Transformers in medical image segmentation: a narrative review.

Background and Objective: Transformers, which have been widely recognized as state-of-the-art tools in natural language processing (NLP), have also come to be recognized for their value in computer vision tasks. With this increasing popularity, they have also been extensively researched in the more complex medical imaging domain. The associated developments have resulted in transformers being on par with sought-after convolution neural networks, particularly for medical image segmentation. Methods combining both types of networks have proven to be especially successful in capturing local and global contexts, thereby significantly boosting their performances in various segmentation problems. Motivated by this success, we have attempted to survey the consequential research focused on innovative transformer networks, specifically those designed to cater to medical image segmentation in an efficient manner. Methods: Databases like Google Scholar, arxiv, ResearchGate, Microsoft Academic, and Semantic Scholar have been utilized to find recent developments in this field. Specifically, research in the English language from 2021 to 2023 was considered. Key Content and Findings: In this survey, we look into the different types of architectures and attention mechanisms that uniquely improve performance and the structures that are in place to handle complex medical data. Through this survey, we summarize the popular and unconventional transformer-based research as seen through different key angles and analyze quantitatively the strategies that have proven more advanced. Conclusions: We have also attempted to discern existing gaps and challenges within current research, notably highlighting the deficiency of annotated medical data for precise deep learning model training. Furthermore, potential future directions for enhancing transformers' utility in healthcare are outlined, encompassing strategies such as transfer learning and exploiting foundation models for specialized medical image segmentation.

The Feasibility and Safety of Temporary Transcatheter Balloon Occlusion of Bilateral Internal Iliac Arteries during Cesarean Section in a Hybrid Operating Room for Placenta Previa with a High Risk of Massive Hemorrhage.

This study aimed to evaluate the feasibility and safety of temporary transcatheter balloon occlusion of bilateral internal iliac arteries (TBOIIA) during cesarean section in a hybrid operating room (OR) for placenta previa (PP) with a high risk of massive hemorrhage. This retrospective study analyzed the medical records of 62 patients experiencing PP with a high risk of massive hemorrhage (mean age, 36.2 years; age range 28-45 years) who delivered a baby via planned cesarean section with TBOIIA in a hybrid OR between May 2019 and July 2021. Operation time, estimated blood loss (EBL), amount of intra- and postoperative blood transfusion, perioperative hemoglobin level, hospital stay after operation, balloon time, fluoroscopy time, radiation dose, rate of uterine artery embolization (UAE) and hysterectomy, and complication-related TBOIIA were assessed. The mean operation time was 122 min, and EBL was 1290 mL. Nine out of sixty-two patients (14.5%) received a blood transfusion. The mean hemoglobin levels before surgery, immediately after surgery and within 1 week after surgery were 11.3 g/dL, 10.4 g/dL and 9.2 g/dL, respectively. In terms of radiation dose, the mean dose area product (DAP) and cumulative air kerma were 0.017 Gy/cm2 and 0.023 Gy, respectively. Ten out of sixty-two patients (16.1%) underwent UAE postoperatively in the hybrid OR. One out of sixty-two patients had been diagnosed with placenta percreta with bladder invasion based on preoperative ultrasound, and thus underwent cesarean hysterectomy following TBOIIA and UAE. While intra-arterial balloon catheter placement for managing PP with a high risk of hemorrhage remains controversial, a planned cesarean section with TBOIIA in a hybrid OR is effective in eliminating the potential risk of intra-arterial balloon catheter displacement, thus reducing intraoperative blood loss, ensuring safe placental removal and conserving the uterus.

Spectrum of imaging findings of chronic granulomatous disease: a single center experience.

The purpose of this pictorial essay is to present and summarize findings of various images of chronic granulomatous disease (CGD). CGD represents a heterogeneous group of disorders caused by defective generation of respiratory bursts in human phagocytes. This defect results in abnormal phagocytic functions and defective killing of bacteria by phagocytes. CGD may involve many organs and present with recurrent infections and inflammations. Radiologists should consider the possibility of CGD when a patient presents with atypical and recurrent infection. They must also consider other concurrent infections a patient may have.

Prospective randomized trial comparing pushable coil and detachable coil during percutaneous implantation of port-catheter system for hepatic artery infusion chemotherapy.

