Acta Radiologica

Background: Paper printers have been used to document radiological findings in some hospitals. It is critical to establish whether paper printers can achieve the same efficacy and quality as dry laser printers for full-field digital mammography (FFDM).

Purpose: To compare the image quality and detection rate of dry laser printers and paper printers for FFDM.

Material and Methods: Fifty-five cases (25 with single clustered microcalcifications and 30 controls) were selected by a radiologist not participating in the image review. All images were printed on film and paper by one experienced mammography technologist using the processing algorithm routinely used for our mammograms. Two radiologists evaluated hard copies from dry laser printers and paper printers for image quality and detectability of clustered microcalcifications. For the image quality comparisons, agreement between the reviewers was evaluated by means of kappa statistics. The significance of differences between both of the printers was determined using Wilcoxon's signed-rank test. The detection rate of two printing systems was evaluated using receiver operating characteristic (ROC) analysis.

Results: From 110 scores (55 patients, two readers) per printer system, the following quality results were achieved for dry laser printer images: 70 (63.6%) were rated as good and 40 (36.4%) as moderate. By contrast, for the paper printer images, 25 scores (22.7%) were rated as good and 85 (77.3%) as moderate. Therefore, the image quality of the dry laser printer was superior to that achieved by the paper printer (P=0.00). The average area-under-the-curve (Az) values for the dry laser printer and the paper printer were 0.991 and 0.805, respectively. The difference was 0.186. Results of ROC analysis showed significant difference in observer performance between the dry laser printer and paper printer (P=0.0015).

Conclusion: The performance of dry laser printers is superior to that of paper printers. Paper printers should not be used in FFDM.

Background: Mammographic tumor size measurement can be difficult because breast structures are superimposed onto a two-dimensional (2D) plane, potentially obscuring the tumor outline. Breast tomosynthesis (BT) is a 3D X-ray imaging technique in which low-dose images are acquired over a limited angular range at a total dose comparable to digital mammography (DM). These low-dose images are used to mathematically reconstruct a 3D image volume of the breast, thus reducing the problem of superimposed tissue.

Purpose: To investigate whether breast cancer size can be more accurately assessed with breast tomosynthesis than with digital mammography and ultrasonography (US), by reducing the disturbance effect of the projected anatomy.

Material and Methods: A prototype BT system was used. The main inclusion criterion for BT examination was subtle but suspicious findings of breast cancer on 2D mammography. Sixty-two women with 73 breast cancers were included. BT, DM, and US sizes were measured independently by experienced radiologists without knowledge of the pathology results, which were used as reference.

Results: The tumor outline could be determined in significantly more cases with BT (63) and US (60) than DM (49). BT and US size correlated well with pathology (R=0.86 and R=0.85, respectively), and significantly better than DM size (R=0.71). Accordingly, staging was significantly more accurate with BT than with DM.

Conclusion: The study indicates that BT is superior to DM in the assessment of breast tumor size and stage.

Background: The risk of complications and discomfort in patients who undergo prolonged infusion of a thrombolytic agent is significant when conventional catheter-directed thrombolysis is used to treat lower extremity deep vein thrombosis (DVT).

Purpose: To evaluate the feasibility and safety of single-session endovascular treatment for symptomatic lower extremity DVT.

Material and Methods: Single-session endovascular treatment for lower extremity DVT was performed on 29 limbs in 26 patients diagnosed with acute DVT in our institution. Nine patients were male and 17 female, with a mean age of 64 years (range 28–82 years). At 5–10 min after the locoregional injection of the thrombolytic agent (urokinase) via a 5-Fr catheter to soften the thrombus, aspiration thrombectomy was performed with a large-bore sheath. In patients with an underlying anatomical stenosis or obstruction, combined angioplasty with or without stent placement was performed immediately after the complete removal of the thrombus. We then evaluated the technical and clinical outcomes of the procedure, along with any complications or recurrences of DVT.

Results: Technical success was achieved in 24 procedures (82.8%) of single-session endovascular treatment for lower extremity DVT, and clinical success was achieved in 22 (75.9%) of these single-session procedures. Additional catheter-directed thrombolysis procedures were performed on five limbs after repeated aspiration thrombectomies failed to completely remove thrombi in those limbs. Stenotic or occlusive lesions were revealed in 24 limbs and percutaneous angioplasty procedures with or without stent placement were performed in these cases. No major complications resulted from the procedure.

Conclusion: Single-session endovascular treatment is a feasible technique that provides acceptable technical and clinical success with excellent safety for treating symptomatic lower extremity DVT.

