Optimal entry position on the lateral femoral surface for outside-in drilling technique to restore the anatomical footprint of anterior cruciate ligament

Purpose

To investigate the optimal starting points for drilling on the lateral femoral condyle for better coverage of the anatomical footprint of the anterior cruciate ligament (ACL) using the outside-in (OI) technique in a single-bundle ACL reconstruction.

Methods

Femoral tunnel drilling was simulated on three-dimensional bone models from 40 subjects by connecting the centre of the ACL footprint with various points on the lateral femoral surface. The percentage of the femoral footprint covered by apertures of the virtual tunnel sockets with 9 mm diameter was calculated for each tunnel.

Results

The mean percentages of the femoral footprint covered by the apertures of the virtual tunnel sockets were significantly higher when drilled at 2 and 3 cm from the lateral epicondyle on a 45° line and a 60° line anterior from the proximal–distal axis than the other points. However, articular cartilage damage was occurred in nine subjects at 3 cm on a 60° line and eight subjects at 3 cm on a 45° line. Posterior wall blowout occurred in five subjects at 3 cm on a 45° line. Thus, OI drilling at 3 cm from the epicondyle has a risk of these complications.

Conclusion

During the OI drilling of the femoral tunnel, connecting the centre of the anatomical footprint of the ACL and the entry drilling point at 2 cm from the lateral epicondyle on between the 45° line and the 60° line anterior from the proximal–distal axis provides an oval-shaped socket aperture that covers and restores the native ACL footprint as nearly as possible.

Level of evidence

III.

     

Preparation and biological evaluation of 3-[(76)Br]bromo-α-methyl-L-tyrosine, a novel tyrosine analog for positron emission tomography imaging of tumors

Introduction

3-[¹⁸F]fluoro-α-methyl-l-tyrosine ([¹⁸F]FAMT) is a useful amino acid tracer for positron emission tomography (PET) imaging of malignant tumors. FAMT analogs labeled with ⁷⁶Br, a positron emitter with a long half-life (t_1/2=16.1 h), could potentially be widely used as amino acid tracers for tumor imaging. In this study, 3-[⁷⁶Br]bromo-α-methyl-l-tyrosine ([⁷⁶Br]BAMT) was designed, and its usefulness was evaluated as a novel PET tracer for imaging malignant tumors.

Methods

In this study, both [⁷⁶Br]BAMT and [⁷⁷Br]BAMT were prepared. The in vitro and in vivo stability of [⁷⁷Br]BAMT was evaluated by HPLC analysis. Cellular uptake and retention of [⁷⁷Br]BAMT and [¹⁸F]FAMT were evaluated using LS180 colon adenocarcinoma cells. Biodistribution studies were performed in normal mice and in LS180 tumor-bearing mice, and the tumors were imaged with a small-animal PET scanner.

Results

[⁷⁷Br]BAMT was stable in vitro but was catabolized after administration in mice. Cellular accumulation and retention of [⁷⁷Br]BAMT were significantly higher than those of [¹⁸F]FAMT. In biodistribution studies, the tumor accumulation of [⁷⁷Br]BAMT was higher than that of [¹⁸F]FAMT. However, some level of debromination was seen, which caused more retention of radioactivity in the blood and organs than was seen with [¹⁸F]FAMT. PET imaging with [⁷⁶Br]BAMT enabled clear visualization of the tumor, and the whole-body image using [⁷⁶Br]BAMT was similar to that using [¹⁸F]FAMT.

Conclusions

[⁷⁷Br]BAMT showed high levels of tumor accumulation, and [⁷⁶Br]BAMT enabled clear visualization of the tumor by PET imaging. Although an improvement in stability is still needed, ⁷⁶Br-labeled FAMT analogs could potentially serve as PET tracers for the imaging of malignant tumors.     

