Imaging and pathology findings after an initial negative MRI-US fusion-guided and 12-core extended sextant prostate biopsy session

PURPOSE

A magnetic resonance imaging-ultrasonography (MRI-US) fusion-guided prostate biopsy increases detection rates compared to an extended sextant biopsy. The imaging characteristics and pathology outcomes of subsequent biopsies in patients with initially negative MRI-US fusion biopsies are described in this study.

MATERIALS AND METHODS

We reviewed 855 biopsy sessions of 751 patients (June 2007 to March 2013). The fusion biopsy consisted of two cores per lesion identified on multiparametric MRI (mpMRI) and a 12-core extended sextant transrectal US (TRUS) biopsy. Inclusion criteria were at least two fusion biopsy sessions, with a negative first biopsy and mpMRI before each.

RESULTS

The detection rate on the initial fusion biopsy was 55.3%; 336 patients had negative findings. Forty-one patients had follow-up fusion biopsies, but only 34 of these were preceded by a repeat mpMRI. The median interval between biopsies was 15 months. Fourteen patients (41%) were positive for cancer on the repeat MRI-US fusion biopsy. Age, prostate-specific antigen (PSA), prostate volume, PSA density, digital rectal exam findings, lesion diameter, and changes on imaging were comparable between patients with negative and positive rebiopsies. Of the patients with positive rebiopsies, 79% had a positive TRUS biopsy before referral (P = 0.004). Ten patients had Gleason 3+3 disease, three had 3+4 disease, and one had 4+4 disease.

CONCLUSION

In patients with a negative MRI-US fusion prostate biopsy and indications for repeat biopsy, the detection rate of the follow-up sessions was lower than the initial detection rate. Of the prostate cancers subsequently found, 93% were low grade (≤3+4). In this low risk group of patients, increasing the follow-up time interval should be considered in the appropriate clinical setting.Prostate cancer is the most common cancer in males, with an estimated 238 590 new diagnoses annually in the USA, and it is the second leading cause of cancer-related mortality in males (1). One in six males will develop prostate cancer in his lifetime (1). The current standard of care for diagnosing and grading prostate cancer is a 12-core extended sextant biopsy obtained with transrectal ultrasonography (TRUS) guidance (2, 3). As magnetic resonance imaging (MRI) has superior contrast resolution than ultrasonography (US), it is possible for multiparametric MRI (mpMRI) to detect prostate cancer with high reliability (4). Since clinically insignificant cancer is often invisible to magnetic resonance (MR), prostate MRI preferentially detects more aggressive cancers (5–9). MRI can be used to guide the prostate biopsy, either using a direct “in-gantry” approach or by using MRI-US fusion, which was developed as an office-based alternative (10). MRI-US targeted biopsies have about twice the per-core detection rate of sextant biopsies (11), and have been shown to be particularly useful for prostates measuring greater than 40 mL, which typically have lower rates of cancer detection than smaller prostate glands (12).Since TRUS-guided biopsies have a relatively low sensitivity, many patients with a rising prostate-specific antigen (PSA), but an initial negative biopsy, undergo additional biopsies with progressively lower yields. In a study of sequential systematic biopsies in 1051 males, the detection rate of successive biopsies was 22%, 10%, 5%, and 4%, respectively (13). The third and fourth TRUS-guided biopsy sessions detected lower grade cancers and were found to have higher morbidity than the first two biopsies. Recently, MRI-US fusion biopsy has been reported to increase cancer detection rates in the setting of a prior negative TRUS biopsy (14, 15).While MRI-US fusion biopsy is promising in the setting of previous negative random sampling, the response to a negative MRI-US fusion biopsy is less clear. Since a MRI-US fusion biopsy increases prostate cancer detection, this population should have a lower disease burden than patients with an initial negative TRUS-guided biopsy alone. Now that MRI-US fusion biopsies have been available for several years, such data are beginning to accumulate. Here, we investigate the detection rates of subsequent biopsies in patients with an initial negative MRI-US fusion prostate biopsy.     

Deep Learning Network for Segmentation of the Prostate Gland With Median Lobe Enlargement in T2-weighted MR Images: Comparison With Manual Segmentation Method

PurposeAim of this study was to evaluate a fully automated deep learning network named Efficient Neural Network (ENet) for segmentation of prostate gland with median lobe enlargement compared to manual segmentation.Materials and MethodsOne-hundred-three patients with median lobe enlargement on prostate MRI were retrospectively included. Ellipsoid formula, manual segmentation and automatic segmentation were used for prostate volume estimation using T2 weighted MRI images. ENet was used for automatic segmentation; it is a deep learning network developed for fast inference and high accuracy in augmented reality and automotive scenarios. Student t-test was performed to compare prostate volumes obtained with ellipsoid formula, manual segmentation, and automated segmentation. To provide an evaluation of the similarity or difference to manual segmentation, sensitivity, positive predictive value (PPV), dice similarity coefficient (DSC), volume overlap error (VOE), and volumetric difference (VD) were calculated.ResultsDifferences between prostate volume obtained from ellipsoid formula versus manual segmentation and versus automatic segmentation were statistically significant (P < 0.049318 and P < 0.034305, respectively), while no statistical difference was found between volume obtained from manual versus automatic segmentation (P = 0.438045). The performance of ENet versus manual segmentations was good providing a sensitivity of 93.51%, a PPV of 87.93%, a DSC of 90.38%, a VOE of 17.32% and a VD of 6.85%.ConclusionThe presence of median lobe enlargement may lead to MRI volume overestimation when using the ellipsoid formula so that a segmentation method is recommended. ENet volume estimation showed great accuracy in evaluation of prostate volume similar to that of manual segmentation.     

Nasopharyngeal carcinoma tumor volume measurement.

Tumor volume was measured in 69 patients with nasopharyngeal carcinoma. On transverse nonenhanced T1-weighted and gadolinium-enhanced T1-weighted magnetic resonance (MR) images, segmentation was performed by means of seed growing and knowledge-based fuzzy clustering methods. Data were compared with those collected with the manual tracing method and analyzed for interoperator variance and interobserver reliability. There was no significant difference between the volumes determined with manual tracing or semiautomated segmentation (P >.05). On the volume level, Pearson correction coefficients were close for both the manual tracing and semiautomated methods. Significant differences in interoperator variance existed between the two methods on the pixel level (P <.05). Compared with manual tracing, the semiautomated method helped reduce interoperator variance and obtain higher interobserver reliability. Findings in the current study validate the use of semiautomated volume measurement methods for nasopharyngeal carcinoma.     