The purpose of this study was to prospectively compare the efficacy and controllability of pushable coil and detachable coil during embolization of gastroduodenal artery (GDA) while performing percutaneous implantation of port-catheter system for hepatic artery infusion chemotherapy. Fifty patients (M:F = 42:8, age: 31-81 years) with advanced hepatocellular carcinoma undergoing port-catheter system implantation were randomized into pushable coil group and detachable coil group. During catheter fixation, GDA was embolized as close to the origin as possible. Success rate, number of coils used, number of coils removed due to malposition after deployment, time to occlusion, uncoiled GDA length, pushability, and complications were compared. Pushability was graded as no tension, slight tension, and difficult to advance. Embolization was successful in 49 patients. One failure resulted from repeated regurgitation of pushable coil into hepatic artery. Number of coils used and removed coils, time to occlusion, and uncoiled GDA length were 1-3 (mean 2.32), 5 coils in 3 patients, 4-20 min (mean 8.00), and 0-15.0 mm (mean 3.36) in pushable coil group, and 1-5 (mean 2.12), 2 coils in 2 patients, 2-15 min (mean 7.40), and 0-10.2 mm (mean 2.92) in detachable coil group, respectively, without significant difference. Pushability was no tension (n = 24) and slight tension (n = 1) in pushable coil group and no tension (n = 16), slight tension (n = 7), and difficult to advance (n = 2) in detachable coil group. One hepatic artery dissection occurred in the failed case during coil removal. Pushable coils and detachable coils had similar efficacy and controllability during GDA embolization, although there was a trend favoring detachable coil.

Single-session aspiration thrombectomy of lower extremity deep vein thrombosis using large-size catheter without pharmacologic thrombolysis.

PURPOSE: To retrospectively evaluate the efficacy of single-session aspiration thrombectomy using large catheters without pharmacologic thrombolysis to treat acute and subacute lower extremity deep vein thrombosis (DVT). METHODS: From January 2008 to December 2011, single-session aspiration thrombectomy using large, 11F introducer catheters to treat acute and subacute lower extremity DVT was performed in 74 limbs of 74 patients (M/F = 23/51, age range 36-88 years), and clinical and imaging follow-up of over 6 months were obtained in 26 patients. Causes of DVT were May-Thurner syndrome (n = 65), malignancy related (n = 6), and pelvic mass (n = 3). A 14F introducer sheath was inserted through the popliteal vein, followed by rotational thrombus maceration and aspiration thrombectomy. Angioplasty and stent placement were performed when needed. Radiological images and medical records were reviewed for immediate and midterm results, complications, and recurrences. RESULTS: Initial technical success rate was 89.2% (66 patients). Stenting was performed in 55 patients. The failures were due to underlying chronic thrombi/DVT (n = 7) and stent failure due to huge pelvic mass (n = 1). There was no procedure-related complication. In the 26 midterm follow-up patients for a duration of 6-48 months, there was no recurrence (n = 20), stent occlusion (n = 3), or femoral vein occlusion (n = 3). One-year primary patency rate in stent/iliac vein, femoral vein, and popliteal/infrapopliteal vein were 88.5, 88.5, and 96.2%, respectively. CONCLUSION: Single-session aspiration thrombectomy for acute and subacute lower extremity DVT using large introducer catheters without pharmacologic thrombolysis is feasible with acceptable immediate and midterm results, excluding complications related to pharmacologic thrombolysis.

Apparent diffusion coefficient of uterine leiomyoma as a predictor of the potential response to uterine artery embolization.

PURPOSE: To determine the utility of the apparent diffusion coefficient (ADC) of uterine leiomyoma for prediction of the potential response to uterine artery embolization (UAE). MATERIALS AND METHODS: This prospective study included 49 patients with uterine leiomyomas who underwent diffusion-weighted magnetic resonance (MR) imaging before UAE between May 2011 and January 2012. All patients also underwent 3-month follow-up MR imaging after UAE. Using conventional and diffusion-weighted MR imaging sequences, 72 uterine leiomyomas ≥ 3 cm were prospectively evaluated. The volume of each leiomyoma was calculated, and quantitative measurement of ADC was performed. Regression analysis was used to evaluate the relationship between ADC and volumetric response after UAE. Receiver operating characteristic curve analysis was performed to determine the sensitivity and specificity of ADC for prediction of the potential response to UAE. Interclass correlation coefficient analysis was used to assess interobserver variability between two radiologists. RESULTS: Volume reduction rates of leiomyomas after UAE ranged from 0.2%-89.1% (mean, 44.1%). ADC ranged from 0.559 × 10(-3) mm(2)/s to 1.814 × 10(-3) mm(2)/s (mean, 1.170 × 10(-3) mm(2)/s). ADC was statistically significantly related to volumetric response of leiomyomas (P = .014). Using a threshold of 1.092 × 10(-3) mm(2)/s, the sensitivity and specificity of ADC for prediction of > 50% volume reduction of the leiomyoma after UAE were 82.6% and 52.3%, respectively. Using a threshold of 1.023 × 10(-3) mm(2)/s, the sensitivity and specificity of ADC for prediction of < 30% volume reduction were 80.8% and 33.3%, respectively. The interclass correlation coefficient for measuring ADC of uterine leiomyomas between two radiologists was 0.98. CONCLUSIONS: ADC of uterine leiomyomas was significantly related to the volume reduction after UAE. ADC may be useful in predicting the potential response to UAE. A high ADC of the uterine leiomyoma may be associated with a greater volume reduction after UAE.