Percutaneous stenting of the superior vena cava (SVC) is usually recommended as a palliative procedure for malignant SVC obstruction with low reported morbidity. Complications are uncommon and usually of minor consequence. We report two unusual cases of cardiac tamponade following SVC stenting in patients with malignant SVC syndrome. Echocardiography allows rapid diagnosis and guides pericardial drainage in the interventional radiology suite.

Background: Concern has been raised regarding the mounting collective radiation doses from computed tomography (CT), increasing the risk of radiation-induced cancers in exposed populations.

Purpose: To compare radiation dose and image quality in a chest phantom and in patients for the diagnosis of pulmonary embolism (PE) at 100 and 120 peak kilovoltage (kVp) using 16-multichannel detector computed tomography (MDCT).

Material and Methods: A 20-ml syringe containing 12 mg I/ml was scanned in a chest phantom at 100/120 kVp and 25 milliampere seconds (mAs). Consecutive patients underwent 100 kVp (n = 50) and 120 kVp (n = 50) 16-MDCT using a “quality reference” effective mAs of 100, 300 mg I/kg, and a 12-s injection duration. Attenuation (CT number), image noise (1 standard deviation), and contrast-to-noise ratio (CNR; fresh clot = 70 HU) of the contrast medium syringe and pulmonary arteries were evaluated on 3-mm-thick slices. Subjective image quality was assessed. Computed tomography dose index (CTDI_vol) and dose–length product (DLP) were presented by the CT software, and effective dose was estimated.

Results: Mean values in the chest phantom and patients changed as follows when X-ray tube potential decreased from 120 to 100 kVp: attenuation +23% and +40%, noise +38% and +48%, CNR −6% and 0%, and CTDI_vol −38% and −40%, respectively. Mean DLP and effective dose in the patients decreased by 42% and 45%, respectively. Subjective image quality was excellent or adequate in 49/48 patients at 100/120 kVp. No patient with a negative CT had any thromboembolism diagnosed during 3-month follow-up.

Conclusion: By reducing X-ray tube potential from 120 to 100 kVp, while keeping all other scanning parameters unchanged, the radiation dose to the patient may be almost halved without deterioration of diagnostic quality, which may be of particular benefit in young individuals.

Background: Pulmonary embolism (PE) is the third most common cause of cardiovascular death. When PE is fatal, right ventricular failure usually occurs within the first few hours, so right ventricular dysfunction (RVD) should be diagnosed rapidly to identify patients who could benefit from fibrinolytic therapy.

Purpose: To determine whether quantification of PE with computed tomography (CT) pulmonary angiography and ventricular measurements is of value in the diagnosis of PE severity and prediction of patient outcome.

Material and Methods: Multidetector-row CT studies of 48 hospitalized patients with proven pulmonary embolism were reviewed. Pulmonary artery (PA) obstructive index was derived for each patient on the basis of location and degree of obstruction. Ventricular measurements, including right ventricular (RV) short axis, left ventricular (LV) short axis, and RV/LV ratio, were evaluated and compared among survivors and nonsurvivors. Also, the ventricular measurements were correlated with the PA obstructive index. RV/LV ratio and related PA obstructive index were correlated to the patient outcome and hospital stay.

Results: Comparison of the PA obstructive index and ventricular measurements between survivors and nonsurvivors showed significant difference in PA obstructive index (P<0.001), RV short axis (P<0.001), and RV/LV ratio (P=0.03), and no significant difference was noted in LV short axis (P=0.95). Good correlation was found between PA obstructive index and LV short axis (−0.326), RV short axis (0.539), and RV/LV ratio (0.696). A significant difference was found between the PA obstructive indexes of the different categories of RV/LV ratio (P<0.001).

Conclusion: PA obstructive index of more than 50% and RV/LV ratio >1.5 are useful diagnostic criteria for severe PE and poor patient outcome.

Background: Whole-body magnetic resonance angiography (WB-MRA) is a noninvasive method for diagnosing the systemic distribution of atherosclerosis. Numerous studies have demonstrated the feasibility and diagnostic performance of WB-MRA, but no studies have investigated patient acceptance of this imaging method.

Purpose: To measure patient acceptance of WB-MRA compared to the gold standard, digital subtraction angiography (DSA), in patients with peripheral arterial disease (PAD).