Evaluation of prostate volume in mpMRI: comparison of the recommendations of PI-RADS v2 and PI-RADS v2.1

PURPOSEWe aimed to evaluate the prostate volumes calculated as recommended in the PI-RADS v2 and PI-RADS v2.1 guidelines, intraobserver and interobserver variability, and the agreement between the two measurement methods.METHODSProstate mpMRI examinations of 114 patients were evaluated retrospectively. T2-weighted sequences in the axial and sagittal planes were used for the measurement of the prostate volume. The measurements were performed by two independent observers as recommended in the PI-RADS v2 and PI-RADS v2.1 guidelines. Both observers conducted the measurements twice and the average values were obtained. In order to prevent bias, the observers carried out measurements at one-week intervals. In order to assess intraobserver variability, observers repeated the measurements again at one-week intervals. The prostate volume was calculated using the ellipsoid formula (W×H×L×0.52).RESULTSIntraclass correlation coefficient (ICC) revealed almost perfect agreement between the first and second observers for the measurements according to both PI-RADS v2 (0.93) and PI-RADS v2.1 (0.96) guidelines. The measurements were repeated by both observers. According to the ICC values, there was excellent agreement between the first and second measurements with respect to both PI-RADS v2 and PI-RADS v2.1 for first (0.94 and 0.96, respectively) and second observer (0.94 and 0.97, respectively). For both observers, the differences had a random, homogeneous distribution, and there was no clear relationship between the differences and mean values.CONCLUSIONThe ellipsoid formula is a reliable method for rapid assessment of prostate volume, with excellent intra- and interobserver agreement and no need for expert training. For the height measurement, the recommendations of the PIRADS v2.1 guideline seem to provide more consistently reproducible results.

The prostate gland is one of the organs for which the disease incidence and prevalence in men increases with age. Prostate volume (PV) has an important role in the evaluation and management of both malignant and benign prostate diseases (1–3). In benign prostatic hyperplasia (BPH), prostate volume is used to decide upon treatment and evaluate response to medical therapy (3–5). In the diagnosis of prostate cancer, one of the important markers is prostate-specific antigen (PSA), but it has low specificity, and therefore PSA derivatives are used to increase its specificity. One example is PSA density, which is obtained by dividing the PSA value by PV. In the treatment of prostate cancer, PV is important, and the effectiveness of brachytherapy decreases in prostates with a volume greater than 50 mL (6). Furthermore, PV is used to identify appropriate patients for brachytherapy and select the number of radioactive seeds, and also determine fractionation for external beam radiation, radical prostatectomy operating planning and continence rate counseling, and focal therapy candidacy preparation (7, 8). For these reasons, it is vital to accurately calculate PV.There are many methods that can be used to calculate PV, with the ellipsoid formula being one of the most preferred since it is easy to apply and highly time-efficient (1–4, 9). Many studies have shown that this method has high accuracy due to the elliptic shape of the prostate (1, 2, 10–13). The ellipsoid formula is obtained by multiplying the height (anterior-posterior), width (medio-lateral) and length (cranio-caudal) values of the prostate by 0.52. These measurements can be performed by transrectal ultrasonography (TRUS) or magnetic resonance imaging (MRI). TRUS has certain disadvantages, such as being operator-dependent and susceptible to sonographic artifacts (14). MRI, which has become increasingly popular in recent years, allows for an accurate definition of the prostate boundaries and multiplanar measurements through its high contrast resolution of soft tissues (1, 5). It also provides more accurate measurements than TRUS (4, 15, 16).In order to ensure global standardization in the reporting of prostate MRI findings, PI-RADS v2 published in 2015, which is the revised version of PI-RADS 1.0, and the last updated version PI-RADS v2.1 made available in 2019, propose different calculation methods for the measurement of height in obtaining PV (17, 18). The midaxial plane is recommended for this measurement in PI-RADS v2, while the midsagittal plane is recommended in PI-RADS v2.1. This study aimed to evaluate the interobserver and intraobserver variability of PV calculated by both measurement methods and the agreement between the two measurement methods.     

Multiparametric MRI guidance in first-time prostate biopsies: what is the real benefit?

PURPOSE

With the increased recognition of the capabilities of prostate multiparametric (mp) magnetic resonance imaging (MRI), attempts are being made to incorporate MRI into routine prostate biopsies. In this study, we aimed to analyze the diagnostic yield via cognitive fusion, transrectal ultrasound (TRUS)-guided, and in-bore MRI-guided biopsies in biopsy-naive patients with positive findings for prostate cancer screening.

METHODS

Charts of 140 patients, who underwent transrectal prostate biopsy after the adaptation of mp-MRI into our routine clinical practice, were reviewed retrospectively. Patients with previous negative biopsies (n=24) and digital rectal examination findings suspicious for ≥cT3 prostate cancer (n=16) were excluded. T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast-enhanced imaging were included in mp-MRI. Cognitive fusion biopsies were performed after a review of mp-MRI data, whereas TRUS-guided biopsies were performed blinded to MRI information. In-bore biopsies were conducted by means of real-time targeting under MRI guidance.

RESULTS

Between January 2012 and February 2014, a total of 100 patients fulfilling the inclusion criteria underwent TRUS-guided (n=37), cognitive fusion (n=49), and in-bore (n=14) biopsies. Mean age, serum prostate specific antigen level, and prostate size did not differ significantly among the study groups. In TRUS-guided biopsy group, 51.3% were diagnosed with prostate cancer, while the same ratio was 55.1% and 71.4% in cognitive fusion and in-bore biopsy groups, respectively (P = 0.429). Clinically significant prostate cancer detection rate was 69.1%, 70.3%, and 90% in TRUS-guided, cognitive fusion, and in-bore biopsy groups, respectively (P = 0.31). According to histopathologic variables in the prostatectomy specimen, significant prostate cancer was detected in 85.7%, 93.3%, and 100% of patients in TRUS-guided, cognitive fusion, and in-bore biopsy groups, respectively.

CONCLUSION

In the first set of transrectal prostate biopsies, mp-MRI guidance did not increase the diagnostic yield significantly.Transrectal ultrasound-guided prostate biopsy (TRUS-guided) to diagnose prostate cancer is currently estimated to be performed in one million men annually in the USA (1). The original random systematic, six-core transrectal prostate biopsy, initially described by Stamey in 1989 (2), has incorporated more cores over time, with laterally directed 12–14 cores being an accepted practice standard. The major limitation of random systematic sampling is that; clinically insignificant cancers are often identified by chance and affect survival data due to lead and length time bias from overdetection and overtreatment of indolent disease (3). Unlike the diagnostic pathways for other organ cancers, which include direct visual or radiologic guidance, the prostate is being sampled by way of standardized, systematic but essentially random approaches.With the aid of multiparametric MRI of the prostate (mp-MRI), clinically relevant localized prostate cancer foci may be identified, selectively sampled, and treated (4–6). Hence attempts are being made to incorporate mp-MRI into routine prostate biopsies. Techniques of MRI-targeted biopsy include visual estimation TRUS-guided biopsy (cognitive fusion); software co-registered MRI-ultrasound TRUS-guided biopsy; and in-bore MRI-guided biopsy.MRI-guided prostate biopsies are particularly useful in the setting of ongoing clinical suspicion of prostate cancer despite previous negative biopsies. Among men with a previous negative biopsy, 72% to 87% of cancers detected by MRI-guidance are clinically significant (7). Likewise, mp-MRI findings can also be utilized to cognitively tailor the initial transrectal prostate biopsy protocol. Among men with no previous biopsy, MRI increases the frequency of significant cancer detection to 50% in low risk and 71% in high risk patients (7).In this study, we aimed to compare the diagnostic efficiency of cognitive fusion, TRUS-guided and in-bore biopsies, which were conducted as the initial sampling modality, in terms of detecting clinically significant prostate cancer.     