Inferior Mesenteric Artery Collaterals to the Uterus during Uterine Artery Embolization: Prevalence, Risk Factors, and Clinical Outcomes.

PURPOSE: To evaluate the prevalence of inferior mesenteric artery (IMA) collaterals to the uterus found during uterine artery embolization (UAE), associated risk factors, and clinical outcomes. MATERIALS AND METHODS: The records of 559 women who underwent UAE during the period 2008-2011 for uterine fibroids or adenomyosis found on magnetic resonance imaging were retrospectively analyzed. If IMA collaterals to the uterus were suspected on aortography performed after embolization, selective angiography was performed. Risk factors for IMA collaterals to the uterus were analyzed, including the presence of adenomyosis, baseline uterine volume, or prior pelvic surgery. RESULTS: Collaterals to the uterus were found from the ovarian artery (n = 21; 3.8%), IMA (n = 7; 1.3%), round ligament artery (n = 1; 0.2%), and internal pudendal artery (n = 1; 0.2%). IMA collaterals were found in seven patients. Of 185 patients, 6 (3.2%) had adenomyosis, with or without fibroids, which was significantly more frequent than the 1 (0.27%) of 374 patients who had fibroids only (P = .006). On multiple logistic regression analysis, the presence of adenomyosis (odds ratio, 19.556; P = .0168) and uterine volume (odds ratio, 1.003; P = .0069) were independent factors for the presence of IMA collaterals. Of the seven patients with IMA collaterals, embolization was not attempted in six, resulting in clinical failure in four. One patient who underwent IMA embolization with coils experienced clinical improvement. CONCLUSIONS: The IMA was the second most common (1.3%) source of collaterals to the uterus. IMA collaterals were more frequent in patients with adenomyosis than in patients with fibroids only, resulting in high frequency of treatment failure.

Aberrant ovarian collateral originating from external iliac artery during uterine artery embolization.

We report a case of a 35-year-old woman who underwent uterine artery embolization (UAE) for symptomatic multiple uterine fibroids with collateral aberrant right ovarian artery that originated from the right external iliac artery. We believe that this is the first reported case in the literature of this collateral uterine flow by the right ovarian artery originated from the right external iliac artery. We briefly present the details of the case and review the literature on variations of ovarian artery origin that might be encountered during UAE.

Degeneration of leiomyoma in patients referred for uterine fibroid embolization: incidence, imaging features and clinical characteristics.

PURPOSE: Imaging features and clinical characteristics of degenerated leiomyoma in patients referred for uterine fibroid embolization (UFE) were analyzed to assess the incidence of degenerated leiomyoma. MATERIALS AND METHODS: Patients referred for UFE between 2008 and 2009 were retrospectively analyzed (n=276). Patients ranged in age from 27 to 51 years (mean 38.0 years). All patients underwent screening MRI with contrast enhancement. Medical histories and clinical symptoms were evaluated. RESULTS: Among the 276 patients who underwent MRI, 14 (5.1%) showed degenerated leiomyomas. Symptoms were abdominal pain (n=4, 26.7%), menorrhagia (n=5, 35.7%) and bulk-related symptoms (n=5, 35.7%) and no symptoms (n=5, 35.7%). Of the 14 patients with degenerated leiomyomas, 5 (42.9%) had a history of pregnancy in the past two years. For T1-weighted imaging (T1WI), a high signal intensity (SI) of the leiomyoma was the most common finding (n=9, 64.3%) and a hyperintense rim (n=4, 28.6%) was the second most common. On T2-weighted imaging (T2WI), a low SI of the leiomyoma was found in six patients (42.9%), a high SI in four (28.6%) and a heterogeneous SI in four (28.6%) patients. Conservative management was performed in 11 (78.6%) patients, surgery in 3 (21.4%) and uterine artery embolization in one (7.1%) patient. CONCLUSION: The incidence of degeneration of leiomyoma in patients referred for UFE was 5.1%. Patients presented with variable clinical symptoms with or without a history of pregnancy. MR imaging showed a high SI on T1WI and various SIs on T2WI without contrast enhancement. An understanding of the degeneration of leiomyomata is essential when considering UFE.