Material and Methods: In a prospective design, 79 consecutive patients (51 male, mean age 67 years) with symptomatic PAD, scheduled to undergo both WB-MRA and DSA, were included. Patient acceptance of each imaging procedure was assessed with a postal questionnaire (13 questions). A five-point rank scale (1, no discomfort; 5, severe discomfort) was used to grade patient discomfort.

Results: One patient was excluded from data analysis (did not undergo DSA). Of the remaining 78 patients, 69 completed the questionnaire (response rate 88%). Overall discomfort scores were higher in DSA compared to WB-MRA (mean 2.1 and 1.7, respectively; P = 0.06). In WB-MRA, overall discomfort was strongly correlated to feeling confined in the MRI system (R = 0.77, P< 0.001). In DSA, discomfort was strongly correlated to arterial puncture (R = 0.66, P< 0.001) and contrast injection (R= 0.65, P< 0.001). Injection of iodinated contrast agent at DSA was graded more uncomfortable than injection of gadolinium-based contrast agent at WB-MRA (mean 2.1 vs. 1.5, respectively; P<0.001). Sixty-two patients (90%) were willing to repeat WB-MRA, and 64 patients (93%) would repeat DSA if they needed another vascular examination. Forty-one patients preferred WB-MRA (60%), 12 patients preferred DSA (17%), and 16 patients had no preference (23%). Patient preference of WB-MRA over DSA was statistically significant (P< 0.001).

Conclusion: Patient acceptance of WB-MRA is superior to that of DSA in patients with PAD, with the majority of patients preferring WB-MRA.

Background: Minimally invasive imaging techniques are increasingly used for clinical decision making in patients with peripheral arterial occlusive disease (PAOD).

Purpose: To assess whether gadofosveset-enhanced three-dimensional (3D) magnetic resonance (MR) angiography could replace digital subtraction angiography (DSA) for the evaluation of lower-extremity PAOD.

Material and Methods: Thirty patients with symptomatic PAOD underwent prospectively both MR angiography and DSA. Gadofosveset-enhanced 3D MR angiography was performed on a 1.5T system equipped with a peripheral angio matrix coil. Four blinded observers independently analyzed MR angiograms and DSA images. The lower arterial vascular system was divided into three anatomic segments (aortoiliac, femoropopliteal, infrapopliteal) for review. The status of each segment was graded as normal, stenosis less than 50%, stenosis greater than 50%, or occluded and/or aneurismatic. Principal and secondary lesions were reported.

Results: Although interobserver agreement for both was excellent, it was higher for DSA (κ=0.92) than for MR angiography (κ=0.86) for reporting the principal and secondary lesions in all segments. For different anatomic locations, the interobserver agreement of MR angiography and DSA was as follows: aortoiliac (κ=0.93, k=0.95), femoropopliteal (κ=0.86, k=0.90), and infrapopliteal (κ=0.78, k=0.85). The lowest agreement was found for MR angiography on infrapopliteal segments (κ=0.78). In four (13.3%) cases, MR angiography showed lesions that were not found by DSA. Five (16.6%) aneurysm cases, not observed by DSA, were shown by MR angiography.

Conclusion: Gadofosveset-enhanced 3D MR angiography can be proposed for first-line imaging in the management of lower-limb PAOD patients and permits the selective use of DSA as a second-line examination when MR angiography fails or in an endovascular approach.

Background: T1-weighted fluid-attenuated inversion recovery (FLAIR) sequence has been reported to provide improved contrast between lesions and normal anatomical structures compared to T1-weighted fast spin-echo (FSE) imaging at 1.5T regarding imaging of the lumbar spine.

Purpose: To compare T1-weighted FSE and fast T1-weighted FLAIR imaging in normal anatomic structures and degenerative and metastatic lesions of the lumbar spine at 3.0T.

Material and Methods: Thirty-two consecutive patients (19 females, 13 males; mean age 44 years, range 30–67 years) with lesions of the lumbar spine were prospectively evaluated. Sagittal images of the lumbar spine were obtained using T1-weighted FSE and fast T1-weighted FLAIR sequences. Both qualitative and quantitative analyses measuring the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and relative contrast (ReCon) between degenerative and metastatic lesions and normal anatomic structures were conducted, comparing these sequences.