Image-guided focal therapy for prostate cancer

The adoption of routine prostate specific antigen screening has led to the discovery of many small and low-grade prostate cancers which have a low probability of causing mortality. These cancers, however, are often treated with radical therapies resulting in long-term side effects. There has been increasing interest in minimally invasive focal therapies to treat these tumors. While imaging modalities have improved rapidly over the past decade, similar advances in image-guided therapy are now starting to emerge—potentially achieving equivalent oncologic efficacy while avoiding the side effects of conventional radical surgery. The purpose of this article is to review the existing literature regarding the basis of various focal therapy techniques such as cryotherapy, microwave, laser, and high intensity focused ultrasound, and to discuss the results of recent clinical trials that demonstrate early outcomes in patients with prostate cancer.Last year in the United States approximately 238 590 men were diagnosed with prostate cancer and 29 720 died as a result of their disease (1). The majority of diagnosed cases represent low-risk, organ-confined disease, and these may be over-treated if conventional treatment methods (i.e., radical prostatectomy and whole-gland external beam radiation therapy) are employed. In this setting, focal therapy has emerged as a treatment alternative that can spare patients from many of the undesired side effects associated with more radical therapies. There is currently a great demand to determine the safest and most effective focal treatment for localized prostate cancer.Critical to the use of focal therapies is the development of good diagnostic methods that can localize cancer accurately, thereby permitting focal therapy. The effectiveness of prostate specific antigen (PSA) plus multiparametric magnetic resonance imaging (MRI), followed by an MRI/transrectal ultrasonography (MRI/TRUS) biopsy is now well documented, and can be considered a strong alternative to current routine screening practice which includes a digital rectal exam or serum PSA followed by a systematic TRUS-guided biopsy. Utility of this new, image-based approach has been reported in a large patient cohort treated at the National Institutes of Health (Bethesda, Maryland, USA) (2) and externally validated by a recent phase III clinical trial by Rastinehad et al. (3). The era of targeted biopsies has naturally led to the development of focal therapy approaches for prostate cancer.Several methods of focal therapy using different ablative mechanisms such as cryotherapy, microwave, laser, and high intensity focused ultrasound (HIFU) have been introduced. However, there are limitations and unknowns for each of them. Little evidence is currently available to prove that any one method is more effective than the others over long-term follow-up. Several of these technologies are not yet Federal Drug Administration (FDA) approved, and they are currently undergoing clinical trials to determine their efficacy, safety, and long-term outcomes. As an added barrier, each new ablative technique requires further specialized training of the provider. Each method has its own set of side effects and/or complications. The three most common concerns regarding focal therapy are: oncologic efficacy, sexual potency, and urinary incontinence.Many patients with low-grade cancers choose active surveillance to monitor their cancers. This includes serial PSA measurements and biopsies. Multiparametric MRI is also increasingly used to monitor patients on active surveillance (4). Unfortunately, many men fall off active surveillance and require some sort of radical therapy. However, until the various focal therapies are proven efficacious in longitudinal studies and it is determined that the “prostate trifecta” (effective cancer treatment, urinary control, and preserved erectile function) can be safely achieved, the dilemma of which treatment to choose will continue to exist for patients and their physicians. In this review, we aim to highlight the history and current status of focal therapy options in prostate cancer, as well as discuss the impact and importance of imaging.     

Endovascular management of iatrogenic renal arterial lesions and clinical outcomes

PURPOSE

We aimed to evaluate iatrogenic renal arterial lesions, including pseudoaneurysm, arteriovenous fistula, and arteriocaliceal fistula, their management by endovascular embolization, and the clinical results.

METHODS

Fifty-five patients (forty males, fifteen females) with a median age of 40 years (range, 8–85 years), who underwent endovascular embolization of iatrogenic renal arterial lesions between March 2003 and December 2013 were included in this retrospective study. Types of iatrogenic lesions and details of embolization procedures were reported. Estimated glomerular filtration rate (eGFR), renal function tests, hemoglobin, and hematocrit levels before and after embolization were recorded and compared.

RESULTS

Median follow-up was 24 months. We identified 53 pseudoaneurysms, 30 arteriovenous fistulas, and 11 arteriocaliceal fistulas in 55 patients, after percutaneous nephrolithotomy (n=26), renal biopsy (n=21), nephrostomy (n=3), renal surgery (n=3), and extracorporeal shock wave lithotripsy (n=2). Median number of pseudoaneurysms was 1 (range, 1–4) with a median size of 7 mm (range, 1.5–35 mm). Fifty-one patients underwent coil embolization. Median number of coils was 5 (range, 2–21) and median renal parenchymal loss was 5% (range, 1%–50%). There were no significant differences between pre- and postoperative eGFR and serum parameters.

CONCLUSION

Iatrogenic renal arterial lesion can be a life threatening condition. Superselective coil embolization is a safe, minimally invasive treatment option with minimal renal parenchymal loss and without significant change in renal function.Iatrogenic renal arterial lesions including pseudoaneurysm (PA), arteriovenous fistula (AVF), and arteriocaliceal fistula (ACF) are rare, but life-threatening conditions (1). The chief symptom usually includes macroscopic hematuria (2, 3). Catheter angiography is the gold standard for both diagnosis and treatment (1).Previous studies have evaluated the iatrogenic renal arterial lesions following partial nephrectomy (1, 3–7), but there were only a few studies on iatrogenic renal arterial lesions following any iatrogenic renal interventions (2). In the present study, to the best of our knowledge, we report the largest series of iatrogenic renal arterial lesions following various renal interventions such as biopsy, percutaneous nephrolithotomy (PCNL), percutaneous nephrostomy, and partial nephrectomy. We focused on clinical presentations, imaging findings, management, and outcomes.     

Natural history of small index lesions suspicious for prostate cancer on multiparametric MRI: recommendations for interval imaging follow-up

PURPOSE

We aimed to determine the natural history of small index lesions identified on multiparametric-magnetic resonance imaging (MP-MRI) of the prostate by evaluating lesion-specific pathology and growth on serial MP-MRI.

MATERIALS AND METHODS

We performed a retrospective review of 153 patients who underwent a minimum of two MP-MRI sessions, on an institutional review board-approved protocol. Index lesion is defined as the lesion(s) with the highest cancer suspicion score based on initial MP-MRI of a patient, irrespective of size. Two study cohorts were identified: (1) patients with no index lesion or index lesion(s) ≤7 mm and (2) a subset with no index lesion or index lesion(s) ≤5 mm. Pathological analysis of the index lesions was performed following magnetic resonance/ultrasound fusion-guided biopsy. Growth rate of the lesions was calculated based on MP-MRI follow-up.