Uterine artery embolization for symptomatic fibroids with high signal intensity on T2-weighted MR imaging.

OBJECTIVE: To evaluate the effectiveness of uterine artery embolization (UAE) for treating symptomatic fibroids with high signal intensity (SI) on magnetic resonance (MR) T2-weighted imaging (T2WI). MATERIALS AND METHODS: A total of 537 cases, consisting of 14 patients with high SI fibroids on T2WI (T2 high group), were retrospectively included and compared with 28 randomly selected patients with low SI fibroids on T2WI (control group). High SI of a predominant fibroid on T2WI was defined as having the same or higher SI than the myometrium. Patient ages ranged from 28 to 52 years (mean, 38.1 years). All patients underwent MRI before and after UAE. Predominant fibroid and uterine volumes were calculated with MR images. Symptom status in terms of menorrhagia and dysmenorrhea was scored on a scale of 0-10, with 0 being no symptoms and 10 being the baseline, or initial symptoms. RESULTS: Of the patients in the T2 high group, 13 out of 14 (92.9%) patients demonstrated complete necrosis of the predominant fibroids. The mean volume reduction rates of the predominant fibroids in the T2 high group was 61.7% at three months after UAE, which was significantly higher than the volume reduction rates of 42.1% noted in the control group (p < 0.05). Changes in symptom scores for menorrhagia and dysmenorrhea after UAE (baseline score minus follow-up score) were 4.9 and 7.5 in T2 high group and they were 5.0 and 7.7 in control group, suggesting a significant resolution of symptoms (p < 0.01) in both groups but no significant difference between the two groups. CONCLUSION: UAE is effective for uttering fibroids showing high SI on T2WI. The mean volume reduction rate of the predominant fibroids three months after UAE was greater in the T2 high group than in the control group.

Contrast-enhanced MR angiography of uterine arteries for the prediction of ovarian artery embolization in 349 patients.

PURPOSE: To assess contrast-enhanced magnetic resonance (MR) angiographic findings of uterine arteries (UAs) and to evaluate the diagnostic utility of this imaging modality for the prediction of ovarian artery (OA) embolization (OAE). MATERIALS AND METHODS: The authors retrospectively evaluated 349 patients who underwent contrast-enhanced MR angiography before UA embolization (UAE) for symptomatic fibroid tumors or adenomyosis. The diameters of the UAs were compared with those of the inferior mesenteric arteries (IMAs) and classified into two groups: group I, in which the diameters of both UAs were the same as or greater than that of the IMA; and group II, in which at least one UA was smaller than the IMA or was not visible. The presence of an enlarged OA was also evaluated. Sensitivity and specificity were calculated for UA diameter, enlarged OA, and the combination of the two. RESULTS: Nine of 22 patients (40.9%) in group II underwent OAE, which was a significantly higher incidence (P < .001) than in group I (nine of 327; 2.8%). Among eight patients with enlarged OAs, six (75%) underwent OAE. Relative UA diameter had a sensitivity of 50% and specificity of 96.1%; the respective values for enlarged OAs were 33.3% and 99.3%. The combination of UA diameter and enlarged OAs showed a sensitivity and specificity of 72.2% and 95.4%, respectively. CONCLUSIONS: In addition to the identification of enlarged OAs, contrast-enhanced MR angiography allows a comparison between UA and IMA diameters and therefore can be helpful for the prediction of OAE.

Uterine artery embolization of large fibroids: comparative study of procedure with and without pretreatment gonadotropin-releasing hormone agonists.