Results: On quantitative evaluation, SNRs of cerebrospinal fluid (CSF), nerve root, and fat around the root of fast T1-weighted FLAIR imaging were significantly lower than those of T1-weighted FSE images (P<0.001). CNRs of normal spinal cord/CSF and disc herniation/ CSF for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted FSE images (P<0.001). ReCon of normal spinal cord/CSF, disc herniation/CSF, and vertebral lesions/CSF for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted FSE images (P<0.001). On qualitative evaluation, it was found that CSF nulling and contrast at the spinal cord (cauda equina)/CSF interface for T1-weighted FLAIR images were significantly superior compared to those for T1-weighted FSE images (P<0.001), and the disc/spinal cord (cauda equina) interface was better for T1-weighted FLAIR images (P<0.05).

Conclusion: The T1-weighted FLAIR sequence may be considered as the preferred lumbar spine imaging sequence compared to T1-weighted FSE, as it has demonstrated superior CSF nulling, better conspicuousness of normal anatomic structures and degenerative and metastatic lesions, and improved image contrast.

Background: The significance of borderline magnetic resonance (MR) findings that are equivocal for a tear of the knee meniscus remains uncertain. Given their higher signal-to-noise ratio (SNR) and greater spatial resolution, these equivocal meniscal tears could be expected to be less frequent using a 3.0T MR system.

Purpose: To investigate the prevalence of equivocal meniscal tears using 3.0T MR, and to study their impact on MR accuracy compared with arthroscopy in the detection of meniscal tears.

Material and Methods: The medical records of 100 patients who underwent 3.0T MR imaging and subsequent arthroscopy of the knee were retrospectively reviewed. Two observers interpreted MR images in consensus, and menisci were diagnosed as torn (abnormality on two or more images), equivocal for a tear (abnormality on one image), or intact, using arthroscopy as the standard of reference. The prevalence of equivocal meniscal tears was assessed, and MR accuracy was calculated as follows: first, considering both torn menisci and equivocal diagnoses as positive for a tear; and second, considering only torn menisci as positive for a tear.

Results: Evidence of meniscal tears on MR images was equivocal in 12 medial (12%) and three lateral (3%) menisci. Of these equivocal MR diagnoses, tears were found at arthroscopy in eight medial and one lateral meniscus. In our study, the specificity and positive predictive value increased for both the medial and lateral meniscus when only menisci with two or more abnormal images were considered to be torn: from 80% and 89% to 91% and 94% for the medial meniscus, and from 91% and 73% to 93% and 78% for the lateral meniscus, respectively.

Conclusion: Subtle findings that are equivocal for a tear of the knee meniscus still make MR diagnosis difficult, even at 3.0T. We recommend that radiologists should rather be descriptive in reporting subtle or equivocal MR findings, alerting the clinician of possible meniscal tear.

Background: Redundancy of the capsule has been considered to be the main pathologic condition responsible for atraumatic posteroinferior multidirectional shoulder instability; however, there is a paucity of measurements providing quantitative diagnosis.

Purpose: To determine the significance of superior-capsular elongation and its relevance to atraumatic posteroinferior multidirectional shoulder instability at magnetic resonance (MR) arthrography.

Material and Methods: MR arthrography was performed in 21 patients with atraumatic posteroinferior multidirectional shoulder instability and 21 patients without shoulder instability. One observer made the measurements in duplicate and was blinded to the two groups. The superior-capsular measurements (linear distance and cross-sectional area) under the supraspinatus tendon, and the rotator interval were determined on MR arthrography and evaluated for each of the two groups.

Results: For the superior-capsular measurements, the linear distance under the supraspinatus tendon was significantly longer in patients with atraumatic posteroinferior multidirectional shoulder instability than in control subjects (P<0.001). The cross-sectional area under the supraspinatus tendon, and the rotator interval were significantly increased in patients with atraumatic posteroinferior multidirectional shoulder instability compared to control subjects (P<0.001 and P=0.01, respectively). Linear distance greater than 1.6 mm under the supraspinatus tendon had a specificity of 95% and a sensitivity of 90% for diagnosing atraumatic posteroinferior multidirectional shoulder instability. Cross-sectional area under the supraspinatus tendon greater than 0.3 cm², or an area under the rotator interval greater than 1.4 cm² had a specificity of more than 80% and a sensitivity of 90%.

Conclusion: The superior-capsular elongation as well as its diagnostic criteria of measurements by MR arthrography revealed in the present study could serve as references for diagnosing atraumatic posteroinferior shoulder instability and offer insight into the spectrum of imaging findings corresponding to the pathologies encountered at clinical presentation.

Background: Age- and sex-related changes of metabolites in healthy adult brains have been examined with different ¹H magnetic resonance spectroscopy (MRS) methods in varying populations, and with differing results. A long repetition time and short echo time technique reduces quantification errors due to T₁ and T₂ relaxation effects and makes it possible to measure metabolites with short T₂ relaxation times.