RESULTS

Patients with small index lesions measuring ≤7 mm (n=42) or a subset with lesions ≤5 mm (n=20) demonstrated either benign findings (86.2% and 87.5%, respectively) or low grade Gleason 6 prostate cancer (13.8% and 12.5%, respectively) on lesion-specific targeted biopsies. These lesions demonstrated no significant change in size (P = 0.93 and P = 0.36) over a mean imaging period of 2.31±1.56 years and 2.40±1.77 years for ≤7 mm and ≤5 mm index lesion thresholds, respectively. These findings held true on subset analyses of patients who had a minimum of two-year interval follow-up with MP-MRI.

CONCLUSION

Small index lesions of the prostate are pathologically benign lesions or occasionally low-grade cancers. Slow growth rate of these small index lesions on serial MP-MRI suggests a surveillance interval of at least two years without significant change.Prostate cancer is the most common solid-organ malignancy in men in the western world, and it is one of the leading causes of cancer-related mortality (1). Widespread prostate specific antigen (PSA)-based screening has resulted in a marked increase in the rate of prostate cancer diagnosis, accompanied by significant downward grade and stage migration, as well as a decrease in mortality rate, though not commensurate with the detection rate (2, 3). Hence, there is a tendency to overtreat clinically-insignificant prostate cancer, leading to concerns regarding the quality of life. This has prompted renewed interest in more conservative management with active surveillance and investigational focal therapy options.Clinically-insignificant prostate cancer has been defined as small tumors with low Gleason grade, although thresholds for these parameters are not fully agreed upon (4–6). For instance, many reports use a lesion size threshold of 0.5 cm³, which corresponds to a spherical lesion with a diameter of approximately 1 cm (7). However, some investigators have used even smaller volume thresholds of 0.2 cm³ and 0.5 cm³ based on overall prostate cancer tumor burden on radical prostatectomy specimens with clinically-insignificant disease. Due to the formalin fixation and tissue contraction of the prostatectomy specimens, these lower volume thresholds would perhaps more accurately correspond to 5 mm and 7 mm diameter spherical lesions in the setting of prostates bearing two to three cancer foci, given the commonly multifocal nature of prostate cancer (8, 9).Multiparametric-magnetic resonance imaging (MP-MRI) of the prostate has been investigated as an anatomic and functional imaging method to aid in cancer detection (9–14). A subset of patients undergoing MP-MRI is found to have small index lesions, which would represent clinically-insignificant disease if found to harbor prostate cancer. In fact, when such lesions are biopsied they often prove to harbor benign tissue or low grade disease, and it would be tempting to use MP-MRI to monitor such patients. However, the optimal imaging interval has not been determined. Herein, we aim to define the natural history of small index lesions detected on MP-MRI, based on lesion-specific biopsy pathology and investigate subsequent growth rates determined by serial MRI studies.     

MR angiography-planned prostatic artery embolization for benign prostatic hyperplasia: single-center retrospective study in 56 patients

PURPOSEWe aimed to evaluate the advantages of magnetic resonance angiography (MRA)-planned prostatic artery embolization (PAE) for benign prostatic hyperplasia (BPH).METHODSIn this retrospective study, MRAs of 56 patients (mean age, 67.23±7.73 years; age range, 47–82 years) who underwent PAE between 2017 and 2018 were evaluated. For inclusion, full information about procedure time and radiation values must have been available. To identify prostatic artery (PA) origin, three-dimensional MRA reconstruction with maximum intensity projection was conducted in every patient. In total, 33 patients completed clinical and imaging follow-up and were included in clinical evaluation.RESULTSThere were 131 PAs with a second PA in 19 pelvic sides. PA origin was correctly identified via MRA in 108 of 131 PAs (82.44%). In patients in which MRA allowed a PA analysis, a significant reduction of the fluoroscopy time (−27.0%, p = 0.028) and of the dose area product (−38.0%, p = 0.003) was detected versus those with no PA analysis prior to PAE. Intervention time was reduced by 13.2%, (p = 0.25). Mean fluoroscopy time was 30.1 min, mean dose area product 27,749 μGy·m², and mean entrance dose 1553 mGy. Technical success was achieved in all 56 patients (100.0%); all patients were embolized on both pelvic sides. The evaluated data documented a significant reduction in international prostate symptom scores (p < 0.001; mean 9.67 points).CONCLUSIONMRA prior to PAE allowed the identification of PA in 82.44% of the cases. MRA-planned PAE is an effective treatment for patients with BPH.

A profound knowledge about pelvic vessel anatomy is essential for achieving successful prostatic artery embolization (PAE), to improve the safety of PAE and to avoid major complications as non-target embolization (1–6). This knowledge can be achieved by using angiographic techniques to show pelvic artery anatomy, although the best method is still controversially discussed. In some studies, computed tomography (CT) angiography (CTA) was used for pre-interventional evaluation as it is described to have high certainty in analyzing prostatic artery (PA) anatomy (1, 3, 7). Other institutes use digital subtraction angiography (DSA) and cone beam CT (CBCT) for analysis without any pre-procedural vessel imaging (8–11). Since peri-interventional DSA findings may be ambiguous and CTA or CBCT would imply additional radiation, magnetic resonance angiography (MRA) seems to be a promising method to analyze PA origin without radiation. However, Maclean et al. (3) recommend CT for planning PAE instead of magnetic resonance imaging (MRI) as the latter is more expensive and more time-consuming. Pisco et al. (5, 12) state that MRA does not have enough resolution for clear identification of PA origin and does not provide the same information as CTA.Currently only a few studies discuss the suitability of MRA for preprocedural planning of PAE. Kim et al. (13) first investigated this subject with a sample size of 17 patients and documented an accuracy of 76.5% for PA origin analysis. However, in this study no clinical evaluation was included. Zhang et al. (4) investigated MRA analysis prior to PAE in a randomized clinical trial with 100 patients. A sensitivity of 91.5% and a significant reduction of procedure time, fluoroscopy time, radiation dose, and contrast medium volume due to pre-interventional MRA were documented. In his review, Prince (14) agrees with Zhang et al. (4) that MRA may be a suitable method for planning PAE.Because of the skeptical comments whether performing MRA prior to PAE is practical on a daily basis in a radiological institution, an assessment of these parameters in a less selective nature was necessary. In addition, contrary to Zhang et al. (4) who used MIP-reconstructions and 5° interval images for their assessment, we used a three-dimensional (3D) reconstruction of the pelvic arterial tree based on the MRA sequences. The main advantage of the 3D reconstruction is that it can be freely rotated in all directions which allowed an easy identification and tracking of the PA.In this study, the advantages and clinical outcome of pre-interventional analysis of PA via MRA as a possible radiation-free planning method and its influence on procedure time and radiation dose were investigated.     

MRI-guided core needle biopsy of the prostate: acceptance and side effects

PURPOSE

We aimed to study side effects, complications, and patient acceptance of magnetic resonance imaging-guided real-time biopsy (MRI-GB) of the prostate.

