKGROUND AND PURPOSE: While CT has found wide use in medical practice, it is also a substantial source of radiation exposure and is associated with an increased lifetime risk of cancer. There is an urgent need for new approaches to reduce the radiation dose in CT. In this regard, ASIR is an alternative method to FBP. We assessed the effect of ASIR on dose reduction in adult head CT. MATERIALS AND METHODS: We retrospectively evaluated a sample of 149 adult head CT examinations that were divided into 2 groups, STD and LD. We lowered the tube current and used ASIR in the LD group. SNR and CNR were analyzed. Dose parameters were recorded while subjective image noise, sharpness, diagnostic acceptability, and artifacts were graded. The Student t test, the Mann-Whitney U test, and κ statistics were used for statistical analyses. RESULTS: We achieved a dose reduction of 31% in the LD group (STD, 2.3 ± 0.1 mSv; LD, 1.6 ± 0.1 mSv; P < .001). There was no significant difference in the noise measured in the air between the 2 comparison groups (P = .273). Noise in the CSF was higher in the STD group (P < .001), while the noise in the WM was higher in the LD group (P < .001). Differences in the CNR between groups were insignificant, but the STD group displayed better SNR values. There was no significant difference in the modal scores of diagnostic acceptability (P = .062) and the artifacts (P = .148) between the 2 groups. Better scores for subjective image noise (P < .001) and sharpness (P = .04) were observed in the STD group. CONCLUSIONS: ASIR appears to be useful in reducing the dose in adult head CT examinations. While the effect of ASIR on noise reduction observed in the present study of head CT is less than that reported previously in abdomen and chest CT, these findings encourage further prospective studies in larger patient samples.

Computed tomographic evaluation of surgically significant vascular variations related with the temporal bone

Variations of the vascular structures related with the temporal bone may cause important problems in diagnosis, treatment planning and surgery. High resolution computed tomography (CT) scans of 700 temporal bones of 350 patients were retrospectively examined for the incidence of dehiscent jugular bulb, high jugular bulb, diverticulum of jugular bulb, anteriorly located sigmoid sinus and dehiscent internal carotid artery. Dehiscent jugular bulb was seen in 27 (3.9%), high jugular bulb was seen in 142 (20.3%), jugular bulb diverticulum was seen in 55 cases (7.9%). The average distance between external acoustic canal and sigmoid sinus was found to be 13.3 mm and in 12.4% of the cases this distance was < 10 mm. Of 700 temporal bones, 10 (1.4%) showed dehiscent carotid canal. To aid diagnosis, treatment planning and surgery, CT scanning is currently a very reliable tool in determining these conditions. Special attention should be paid to the position of the vascular structures in the preoperative temporal bone CT scans.

Primary stenting for complex atherosclerotic plaques in aortic and iliac stenoses

AbstractPurpose: To evaluate the efficacy of primary stenting for complex atherosclerotic plaques in aortic and iliac stenoses that are not amenable to balloon angioplasty alone. Methods: Nineteen patients with complex atherosclerotic plaques were treated with a Palmaz stent (n=19), Wallstent (n=1), Strecker stent (n=1), or Memotherm stent (n=1). A total of 22 stenoses presenting with complex plaque morphology including ulcerated plaques, ulcerated plaques with focal aneurysms, plaques with heavy calcification, severely eccentric plaques, plaques with overhanging edge, and plaques with spontaneous dissection were stented. The lesions were in the aorta (n=1), common iliac artery (n=19), or external iliac artery (n=2). Results: Immediate angiography after stent placement revealed restoration of patency of the stented segment. Focal aneurysms and ulcerated areas were occluded in the follow-up angiographies obtained 4–12 weeks after the procedure. In one case with poor distal runoff and multiple complex lesions of the iliac artery, subacute occlusion occurred. Clinical and angiographic follow-up (3–46 months) revealed patency of all other stented segments. Conclusion: Primary stenting is an effective and reliable approach for complex plaques in stenoses. Patency of the arterial segment with a smooth lumen can be created without the risk of acute complications such as distal embolization, dissection, or occlusion.

Peripheral arterial involvement in neurofibromatosis type 1--a case report.

Neurofibromatosis is a dominantly inherited, progressive, generalized dysplasia of meso dermal and neuroectodermal tissues. Vascular lesions associated with neurofibromatosis type 1 (NF-1) are mainly characterized by stenosis, occlusion, aneurysm, pseudoaneurysm, and rupture or fistula formation of small, medium, and large-sized arteries. The authors hereby present a rare case of NF-1 with bilateral aneurysms and large pseudoaneurysms of the femoral and popliteal arteries and occlusion of the left superficial femoral artery.