Purpose: To examine the effect of age on the metabolite concentrations measured by ¹H MRS in normal supraventricular white matter using a long repetition time (TR) and a short echo time (TE).

Material and Methods: Supraventricular white matter of 57 healthy subjects (25 women, 32 men), aged 13 to 72 years, was examined with a single-voxel MRS at 1.5T using a TR of 6000 ms and a TE of 22 ms. Tissue water was used as a reference in quantification.

Results: Myoinositol increased slightly and total N-acetyl aspartate (NAA) decreased slightly with increasing age. Glutamine/glutamate complex (Glx) showed U-shaped age dependence, with highest concentrations in the youngest and oldest subjects. No significant age dependence was found in total choline and total creatine. No gender differences were found. Macromolecule/ lipid (ML) fractions were reliably measurable only in 36/57 or even fewer subjects and showed very large deviations.

Conclusion: The concentrations of several metabolites in cerebral supraventricular white matter are age dependent on ¹H MRS, even in young and middle-aged people, and age dependency can be nonlinear. Each ¹H MRS study of the brain should therefore take age into account, whereas sex does not appear to be so important. The use of macromolecule and lipid evaluations is compromised by less successful quantification and large variations in healthy people.

Background: Brain metastases and primary high-grade gliomas, including glioblastomas multiforme (GBM) and anaplastic astrocytomas (AA), may be indistinguishable by conventional magnetic resonance (MR) imaging. Identification of these tumors may have therapeutic consequences.

Purpose: To assess the value of MR spectroscopy (MRS) using short and intermediate echo time (TE) in differentiating solitary brain metastases and high-grade gliomas on the basis of differences in metabolite ratios in the intratumoral and peritumoral region.

Material and Methods: We performed MR imaging and MRS in 73 patients with histologically verified intraaxial brain tumors: 53 patients with high-grade gliomas (34 GBM and 19 AA) and 20 patients with metastatic brain tumors. The metabolite ratios of Cho/Cr, Cho/NAA, and NAA/Cr at intermediate TE and the presence of lipids at short TE were assessed from spectral maps in the tumoral core, peritumoral edema, and contralateral normal-appearing white matter. The differences in the metabolite ratios between high-grade gliomas/GBM/AA and metastases were analyzed statistically. Cutoff values of Cho/Cr, Cho/NAA, and NAA/Cr ratios in the peritumoral edema, as well as Cho/Cr and NAA/Cr ratios in the tumoral core for distinguishing high-grade gliomas/GBM/AA from metastases were determined by receiver operating characteristic (ROC) curve analysis.

Results: Significant differences were noted in the peritumoral Cho/Cr, Cho/NAA, and NAA/ Cr ratios between high-grade gliomas/GBM/AA and metastases. ROC analysis demonstrated a cutoff value of 1.24 for peritumoral Cho/Cr ratio to provide sensitivity, specificity, positive (PPV), and negative predictive values (NPV) of 100%, 88.9%, 80.0%, and 100%, respectively, for discrimination between high-grade gliomas and metastases. By using a cutoff value of 1.11 for peritumoral Cho/NAA ratio, the sensitivity was 100%, the specificity was 91.1%, the PPV was 83.3%, and the NPV was 100%.

Conclusion: The results of this study demonstrate that MRS can differentiate high-grade gliomas from metastases, especially with peritumoral measurements, supporting the hypothesis that MRS can detect infiltration of tumor cells in the peritumoral edema.

Background: Arterial input functions may differ between brain regions due to delay and dispersion effects in the vascular supply network. Unless corrected for, these differences may degrade quantitative estimations of cerebral blood flow in dynamic susceptibility contrast magnetic resonance perfusion imaging (DSC-MRI).

Purpose: To investigate in a healthy population (n=44) the properties of voxel-specific arterial input functions that were obtained using a recently published blind estimation approach.

Material and Methods: The voxel-specific arterial input functions were qualitatively and quantitatively assessed, through visual inspection or by comparing time-to-peak (delays) and peak amplitude (dispersion) values between eight regions of the brain. Furthermore, they were compared to arterial input functions selected manually in the middle cerebral artery (MCA), where normally no delay or dispersion of the contrast agent was expected.

Results: The estimated voxel-specific arterial input functions varied between brain regions. Differences in delays and dispersion were larger within one brain region among all participants than between regions in one participant. A good correlation was typically found between the estimated voxel-specific arterial input functions and the manually selected arterial input functions in the MCA region.