METHODS

Fifty-four men (49–78 years) with elevated prostate-specific antigen after at least one negative systematic transrectal ultrasound-guided biopsy (TRUS-GB) were included in a prospective clinical study. Suspicious areas on images were selectively sampled by obtaining a median of four specimens (range, 1–9 specimens) using MRI-GB. In TRUS-GB, a median of 10 specimens (range, 6–14 specimens) were obtained. Telephone interviews were conducted one week after outpatient MRI-GB, asking patients about pain and side effects (hematuria, hemospermia, rectal bleeding, fever, and chills) of the two biopsy procedures and which of the two procedures they preferred. Multinomial regression analysis and Fisher’s exact test was used to test for differences.

RESULTS

MRI-GB was preferred by 65% (35/54), and 82% (44/54) would undergo MRI-GB again. Pain intensity (P = 0.005) and bleeding duration (P = 0.004) were significantly lower for MRI-GB compared with TRUS-GB. Hematuria was less common after MRI-GB compared with TRUS-GB (P = 0.006). A high correlation was given between bleeding intensity and bleeding duration for TRUS-GB (r=0.77) and pain intensity and pain duration for MRI-GB (r=0.65). Although hemospermia, rectal hemorrhage, fever, and chills were less common in MRI, they showed no statistically significant difference.

CONCLUSION

MRI-GB of the prostate seems to have fewer side effects and less pain intensity than TRUS-GB and was preferred by the majority of patients.Several new recommendations about routine prostate-specific antigen (PSA) screening were recently published (1). Nevertheless, guidelines still recommend that patients with PSA levels suspicious for prostate cancer should undergo transrectal ultrasound-guided biopsy (TRUS-GB). The likelihood of detecting cancer by the first TRUS-GB is below 60% and only 16%–29% for repeat biopsy (2, 3). However, a negative systematic TRUS-GB does not definitely rule out prostate cancer in patients with a persistent clinical suspicion (4, 5). In this situation, multiparametric magnetic resonance imaging (MRI) including diffusion-weighted imaging, dynamic contrast-enhanced MRI, and magnetic resonance spectroscopy is being increasingly used to detect prostate cancer and confirm the diagnosis by MRI-guided biopsy (MRI-GB) (6).While several studies are available on the side effects, complications, and pain experienced by patients who undergo TRUS-GB, no study has been published on the acceptance and side effects of MRI-GB of the prostate (7–9). We therefore conducted a survey among patients who underwent MRI-GB of suspicious areas detected by MRI after a history of at least one negative TRUS-GB. The aim of this survey was to evaluate the acceptance of MRI-GB of the prostate in terms of side effects and complications in comparison with TRUS-GB.     

Whole-brain atrophy in multiple sclerosis measured by automated versus semiautomated MR imaging segmentation

BACKGROUND AND PURPOSE: Semiautomated and automated methods are used to measure whole-brain atrophy in multiple sclerosis (MS), but their comparative reliability, sensitivity, and validity are unknown. METHODS: Brain parenchymal fraction (BPF) was measured in patients with MS (n = 52) and healthy control subjects (n = 17) by four methods: semiautomated or automated segmentation and 2D or 3D pulse sequences. Linear measures of atrophy, whole-brain lesion volumes, and clinical data were used to explore validity. RESULTS: The 2D automated method yielded unreliable segmentation and was discarded. The three other BPF methods produced data that were highly intercorrelated and indistinguishable by analysis of variance. In the MS group, semiautomated (2D: 0.84 +/- 0.04, P <.001; 3D: 0.84 +/- 0.05, P =.04) and automated 3D (0.83 +/- 0.05, P =.002) BPFs were lower than controls (semiautomated 2D: 0.88 +/- 0.02; 3D: 0.88 +/- 0.03; automated 3D: 0.88 +/- 0.03). In the MS group, the semiautomated (r = -.79 to -.82) and automated 3D (r = -.81) BPFs inversely correlated with third ventricular width and showed similarly robust correlations with the bicaudate ratio (all r = -.74). The semiautomated and automated BPFs showed similar, moderate correlations with T1 hypointense and FLAIR hyperintense lesion volume, physical disability (Expanded Disability Status Scale) score, and disease duration and similar differences between secondary progressive and relapsing-remitting patients. The intraobserver, interobserver, and test-retest reliability was somewhat higher for the automated than for the semiautomated methods. CONCLUSION: These automated and semiautomated measures of whole-brain atrophy provided similar and nearly interchangeable data regarding MS. They discriminated MS from healthy individuals and showed similar relationships to established disease variables.     

Benign prostatic hyperplasia: clinical overview and value of diagnostic imaging

The term benign prostatic hyperplasia has traditionally been used to describe a constellation of obstructive and irritative voiding symptoms that occur in men as they age. Such symptomatology may be due to a variety of causes, including prostatic enlargement. Thus, the term lower urinary tract symptoms has replaced BPH to describe this symptom complex. The evaluation and treatment of LUTS continues to be a significant part of urology practice in the United States, as well as a significant component of medical resource utilization. Currently, indication for treatment in patients with LUTS is most often based on subjective measurements of symptom severity and bother. Consequently, imaging does not play a major role in the evaluation of such patients. Recent data suggest that the size of the prostate gland may predict which patients with LUTS will develop progressive symptoms and complications. Moreover, both prostate size and the histologic composition of BPH may help to select patients for specific treatment options. Thus, radiologic imaging may eventually play a larger role in the diagnosis and treatment of LUTS in the future. After review of the literature, it appears that routine upper urinary tract imaging in patients with LUTS or BPH is not warranted. Selective use of such imaging tests in patients with BPH and either hematuria, laboratory evidence of renal insufficiency (elevated BUN or creatinine), or a history of urinary tract infection, urolithiasis, previous urinary tract surgery, or congenital or acquired renal disease remains indicated. Local imaging of the prostate can be performed with either MR imaging or TRUS. Although MR imaging provides excellent resolution of internal prostatic anatomy, information with respect to the ratio of glandular to stromal tissue in the prostate, and an accurate estimate of prostate volume, its use in patients with BPH is limited by its high cost and limited availability. In contrast, TRUS remains an important tool in the evaluation of patients with prostatic disease. Similar to MR imaging, TRUS provides excellent images of internal prostatic anatomy and an accurate estimate of prostate volume prior to treatment. In addition, this imaging modality is noninvasive, cost-efficient, easily adapted to office use, and able to provide guidance for transrectal prostate biopsy.     