Subchondral insufficiency fracture of the femoral head after liver transplantation

A 53-year-old woman developed a subchondral insufficiency fracture of the right femoral head after undergoing a liver transplantation. Radiographs obtained at her first visit demonstrated a slight subchondral collapse in the superolateral portion of the femoral head. Magnetic resonance imaging (MRI) disclosed an irregular, discontinuous, low-intensity band on the T1-weighted image. After 7 months of conservative treatment, the hip pain and the radiograph abnormalities had both disappeared. On the follow-up T1-weighted MR image obtained 17 months after the onset, the band of low signal intensity was not obvious. A subchondral insufficiency fracture is one of the diagnoses to be considered in patients presenting with hip pain after a liver transplantation. This work was supported in part by a research grant for intractable disease from the Ministry of Health and Welfare of Japan and a research grant from the Univers Foundation.     

Influence of volumetric 4′-[methyl-<Superscript>11</Superscript>C]-thiothymidine PET/CT parameters for prediction of the clinical outcome of head and neck cancer patients

Objective

This prospective study compared the value of pretreatment 4′-[methyl-¹¹C]-thiothymidine (¹¹C-4DST) volumetric parameters and those of 2-deoxy-2-[18F] fluoro-d-glucose (¹⁸F-FDG) in predicting the clinical outcome in patients with head and neck squamous cell carcinoma (HNSCC).

Methods

Fifty patients with HNSCC underwent ¹¹C-4DST PET/CT and ¹⁸F-FDG PET/CT prior to anticancer therapy. ¹⁸F-FDG metabolic tumor volume (¹⁸F-FDG MTV) and total lesion glycolysis (TLG) were calculated from ¹⁸F-FDG PET, and ¹¹C-4DST MTV and total lesion proliferation (TLP) were calculated from ¹¹C-4DST PET. All parameters were measured for the primary lesion and metastatic lymph nodes. Associations between clinical factors and PET/CT parameters and prognostic value were analyzed.

Results

Receiver-operating characteristic analysis revealed that MTV, TLG, and TLP acquired from the primary lesion and metastatic lymph nodes were good parameters for predicting disease relapse and death. The area under the curves (AUCs) ranged from 0.63 to 0.71 for ¹⁸F-FDG PET/CT parameters. The AUCs of ¹¹C-4DST PET/CT parameters were larger than those of ¹⁸F-FDG (range 0.72–0.81). Univariate analysis revealed that individuals with tumors showing a high value for any PET/CT parameter were at a significantly increased risk of relapse. Upon multivariate analysis, ¹⁸F-FDG MTV, ¹¹C-4DST MTV and ¹¹C-4DST TLP were significant independent factors for relapse-free survival (P = 0.04, P = 0.0001 and P = 0.0005, respectively).

Conclusion

Pretreatment ¹¹C-4DST PET/CT volume-based parameters can provide important prognostic information about patients with HNSCC.

     

Multiparametric voxel-based analyses of standardized uptake values and apparent diffusion coefficients of soft-tissue tumours with a positron emission tomography/magnetic resonance system: Preliminary results

Objectives

To investigate the usefulness of voxel-based analysis of standardized uptake values (SUVs) and apparent diffusion coefficients (ADCs) for evaluating soft-tissue tumour malignancy with a PET/MR system.

Methods

Thirty-five subjects with either ten low/intermediate-grade tumours or 25 high-grade tumours were prospectively enrolled. Zoomed diffusion-weighted and fluorodeoxyglucose (¹⁸FDG)-PET images were acquired along with fat-suppressed T2-weighted images (FST2WIs). Regions of interest (ROIs) were drawn on FST2WIs including the tumour in all slices. ROIs were pasted onto PET and ADC-maps to measure SUVs and ADCs within tumour ROIs. Tumour volume, SUVmax, ADCminimum, the heterogeneity and the correlation coefficients of SUV and ADC were recorded. The parameters of high- and low/intermediate-grade groups were compared, and receiver operating characteristic (ROC) analysis was also performed.

Results

The mean correlation coefficient for SUV and ADC in high-grade sarcomas was lower than that of low/intermediate-grade tumours (?0.41?±?0.25 vs. ?0.08?±?0.34, P?<?0.01). Other parameters did not differ significantly. ROC analysis demonstrated that correlation coefficient showed the best diagnostic performance for differentiating the two groups (AUC 0.79, sensitivity 96.0%, specificity 60%, accuracy 85.7%).

Conclusions

SUV and ADC determined via PET/MR may be useful for differentiating between high-grade and low/intermediate-grade soft tissue tumours.