Postcatheterization Femoral Arteriovenous Fistulas: Endovascular Treatment with Stent-Grafts

AbstractPurpose: To report our results of stent-graft implantation for the endovascular treatment of postcatheterization femoral arteriovenous fistulas (AVFs) occurring between the deep femoral artery and the femoral vein. Methods: Endovascular treatment of iatrogenic femoral AVFs as a result of arterial puncture for coronary angiography and/or angioplasty was attempted in 10 cases. Balloon-expandable stent-grafts, one for each lesion, were used to repair the fistulas, which were between the deep femoral artery and the femoral vein in all cases. Stent-graft implantation to the deep femoral artery was performed by a contralateral retrograde approach. Results: All stent-grafts were deployed successfully. Complete closure of the fistulas was accomplished immediately in nine of 10 cases. In one case, complete closure could not be obtained but the fact that the complaint subsided was taken to indicate clinical success. In three cases, side branch occlusion of the deep femoral artery occurred. No complications were observed after implantation. Follow-up for 8–31 months (mean 18.5 months) with color Doppler ultrasonography revealed patency of the stented arterial segments without recurrent arteriovenous shunting in those nine patients who had successful immediate closure of their AVFs. Conclusion: Our results with a mean follow-up 18.5 months suggest that stent-graft implantation for the closure of postcatheterization femoral AVFs originating from the deep femoral artery is an effective, minimally invasive alternative procedure.

Clinical approach to graft hepatic artery thrombosis following living related liver transplantation

Abstract: Hepatic artery thrombosis (HAT) has an occurrence rate of 1.7–26% following living donor liver transplantation (LDLT) and is one of the most common reasons for graft loss and mortality in this population. There is a higher incidence of HAT in pediatric recipients. The aim of this case report is to discuss clinical approaches for the treatment of HAT occurring in the early post‐operative period after LDLT. An 11‐month‐old, 7.8‐kg female with cirrhosis secondary to biliary atresia underwent LDLT at Gazi University Hospital in Ankara. The graft was a left lateral segment from her father with a left hepatic artery (HA) of 2 mm diameter and a graft weight/recipient body weight ratio of 2.0%. After an uneventful early post‐operative period, HAT was diagnosed by Doppler ultrasonography (USG) on the fifth post‐operative day. Following angiographic evaluation, immediate exploration and reanastomosis was performed using an operation microscope. Post‐operatively, the HA was patented by Doppler USG and graft function returned to normal. Now, 42 months later, the patient continues to do well with normal graft function, using a regimen of tacrolimus monotherapy for immunosuppression. In countries which have very limited resources for urgent re‐transplantation, given their serious donor shortage, graft salvage may be the only option for patient survival when HAT occurs. In these circumstances, early diagnosis and immediate revascularization may be the only method for graft salvage. A daily routine of Doppler USG examination in the early post‐operative period may provide a method for the early diagnosis of HAT, before liver enzymes are elevated and hepatic necrosis has begun.

Spontaneous thrombosis of a vein of Galen aneurysmal malformation: possible effects of contrast media

Abstract. A 5-year-old boy with macrocephaly and mental retardation was referred for radiologic evaluation. After cranial CT and MR imaging, the diagnosis of mural type vein of Galen aneurysmal malformation was established by angiography. Two weeks later, preembolization angiography revealed complete thrombosis of the malformation. Although it is a very rare event, vein of Galen aneurysmal malformation may spontaneously thrombose following diagnostic angiography. Possible effects of contrast media on thrombosis were discussed.

Thromboangiitis obliterans (Buerger's disease) in women (a reevaluation).

Thromboangiitis obliterans (TAO) is an occlusive vascular disease tradition ally known to be almost exclusive to young male smokers. The disease was con sidered to be extremely rare in women, seen only as isolated, novel case reports in the literature. In the past decade, however, a dramatic increase in the inci dence of female TAO has been observed. In this paper the authors report 7 cases of clinically and angiographically verified female TAO. The world literature in regard to the diagnostic criteria, changing incidence, and etiology is reviewed. They conclude that the increased use of tobacco among young women in the past two to three decades is responsi ble for this dramatic change.

Scrotal arteriovenous malformation and its preoperative embolization

Abstract. Arteriovenous malformations of the scrotum are extremely rare. A case of scrotal arteriovenous malformation and its preoperative embolization in a child is presented.

Percutaneous management of bile duct stones

This article presents a review of the interventional radiological procedures in the percutaneous management of the bile duct stones through T-tube or transhepatic tracts. Interventional stone removal techniques mainly include extraction through the T-tube tract with baskets or forceps and expulsion into the duodenum by means of baskets or balloon catheters with the dilatation of the sphincter of Oddi. Fragmentation or size reduction of the stone, dilatation of the strictures and cholangioscopic assistance can facilitate the procedures.