Clinical applications of PET/MRI: current status and future perspectives

Fully integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) scanners have been available for a few years. Since then, the number of scanner installations and published studies have been growing. While feasibility of integrated PET/MRI has been demonstrated for many clinical and preclinical imaging applications, now those applications where PET/MRI provides a clear benefit in comparison to the established reference standards need to be identified. The current data show that those particular applications demanding multiparametric imaging capabilities, high soft tissue contrast and/or lower radiation dose seem to benefit from this novel hybrid modality. Promising results have been obtained in whole-body cancer staging in non-small cell lung cancer and multiparametric tumor imaging. Furthermore, integrated PET/MRI appears to have added value in oncologic applications requiring high soft tissue contrast such as assessment of liver metastases of neuroendocrine tumors or prostate cancer imaging. Potential benefit of integrated PET/MRI has also been demonstrated for cardiac (i.e., myocardial viability, cardiac sarcoidosis) and brain (i.e., glioma grading, Alzheimer’s disease) imaging, where MRI is the predominant modality. The lower radiation dose compared to PET/computed tomography will be particularly valuable in the imaging of young patients with potentially curable diseases. However, further clinical studies and technical innovation on scanner hard- and software are needed. Also, agreements on adequate refunding of PET/MRI examinations need to be reached. Finally, the translation of new PET tracers from pre-clinical evaluation into clinical applications is expected to foster the entire field of hybrid PET imaging, including PET/MRI.Both positron emission tomography (PET) and magnetic resonance imaging (MRI) are well-established imaging modalities that have been clinically available for more than 30 years. However, the combination of PET and computed tomography (CT) into PET/CT has heralded a new era of hybrid imaging driven by the rapid ascend of PET/CT and the decline of stand-alone PET. The integration of PET and CT into a hybrid system provided added value that exceeds the sum of its parts, in particular fast and accurate attenuation correction and the combination of anatomical and molecular information.Inspired by the vast success of PET/CT, the combination of PET and MRI was an obvious goal. Therefore initial solutions comprised the software based co-registration and post-hoc fusion (1) of independently acquired PET and MRI data, as well as shared tabletop sequential PET and MRI acquisition (2, 3). While the integration of PET and CT into a hybrid system was challenging but technically feasible, the integration of PET and MRI was considered extremely demanding, if not impossible. Two main technical challenges that had to be solved: in the first place development of a PET insert that is compatible to high magnetic field strengths normally used in MRI, and vice versa development of a magnetic resonance (MR) scanner that guarantees a stable and homogenous magnetic field in the presence of a PET insert. Conventional PET detectors consist of scintillation crystals and photomultipliers, and the latter, being very sensitive to magnetic fields, cannot be used in integrated PET/MRI systems. Hence, one approach was to replace photomultipliers by avalanche photodiodes (APDs), which are insensitive to even strong magnetic fields (4). The scintillation crystals used in PET/MRI scanners are usually composed of lutetium ortho-oxysilicate, with the advantage of only minor disturbances of magnetic field homogeneity (Fig. 1). Next generation PET/MRI scanners could be based on silicon photomultiplier PET detectors, which showed better performance characteristics than the APDs and, in contrast to these, are capable of time-of-flight imaging (5). Secondly, the development of MR-based attenuation correction methods is necessary, as the commonly used method for attenuation correction in PET/CT systems, which is based on the absorption of X-rays, is not transferable to MRI. Hence, different methods for attenuation correction in PET/MRI systems have been proposed, one of which consists of segmentation of the attenuation map into four classes (background, lung tissue, fat, and soft tissue) (6). In principle, the MR-based attenuation map is created with a two-point Dixon sequence (7), providing water-only and fat-only images, which are combined and segmented to form an MR-based attenuation map. The method proved its technical feasibility with the limitation that in bone tissue and in its vicinity standardized uptake values (SUV) derived from PET/MRI systems might be erroneously underestimated when compared to SUVs derived from PET/CT (8). Therefore, SUVs derived from PET/MRI systems should be interpreted carefully until a larger experience with the new method of PET/MRI exists.Open in a separate windowFigure 1.Diagram of an integrated PET/MRI scanner with capability of simultaneous PET and MRI data acquisition. Image courtesy of Siemens Healthcare, Erlangen, Germany.In 2010, the first fully integrated whole-body PET/MR hybrid imaging system based on APD technology and MR-based attenuation correction became commercially available (Biograph mMR, Siemens Healthcare, Erlangen, Germany) (9). As of December 2013 more than 50 of these systems have been sold (>40 installed, 10 ordered) in Europe, North America, Asia, and Australia (10).     

Perfusion CT imaging of the liver: review of clinical applications

Perfusion computed tomography (CT) has a great potential for determining hepatic and portal blood flow; it offers the advantages of quantitative determination of lesion hemodynamics, distinguishing malignant and benign processes, as well as providing morphological data. Many studies have reported the use of this method in the assessment of hepatic tumors, hepatic fibrosis associated with chronic liver disease, treatment response following radiotherapy and chemotherapy, and hepatic perfusion changes after radiological or surgical interventions. The main goal of liver perfusion imaging is to improve the accuracy in the characterization of liver disorders. In this study, we reviewed the clinical application of perfusion CT in various hepatic diseases.The advent of multidetector CT has given rise to the acquisition of images with higher quality and accuracy. Multidetector CT has been developed as a noninvasive imaging modality for evaluation of vascular anatomy. It has also made it possible to perform CT angiography of the hepatic vessels. New generation CT systems with multidetector are capable of performing volumetric imaging. These systems provide a single rotational acquisition and almost the whole upper abdomen can be appraised by means of serial rotational acquisitions at a single location in the z-direction. Multidetector CT imaging is used extensively for the preoperative selection of living related liver donors, as well as evaluation of the vascular anatomy of the recipients (1). This imaging technique is also used for the initial evaluation and follow-up of most patients with hepatic metastases, providing valuable information about the number, size, and distribution of hepatic metastases and the presence and extent of extrahepatic disease (1).Perfusion CT imaging permits the qualitative and quantitative assessment of liver perfusion. In perfusion CT, a quantitative tissue perfusion map is obtained from dynamic CT data and displayed using a color scale permitting the quantification of tissue perfusion in absolute units at high spatial resolution (2). Perfusion CT efficiently locates abnormal tissue perfusion which is difficult to detect accurately with conventional CT (3). Functional assessment of the perfusion of normal and pathologic tissues is performed by means of quantitative or semiquantitative parameters, such as blood flow (BF), blood volume (BV), mean transit time (MTT), portal liver perfusion (PLP), arterial liver perfusion (ALP) and hepatic perfusion index (HPI). Perfusion CT measures the temporal changes in tissue density through a series of dynamically acquired CT images after intravenous injection of an iodinated contrast material (4, 5). Perfusion CT may be performed quickly and provide valuable data for diagnosis. However, there are some limitations of this method such as long breath-holding for portal flow measurement, separation of arterial and portal blood flow, additional radiation exposure, limited craniocaudal scan range, and standardization of analytic methods (2). In this article, we reviewed the basic principles and technique of perfusion CT, and discussed its various clinical applications in liver imaging.     