Conclusion: Given knowledge of neurovascular anatomy, the current blind approach seemingly produced reasonable estimates of voxel-specific arterial input functions. In addition to potentially reducing quantification errors in DSC-MRI, these user-independent voxel-specific arterial input functions could be useful for visualizing abnormal blood supply patterns in patients.

Background: Increased levels of lactate are observed by ¹H magnetic resonance spectroscopy (¹H-MRS) in rat brains after stroke. However, it is not known whether the changes in lactate levels are predictive of the degree of neuronal damage.

Purpose: To investigate the correlation between changes in lactate and lipid levels measured by ¹H-MRS and neuronal cell damage in the rat brain.

Material and Methods: A middle cerebral artery occlusion (MCAO) model was used to evaluate focal ischemia in rats (n=36). After MCAO for 90 min T2-weighted images (T2WIs), diffusion-weighted images (DWIs), and ¹H-MRS data were obtained from brains immediately, 6 hours, 9 hours, 12 hours, 18 hours, 24 hours, 3 days, and 7 days after reperfusion. Infarct volumes were measured in T2WIs obtained 4 weeks after reperfusion. The degree of neuronal damage was measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining in three rats from each group at the same time as brain images were collected.

Results: Creatine (Cr)-normalized lactate + lipid levels ([Lac+Lip]/Cr) were negatively correlated with Cr-normalized N-acetyl-L-aspartate levels (NAA/Cr) and positively correlated with TUNEL-positive cell numbers up to 24 hours after reperfusion. (Lac+Lip)/Cr at 6 hours and 9 hours was significantly correlated with NAA/Cr at 7 days, but there was no significant correlation between (Lac+Lip)/Cr during the first 24 hours and infarct volume at 4 weeks.

Conclusion: Up to 24 hours after reperfusion, (Lac+Lip)/Cr was strongly negatively correlated with NAA/Cr, and was a good predictor of neuronal damage at 7 days; however, it was not predictive of final infarct volume at 4 weeks.

Background: The concentration of N-acetylaspartate (NAA) in hippocampus, as measured with magnetic resonance spectroscopy (MRS), and the ratio of NAA/(choline (Cho) + creatine (Cr)) are valuable tools in the lateralization of temporal lobe epilepsy (TLE). MRS of hippocampus is also increasingly used to study certain psychiatric and degenerative diseases. However, the reliability of such measurements of hippocampus has been questioned.

Purpose: To re-evaluate MRS imaging data from prior control subjects with regard to variation of metabolite concentrations in hippocampus from anterior to posterior and the partial volume ®contribution to the measurements from adjacent tissue.

Material and Methods: Twelve healthy subjects, mean age 33 years, were studied with MRS imaging. The measurement volume was angled along the temporal horns and metabolite concentration images were reconstructed at the MR system. Regions of interest (ROIs) in the anterior, medial, and posterior parts of both hippocampi were evaluated. Signal normalization to the total MRS signal from all ROIs permitted pooling of individual data with different and unknown signal scaling. One subject was re-examined with a high resolution three-dimensional (3D) volume of the brain for evaluation of partial volumes in the MRS examination.

Results: Overall, there were significantly lower concentrations of NAA in the anterior parts, and of (Cho+Cr) in the posterior parts, while the NAA/(Cho+Cr) ratio in the posterior parts of the mesial temporal lobes was significantly higher. Hippocampus accounted for one-half, one-third, and one-quarter of the anterior, middle, and posterior ROIs, respectively. The NAA/(Cho+Cr) ratio thus showed a reverse relationship to the relative volume of hippocampal tissue within the ROI.

Conclusion: Metabolite concentrations in the mesial temporal lobe obtained with MRS imaging represent the mean value of hippocampus and a considerable amount of adjacent tissue. To assess the hippocampus alone, an actual voxel well below 1 cm³ and a sub-centimeter slice thickness are required.

Emergency Radiology: The Requisites. By J. A. Soto and B. C. Lucey. Philadelphia, PA: Mosby Elsevier, 2009. ISBN 978-0-323-05407-2. 397 pages. Price (hardcover): € 75.

Emergency Radiology Case Review Series. By S. E. Mirvis, K. Shanmuganathan, L. Miller, and C. Sliker. Philadelphia, PA: Mosby Elsevier. ISBN 978-0-323-04957-3. 415 pages. Price (paperback): €39.