Key Points

? PET/MR allows voxel-based comparison of SUVs and ADCs in soft-tissue tumours. ? A comprehensive assessment of internal heterogeneity was performed with scatter plots. ? SUVmax or ADCminimum could not differentiate high-grade sarcoma from low/intermediate-grade tumours. ? Only the correlation coefficient between SUV and ADC differentiated the two groups. ? The correlation coefficient showed the best diagnostic performance by ROC analysis.

     

Grading diffuse gliomas without intense contrast enhancement by amide proton transfer MR imaging: comparisons with diffusion- and perfusion-weighted imaging

Objectives

To investigate whether amide proton transfer (APT) MR imaging can differentiate high-grade gliomas (HGGs) from low-grade gliomas (LGGs) among gliomas without intense contrast enhancement (CE).

Methods

This retrospective study evaluated 34 patients (22 males, 12 females; age 36.0?±?11.3 years) including 20 with LGGs and 14 with HGGs, all scanned on a 3T MR scanner. Only tumours without intense CE were included. Two neuroradiologists independently performed histogram analyses to measure the 90th-percentile (APT₉₀) and mean (APT_mean) of the tumours’ APT signals. The apparent diffusion coefficient (ADC) and relative cerebral blood volume (rCBV) were also measured. The parameters were compared between the groups with Student’s t-test. Diagnostic performance was evaluated with receiver operating characteristic (ROC) analysis.

Results

The APT₉₀ (2.80?±?0.59 % in LGGs, 3.72?±?0.89 in HGGs, P?=?0.001) and APT_mean (1.87?±?0.49 % in LGGs, 2.70?±?0.58 in HGGs, P?=?0.0001) were significantly larger in the HGGs compared to the LGGs. The ADC and rCBV values were not significantly different between the groups. Both the APT₉₀ and APT_mean showed medium diagnostic performance in this discrimination.

Conclusions

APT imaging is useful in discriminating HGGs from LGGs among diffuse gliomas without intense CE.

Key Points

? Amide proton transfer (APT) imaging helps in grading non-enhancing gliomas ? High-grade gliomas showed higher APT signal than low-grade gliomas ? APT imaging showed better diagnostic performance than diffusion- and perfusion-weighted imaging

     

Direct imaging of hyperpolarized 129Xe alveolar gas uptake in a mouse model of emphysema

MRI of hyperpolarized ¹²⁹Xe dissolved in pulmonary tissues, and blood has the potential to offer a new tool for regional evaluation of pulmonary gas exchange and perfusion; however, the extremely short T and low magnetization density make it difficult to acquire the image. In this study, an ultrashort echo‐time sequence was introduced, and its feasibility to quantitatively assess emphysema‐like pulmonary tissue destruction by a combination of dissolved‐ and gas‐phase ¹²⁹Xe lung MRI was investigated. The ultrashort echo‐time has made it possible to acquire dissolved ¹²⁹Xe images with reasonably high spatial resolution of 0.625 × 0.625 mm² and to obtain T of 0.67 ± 0.30 ms in a spontaneously breathing mouse at 9.4 T. The regional dynamic alveolar gas uptake as well as subsequent transport by pulmonary blood flow was also visualized. The ratio of ¹²⁹Xe magnetization that diffused into the septa relative to the gas‐phase magnetization F was regionally evaluated. The mean F value of elastase‐treated mice was 2.28 ± 0.46%, which was significantly reduced from that of control mice 3.41 ± 0.48% (P = 0.0052). This reflects the reduced uptake efficiency due to alveolar tissue destruction and is correlated with the histologically derived alveolar surface‐to‐volume ratio. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

CT analysis of the effect of pirfenidone in patients with idiopathic pulmonary fibrosis

Purpose

Pirfenidone is a new, anti-fibrotic drug used for the treatment of idiopathic pulmonary fibrosis (IPF). The aim of this study was to evaluate the utility of computed tomography (CT) in the imaging assessment of the response to pirfenidone therapy.