OBJECTIVE: The purpose of this study was to evaluate the safety of pretreatment with gonadotropin-releasing hormone (GnRH) agonists before uterine artery embolization (UAE) of large fibroids. MATERIALS AND METHODS: The cases of 40 patients with large fibroids (≥ 10 cm) were retrospectively analyzed. Among the 40 patients, 28 (control group) underwent UAE without pretreatment with GnRH agonists, and 12 (GnRH group) received GnRH agonists 1-5 times before UAE. MRI was used to assess necrosis of large fibroids and their volumes in both groups within 3 months after UAE. RESULTS: Complete necrosis of large fibroids after UAE was achieved in 39 of 40 patients (97.5%). Only one patient, who was in the control group, had incomplete necrosis of the predominant fibroid. When GnRH agonists were administered before UAE, the mean volume reduction rate of fibroids was 36.3%. The final mean volume reduction rates of the predominant fibroids and the uterus after UAE in the GnRH group were 56.5% (range, 38-79%) and 50.8% (range, 35-72%), significantly higher than the volume reduction rates of 35.1% (range, 7-65%) and 34.9% (range, 16-54%) in the control group (p < 0.001). Grade D complications were not seen in the GnRH group but occurred in four patients in the control group. CONCLUSION: Pretreatment with GnRH agonists before UAE of large fibroids was safe for patients with large fibroids and did not prevent performance of UAE.

Uterine artery embolization (UAE) for diffuse leiomyomatosis of the uterus: clinical and imaging results.

PURPOSE: The aim of the current study was to evaluate the efficacy of uterine artery embolization (UAE) in the management of diffuse uterine leiomyomatosis with mid-term follow-up. MATERIALS AND METHODS: All patients who underwent UAE between 2008 and 2010 for symptomatic fibroids were analyzed. Among 360 cases, a total of 7 patients with diffuse uterine leiomyomatosis diagnosed based on MRI were included in this retrospective study. Patient ages ranged from 29 to 38 (mean 32.7) years. The median follow-up period was 16 (range; 6-31) months. The embolic agent was non-spherical polyvinyl alcohol particles. All patients underwent follow-up MRI at 3 months after UAE. Uterine volumes were calculated using MRI. Menorrhagia symptom changes were assessed at mid-term follow-up. RESULTS: There were no technical failures to catheterize the uterine artery and no adverse events requiring therapy after UAE. Contrast-enhanced MRI showed complete necrosis of the leiomyomatous nodules in 5 patients (71%) 3 months after embolization. Two patients (28%) showed mostly leiomyomatous nodules that were necrotized, some of which were still viable. All 7 patients with menorrhagia had improvement of symptoms at the mid-term follow-up. The initial mean uterine volume was 601.30 ± 533.92 cm(3) and was decreased to a mean of 278.81 ± 202.70 cm(3) at 3 months follow-up, for a mean uterus volume reduction rate of 50.1% (p<0.05). One patient became pregnant 5 months after UAE treatment. CONCLUSION: UAE was a highly effective treatment for diffuse uterine leiomyomatosis with mid-term durability and may be a valuable alternative to hysterectomy.

Limited efficacy of uterine artery embolization for cervical leiomyomas.

PURPOSE: To explore the effectiveness of uterine artery embolization (UAE) in treating symptomatic fibroids in the uterine cervix. MATERIALS AND METHODS: Among 537 patients who underwent UAE, 10 who had fibroids located in the cervix were retrospectively analyzed. The mean diameter of the fibroids was 6.0 cm. Seven of the 10 patients presented a total of 10 fibroids in the uterine body or fundus simultaneously. Fibroids of the cervix and fibroids in the body or fundus were compared in terms of the effects of UAE on the treatment thereof and vascularity on angiographic findings. Cervical leiomyomas were classified into three grades based on the vascularity seen on aortography, from grade I, indicating poor vascularity, to grade III, indicating hypervascularity. Necrosis of fibroids was assessed by magnetic resonance imaging 3 months after UAE. RESULTS: Complete necrosis of leiomyomas in the uterine cervix was seen in only two of the 10 patients (20%), whereas all fibroids in the uterine body or fundus were completely infarcted (P < .05). Partial necrosis (PN) of the fibroid with a thin viable rim was seen in two patients, whereas PN with a thick rim was seen in four and no necrosis was seen in two. Grade I (ie, poor) vascularity was noted in five of nine patients (55.6%) with cervical fibroids larger than 3 cm. CONCLUSIONS: Poor vascularity was a frequent finding among cervical leiomyomas, and the outcomes of UAE for cervical leiomyomas were disappointing, indicating a need for caution in selecting and counseling patients for this treatment.

CT findings after nephron-sparing surgery of renal tumors.

OBJECTIVE: The purpose of this article is to show the CT findings of the various postoperative changes, surgical complications, and tumor recurrence after nephron-sparing surgery for the treatment of renal tumors. CONCLUSION: Familiarity with the various postoperative changes after nephron-sparing surgery may help radiologists in differentiating these changes from tumor recurrence or surgical complications.