Imaging of facial nerve schwannomas: diagnostic pearls and potential pitfalls

Schwannomas are uncommon in the facial nerve and account for less than 1% of tumors of temporal bone. They can involve one or more than one segment of the facial nerve. The clinical presentations and the imaging appearances of facial nerve schwannomas are influenced by the topographical anatomy of the facial nerve and vary according to the segment(s) they involve. This pictorial essay illustrates the imaging features of facial nerve schwannomas according to their various anatomical locations and also reviews the pertinent differential diagnoses and potential diagnostic pitfalls.Facial nerve schwannomas (FNSs) are rare slow-growing tumors, accounting for less than 1% of all temporal bone tumors. They are typically solitary, unilateral, and sporadic in nature. FNSs may be bilateral as part of neurofibromatosis-2 spectrum (1, 2). Rarely, multiple schwannomas may involve peripheral branches of the facial nerve (FN) (3). The age of presentation varies from 5 to 84 years. No gender or side predilection is seen (4, 5).Histologically, FNSs are neuroectodermal in origin. They are encapsulated, benign tumors arising from the Schwann cells. They may show intratumoral cystic change and hemorrhage (3, 4, 5). Malignant schwannoma of the FN is extremely rare (6). FNSs commonly present with peripheral facial neuropathy and/or various otologic symptoms including sensorineural and conducting hearing loss (2–5). Facial paralysis is often seen at a later stage or may not be seen at all. The reasons for this are thought to be neuronal tolerance induced by the extremely slow growth of the tumor, abundant tumor vascularity, and commonly associated dehiscence of adjacent bone (7). Occasionally, FNSs may present as an intraparotid mass or as an intracranial lesion (2–5).The clinical presentations and the imaging appearances of FNSs are influenced by the topographical imaging anatomy of the FN and vary according to the segment(s) they involve (8). Here, we briefly describe the anatomy of the FN, followed by general imaging features of FNSs on computed tomography (CT) and magnetic resonance imaging (MRI), and appropriate imaging protocols. Tumor involving each segment is reviewed in relation to its characteristic clinical presentations emphasizing diagnostic pearls and potential pitfalls. The imaging examples of FNSs illustrated in this pictorial review are all histopathologically proven cases.     

Detection of prostate cancer with three-dimensional transrectal ultrasound: correlation with biopsy results

Objectives

The aim of this study was to evaluate the role of three-dimensional transrectal ultrasound in the diagnosis of prostate cancer.

Methods

A total of 112 patients with elevated serum prostate-specific antigen (PSA) or a positive digital rectal examination were evaluated using three-dimensional greyscale transrectal ultrasound (3D-GS TRUS) and three-dimensional power Doppler sonography (3D-PDS). Target biopsies were obtained together with 12 core systematic biopsies. Pathological results were correlated with the imaging data.

Results

Cancers were detected in 269 biopsy sites from 41 patients. 229 sites of cancer were depicted by 3D-GS TRUS and 213 sites were depicted by 3D-PDS. 30 sites were missed by both 3D-GS TRUS and 3D-PDS. Abnormal prostate images depicted by 3D-GS TRUS and 3D-PDS were associated with lesions with a Gleason score of 6.9 or higher.

Conclusion

The detection rates of prostate cancer were significantly improved with 3D-GS TRUS and 3D-PDS on serum PSA levels >10 ng ml^–1 or 20 ng ml^–1. 3D-GS TRUS and 3D-PDS may improve the biopsy yield by determining appropriate sites for target and systematic biopsies. The abnormalities detected by 3D ultrasound were associated with moderate- and high-grade prostate cancers. However, based on the number of false-negative TRUS results, the use of systematic prostate biopsies should not be eliminated.Prostate cancer is a common malignancy in older males. Previous autopsy studies have shown that one-third of males over 50 years old have latent cancer, yet only 10% develop clinically significant carcinomas during their lifetime [1]. The exact mechanism mediating the progression of microfocal cancers into symptomatic forms of the disease has not been elucidated. Since prostate cancers demonstrate remarkably heterogeneous behaviours ranging from slow-growing lesions to aggressive tumours that metastasise rapidly [2], the diagnosis and treatment of prostate cancers is very challenging. The current methods of screening for prostate cancer include measuring serum prostate-specific antigen (PSA) levels, digital rectal examination and transrectal ultrasound (TRUS) scanning and biopsy. However, controversy surrounds which screening method is the most clinically significant for detecting lesions.Since approximately 20–50% of prostate cancers are invisible by greyscale (GS) TRUS [3], GS TRUS has limited value for detection of prostate cancer [4,5]. In addition, 35% of lesions missed by GS TRUS are moderate- or high-grade tumours [6]. Colour Doppler ultrasound, as an important adjunct to GS TRUS, could improve detection of prostate cancer, although in one study 16% of cases with clinically significant cancer were still missed by this method [7].Three-dimensional (3D) TRUS is a relatively new imaging modality. Preliminary studies have shown improved cancer detection with 3D TRUS when compared with two-dimensional TRUS [8,9]. However, it is still unknown which malignant lesions may be detected by 3D TRUS. Furthermore, 3D TRUS has not been analysed in correlation with the site-specific biopsy pathological results.The purpose of this study was to assess the role of 3D-GS TRUS and 3D power Doppler sonography (3D-PDS) in the diagnosis of prostate carcinoma. This study correlated 3D-GS TRUS and 3D-PDS data with biopsy pathological results using a site-by-site analysis that included target and systematic biopsies.     

Effect of imaging parameters on the accuracy of apparent diffusion coefficient and optimization strategies

PURPOSE

We aimed to investigate the effect of key imaging parameters on the accuracy of apparent diffusion coefficient (ADC) maps using a phantom model combined with ADC calculation simulation and propose strategies to improve the accuracy of ADC quantification.

METHODS

Diffusion-weighted imaging (DWI) sequences were acquired on a phantom model using single-shot echo-planar imaging DWI at 1.5 T scanner by varying key imaging parameters including number of averages (NEX), repetition time (TR), echo time (TE), and diffusion preparation pulses. DWI signal simulations were performed for varying TR and TE.

RESULTS

Magnetic resonance diffusion signal and ADC maps were dependent on TR and TE imaging parameters as well as number of diffusion preparation pulses, but not on the NEX. However, the choice of a long TR and short TE could be used to minimize their effects on the resulting DWI sequences and ADC maps.