Materials and methods

Subjects were 78 patients with IPF who underwent CT on two occasions with one-year interval (38 consecutive patients treated with pirfenidone and 40 age-matched control). Changes in the fibrous lesion on sequential CTs were assessed as visual score by two radiologists. We measured the volume and change per year of fibrous pattern (F-pattern) quantitatively using a computer-aided system on sequential CTs.

Results

The baseline vital capacity (%pred VC) was 74.0 ± 14.0% in the pirfenidone group and 74.6 ± 16.6% in controls (p = NS). Deterioration of respiratory status was defined as 10% or greater decline in %pred VC value after 12-month treatment. A significantly larger proportion of pirfenidone-treated patients showed stable respiratory status (21 of 38, 65.6%) than the control (15 of 40, 37.5%). The change in fibrous lesion was significantly smaller in the pirfenidone group than the control in both of visual score (p = 0.006) and computer analysis (p < 0.001). The decline in VC correlated significantly with the increase in fibrotic lesion (p < 0.001).

Conclusion

CT can be used to assess pirfenidone-induced slowing of progression of pulmonary fibrosis.     

Primary staging of laryngeal and hypopharyngeal cancer: CT,MR imaging and dual-energy CT

Laryngeal and hypopharyngeal cancer, in particular T4a disease associated with cartilage invasion and extralaryngeal spread, needs to be evaluated accurately because treatment can impact heavily on a patient's quality of life. Reliable imaging tools are therefore indispensible. CT offers high spatial and temporal resolution and remains the preferred imaging modality. Although cartilage invasion can be diagnosed with acceptable accuracy by applying defined criteria for combinations of erosion, lysis and transmural extralaryngeal spread, iodine-enhanced tumors and non-ossified cartilage are sometimes difficult to distinguish. MR offers high contrast resolution for images without motion artifacts, although inflammatory changes in cartilage sometimes resemble cartilage invasion. With dual-energy CT, combined iodine overlay images and weighted average images can be used for evaluation of cartilage invasion, since iodine enhancement is evident in tumor tissue but not in cartilage. Extralaryngeal spread can be evaluated from CT, MR or dual-energy CT images and the routes of tumor spread into the extralaryngeal soft tissue must be considered; (1) via the thyrohyoid membrane along the superior laryngeal neurovascular bundle, (2) via the inferior pharyngeal constrictor muscle, and (3) via the cricothyroid membrane. Radiologists need to understand the advantages and limitations of each imaging modality for staging of laryngeal and hypopharyngeal cancer.     

Quantitative assessment of right ventricular function and pulmonary regurgitation in surgically repaired tetralogy of Fallot using 256-slice CT: comparison with 3-Tesla MRI

Objectives

To compare 256-slice cardiac computed tomography (CCT) with cardiac magnetic resonance (CMR) imaging to assess right ventricular (RV) function and pulmonary regurgitant fraction (PRF) in patients with repaired tetralogy of Fallot (TOF).

Methods

Thirty-three consecutive patients with repaired TOF underwent retrospective ECG-gated CCT and 3-Tesla CMR. RV and left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF) were measured using CCT and CMR. PRF-CCT (%) was defined as (RVSV???LVSV)/RVSV. PRF-CMR (%) was measured by the phase-contrast method. Repeated measurements were performed to determine intra- and interobserver variability.

Results

CCT measurements, including PRF, correlated highly with the CMR reference (r?=?0.71–0.96). CCT overestimated RVEDV (mean difference, 17.1?±?2.9 ml), RVESV (12.9?±?2.1 ml) and RVSV (4.2?±?2.0 ml), and underestimated RVEF (?2.6?±?1.0 %) and PRF (?9.1?±?2.0 %) compared with CMR. The limits of agreement between CCT and CMR were in a good range for all measurements. The variability in CCT measurements was lower than those in CMR. The estimated effective radiation dose was 7.6?±?2.6 mSv.

Conclusions

256-slice CCT can assess RV function and PRF with relatively low dose radiation exposure in patients with repaired TOF, but overestimates RV volume and underestimates PRF.

Key points

? 256-slice CT assessment of RV function is highly reproducible in repaired TOF. ? Pulmonary regurgitation can be evaluated by biventricular systolic volume difference. ? CT overestimates RV volume and underestimates pulmonary regurgitation, compared with MRI.