CONCLUSION

This study shows that TR and TE imaging parameters affect the diffusion images and ADC maps, but their effect can be minimized by utilizing diffusion preparation pulses. Another key imaging parameter, NEX, is less relevant to DWI and ADC quantification as long as DWI signal-to-noise ratio is above a certain level. Based on the phantom results and data simulations, DWI acquisition protocol can be optimized to obtain accurate ADC maps in routine clinical application for whole body imaging.Diffusion-weighted imaging (DWI) measures the degree of water mobility, i.e., random Brownian motion, in vivo and is a noninvasive tool (1–3). DWI has been used mainly in cranial magnetic resonance imaging (MRI) applications to visualize stroke, neoplasms, intracranial infections, traumatic brain injury, and demyelinating processes since early 1990s (4–8). However, in recent years, DWI applications has been extended to breast, musculoskeletal, liver, prostate, pelvis, and general whole body imaging with the development of multichannel coils, parallel imaging, faster gradients, and MRI hardware (9–14). DWI can provide a quantitative map of water diffusion coefficient. Water diffusion coefficient can be calculated from diffusion-weighted images using at least two different DWI values. DWI is achieved by applying diffusion gradients and is called the b-value. Water diffusion coefficient in the tissue is called apparent diffusion coefficient (ADC) and can be calculated from diffusion-weighted images using a linear regression analysis. The term “apparent” is used for diffusion coefficient to differentiate from true diffusion coefficient since the measured water diffusion coefficient in the tissue is influenced by a number of other factors such as capillary network orientation and gross motion in addition to random Brownian motion. ADC measurements are considered to be of greater importance in differential diagnosis of various pathological conditions and its accurate measurement is of great importance (12, 13, 15–18).In the past, the magnetic resonance gradients were much slower and repetition time (TR) and echo-time (TE) were quite long. Thanks to the fast pace of advancement in MRI, the imaging parameters were shortened significantly. Therefore, TR and TE could be reduced in such a way that they could be comparable to tissue relaxation times (T1 and T2) in order to reduce susceptibility artifacts and the total scan time for various DWI applications. As a result of this development, the selection of user controlled imaging parameters, such as TE, number of averages (NEX), number of diffusion preparation pulse, b-value and TR, became much more relevant to DWI and ADC mapping (19–22). However, dependency of ADC maps on some of the user controlled imaging parameters were investigated by few studies in a limited manner (19–25). It is important to mention that even though multi-shot and three-dimensional (3D) DWI sequences are recently proposed to improve diffusion image quality (26–28), single-shot echo-planar imaging (ssEPI) pulse sequence has been the primary sequence in use for DWI in clinical practice for the last two decades.The purpose of this study is to systematically investigate the effects of user controlled diffusion-weighted MRI parameters on ADC values by uniquely combining phantom studies with diffusion signal simulations and to give an insight into optimizing those parameters to obtain more precise ADC maps using the most commonly used ssEPI-based DWI sequence.     

The utility of acoustic radiation force impulse imaging in diagnosing acute appendicitis and staging its severity

PURPOSE

The aim of this study was to investigate the feasibility of using acoustic radiation force impulse (ARFI) imaging to diagnose acute appendicitis.

METHODS

Abdominal ultrasonography (US) and ARFI imaging were performed in 53 patients that presented with right lower quadrant pain, and the results were compared with those obtained in 52 healthy subjects. Qualitative evaluation of the patients was conducted by Virtual Touch™ tissue imaging (VTI), while quantitative evaluation was performed by Virtual Touch™ tissue quantification (VTQ) measuring the shear wave velocity (SWV). The severity of appendix inflammation was observed and rated using ARFI imaging in patients diagnosed with acute appendicitis. Alvarado scores were determined for all patients presenting with right lower quadrant pain. All patients diagnosed with appendicitis received appendectomies. The sensitivity and specificity of ARFI imaging relative to US was determined upon confirming the diagnosis of acute appendicitis via histopathological analysis.

RESULTS

The Alvarado score had a sensitivity and specificity of 70.8% and 20%, respectively, in detecting acute appendicitis. Abdominal US had 83.3% sensitivity and 80% specificity, while ARFI imaging had 100% sensitivity and 98% specificity, in diagnosing acute appendicitis. The median SWV value was 1.11 m/s (range, 0.6–1.56 m/s) for healthy appendix and 3.07 m/s (range, 1.37–4.78 m/s) for acute appendicitis.

CONCLUSION

ARFI imaging may be useful in guiding the clinical management of acute appendicitis, by helping its diagnosis and determining the severity of appendix inflammation.Acute appendicitis is among the most common causes of acute abdominal pain (1, 2). Despite significant improvements in medical technology, the diagnosis of appendicitis is typically based on clinical findings, resulting in a false-positive rate of 8%–30% (3–6). It is widely understood that ultrasonography (US) and computed tomography (CT) are effective imaging modalities in the detection of appendicitis, although certain limitations to both techniques are apparent. Namely, visualization of the appendix is impossible in nearly 15% of healthy people, and among patients with suspected appendicitis, detection of tip appendicitis or periappendiceal inflammation is relatively poor (7–11). Previous studies employing graded-compression US reported widely variable rates of diagnostic accuracy, with sensitivity ranging from 44% to 100% and specificity ranging from 47% to 99% (12).The use of scoring systems enhances the sensitivity and specificity of the available imaging modalities in the diagnosis of acute appendicitis. In addition, scoring systems aim to minimize the risk of clinical complications and avoid the costs associated with delayed diagnosis or unnecessary appendectomies. Among current scoring systems, the Alvarado system has proven to be a cost-effective method of classifying patients according to acute appendicitis risk. The efficacy of the Alvarado system has been demonstrated in clinical studies, which identified a diagnostic cutoff score of 4–6 for acute appendicitis. Appendectomy is strongly indicated among patients with a score of ≥7, while patients scoring 5 or 6 should receive follow-up care (13). However, the sensitivity and specificity of the Alvarado system do not exceed 90%.The mechanical properties of a tissue can be determined using acoustic radiation force impulse (ARFI) imaging. The technique of ARFI imaging comprises two different methods: Virtual Touch™ tissue imaging (VTI) and Virtual Touch™ tissue quantification (VTQ). VTI provides a qualitative map (elastogram) of relative stiffness for a user-defined region of interest. Using this method, stiff tissue may be differentiated from soft tissue even if it is appearing isoechoic using conventional US imaging. VTQ is a modified application of US ARFI imaging that generates shear wave velocity (SWV) corresponding to tissue stiffness. VTQ has been used to determine tissue elasticity of a variety of organ systems, inflammatory processes, congestion, and fibrosis. ARFI imaging capability is an integral component of the existing US equipment and may be performed as a part of standard US procedures. SWV can be quantified through the application of standard B-mode US. Recent data demonstrated a strong correlation between ARFI imaging and hepatic fibrosis staging (6–8), and investigations of renal tumor diagnosis have also been conducted (14–17). The diagnosis of acute appendicitis by quantitative real-time elastography has been previously reported, although clinical data demonstrating the efficacy of the technique in a substantial number of patients is lacking (18). The aim of the present study was to evaluate the efficacy of ARFI imaging in diagnosis of acute appendicitis.     

Clinical,pathological, and imaging characteristics of primitive neuroectodermal tumors of the spine

Primitive neuroectodermal tumors (PNETs) located in the spine are extremely rare, and information concerning these tumors in the medical literature is limited to single case reports. This pictorial essay presents the clinical, pathological, and imaging characteristics of PNET of the spine.Primitive neuroectodermal tumors (PNETs) are malignant tumors thought to arise from the neural ectoderm and comprise undifferentiated small round cells (1–3). PNETs located in the spine are extremely rare, and information concerning these tumors in the medical literature is limited to single case reports (4–5). This pictorial essay presents the clinical, pathological, and imaging characteristics of PNET of the spine.